The age old view of seeing modern medicine as being scientifically up-to-date is rapidly fading away. More and more people are falling outside of medicine’s ability to care for them and seeking help elsewhere. Nowhere is this more evident than with systemic fungal candida. Medical doctors don’t acknowledge its existence, except in severely immunosuppressed patients as those with AIDS, some cancers, and patients taking drugs to suppress the immune system.
Science has published over 62,000 studies about candida since the introduction of antibiotics in the mid-1940s, with scientists weighing in on its effects in all types of individuals, including those with healthy immune systems. Obviously, there is a huge gap between science and medicine when it comes to candida.
While medical doctors continue to insist that candida only affects the immunosuppressed, scientists and researchers state otherwise, and extend the list of those affected to include: diabetics, premature infants, surgical patients (4)(5)(6); hospitalized patients, especially in Intensive Care Units, or having major injuries, burn victims (5); nutritional deficiencies, dentures, salivary abnormalities (7); as well as aging (7)(8)(9)(10); stress (2); Alcoholism, cirrhosis, tuberculosis, intravenous drug abuse, and granulocytopenia (6).
Researchers continuously broaden the scope of those being affected. Valdimarsson et al. state that there are no common immunological denominators (1). Senet states that the pathogenic behavior of Candida may appear following even a slight modification of the host (2). Berg et al. on behalf of Biocodex Pharmaceuticals states that Candida spreads in immunocompetent individuals (3).
Medical doctors state that candida only causes problems in immunosuppressed individuals, yet there are over 100 symptoms, conditions, and diseases that can be caused by or modulated by candida. The common factor in all of these is not immunosuppression, but inflammation. Candida causes an increase in Matrix Metalloproteases (MMPs) and a decrease in inhibitors of MMPs that can lead to Lupus, Scleroderma, Glaucoma, Cirrhosis, Fibrosis, Tumors, Dementia, Aortic Aneurysms, Arthritis, Psoriasis, Multiple Sclerosis, Rheumatism, Crohn’s, and autoimmune conditions and syndromes (11)(12)(13).
Given that fungal candida is associated with so many symptoms, conditions, and diseases, one would think that a medical doctor would be aware of well-documented, evidence-based, scientifically-backed research that demonstrates time and time again a common causative agent. Once this cause was known, it would serve the best interests of the patient to be aware of and avoid when possible, the use of any predisposing factors that would create such a cause. If for some reason this was unavoidable, then the doctor should provide the patient with this information and then instruct them on how to compensate and remedy any imbalances caused by it. This however, as far as candida is concerned, does not happen in medicine today. If it did, medical doctors would be acutely aware that antibiotics cause systemic fungal conditions whenever they are used, and that this can then then lead to other conditions and diseases. Upon giving antibiotics, they would recommend that the patient follow protocols that can help to correct and remedy the effects of antibiotics in the body.
The widespread use of antibiotics, which induce neutropenia, an abnormally low number of neutrophils (white blood cells), and immune system suppression is commonly attributed by science to be the most consistent cause of systemic Candida (14)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(7)(2)(26)(27)(28)(29)(3)(30)(32)(33). Corticosteroids suppress immune system function and can lead to fungal candida (34)(21)(3). Intestinal homeostasis is critical for human health (15)(4)(2)(27)(3)(31). This is just a sampling of what’s documented, but medicine acknowledges none of it in the practice of medicine.
The science of candida and how it affects the body goes far beyond what is written here. The ability of antibiotics to create systemic fungal candida is documented in thousands of studies dating back to the introduction of antibiotics in the 1940s. This gap between science and the practice of modern medicine is a major cause of sickness and illness today. In truth, it cannot be referred to as a gap, for it is a wide chasm that millions of people fall into while under modern medical care. As modern medicine continues its decline, patients will search for the truths that lead them back to a state of health and a life of vitality.
Start living a healthier life today. Dr. McCombs Candida Plan.
1. Immunological phenomena associated with chronic mucocutaneous candidiasis have recently been intensively studied by many workers (reviewed by Kirkpatrick, Rich & Bennett, 1971). The results have shown that there is no common immunological denominator in this disease. The most common finding, however, is defective cellular immunity, which may or may not be accompanied by failure of in vitro lymphocyte transformation.
Immunological Feautures in a Case of Chronic Granulomatous Candidiasis and its Treatment with Transfer Factor
H. VALDIMARSSON, C. B. S. WOOD, J. R. HOBBS AND P. J. L. HOLT
2. Clinical studies show that any modification of the host immune status can facilitate the proliferation of endogenous Candida which, according to the importance of the immune deficiency, can provoke diseases ranging from benign localized mucocutaneous candidosis to sometimes lethal systemic invasions. The pathogenic behavior of Candida cells is mainly due to a very high phenotypic biodiversity. Following even very slight environmental modifications, it may change its behavior through the appearance of new or amplified such as tube formation, adherence, protease secretion, etc. Together with the impairment of host defenses, these new invasive properties lead to the so-called opportunistic pathogenicity of Candida cells. From a host point of view, after the integrity of surface teguments, the mucosal protection is ensured by the Th1 “cellular” immune response which, through pro-inflammatory cytokine production, boosts the efficacy of the phagocytes (Polymorphonuclear cells and macrophages). Neutrophils are of particular importance as deep seated Candida proliferation is mostly associated with neutropenia. Whatever the pathogenic process, it is mostly due to modifications provoked by increasing medical awareness which makes patients more susceptible to illness. A better knowledge of the precise mechanisms involved and would lead to improved strategies for prevention.
Stress is an often forgotten cause of temporary immunodeficiency. Neuroendocrine regulation and chronobiological effects may notably modulate the immune system and provide the opportunity of fungal proliferation.
As Wilson (1962) put it: “C. albicans is a better clinician and can discover abnormalities in persons much earlier in the course of the development of such abnormalities than we can with our chemical tests”.
The pathogenic behaviour of Candida may appear following even a slight modification of the host.
Risk factors and physiopathology of Candidiasis
3. We previously reported that the primary defense mechanisms inhibiting translocation from the GI tract are an ecologically balanced GI microflora (preventing intestinal microbial overgrowth or colonization by exogenous microorganisms, or both), the host immune defense system, and the physical barrier of an intact intestinal mucosa. Oral antibiotics are especially effective in disrupting the GI ecologic equilibrium, leading to intestinal overgrowth by certain normal flora bacteria and their subsequent translocation from the GI tract.
All mice were given streptomycin and penicillin ad libitum for 4 days (0-4) in drinking water to reduce their indigenous GI microflora.
Prednisolone immunosuppression increased the mean numbers of C albicans translocating to the MLN (mesenteric lymph node) from 775 to 9336 C albicans/g MLN.
Also, placing fresh C albicans in the drinking water each day was as effective a method of colonizing mice with the organism as was daily intragastric inoculation of C albicans.
Viable C albicans translocated across the GI mucosal barrier to the MLN in immunocompetent, antibiotic-decontaminated mice colonized with C albicans, but the translocating C albicans did not spread systemically from the MLN to other organs. S. boulardii treatment reduced the incidence of MLN positive for C albicans in these immunocompetent mice but did not reduce the mean numbers of C albicans per gram of MLN. The ileal and cecal populations of C albicans were not decreased whether S. boulardii was given prior to or following C albicans challenge.
Disruption of the intestinal microecology by oral antibiotics to cause intestinal microbial overgrowth and increased microbial translocation is clinically relevant since antibiotic therapy also predisposes humans to intestinal microbial overgrowth and infection by various bacteria and yeasts, such as C albicans.
