[The microbiota and infectious diarrhea]. / Le microbiote dans les diarrhées infectieuses.

Understanding the importance of the fecal microbiota has been key in understanding the pathophysiology of some infectious diarrheas. In addition to normal protective measures of bile, gastric acid, and immune response, among others, we now know that the healthy gut flora protects us from some infectious diarrheas. Antibiotic associated diarrhea (AAD) is an excellent example, as antibiotics perturb the normal flora; the resulting diarrhea may be due to changes in short chain fatty acid metabolism. A severe form of AAD is due to Clostridium difficile, a pathogen that can cause severe diarrhea, colitis and even death. Recurrent Clostridium difficile diarrhea is a difficult clinical problem to treat successfully because one recurrence makes further recurrences more likely, probably because antibiotics are still needed to treat and thus the fecal flora remains abnormal. There is no single effective treatment but therapies include pulsed and tapered antibiotics, the probiotic Saccharomyces boulardii as an adjunct to antibiotics, and even fecal flora reconstitution. It is likely that we will learn even more in the future about the beneficial effect of our microbiota.

Prospective study of high grade anal squamous intraepithelial neoplasia in a cohort of homosexual men: influence of HIV infection, immunosuppression and human papillomavirus infection.

OBJECTIVE: To determine the risk of developing high grade anal squamous intraepithelial neoplasia (HG-AIN) in relation to HIV infection and immunosuppression, after controlling for the effects of human papillomavirus (HPV) infection. DESIGN: Prospective cohort study of 158 HIV-seropositive and 147 HIV-seronegative homosexual men presenting to a community-based clinic with initially negative anal cytologic and colposcopic findings. METHODS: Subjects completed self-administered questionnaires, underwent cytologic screening, and standardized unaided and colposcopic examination of the proximal anal canal for presence of abnormalities suggestive of AIN. Anal specimens were screened for HPV DNA. RESULTS: HG-AIN developed in eight (5.4%) and 24 (15.2%) HIV-seronegative and -seropositive men, respectively. Risk of HG-AIN among HIV-seronegative men was associated with detection of anal HPV types 16 or 18 by Southern transfer hybridization (STH), detection of HPV 16 or 18 at the lower levels by polymerase chain reaction but not by STH, and with number of positive HPV tests; HG-AIN risk among HIV-seropositive men was associated with detection of HPV 16 or 18 only by STH, detection of HPV types other than 16 or 18, CD4 count < or = 500 x 10(6)/l, and number of positive HPV tests. HIV-induced immunosuppression remained an independent predictor of HG-AIN after adjusting for type and level of detection of HPV; HIV infection predicted HG-AIN risk after adjustment for number of positive HPV tests. CONCLUSIONS: The association of HG-AIN with HIV, independent of HPV type, level of HPV detection and number of positive HPV tests, suggests that this increased risk cannot be entirely explained by an effect of HIV on HPV detection. Future studies focusing on factors more specific to the local microenvironment in the anal canal should help clarify these issues.

Effect of HIV infection on the natural history of anal human papillomavirus infection.

OBJECTIVE: To identify risk factors for the detection of prevalent and incident anal human papillomavirus (HPV) infection, and HPV persistence among HIV-seropositive and seronegative homosexual men. DESIGN: Longitudinal study of 287 HIV-seronegative and 322 HIV-seropositive men attending a community-based clinic. METHODS: Subjects underwent an interview and examination; specimens were collected for HIV serology and assessment of anal HPV and HIV DNA. RESULTS: Anal HPV DNA was detected at study entry in 91.6% of HIV-infected men, and 65.9% of men not infected with HIV. HPV detection was associated with lifetime number of sexual partners and recent receptive anal intercourse (HIV-seronegative men), decreased CD4+ lymphocyte count (HIV-seropositive men), and anal warts (all men). Among men negative for HPV at study entry, subsequent detection of HPV was associated with HIV, unprotected receptive anal intercourse, and any sexual contact since the last visit. Among men positive for HPV at study entry, subsequent detection of additional HPV types was more common among HIV-seropositive men. Becoming HPV negative during follow-up was less common among men with HIV or high HPV levels at study entry. Among those with HIV, HPV persistence was associated with presence of anal HIV DNA, but not with CD4+ lymphocyte count. CONCLUSIONS: Risk of anal HPV infection appears to increase with sexual exposure, epithelial trauma, HIV infection and immune deficiency. Incident infection may result from recent sexual exposure or reactivation of latent infection. Further studies are needed to elucidate the mechanism by which HIV DNA in the anal canal increases the risk of HPV persistence.

