SUMMARY In inflammatory bowel disease, the relationship between a host and gut microbial community goes awry. We have characterized the fecal microbial communities in a mouse IBD model driven by T-bet deficiency in the innate immune system. 16S rRNA-based analysis of T-bet−/− × Rag2−/− and Rag2−/− mice revealed distinctive communities that correlate with host genotype. Culture-based surveys, invasion assays, antibiotic treatment, and TNF-α blockade disclosed that the presence of Klebsiella pneumoniae and Proteus mirabilis correlates with colitis in T-bet−/− × Rag2−/− animals, and that T-bet−/− × Rag2−/− derived strains can elicit colitis in Rag2−/− and wild-type adults. Cross-fostering experiments provided evidence for the role of these organisms in maternal transmission of disease. This model provides a foundation for defining how gut microbial communities work in concert with specific culturable colitogenic agents to cause IBD, and a foundation for conducting proof-of-concept tests of new preventative or therapeutic measures directed at components of the gut microbiota and/or host.
A substance producing cytotoxicity in tissue culture was detected in stool specimens from all of four patients with pseudomembranous colitis due to antibiotics and in one of 54 with antibiotic-associated diarrhea. These stools also caused enterocolitis when injected intracecally into hamsters. On each occasion, cytotoxicity in tissue culture and enterocolitis in hamsters were neutralized by pretreatment with gas-gangrene antitoxin. The toxicity in both tissue cultures and hamsters could be reproduced with broth cultures of clostridia strains isolated from four of the five stools. These results suggest that toxin-producing clostridia are responsible for antibiotic-associated pseudomembranous colitis.
SUMMARYBacterial vaginosis (BV) is the most commonly reported microbiological syndrome among women of childbearing age. BV is characterized by a shift in the vaginal flora from the dominantLactobacillusto a polymicrobial flora. BV has been associated with a wide array of health issues, including preterm births, pelvic inflammatory disease, increased susceptibility to HIV infection, and other chronic health problems. A number of potential microbial pathogens, singly and in combinations, have been implicated in the disease process. The list of possible agents continues to expand and includes members of a number of genera, includingGardnerella,Atopobium,Prevotella,Peptostreptococcus,Mobiluncus,Sneathia,Leptotrichia,Mycoplasma, and BV-associated bacterium 1 (BVAB1) to BVAB3. Efforts to characterize BV using epidemiological, microscopic, microbiological culture, and sequenced-based methods have all failed to reveal an etiology that can be consistently documented in all women with BV. A careful analysis of the available data suggests that what we term BV is, in fact, a set of common clinical signs and symptoms that can be provoked by a plethora of bacterial species with proinflammatory characteristics, coupled to an immune response driven by variability in host immune function.
The capsular polysaccharide complex from Bacteroides fragilis promotes the formation of intra-abdominal abscesses--a pathologic host response to infecting microorganisms. This complex consists of two distinct polysaccharides, each with repeating units that have positively charged amino groups and negatively charged carboxyl or phosphate groups. Analysis of these polysaccharides as well as other charged carbohydrates before and after chemical modification revealed that these oppositely charged groups are required for the induction of intra-abdominal abscesses in a rat model.
OBJECTIVES-To evaluate the adequacy of discharge room cleaning and the impact of a cleaning intervention on the presence of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) on environmental surfaces in intensive care unit (ICU) rooms. DESIGN-Prospective environmental study.SETTING AND SAMPLE-Convenience sample of ICU rooms in an academic hospital. METHODS AND INTERVENTION-The intervention consisted of (1) a change from the use of pour bottles to bucket immersion for applying disinfectant to cleaning cloths, (2) an educational campaign, and (3) feedback regarding adequacy of discharge cleaning. Cleaning of 15 surfaces was evaluated by inspecting for removal of a preapplied mark, visible only with an ultraviolet lamp ("black light"). Six surfaces were cultured for MRSA or VRE contamination. Outcomes of mark removal and culture positivity were evaluated by χ 2 testing and generalized linear mixed models, clustering by room. RESULTS-The black-light mark was removed from 44% of surfaces at baseline, compared with 71% during the intervention (P <.001). The intervention increased the likelihood of removal of blacklight marks after discharge cleaning (odds ratio, 4.4; P < .001), controlling for ICU type (medical vs surgical) and type of surface. The intervention reduced the likelihood of an environmental culture positive for MRSA or VRE (proportion of cultures positive, 45% at baseline vs 27% during the intervention; adjusted odds ratio, 0.4; P = .02). Broad, flat surfaces were more likely to be cleaned than were doorknobs and sink or toilet handles.CONCLUSIONS-Increasing the volume of disinfectant applied to environmental surfaces, providing education for Environmental Services staff, and instituting feedback with a black-light marker improved cleaning and reduced the frequency of MRSA and VRE contamination.Address reprint requests to Susan S. Huang, MD, MPH, University of California-Irvine Medical Center, Division of Infectious Diseases, Building 53, Suite 215, 101 The City Dr., Orange, CA 92868 (E-mail: sshuang@partners.org). Potential conflicts of interest. R.P. has received research grants from Sanofi-Aventis, GlaxoSmithKline, Pfizer, and TAP Pharmaceuticals in the past 2 years. D.S.Y. has received research support from Sage Products. All other authors report no conflicts of interest relevant to this article. Environmental contamination with pathogens commonly occurs during routine medical care. Many studies have described transmission of pathogenic organisms through contact with contaminated room surfaces. 1-3 Of particular concern is the potential for transmission of multidrug-resistant organisms, such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE), which are associated with healthcare-associated infections, increased lengths of stay in hospitals, increased healthcare costs, and increased mortality. 4-7 NIH Public AccessCleaning is essential to reduce environmental reservoirs of known hospital-acquired pathogens...
CD1d-restricted T cells are implicated as key players in host defense against various microbial infections. However, the mechanisms involved and the role they play, if any, at the mucosal surfaces where pathogenic infections are initiated is unknown. In a murine pneumonia model established by intranasal application of Pseudomonas aeruginosa, CD1d(-/-) mice showed markedly reduced pulmonary eradication of P. aeruginosa compared with wild-type mice; this was associated with significantly lower amounts of macrophage inflammatory protein-2 and reduced numbers of neutrophils within the bronchoalveolar lavage fluid. Corollarily, treatment of mice with alpha-galactosylceramide--a lipid that activates CD1d-restricted T cells--increased the amount of interferon-gamma; this was associated with rapid pulmonary clearance through enhanced phagocytosis of P. aeruginosa by alveolar macrophages. These results reveal a crucial role played by CD1d-restricted T cells in regulating the antimicrobial immune functions of macrophages at the lung mucosal surface.
Clindamycin-associated enterocolitis in hamsters was studied to detect and characterize a transmissible agent. It was found that the disease could be transferred by cecal contents and filtrates of cecal contents (pore size of filter, 0.02 micron) obtained from animals after administration of clindamycin. Subsequent work showed that enterocolitis could be produced with broth cultures of a species of Clostridium recovered from cecal contents of animals with clindamycin-induced disease. The cell-free supernatant of this strain also caused enterocolitis. Cecal contents from animals with clindamycin-induced disease incubated with gas gangrene antitoxin failed to cause intestinal lesions. These experiments indicate that clindamycin-associated colitis in hamsters is due to a clindamycin-resistant, toxin-producing strain of Clostridium.
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