Oral antibiotic therapy in humans often leads to colonization and over-growth of the GI tract by C. albicans (Stone HH, Geheber CE, Kolb LD, Kitchens WR. Alimentary tract colonization by Candida albicans. J Surg Res 1973;14:273-6.)
Inhibition of Candida albicans Translocation from the Gastrointestinal Tract of Mice by Oral Administration of Saccharomyces boulardii
R. Berg, P. Bernasconi, D. Fowler, and M. Gautreaux
Dept of Microbiology and Immunology, Lousiana State University Medical Center, Shreveport and BIOCODEX, Montrouge, France
The Journal of Infectious Diseases, Vol. 168, No. 5 (Nov., 1993), pp. 1314-1318
4. Candida albicans is a component of the normal flora of the alimentary tract and also is found on the mucocutaneous membranes of the healthy host. However, when immune defenses are compromised or the normal microflora balance is disrupted, Candida transforms itself into an opportunistic pathogenic killer. Candida is the leading cause of invasive fungal disease in premature infants, diabetics, and surgical patients, and of oropharyngeal disease in AIDS patients. As the induction of cell-mediated immunity to Candida is of critical importance in host defense, we sought to determine whether human dendritic cells (DC) could phagocytose and degrade Candida and subsequently present Candida antigens to T cells. Immature DC obtained by culture of human monocytes in the presence of granulocyte-macrophage colony-stimulating factor and interleukin-4 phagocytosed unopsonized Candida in a time-dependent manner, and phagocytosis was not enhanced by opsonization of Candida by the mannose-fucose receptor. Upon ingestion, DC killed Candida as efficiently as human M, and fungicidal activity was not enhanced by the presence of fresh serum. Although phagocytosis of Candida by DC stimulated the production of superoxide anion, inhibitors of the respiratory burst (or NO production) did not inhibit killing of Candida, even when phagocytosis was blocked by preincubation of DC with cytochalasin D. Further, although apparently only modest phagolysosomal fusion occurred upon DC phagocytosis of Candida, killing of Candida under anaerobic conditions was almost equivalent to killing under aerobic conditions. Finally, DC stimulated Candida-specific lymphocyte proliferation in a concentration-dependent manner after phagocytosis of both viable and heat-killed Candida cells. These data suggest that, in vivo, such interactions between DC and C. albicans may facilitate the induction of cell-mediated immunity. in serum. Like macrophages (M), DC recognized
Despite appropriate therapy, mortality from systemic Candida infections in immunocompromised individuals is nearly 30%. In human immunodeficiency virus-infected individuals who have not yet developed advanced immunodeficiency, the prevalence of oropharyngeal Candida is from 7 to 48% of patients. As the immunodeficiency in AIDS patients progresses, the prevalence of oral candidiasis increases to 43 to 93%. Furthermore, the development of oral candidiasis in the early stages of human immunodeficiency virus infection is highly predictive of worsening immunodeficiency.
Candida albicans Is Phagocytosed, Killed, and Processed for Antigen Presentation by Human Dendritic Cells
Simon L. Newman and Angela Holly
5. A new study has uncovered the genetic wiring diagram underlying the infectiousness of Candida albicans, a fungus that causes thrush in babies, vaginal infections in women, and life-threatening infections in chemotherapy and AIDS patients. The study, led by Dr. Gerald R. Fink, Director of the Whitehead Institute for Biomedical Research, reveals that one key to Candida’s infectiousness lies in its ability to switch from a rounded form to filamentous forms. Fungal infections in hospitalized patients have almost doubled throughout the 1980s, often with life-threatening results in individuals with weakened immune systems. Candida, in particular, poses a serious threat and is associated with high mortality rates in patients undergoing chemotherapy. Candida is also a major cause of infection in hospitalized patients, especially those in Intensive Care Units, patients after major injuries or surgery, patients with burns, and premature babies.
In this study, Dr. Fink and his colleagues used molecular biology techniques to identify the components of the filamentation circuit in yeast. With the recently completed yeast genome to guide them, the scientists began to knock out suspicious genes and, by a process of elimination, discovered the culprits that are responsible for filamentation. Once scientists identified the key yeast filamentation genes, they simply plucked out the analogous genes in Candida. “Candida albicans is three hundred million years apart evolutionarily from yeast-as far away in evolution as humans are from turtles-and yet, the basic logic circuit was conserved,” says Dr. Fink.
Discovery Of Genetic Pathways May Provide New Ways To Combat Candida Infections
Gerald R. Fink, et al.
6. Although healthy subjects may host fungal diseases, various predisposing factors that depress the immune system have been implicated in most patients developing fungal infections or fungal arthritis, or both. Alcoholism, cirrhosis, diabetes, tuberculosis, cancer, prematurity, treatment with corticosteroids, cytotoxic drugs, prolonged use of intravenous antibiotics, intravenous drug abuse, granulocytopenia, and marrow hyperplasia are among the predisposing factors. Neonates are the first group of patients in whom haematogenously originated Candida arthritis can occur. The illness is a hospital acquired disease of sick children with underlying diseases such as the respiratory distress syndrome, and gastrointestinal defects. C albicans, which is responsible for more than 80% of the reported cases, and C tropicalis are the species responsible for this disease. Arthritis is usually present with accompanying metaphysial osteomyelitis. Bone infection might originate from the infected synovium or via the metaphysical vessels. Polyarthritis occurs in most patients and the knee is the joint most often affected.
Arthritis originated by haematogenous dissemination beyond the neonatal period is usually a complication of disseminated candidiasis in patients with serious underlying disorders or intravenous drug abusers. C albicans is again the causative organism in about 80% of cases, and C tropicalis is responsible for most of the remaining cases. Two distinct clinical presentations can be observed: (a) acute onset of constitutional and synovial symptoms (about two thirds ofpatients), with the aetiological diagnosis established within the first week, and (b) indolent presentation, with mild systemic and arthritic symptoms, and delay in the diagnosis for months or years.
Marta L Cuellar, Luis H Silveira, Luis R Espinoza
Annals of the Rheumatic Diseases 1992
7. With the increasing number of immune compromised patients, fungi have emerged as major causes of human disease. Risk factors for systemic candidiasis include presence of intravascular catheters, receipt of broad-spectrum antibiotics, injury to the gastrointestinal mucosa and neutropenia. Within a species, the fungal morphotype (e.g. yeast, pseudohyphae and hyphae of Candida albicans) may be an important determinant of the host response. Whereas yeasts and spores are often effectively phagocytosed, the larger size of hyphae precludes effective ingestion.
Differentiation of CD4+ T cells along a T-helper (Th) cell type 1 (Th1) or type 2 (Th2) pathway and development of specific Th responses, is an essential determinant of the host’s susceptibility or resistance to invasive fungal infections. Development of Th1 responses is influenced by the concerted action of cytokines, such as interferon (INF)-c, interleukin (IL)-6, tumour necrosis factor (TNF)-a, and IL-12, in the relative absence of Th2 cytokines, such as IL-4 and IL-10 (Romani, 2002).
Oropharyngeal candidiasis (OPC) is among the most common mycotic infections of immunocompromised patients. Development of infection depends upon both systemic and local determinants. Risk factors for oral candidiasis include extremes in age, diabetes mellitus, particularly when glycemic control is poor, nutritional deficiencies, use of broad spectrum antibiotics and immunosuppression (especially of cell-mediated immunity) (Klein et al., 1984; Guggenheimer et al., 2000). Local factors that promote infection include dentures, salivary abnormalities, treatment with inhaled steroids, and destruction of mucosal barriers with radiotherapy for head and neck cancers or cytotoxic chemotherapy. Human immunodeficiency virus (HIV) is one of the most important predisposing conditions worldwide. AIDS patients have a particularly high incidence of mucosal candidiasis, which is often recurrent and, when it involves the esophagus, can be disabling (Sangeorzan et al., 1994). Local defence mechanisms against mucosal infection include salivary proteins, such as lactoferrin, beta-defensins, histatins, lysozyme, transferrin, lactoperoxidase, mucins, and secretory immunoglobulin A. These impair adhesion and growth of Candida in the oropharyngeal cavity. Development of OPC has been associated with a salivary Th2-type cytokine profile (Leigh et al., 1998).