Intestinal spirochetosis in homosexual men.

Previous studies have demonstrated intestinal spirochetosis in rectal biopsy specimens from 2 to 7 percent of heterosexual and 36 percent of homosexual patients, but the role of intestinal spirochetosis in the pathogenesis of intestinal disease remains unclear. To assess the clinical, histologic, and microbiologic correlates of intestinal spirochetosis in a high-risk group, rectal biopsy specimens from 130 homosexual men, 92 percent of whom had intestinal symptoms, were evaluated. All men were extensively evaluated for rectal and enteric pathogens. Intestinal spirochetosis was identified in rectal biopsy specimens from 39 (30 percent) men; 15 percent of biopsy specimens revealed intestinal spirochetosis on hematoxylin and eosin plus alcian blue staining, and positive results were found in 30 percent on silver staining. No rectal biopsy specimens from 79 control patients with a variety of gastrointestinal symptoms demonstrated evidence of spirochetosis on hematoxylin and eosin, alcian blue, or silver staining (p less than 0.0001). Fifty-six percent of rectal biopsy specimens from men with intestinal spirochetosis were normal, and no specific histologic abnormality was correlated with intestinal spirochetosis. There were no differences in the presence of or type of intestinal symptoms, sigmoidoscopic appearance of the mucosa, type of sexual practice, or prior antibiotic use in men with and without spirochetosis. Other intestinal pathogens were frequent in both groups, and only rectal gonorrhea was significantly associated with intestinal spirochetosis. It is concluded that homosexual men with intestinal symptoms have an increased prevalence of spirochetosis, often in association with Neisseria gonorrhoeae. Independent association of spirochetosis with clinical or histologic findings could not be demonstrated.

Gastric protection by misoprostol against 1,300 mg of aspirin. An endoscopic dose-response study.

Misoprostol at a dose of 200 micrograms inhibits gastric acid secretion and protects the gastric mucosa against the injurious effects of a single 1,300-mg dose of aspirin. The purpose of this study was to determine whether lower subantisecretory doses of misoprostol protect the gastric mucosa in this single-dose aspirin model. Protection was defined as no more than 10 hemorrhagic spots and no more than two hemorrhagic streaks. A total of 140 men participated in the two phases of the study. In the first phase, groups of 10 subjects each received placebo or misoprostol in doses of 200 micrograms, 100 micrograms, 50 micrograms, or 25 micrograms in a double-blind design. All misoprostol doses protected 50 to 70 percent of subjects as compared with 20 percent of subjects in the placebo group. To expand the number of observations, 90 additional subjects in groups of 30 each were evaluated after receiving misoprostol 50 micrograms or 25 micrograms or placebo. Misoprostol 50 micrograms protected 14 of 30 subjects (47 percent), 25 micrograms protected 11 of 30 (37 percent), and placebo protected six of 30 (20 percent). The dose-response trend was statistically significant (p less than 0.05). It is concluded that misoprostol protects the gastric mucosa against a single 1,300-mg dose of aspirin and that there is a significant dose-response relationship.

The role of rectal biopsy in infectious colitis.

Rectal biopsy has a dual role in the diagnosis of infectious colitis. It can usually differentiate acute self-limited colitis (ASLC) from idiopathic inflammatory bowel disease (IBD), and it can also sometimes diagnose the specific infection in ASLC. Seven histologic features reliably differentiate IBD from ASLC: crypt distortion, crypt atrophy, a villous appearance of the surface epithelium, epithelioid granulomas, basally located isolated giant cells, basal lymphoid aggregates, and a lamina propria infiltrate of both acute and chronic inflammatory cells. One or more of these findings is frequent in rectal biopsies from patients with IBD, but rare in ASLC. Thus, the diagnosis of ASLC is made by the absence of the findings that characterize IBD. The usual histopathological picture of ASLC is nonspecific: normal architecture and increased numbers of acute inflammatory cells in the lamina propria. Certain findings may suggest a specific diagnosis. Granulomas may be present in specimens from homosexual men with proctitis due to C. trachomatis or T. pallidium. Granulomas are also present in schistosomiasis, tuberculosis, histoplasmosis, and yersinia enterocolitica infection. Typical viral inclusions can be seen in herpes simplex virus type II and cytomegalovirus infections. Specific parasites may be seen in biopsies from patients with amebiasis, schistosomiasis, and cryptosporidiosis. Intestinal spirochetosis is frequent in male homosexuals.