Cell-mediated immunity plays the dominant role in prevention of candidiasis at the gastrointestinal surfaces. In AIDS, development of oropharyngeal and oesophageal candidiasis correlates with declining CD4+ lymphocyte counts. OPC is also associated with T cell immunosuppression from corticosteroid therapy, organ transplantation, cancer chemotherapy and chronic mucocutaneous candidiasis (CMC). Candida species have emerged as an important cause of bloodstream and deep tissue infections. Risk factors for Candidaemia include breakdown of mucosal barriers due to cytotoxic chemotherapy and surgical procedures, neutropenia, changes in the gut flora due to antibiotics, and invasive interventions that breach the skin, such as intravenous lines and drains (Wey et al., 1989). Common sites of dissemination include the bloodstream, kidney, liver, spleen, and endovascular structures. Quantitative and qualitative abnormalities of neutrophils and monocytes are associated with systemic candidiasis. Patients with lymphoma, leukaemia, chronic granulomatous disease, and recipients of intensive cancer chemotherapy with resultant neutropenia are at increased risk for disseminated infection. Similar to the situation with Aspergillus hyphae, the large size of Candida hyphae and pseudohyphae may preclude phagocytosis. Achieving a balance between Th1 and Th2 cytokines may be important for optimal antifungal protection while minimizing immune-mediated damage. In vivo models indicate that T regulatory cells attenuate Th1 antifungal responses, induce tolerance to the fungus and participate in the development of long lasting protective immunity after yeast priming (Montagnoli et al., 2002; Romani, 2004).
Dendritic cells play an important role in linking innate with adaptive immunity. Dendritic cells that ingest the yeast form induce differentiation of CD4+ T cells toward a Th1 pathway. In contrast, hyphae induce Th2 responses (d’Ostiani et al., 2000). Neutrophils, macrophages and natural killer (NK) cells also modulate adaptive responses to the fungus. Neutrophils differentially induce Th1 and Th2 responses depending on whether the exposure is to yeast or hyphae.
The syndrome of chronic disseminated candidiasis (CDC, also known as hepatosplenic candidiasis) predominantly affects patients with haematological malignancies upon recovery from neutropenia. CDC is characterized by increased serum levels of IL-10 and local production of Th2-inducing cytokines by hepatocytes and by infected mononuclear cells (Roilides et al., 1998b; Letterio et al., 2001). Thus, although neutropenia is a major predisposing factor, the propensity for persistence of the fungus in infected tissues may be a consequence of cell-mediated immune dysregulation with suppression of Th1 and overexpression of Th2 responses.
The Immune Response to Fungal Infections
Shmuel Shoham1 and Stuart M. Levitz
Section of Infectious Diseases, Washington Hospital Center, Washington, DC, and 2Department of Medicine, Boston Medical Center and Boston University School of Medicine, Boston, MA, USA
British Journal of Haematology, 129, 569–582
8. The study indicates that host age is a determining factor in yeast carriage. From the neonatal period, humans go through several dentition periods, and the emergence and substitution of teeth and changes in living habits greatly change the environment of the oral cavity, and therefore influence colonization by oral commensal organisms, certainly.
including Candida spp. Russell and Lay showed that the frequency of oral yeast carriage at birth was low, doubled by the time that infants were discharged from the hospital at about seven-day old, and increased sharply after one month old. Kleinegger et al. demonstrated that the frequency of oral yeast carriage was 44% of the examined individuals in a group aged from 0.5 to 1.5, 24% in a 5-7-year-old group, 40% in a 15- to 18-year-old group.
In a review by Odd in 1988, the highest reported frequencies were 71% of school children in the United Kingdom, and 56% of children in Israel. Different sampling and identification methods for Candida spp. would also certainly influence the results. Because of the uneven distribution of C. albicans throughout the oral cavity, swab samples can yield false-negative culture more often than oral rinse samples or imprint culture. The number of false-negative cultures was reduced by the swabbing of two sitesrather than one. In conclusion, our observations indicate that there is an increased risk of dental caries with C. albicans carriage rates in preschool and school children.
Oral Candida albicans carriage in healthy preschool and school children
Rokiewicz D, Daniluk T, Zaremba ML2, Cylwik-Rokicka D , Stokowska W,
Pawińska M, Dąbrowska E, Marczuk-Kolada G, Waszkiel D
9. The prevalence of opportunistic fungal infections has increased dramatically among the aged population in recent years. Thiswork investigated the effect of ageing on murine defenses against Candida albicans. Aged C57BL/6 mice that were experimentallyinfected intravenously had a significantly impaired survivaland a higher tissue fungal burden compared with young mice.In vitro production of tumour necrosis factor (TNF)- by macrophagesfrom aged mice in response to yeast cells and hyphae of C. albicanswas significantly lower than production by macrophages fromyoung mice. In vitro production of cytokines, such as TNF- andgamma interferon (IFN-), by antigen-stimulated splenocytes frommice intravenously infected with C. albicans cells was alsodiminished in old mice. This decrease in production of T helper1 cytokines in old mice correlated with a diminished frequencyof IFN–producing CD4+ T lymphocytes, although the ability todevelop an acquired resistance upon vaccination (primary sublethalinfection) of mice with the low-virulence PCA2 strain was notaffected in aged mice. The diversity of antigens recognizedby C. albicans-specific antibodies in sera from infected agedmice was clearly diminished when compared with that from infected young mice. Taken together, these data show that aged mice developan altered innate and adaptive immune response to C. albicans and are more susceptible to systemic primary candidiasis.
Impaired immune response to Candida albicans in aged mice
Celia Murciano, Eva Villamón, Alberto Yáñez, José-Enrique O’Connor, Daniel Gozalbo and M. Luisa Gil
10. Previous work by our group showed that aged C57BL/6 mice develop an altered innate and adaptive immune response to Candida albicans and are more susceptible to systemic primary candidiasis. In this work, we used young (2-3 months old) and aged (18-20 months old) C57BL/6 mice to study in vitro the influence of aging on (1) the fungicidal activity of neutrophils and macrophages, (2) the production of cytokines by resident peritoneal macrophages in response to C. albicans, and (3) cell surface Toll-like receptor (TLR) 2 expression on resident peritoneal macrophages. Our results indicate that murine phagocytes have a fungicidal activity well preserved with aging. In vitro production of proinflammatory cytokines (IL-6, IL-1beta, and tumor necrosis factor-alpha and chemokines (MIP-2) by purified (CD11b(+)) peritoneal macrophages in response to yeasts and hyphae of C. albicans was significantly lower in aged mice as compared with young mice. However, the production of IL-10 by macrophages, in response to C. albicans, was similar in both young and aged animals. Moreover, baseline TLR2 surface expression level was lower on aged macrophages than on control macrophages. Taken together, these data indicate that the increased susceptibility to C. albicans disseminated infections in aged mice is correlated with defects in TLR2 expression and in cytokine production, but not with an impaired fungicidal activity.
Influence of aging on murine neutrophil and macrophage function against Candida albicans.