Behaviour of Saccharomyces boulardii in recurrent Clostridium difficile disease patients.

BACKGROUND: Despite recent interest in therapeutic microorganisms taken orally, little is known about the pharmacodynamics of these agents in a target population of patients with disease. The present study reports the stool concentrations of Saccharomyces boulardii in a patient population with Clostridium difficile disease (CDD) and correlates stool concentrations with efficacy. METHODS: Patients with recurrent CDD all received a 10-day standard antibiotic regimen together with 28 days of S. boulardii or placebo. Stool samples were collected from patients at various time points and assayed for S. boulardii. RESULTS: The mean concentration of S. boulardii of patients who recurred was 2.5 x 104 CFU/g compared to 1 x 106 CFU/g in patients that did not recur (P=0.02). Patients with low yeast concentrations in their stools (<104/g) recurred more often (14/15, 93%) compared with patients with higher levels (19/35, 54%, P=0.007). Clearance of S. boulardii was rapid; only 4% had positive stools 3 days after stopping dosing. CONCLUSIONS: After chronic dosing of S. boulardii, patients with low stool concentrations had a higher likelihood of recurrence of CDD. Stool concentrations were also lower during periods of diarrhoea. These results show the importance of characterizing the dynamics of a therapeutic microorganism in patients with disease, as kinetic studies in healthy volunteers may not give a true reflection of the disturbed microecology in the disease state.

Observer variation in the diagnosis of dysplasia in Barrett's esophagus.

The potential value of biopsy surveillance of patients with Barrett's esophagus for dysplasia is diminished by a lack of agreement on the diagnostic criteria for dysplasia. In a preliminary consensus conference, experienced gastrointestinal pathologists from four medical centers agreed on criteria for a five-tiered histologic classification of dysplasia in Barrett's esophagus--negative for dysplasia, indefinite for dysplasia, low-grade dysplasia, high-grade dysplasia, and intramucosal carcinoma. Eight morphologists in the four centers tested the criteria for interobserver agreement by examining a set of coded slides that had been chosen to include some especially difficult interpretative problems in all five histologic classifications. Interobserver agreement of 85 and 87% was achieved in successive reviews when the combined group of high-grade dysplasia and intramucosal carcinoma was compared with the combined group of low-grade dysplasia, indefinite for dysplasia, and negative for dysplasia. Comparison of other groups yielded less agreement. For example, negative for dysplasia could be distinguished from all other diagnoses with an interobserver agreement of 72%. We conclude that experienced gastrointestinal morphologists can diagnose high-grade dysplasia and intramucosal carcinoma with a high degree of agreement and thus can detect those patients who may need immediate rebiopsy or esophageal resection. Either further refinement of histologic criteria or alternate diagnostic methods will be needed to achieve the reproducible diagnosis of indefinite changes and low-grade dysplasia. This is important because patients with such changes theoretically merit closer endoscopic surveillance.

Recurrent Clostridium difficile disease: epidemiology and clinical characteristics.

OBJECTIVE: To describe the epidemiology, diagnosis, risk factors, patient impact, and treatment strategies for recurrent Clostridium difficile-associated disease (CDAD). DESIGN: Data were collected as part of a blinded, placebo-controlled clinical trial testing a new combination treatment for recurrent CDAD. Retrospective data regarding prior CDAD episodes were collected from interviews and medical-chart review. Prospective data on the current CDAD episode, risk factors, and recurrence rates were collected during a 2-month follow-up. SETTINGS: National referral study. PARTICIPANTS: Patients with recurrent CDAD. INTERVENTIONS: Treatment with a 10-day course of low-dose (500 mg/d) or high-dose (2 g/d) vancomycin or metronidazole (1 g/d). RESULTS: Recurrent CDAD was found to have a lengthy course involving multiple episodes of diarrhea, abdominal cramping, nausea, and fever. CDAD may recur over several years despite frequent treatment with antibiotics. Recurrence rates were similar regardless of the choice or dose of antibiotic. Recurrent CDAD is not a trivial disease: patients may have multiple episodes (as many as 14), may require hospitalization, and the mean lifetime cost of direct medical care was $10,970 per patient. Fortunately, the disease does not become progressively more severe as the number of episodes increase. Two risk factors predictive for recurrent CDAD were found: increasing age and a decreased quality-of-life score at enrollment. CONCLUSIONS: Recurrent CDAD is a persistent disease that may result in prolonged hospital stays, additional medical costs, and rare serious complications.