Murciano Celia; Yáñez Alberto; O’Connor José E; Gozalbo Daniel; Gil María Luisa
11. A variety of morphological changes in the basement membrane (BM) are known to occur in inflammatory diseases. Modifications of the BM can be associated with significant changes in protein content. Candida albicans (C. albicans) is normally a commensal organism and is a member of the natural flora of a large number of healthy individuals. However, under certain conditions, C. albicans can invade host tissues, causing inflammation and tissue damage. The aim of this study was to investigate the effect of C. albicans on the expression and production of structural (laminin-5 and type IV collagen) and inflammatory
Basement membrane protein and matrix metalloproteinase deregulation in engineered human oral mucosa following infection with Candida albicans.
12. Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that are a subfamily of metzincins. Matrix metalloproteinases are responsible for much of the turnover of extracellular matrix components and are key to a wide range of processes including tissue remodeling and release of biological factors. Imbalance between the MMPs and endogenous tissue inhibitors of metalloproteinases (TIMPs) can result in dysregulation of many biologic processes and lead to the development of malignancy, cardiovascular disease, and autoimmune and inflammatory disorders. MMP production by monocyte/macrophages is dependent on the cell type, state of differentiation, and/or level of activation and whether they are infected, e.g., by HIV-1. MMP expression by HIV-1 infected monocytes and macrophages may alter cellular trafficking and contribute to HIV-associated pathology such as HIV-associated dementia (HAD). This review will provide a classification of the MMP super-family with particular reference to those produced by monocyte/macrophages, describe their regulation and function within the immune system, and indicate their possible roles in the pathogenesis of disease, including HIV-associated dementia.
Dysregulation in the levels and control of MMPs can lead to pathological processes (including tumor growth and migration, arthritis, cirrhosis, aortic aneurysms, and fibrosis) and diseases (such as glaucoma, lupus, scleroderma, multiple sclerosis, and HIV-1 associated dementia). MMPs play an important role in immunological functions including ECM for leukocyte migration, modulating chemokine, and cytokine activity through both their activation and inactivation and defensins activation.
MMPs regulate numerous biologic processes through their proteolytic function, in both normal and pathological states. They alter the cellular milieu and cell behavior through proteolytic turnover of matrix components, by releasing molecules expressed on the surface of cells and by cleaving cell surface receptors or cell-cell adhesion proteins.
Cells of the monocyte/macrophage lineage, including blood monocytes, dendritic cells, and tissue macrophages such as microglia secrete diverse MMPs in large quantities.
Induction of MMPs can modulate DC functions including DC migration through endothelial barriers. Cell migration is critical for dendritic cells (DCs) in the initiation of the immune response.
HIV-infected patients frequently report gingival inflammation and may develop progressive periodontal tissue breakdown or require dental extraction due to weakened attachment. HIV-related periodontal disease, including gingivitis; periodontitis; and bacterial, viral and fungal infections has been associated with increased levels of MMP-1, -3, and -8 in saliva from HIV-infected individuals, and these MMPs may play a role in the development of HIV-associated periodontitis.
Matrix metalloproteinases, their production by monocytes and macrophages and their potential role in HIV-related diseases
Nicole L. Webster and Suzanne M. Crowe
13. IL-17-producing CD4+ T helper cells (TH17) have been extensively investigated in mouse models of autoimmunity1. However, the requirements for differentiation and the properties of pathogen-induced human TH17 cells remain poorly defined. Using an approach that combines the in vitropriming of naive T cells with the ex vivo analysis of memory T cells, we describe here two types of human TH17 cells with distinct effector function and differentiation requirements. Candida albicans-specific TH17 cells produced IL-17 and IFN-γ, but no IL-10, whereas Staphylococcus aureus-specific TH17 cells produced IL-17 and could produce IL-10 upon restimulation. IL-6, IL-23 and IL-1β contributed to TH17 differentiation induced by both pathogens, but IL-1β was essential in C. albicans-induced TH17 differentiation to counteract the inhibitory activity of IL-12 and to prime IL-17/IFN-γ double-producing cells. In addition, IL-1β inhibited IL-10 production in differentiating and in memory TH17 cells, whereas blockade of IL-1β in vivo led to increased IL-10 production by memory TH17 cells. We also show that, after restimulation, TH17 cells transiently downregulated IL-17 production through a mechanism that involved IL-2-induced activation of STAT5 and decreased expression of ROR-γt. Taken together these findings demonstrate that by eliciting different cytokines C. albicans and S. aureus prime TH17 cells that produce either IFN-γ or IL-10, and identify IL-1β and IL-2 as pro- and anti-inflammatory regulators of TH17 cells both at priming and in the effector phase.
Pathogen-induced human TH17 cells produce IFN-γ or IL-10 and are regulated by IL-1β
14. Phagocytic cells of the innate immune system, such as macrophages and neutrophils, are a primary line of defense against microbial infections. Patients with defects in innate immunity, such as those with chronic granulomatous disease or neutropenia, are extremely sensitive to a variety of infections. When a phagocyte recognizes the presence of an invading cell, it engulfs the microbe with its membrane to form the phagosome, an intracellular compartment containing the microbe. This compartment matures by fusion with lysosomes to create the phagolysosome, an organelle replete with antimicrobial compounds and an acidic pH. Internalization creates a hostile environment for the microorganism, which,of course, is the intent. The phagolysosome is a precarious neighborhood even before the onslaught of antimicrobial compounds. Engulfment by the macrophage thrusts the microorganism into an alien milieu, one devoid of key nutrients necessary for metabolism and division. Survivingthe antimicrobial assault in the phagolysosome depends on themicrobe’s ability to synthesize the proteins and other cellular components necessary to counteract these stresses. Thus, a pathogen must find the requisite nutrients to provide the building blocks for these complex macromolecules and the energy with which to synthesize them.
In this article we consider the initial responses of several microbes to nutrient deprivation inside the macrophage. The first of these, Mycobacterium tuberculosis, the bacterium that causes tuberculosis, resides for prolonged periods within the macrophage, in which it can proliferate and subsequently spreadthroughout the body. The second, the yeast Saccharomyces cerevisiae,is killed efficiently by the macrophage. The third, the opportunistic fungal pathogen Candida albicans, survives ingestion by changing rapidly from a yeast to a filamentous morphology, lysing the macrophage from the inside out. Once free, C. albicans cells are able to disseminate through the body. The interaction of C. albicans with the macrophage is transient, as opposed to the long-term persistence of M. tuberculosis. Although the outcomes of this macrophage capture are quite different among the three microbes, the initial responses of all three to the internal environment are remarkably similar: induction of the glyoxylatecycle, a pathway that permits the utilization of compounds withtwo carbons (C2compounds), such as acetate, to satisfy cellular carbon requirements.
Systemic fungal infections have increased dramatically in prevalence and severity over the last few decades, in concert with the number of patients living for extended periods with significant immune dysfunction. AIDS, cancer chemotherapy, and organ transplantation have all contributed to this rise, as has the widespread use of antibiotics. The most common systemic fungal infection is candidiasis, which accounts for well over half of these invasive mycoses. A single species, C. albicans, causes the majority of these infections. C. albicans, which also causes oropharyngeal thrush and vaginitis, is normally a commensal of the mammalian gastrointestinal tract, in which it lives without adverse effectson the host. Both C. albicans and S. cerevisiae are readily phagocytksed by cultured macrophages in the presence of serum. While the macrophages efficiently kill S. cerevisiae, engulfment induces C. albicans cells to grow in a filamentous morphology. These hyphal filaments can penetrate through the membrane of the phagocytic cell, releasing the fungal cell back into the extracellular medium while killing the macrophage in the process. The different outcomes are not surprising; C. albicans is a common pathogen while S.cerevisiae is rarely found in human hosts.
The primary function of the glyoxylate cycle is to permit growth when C2 compounds, such as ethanol and acetate, are the only sources of carbon. The glyoxylate pathway (also dubbed the glyoxylate shunt, forclear reasons) bypasses these decarboxylations, allowing C2 compounds to serve as carbon sources in gluconeogenesis and to be incorporated into glucose and, from there, into aminoacids, DNA, and RNA. Glucose, as the preferred carbon sourcein most organisms, can be both converted into five-carbon sugars(such as ribose and deoxyribose) via the pentose phosphate pathwayand catabolized to acetyl-CoA via glycolysis. In microorganisms, however, glucose is frequently not available,and simple carbon compounds provide the only accessible carbon.
With the population of immunocompromised people on the rise, the frequency of invasive fungal infections continues to increase, making the need for effective treatments more imperative.
Life and Death in a Macrophage: Role of the Glyoxylate Cycle in Virulence
Michael C. Lorenz and Gerald R. Fink
15. Intestinal homeostasis is critical for efficient energy extraction from food and protection from pathogens. Its disruption can lead to an array of severe illnesses with major impacts on public health, such as inflammatory bowel disease characterized by self-destructive intestinal immunity. However, the mechanisms regulating the equilibrium between the large bacterial flora and the immune system remain unclear. Intestinal lymphoid tissues generate flora-reactive IgA-producing B cells, and include Peyer’s patches and mesenteric lymph nodes, as well as numerous isolated lymphoid follicles (ILFs). Here we show that peptidoglycan from Gram-negative bacteria is necessary and sufficient to induce the genesis of ILFs in mice through recognition by the NOD1 (nucleotide-binding oligomerization domain containing 1) innate receptor in epithelial cells, and -defensin 3- and CCL20-mediated signalling through the chemokine receptor CCR6. Maturation of ILFs into large B-cell clusters requires subsequent detection of bacteria by toll-like receptors. In the absence of ILFs, the composition of the intestinal bacterial community is profoundly altered. Our results demonstrate that intestinal bacterial commensals and the immune system communicate through an innate detection system to generate adaptive lymphoid tissues and maintain intestinal homeostasis.
Lymphoid tissue genesis induced by commensals through NOD1 regulates intestinal homeostasis
Djahida Bouskra, Christophe Brézillon, Marion Bérard, Catherine Werts, Rosa Varona, Ivo Gomperts Boneca & Gérard Eberl
16. Humans rely on their native microbiota for nutrition and resistance to colonization by pathogens; furthermore, recent discoveries have shown that symbiotic microbes make essential contributions to the development, metabolism, and immune response of the host. Co-evolved, beneficial, human–microbe interactions can be altered by many aspects of a modern lifestyle, including urbanization, global travel, and dietary changes, but in particular by antibiotics. The acute effects of antibiotic treatment on the native gut microbiota range from self-limiting “functional” diarrhea to life-threatening pseudomembranous colitis. The long-term consequences of such perturbations for the human–microbial symbiosis are more difficult to discern, but chronic conditions such as asthma and atopic disease have been associated with childhood antibiotic use and an altered intestinal microbiota. Because many chemical transformations in the gut are mediated by specific microbial populations, with implications for cancer and obesity, among other conditions, changes in the composition of the gut microbiota could have important but undiscovered health effects.
The Pervasive Effects of an Antibiotic on the Human Gut Microbiota, as Revealed by Deep 16S rRNA Sequencing
Les Dethlefsen , Sue Huse, Mitchell L. Sogin, David A. Relman
17. A transporter in the colon called SLC5A8 plays an important role in enabling the colon to get the last bit of good out of food before the unusable is flushed away, according to research currently published online as an accelerated communication in the Journal of Biological Chemistry. The finding that SLC5A8 is the transporter helps clarify why fruits and vegetables are good for you and why antibiotics, which wipe out good bacteria along with bad, should only be taken when absolutely necessary, upset the model and colonic cells get sick and may even become cancerous. “We do not make the enzyme to digest cellulose; bacteria make the enzyme in the colon,” says Dr. Ganapathy. “Therefore, you need to eat dietary fiber to provide the food for bacteria. Otherwise, they are not going to su’”/>rvive there. Antibiotics can wipe out good bacteria as well, leaving a void where disease-causing bacteria can grow.” “The gut is a huge immune organ; there are more immune cells in our gut than there are in the rest of the body put together,” says Dr. Robert G. Martindale, MCG gastrointestinal surgeon and nutritionist with a special interest in probiotics giving patients good bacteria to restore a healthy flora. “The work that Dr. Ganapathy is doing is showing very nicely that if, in fact, we keep this short-chain fatty acid transporter healthy, we then can keep the whole immune system healthy.” Immune cells also have a specific receptor for short-chain fatty acids on the cell surface, and Drs. Ganapathy and Martindale are pursuing the idea that the SLC5A8 transporter is delivering these fatty acids to immune cells to interact with the receptors and keep the immune cells vigilant as well.
Transporter’s function provides support for eating vegetables, limiting antibiotics
Dr. Vadivel Ganapathy
18. Although Candida albicans is present in many mammals including humans, normal bacterial flora and various immune factors usually restrict the growth of C. albicans in the alimentary tracts of immune competent hosts. Infection of the alimentary tract mucosae, including the mucosae of the oropharynx, esophagus, and gastrointestinal tract, with C. albicans is occurring with greater frequency, presumably because of the increased population of immune compromised individuals. Recent evidence suggests that cell-mediated immunity, and more specifically, CD41 T lymphocytes, play an important role in resistance to mucosal candidiasis. Patient populations with AIDS or other defects in cellular immune function show an increased incidence of mucocutaneous, but not necessarily disseminated, candidiasis, whereas patients with phagocytic cell defects, such as those that occur in patients with neutropenic or chronic granulomatous disease states, show a higher incidence of disseminated candidiasis. A combination of defective cell-mediated immunity and phagocytic cell defects in athymic beige (bg/bg nu/nu) mice was found to predispose them to severe mucosal candidiasis with subsequent Candida dissemination. Existing mouse models of mucosal candidiasis use combinations of chemically induced immune suppression, elimination or alteration of the host microflora by administration of antibiotics, high inocula, trauma, infant animals, or animals with congenital, functional, physiological, immunological, or metabolic defects to facilitate colonization of the gastrointestinal tract by C. albicans.