Ecological means of control of diarrhea.

In summary, altered intestinal ecology is very important in the pathogenesis of antibiotic-associated diarrhea and pseudomembranous colitis. Prevention of AAD has been demostrated with LactobacillusGG, Enterococcus SF68, and S. boulardii. While therapy with antibitics such as vancomycin or metranidazole is effective for PMC, relapse can occur and is difficult to treat. Antibiotics can be given, but another approach of restoring the normal colonic ecology may be more effective. Such therapy has included use of the nontoxigenic strains of C. difficile, rectal infusions of homologous feces or mixtures of bacteria, and oral administration of Lactobaccillus GG and the live yeast Saccharomyces boulardii. It is clear that many factors influence normal colonic homeostasis, including and individual's age, health, nutritions, medication, presence of gastrointentinal desease or surgery. The fetal flow is complex. Some factors related to C. difficile and disease production are known. For instance, only toxigenic strains cause disease, but rates of carrieage vary and not everyone with toxigenic strains of C. difficile will become ill. Studies of healthy volutenteers who took an oral cephalosporin antibiotic revealed that over 90% of them became colonized with C. difficile, and some excreted the organism for up to 26 days. Some volunteers had loose stools, but not was clinically ill[11]. Similary, neonates have a high rate of carriage of C. difficile and toxin (up to 60%), but usually are asymptomatic. Obviously, other factors besides presence of organism determine development of diseases. One such factor may the state of the immune system. In support of this are reports of recurrent C. difficile colitis in hypogammaglobulinemic children, and successful treatment of recurrent C. difficile colitis with intravenous gamma glubulin [51]. But recent studies of mucosal (secretory) IgA levels in C. difficile-associated diarrhea showed no clear-cut relaxationship of systemic or mucosol antibodies toxin A with the clinical course of C. Difficle infection [52] Other factors have not been explored, such as the influence of the diet. In addition, the intestinal flora may be allerted by bile acid production and/or pancreatics proteases.

Pseudomembranous colitis: an update.

Clostridium difficile is the most common nosocomial infection of the gastrointestinal tract. Most cases are associated with antibiotic therapy that alters the fecal flora, allowing overgrowth of C difficile with production of its toxins. Diagnosis is made by detection of the organism or toxin in the stools. A variety of different tests can be used, but none is perfect. A stool culture can be positive in someone without diarrhea, ie, a carrier. While the cytotoxin is the gold standard, it is expensive, and there is a delay before results are available. Thus, many laboratories use the enzyme-linked immunoassay tests to detect toxin of C difficile because they are a more rapid screen. Depending on the specific test used, they can detect toxin A, toxin B or occasionally both. Sensitivity and specificity rates vary. First line therapy for C difficile disease should be metronidazole 250 mg qid for 10 days. Vancomycin should be reserved for severe cases where metronidazole has failed or where metronidazole cannot be tolerated or is contraindicated. Recurrent C difficile disease is a particularly vexing clinical problem. A variety of biotherapeutic approaches have been used. Retreatment with antibiotics is almost always necessary. In addition, the nonpathogenic yeast Saccharomyces boulardii has been showed to be of benefit as an adjunct in preventing further recurrences.

Collating collagenous colitis cases.

Between 1980 and 1993, collagenous colitis was diagnosed in 56 patients at UCLA. These authors evaluated the histology of almost 300 biopsies from these patients to further clarify the relationship between diagnostic histology and site of biopsy. As expected, their patients were predominately women (71%), with a mean age at diagnosis of 59 yr. Chronicity of diarrheal symptoms ranged from 3 months to 15 yr. Diagnostic subepithelial collagen thickness was variable throughout the colon. The highest yield was in transverse colon (83%), right colon (70%), and lowest in rectosigmoid (66%). Diagnostic collagen thickness was >15 microm in most biopsies, but was detected most readily when >30 microm--a threshold the authors suggest increases the diagnostic com-fort level. They recommend flexible sigmoidoscopy as adequate for diagnosis of most patients with collagenous colitis, noting colonoscopy is often used to clarify diagnosis, i.e., when only mild or focal colitis is seen distally.

Clostridium difficile disease: diagnosis and treatment.