New Model Of Oropharyngeal and Gastrointestinal Colonization by Candida albicans in CD41 T-Cell-Deficient Mice for Evaluation of Antifungal Agents
AMY M. FLATTERY, GEORGE K. ABRUZZO, CHARLES J. GILL, JEFFREY G. SMITH, AND KEN BARTIZAL
19. Underlying acquired immunity to the fungus Candida albicans is usually present in adult immunocompetent individuals and is presumed to prevent mucosal colonization progressing to symptomatic infection. Exploration of immunological events leading to Candida resistance or susceptibility has indicated the central role of the innate and adaptive immune systems, the relative contribution of which may vary depending on the site of the primary infection. Nevertheless, acquired resistance to infection results from the development of Th1 responses. Cytokines produced by Th1 cells activate phagocytic cells to a Candidacidal state. In contrast, cytokines produced by Th2 cells inhibit Th1 development and deactivate phagocytic effector cells. Because reciprocal influences have been recognized between innate and adaptive Th immunity, it appears that an integrated immune response determines the life-long commensalism of the fungus at the mucosal level, as well as the transition from mucosal saprophyte to pathogen. However, if the ability of C. albicans to establish a disseminated infection involves neutropenia as a major predisposing factor, its ability to persist in infected tissues or to behave as a commensal may involve primarily downregulation of host cell-mediated adaptive immunity. As a commensal, C. albicans may be endowed with the ability to elude the host’s immunological surveillance, thus allowing its persistence on mucosal surfaces. Th1 and Th2 CD41 T-cells develop from a common, naïve CD41 T-cell precursor, and several parameters have been shown to influence the pathway of differentiation of CD41 T-cell precursors. Among these, cytokines appear to play a major role, acting not only as modulators of antifungal effector functions but also as key regulators in the development of the different Th subsets from precursor Th cells. Studies in mice have shown that development of protective AntiCandidal Th1 responses requires the concerted actions of several cytokines, such as interferon (IFN)-g, transforming growth factor (TGF)-b, interleukin (IL)-6 , tumor necrosis factor (TNF)-a, and IL-12, in the relative absence of inhibitory Th2 cytokines, such as IL-4 and IL-10, which inhibit development of Th1 responses. Early in infection, neutralization of Th1 cytokines (IFN-g and IL-12) leads to the onset of Th2 rather than Th1 responses, while neutralization of Th2 cytokines (IL-4 and IL-10) allows development of Th1- rather than Th2-cell responses. TNF/lymphotoxin (LT)-a and IL-6 deficiencies render mice highly susceptible to C. albicans infections. Studies in humans have reinforced this concept, by showing that acquired immunity to C. albicans correlates with the expression of local or peripheral Th1 reactivity, whereas susceptibility to the infection seen in thermally injured patients, in patients with human immunodeficiency virus (HIV) infection, or in patients with chronic mucocutaneous or hepatosplenic candidiasis correlates with a biased Th2 response to the fungus. Altogether these data demonstrate that susceptibility to primary and secondary C. albicans infections in cytokine-deficient mice correlates with the failure to develop anti-Candidal, protective Th1 responses and with the occurrence of unprotective IL-4- and IL-10-producing Th2 cells. However, an important immunoregulatory role has been attributed to neutrophils recently. Neutrophils, more than macrophages, were endowed with the ability to produce directive cytokines such as IL-10 and IL-12. Most importantly, IL-12 appeared to be released in response to a low-virulence Candida strain that initiates Th1 development in vivo, but IL-10 was released in response to a virulent strain. Human neutrophils also produced bioactive IL-12 in response to a mannoprotein fraction of C. albicans, capable of inducing Th1 cytokine expression in peripheral blood mononuclear cells. By producing directive cytokines such as IL-10 and IL-12, neutrophils influenced antifungal Th-cell development, as evidenced by the inability of neutropenic mice to mount protective antiCandidal Th1 responses. Production of IL-12 by neutrophils occurred independently of TNF-a and IFN-g. It was impaired upon iron overload but increased upon in vitro priming with IL-4 through upregulation of IL-4 receptor expression. Human studies confirm the multiple and complex role neutrophils have in candidiasis. First, risk factors for invasive fungal infections are not the same in all neutropenic patients. Secondly, chronic systemic candidiasis initiated by neutropenia may persist in spite of normal neutrophil counts and adequate antifungal therapy. Third, some patients, particularly transplant recipients who have adequate or even normal neutrophil counts, may be at high risk for invasive mycoses.
Innate and adaptive immunity in Candida albicans infections and saprophytism
20. Candida albicans infections often occur during or shortly after antibacterial treatment. Phagocytosis by polymorphonuclear neutrophil granulocytes (PMN) is the most important primarily defence mechanism against C. albicans. Certain antibiotics such as some fluoroquinolones (FQ) are known to influence phagocyte functions. Thus, we investigated the influence of older and newer FQ on the phagocytosis and killing of C. albicans by human PMN paying special attention to CD11b expression of these cells as an indicator of the degree of their activation. In order to obtain comprehensive and comparable results we tested 13 FQ over a wide range of concentrations and in a time dependent manner in a standardized approach. When used at therapeutic concentrations, the FQ tested did not influence to a clinically significant degree the phagocytosis or the killing of C. albicans by human PMN and also not their activation. However, at high concentrations those FQ with cyclopropyl-moiety at position N1 showed increase in CD11b expression and diminished phagocytosis and oxidative burst.
Influence of fluoroquinolones on phagocytosis and killing of Candida albicans by human polymorphonuclear neutrophils
Thomas Grúger; Caroline Mörler; Norbert Schnitzler; Kerstin Brandenburg; Sabine Nidermajer; Regine Horré; Josef Zúndorf
21. We studied the effects of eight antibiotics, cyclosporin and corticosteroids on the in vitro secretion of GM-CSF and G-CSF by monocytes, T lymphocytes and endothelial cells. The aim was to evaluate a possible mechanism for these drugs in the delay of haemopoietic recovery after high-dose chemotherapy or bone marrow transplantation. Corticosteroids were prominent inhibitors of GM-CSF secretion by monocytes and T lymphocytes, but not by endothelial cells. In contrast, G-CSF secretion by monocytes was unchanged whereas that of endothelial cells was enhanced in the presence of corticosteroids. Cyclosporin efficiently down-regulated GM-CSF secretion by T lymphocytes and had also a minor effect on CSF secretion by endothelial cells, whereas monocyte secretion was unaffected. Stimulated T lymphocytes derived from patients under treatment with cyclosporin had impaired capacity to secrete GM-CSF compared to controls. Among the antibiotics, cephalosporins inhibited GM-CSF secretion by T lymphocytes, and GM- and G-CSF secretion by endothelial cells. Ciprofloxacin and sulphmethoxazole had minor effects on GM-CSF secretion by T lymphocytes and endothelial cells. No antibiotic significantly influenced GM-CSF secretion by monocytes.
Effects of immunosuppressive drugs and antibiotics on GM-CSF and G-CSF secretion in vitro by monocytes, T lymphocytes and endothelial cells
Lenhoff S.; Olofsson T.
22. Some antimicrobial agents have been reported to modify the host immune andinflammatory responses both in vivo and in vitro. Fosfomycin (FOM) andclarithromycin (CAM) have immunomodulatory activity on human lymphocytefunction. In the present study, we examined the effects of FOM and CAM oncytokine synthesis by lipopolysaccharide (LPS)- stimulated human monocytesin comparison with that of dexamethasone in vitro. The three drugs demonstrated positive or negative effects on the synthesis of various cytokines by LPS-primed monocytes. They suppressed the synthesis of tumor necrosis factor alpha, interleukin 1 alpha (IL-1 alpha), IL-1 beta, theIL-1 receptor antagonist, and granulocyte- macrophage colony-stimulating factor in a concentration-dependent manner at concentrations between 1.6and 40 micrograms/ml. On the contrary, the drugs showed different actionson the synthesis of IL-6 and IL-10. Namely, FOM enhanced both IL-6 andIL-10 synthesis, CAM enhanced only IL-10 synthesis, but dexamethasone deeply suppressed the synthesis of both cytokines. These data indicate that anti-bacterial agents may modify acute-phase inflammatory responses through their effects on cytokine synthesis by monocytes.
Modulatory effect of antibiotics on cytokine production by human monocytes in vitro
K Morikawa, H Watabe, M Araake and S Morikawa
23. Experimental subcutaneous Candida albicans infections in mice were used to examine the manner in which this pathogen is cleared in animals recovering from cyclophosphamide-induced leucopenia. In this system, infections at the inoculation sites progressed rapidly during a 6 day period of leucopenia to form arrays of parallel filamentous organisms that effectively isolated those in the interior from contact by neutrophils, even when the leucopenia had resolved. Dense collections of organisms also developed at sites of metastatic infection in the kidneys. A majority of the organisms were found to be viable when they were retrieved from the infected subcutaneous sites of animals that had recovered from leucopenia and whose abscesses had begun to drain spontaneously. Removal of the protective arrays of fungal cells appeared to be accomplished by drainage of abscess contents through the surface of the skin or into the collecting system of the kidney. Drainage of the subcutaneous abscesses did not occur in the cyclophosphamide-treated animals until after the neutrophilic infiltrates had developed, suggesting that this drainage process was mediated by neutrophils rather than by the organisms themselves. In summary, the above findings demonstrate that C. albicans infections in leucopenic hosts may progress to the extent that they would be very difficult to clear solely through the microbicidal processes of returning neutrophils. However, neutrophils also appear to promote the removal of masses of viable fungal cells to the exterior of the body.
Arrays of Candida albicans pseudohyphae that protect the organisms from neutrophil fungicidal mechanisms in experimental infections of mice
P.G. Sohnle; B.L. Hahn; D.K. Wagner
24. Phagocytes are an essential defence against infection. Since drugs which affect their function may alter the outcome of infections, we have studied the effect of nine antibiotics on phagocyte function in vitro. The effects of antibiotics on the respiratory burst function of phagocytes from healthy adult donors were investigated using lucigenin-enhanced chemiluminescence in response to serum-opsonised zymosan. Aminoglycosides showed dose-dependent suppression of polymorphonuclear leucocyte chemiluminescence, except streptomycin which caused enhancement. Erythromycin caused profound suppression of chemiluminescence from both polymorphonuclear leucocytes and monocytes. Benzylpenicillin and the cephalosporins caused variable suppression of phagocyte chemiluminescence: cefotaxime increased monocyte chemiluminescence in some experiments. None of the drugs produced suppression at clinically relevant plasma concentrations, but erythromycin and some other drugs are preferentially concentrated in phagocytes to levels which suppress their oxidative metabolism in vitro. It is therefore possible that some antibiotics alter phagocyte function: ex vivo studies of phagocyte function in patients taking antibiotics would be valuable.
Antibiotic effects on phagocyte chemiluminescence in vitro
L. A. Pierce, W. O. Tarnow-Mordi and I. A. Cree
25. Drug-induced neutropenia is one of the most common causes of neutropenia. Drugs can decrease neutrophil production through toxic, idiosyncratic, or hypersensitivity mechanisms or increase peripheral neutrophil destruction through immune mechanisms. It may result from aminopyrine, propylthiouracil , penicillin, or other antibiotics. Severe dose-related neutropenia occurs predictably after cytotoxic cancer drugs or radiation therapy suppresses bone marrow production. Neutropenia due to ineffective marrow production can occur in megaloblastic anemias caused by vitamin B12 or folate deficiency. Usually, macrocytic anemia and sometimes mild thrombocytopenia develop simultaneously. Infections can cause neutropenia by impairing neutrophil production or by inducing immune destruction or rapid use of neutrophils.
The Merck Manuals Online Medical Library
26. Substantial clinical evidence has been accumulated, showing that candidiasis is a medical problem of increasing magnitude. That patients on antibiotics experience proliferation of Candida albicans in the alimentary canal is no longer a point for dispute. That the increased incidence of severe fungus infections is associated with antibiotic therapy, particularly in patients with subnormal defense mechanisms, is being increasingly accepted. A recent report has presented an analysis of published experimental and clinical data which indicate that the two clinically disparate conditions-the ostensibly benign proliferation of C. albicans, and the invasion and spread of the organism in debilitated patients-are interrelated. This report presents evidence that the antibiotics enhance the invasiveness of the C. albicans, not only by a direct effect on the intestinal flora, and on the Candida itself, but also by depressing the host defense mechanisms.
Mechanisms by Which Antibiotics Increase the Incidence and Severity of Candidiasis and Alter the Immunological Defenses
MILDRED S. SEELIG (June, 1966)
27. Mammals are superorganisms, being a composite of mammalian and microbial cells existing in symbiosis. Although the microbiota is not essential for life, commensal and intestinal epithelial cell interactions are critical for the maturation of the immune system. Antibiotic treatment alters this delicate balance by causing compositional changes in the intestinal microbiota, and may lead to a homeostatic imbalance through alterations in expression of IEC tight junction proteins, mucin, antimicrobial peptides, and cytokines. Dysregulation of the homeostasis between mammals and their intestinal symbionts has been shown to predispose the host to enteric infection, and may lead to development of inflammatory bowel diseases. The composition of the microbiota is significantly affected by the use of antibiotics, which are often used extensively, and can lead to antibiotic-associated diarrhea and development of secondary infections such as urinary tract infections. The alteration in microbiota composition is believed to reduce carbohydrate fermentation and impair metabolism of bile acids, as well as creating niches for pathogens to proliferate. A recent investigation by Sekirov et al. has shown that antibiotic-mediated disturbance in the composition, but not total numbers of the intestinal microbiota predisposes mice to higher colonization by Salmonella typhimurium and more severe pathology. This shows that altering the microbiota composition, without creating vacant niches in the microbial community, predisposes the host to enteric infection. The intestinal epithelium and its protective mucus layer cover are the primary defenses against pathogen permeation and commensal leakage into the underlying LP. Colonization of the gut by probiotics results in protection of the epithelial barrier by maintaining tight junction protein expression and preventing apoptosis upon chemically induced colitis. Therefore, changing the composition of the microbiota, through antibiotic administration, could change the strength of the IEC barrier through alterations in tight junction protein expression. Decreased expression of tight junction proteins would increase the permeability of the IEC barrier allowing commensal leakage into the underlying LP, leading to inflammation that is indicative of IBD. Current findings suggest that probiotic strains may protect the host from intestinal inflammation by induction of mucus-associated genes, which strengthens the mucus barrier and protects against colonization by enteric pathogens. Impaired antimicrobial defense results in enhanced bacterial penetration into the LP resulting in an inflammatory response and tissue damage. Antimicrobial proteins secreted by IECs (enterocytes and paneth cells) include defensins, cathelicidins, and C-type lectins (RegIIIβ and RegIIIγ). They function by disrupting bacterial surface structures and contribute to the maintenance of microbiota composition. A recent study showed that administration of a combination of the broad-spectrum antibiotics metronidazole, neomycin, and vancomycin led to significant depletion of the microbiota and decreased expression of RegIIIγ by IECs. RegIIIγ expression has been shown to rely on IEC stimulation by microbes and their products. This decrease in both microbiota and RegIIIγ resulted in increased intestinal colonization by vancomycin-resistant Enterococcus.
Host immune response to antibiotic perturbation of the microbiota
M Wlodarska and B B Finlay
28. Candida albicans is the primary cause of candidemia in hospitalized patients, and the intestinal tract is considered the source of most systemic infections. C. glabrata has emerged as the second or third most frequent cause of candidemia, but little is known about its epidemiology and pathogenesis. Our goal was to compare the intestinal colonization and extra-intestinal dissemination of C. glabrata and C. albicans (wild type and filamentation-defective mutant). Mice were pretreated with antibacterial agents to alter their resident microflora, and then orally inoculated with C. glabrata and/or C. albicans. Elimination of detectable cecal bacteria facilitated colonization with both Candida species. Selective elimination of aerobic/facultative gram-negative bacilli did not noticeably affect Candida colonization, but Escherichia coli overgrowth inhibited colonization. In all situations, C. glabrata colonized the cecum equally well or better than C. albicans, and the ability of C. albicans to form filaments did not facilitate colonization. In vitro generation times had little relevance to the resulting cecal population levels of C. glabrata and C. albicans, and neither species readily disseminated to mesenteric lymph nodes. Thus, like C. albicans, the intestinal tract may be an epidemiological reservoir for C. glabrata and antibiotic-induced alterations in intestinal bacteria may facilitate colonization.
Comparative abilities of Candida glabrata and Candida albicans to colonize and translocate from the intestinal tract of antibiotic-treated mice
Michelle J. Henry-Stanley; Robb M. Garni; Mary Alice Johnson; Catherine M. Bendel; Carol L. Wells
29. A quantitative assay of Candidacidal activity based on differential staining of nonviable Candida albicans by methylene blue was developed and applied to studies of leukocytes from normal individuals and patients with fungal and other infections.
Serum factors were necessary for optimal phagocytosis of C. albicans but lacked direct Candidacidal activity. Normal human neutrophils (38 studies) killed 29.0 ± 7.4% of ingested C. albicans in 1 hr. Eosinophils and monocytes killed a smaller percentage. Neutrophil Candidacidal activity did not require protein or ribonucleic acid synthesis by the leukocyte but was inhibited by anaerobic conditions, potassium cyanide, and colchicine. Leukocytes of a patient with hereditary myeloperoxidase deficiency and of three children with chronic granulomatous disease phagocytized C. albicans normally, yet failed to kill them. Our data suggest that the neutrophil can play an important role in resistance to Candida infection and that the lysosomal enzyme myeloperoxidase and its oxidant substrate hydrogen peroxide are the major participants in neutrophil Candidacidal activity. Candidacidal activity was virtually absent under anaerobic conditions and was considerably diminished by 10-3 M cyanide or 10-4 M colchicine.
Several workers have shown that serum will induce yeast-phase C. albicans to form pseudo-germ tubes and grow in the mycelial phase. This change occurs in a few hours, is specific for C. albicans, and has been proposed as a rapid means of differentiating C. albicans from other Candida species. In our studies, considerable difference was found between the Candidacidal abilities of normal human neutrophils and monocytes. Whereas neutrophils killed 29.0 ± 7.4% of the ingested C. albicans in 1 hr, monocytes killed only 4 ± 2%. Anaerobic conditions inhibit neutrophil Candidacidal and bactericidal activity, perhaps by curtailing the generation of hydrogen peroxide, the oxidant substrate of MPO. In one case, that of a child with the Swiss type of familial lymphocytopenic agammaglobulinemia, disseminated candidiasis followed antibiotic therapy for bacterial infection. Although the patient’s immunological deficiency cannot be discounted as a predisposing factor, antibiotic therapy has been reported to precede disseminated candidiasis in children. Substantial clinical and experimental evidence indicates that the neutrophil is a major participant in the host response to systemic Candida infection. In experimental Candida infections, the disappearance of organisms from the tissue lesions parallels the appearance of neutrophils. Leukopenia is a common predisposing factor in disseminated candidiasis in man. Finally, the present studies establish that normal neutrophils can kill ingested C. albicans, although serum itself lacks Candidacidal activity.
Interaction of Candida albicans with Human Leukocytes and Serum
ROBERT I. LEHRER AND MARTIN J. CLINE
30. Polymorphonuclear neutrophils (PMNs) are the most important cell type involved in the early nonspecific host response to bacterial and fungal cell pathogens. They function primarily as phagocytic cells to ingest, degrade, and remove microbial pathogens. The activation of PMNs by microbial stimuli is enhanced by numerous inflammatory cytokines, most notably tumor necrosis factor-a (TNF-a), interleukin 1ß (IL-1ß), IL-3, IL-6, IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), and G-CSF.
With a half-life of 8-20 hours, PMNs are short-lived cells. In the absence of inflammatory stimuli, PMNs undergo genetically programmed cell death, or apoptosis, characterized by cytoplasmic shrinkage, nuclear condensation, membrane blebbing, DNA fragmentation, and formation of apoptotic bodies. Early in the apoptotic process, phosphatidylserine is exposed on the cell surface by flipping from the inner to the outer leaflets of the cytoplasmic membrane. This event is thought to be important for macrophage recognition of cells undergoing apoptosis, thus allowing the cells to be removed after their death with minimal inflammation. In addition, apoptosis of human PMNs is thought to be critical for control of the inflammatory process and maintenance of homeostasis, although its regulatory mechanisms are not completely understood. Numerous pathologic conditions (certain cancers, autoimmune and neurodegenerative disorders, sepsis), microbial pathogens (human immunodeficiency virus, herpes viruses, Mycobacterium tuberculosis), chemicals (N-formyl-methionyl-leucyl-phenylalanine), and drug therapies (cyclosporine, macrolides, cancer chemotherapy, glucocorticoids) have been shown to alter apoptosis, in part through fibroblast-associated (Fas, CD95), caspase-dependent, and cytokine-signaling mechanisms.[4-6]
Several of these cytokines are known to initiate and/or regulate apoptosis.[6-10] Certain protein and DNA inhibitors, such as erythromycin, clindamycin, and fluoroquinolones, have been shown to decrease the production of proinflammatory cytokines (TNF-a, IL-1, IL-6) by stimulated phagocytes while increasing production of the antiinflammatory cytokine IL-10.[20-23] Whereas TNF-a begins the caspase cascade leading to cellular apoptosis, IL-1 is a suppressor. In addition, TNF-a is a potent inducer of nuclear factor-kB, a transcription factor contributing to the antiapoptotic pathway.[25,26] It is not clear how the same TNF stimulus can activate both apoptotic and antiapoptotic mechanisms or what factors can shift the balance.[6,24]
To our knowledge, the only other published study assessing the influence of antibiotics on PMN apoptosis found that erythromycin shortened neutrophil survival in a dose-dependent fashion.
Effect of Antibiotics on Polymorphonuclear Neutrophil Apoptosis
Daniel P. Healy, Pharm.D., Paul A. Silverman, Pharm.D., Alice N. Neely, Ph.D., Ian Alan Holder, Ph.D., George F. Babcock, Ph.D.
31. The human colon contains the most abundant and diverse assemblage of bacteria in the body. Symbiotic interactions with and within this complex community are now recognized as important predictors of human health. Aberrant community structures are associated with complex diseases like obesity, irritable bowel syndrome, and immune dysfunction. Antibiotic administration can disrupt the colonic ecosystem, which, in turn, leaves patients vulnerable to gastrointestinal disease.
One measure of ecosystem stability, in terms of maintaining function, is the ability to resist invasion and subsequent dominance by immigrating organisms. For the gut ecosystem, antibiotic therapy represents a strong perturbation that shifts the relative proportion of community members, allowing opportunists to establish. Antibiotic therapies exclude members of the community by eradicating them directly or indirectly by breaking necessary mutualistic interactions. During such events in murine models, the community structure was disrupted and enteric pathogens reached high numbers. Similar observations underlie the proposed colonization resistance or barrier function, provided to the host by the gut microbiota, preventing the ingress of pathogens into the gut ecosystem.
During a case-control study of subjects taking capsules of 150 mg clindamycin (orally), each individual was sampled prior to antibiotic treatment and at set time points throughout the following 2-year posttreatment. The overall diversity of this division decreased upon antibiotic treatment and remained reduced during the entire 2 years of the study. The authors also show that the dominant community members changed markedly in relative abundance during the first 3 weeks of the posttreatment, suggesting that these effects were not exclusive to the rest of the microbiota.
A number of opportunistic pathogens can cause disease during antibiotic therapy, including Salmonella spp., Clostridium perfringens, Klebsiella oxytoca, S. aureus, Candida albicans, and C. difficile.
Pseudomembranous colitis in the distal colon and rectum is fatal in 6%–30% of cases. Disease onset occurs several days to several weeks after initial antibiotic treatment and certain drugs, such as clindamycin, cephalosporins, fluoroquinolones, and -lactams, are associated with greater risk of CDAD.