Clostridium difficile is the most common nosocomial pathogen of the gastrointestinal tract. Disease is usually a consequence of antibiotic therapy, but sporadic cases do occur. Cytotoxin assay for toxin B remains the gold standard for confirming diagnosis. Several rapid enzyme immunoassay tests are available, but specificity and sensitivity vary; a negative test may not exclude disease. Oral metronidazole 250 to 500 mg four times a day is the recommended first-line therapy; vancomycin (125 mg four times a day) should be reserved for patients who cannot tolerate metronidazole, who do not respond to this drug, or who should not take it for various reasons (i.e., pregnancy). Recurrent C. difficile disease is a difficult problem. The nonpathogenic yeast Saccharomyces boulardii has been shown in controlled trials to be effective in reducing recurrences when given as an adjunct to standard therapy. Prevention of epidemics relies on careful hand washing and environmental decontamination.

Serial sectioning of a portion of a rectal biopsy detects more focal abnormalities: a prospective study of patients with inflammatory bowel disease.

The diagnostic accuracy of two different methods of sectioning rectal biopsies was evaluated prospectively. The frequency of focal and diffuse findings in more than 80 serial sections from a limited portion of the well-oriented areas of 74 biopsies was compared with that found in three or more step sections distributed throughout the well-oriented areas of the same rectal biopsies from patients with known or suspected inflammatory bowel disease (IBD). Significantly more focal abnormalities (granulomas, giant cells, histiocytic collections) were detected by serial sectioning than by step sectioning. For example, serial sectioning increased the ability to detect granulomas by 50% compared to step sectioning. Serial sectioning provided no significant advantage in the detection of diffuse abnormalities (abnormal architecture, decreased mucus, nonspecific inflammation, crypt abscess). Serially sectioning part of a biopsy is superior to step sectioning more of the biopsy in detecting focal abnormalities.

Etiological role of mycobacterium in Crohn's disease: An assessment of the literature.

A possible etiologic role for mycobacteria in Crohn's disease has been the subject of much investigation. This paper critically reviews the literature exploring 4 major areas: (1) attempts to culture mycobacteria from intestinal specimens; (2) indirect detection of organisms in intestinal specimens by techniques including immunohistochemistry, nucleic acid hybridization and polymerase chain reaction; (3) detection of serum antibodies to mycobacteria, and (4) results of antimycobacterial drug trials in treating patients with Crohn's disease. While the evidence does not support an etiologic role for mycobacteria in Crohn's disease, newer techniques may change this conclusion.

Self-limited cytomegalovirus colitis in immunocompetent individuals.

We report 3 cases of isolated acute cytomegalovirus colitis in immunocompetent individuals. Each case was documented by the presence of cytomegalovirus inclusions in colonic biopsy specimens. All had a self-limited illness. Two of these cases occurred after anal intercourse and 1 case had no probable known cause. At follow-up from 2 to 6 yr later, none of the 3 patients has had any gastrointestinal symptoms. Additional biopsy specimens were obtained from 2 patients and no evidence of residual cytomegalovirus was seen by light microscopy or by in situ hybridization. Although cytomegalovirus colitis in immunosuppressed individuals is well recognized, these are the first reports of a nonfatal cytomegalovirus colitis in immunocompetent hosts.

Infectious causes of chronic diarrhea.

Chronic diarrhea can be seen in association with specific pathogens, usually parasites and occasionally some bacteria. This article reviews pathogens causing chronic diarrhea in immunocompetent individuals and provides a rational diagnostic approach.

Rectal biopsy helps to distinguish acute self-limited colitis from idiopathic inflammatory bowel disease.

A retrospective blind evaluation of rectal biopsy specimens from 44 patients with acute self-limited colitis and 104 patients with idiopathic inflammatory bowel disease was done. Seven histologic features proved highly discriminant because they occurred often in idiopathic inflammatory bowel disease but rarely, if at all, in acute self-limited colitis. The features with a high predictive probability (87%-100%) of diagnosing idiopathic inflammatory bowel disease were distorted crypt architecture, increased numbers of both round cells and neutrophils in the lamina propria, a villous surface, epithelioid granuloma, crypt atrophy, basal lymphoid aggregates, and basally located isolated giant cells. One or more of these features was present in 79% of all idiopathic inflammatory bowel disease cases. They were seen in both acute and chronic idiopathic inflammatory bowel disease. The biopsy features favoring acute self-limited colitis were less useful. Biopsy diagnosis of acute self-limited colitis is thus primarily based on the absence of histologic criteria favoring idiopathic inflammatory bowel disease. This study provides objective validation of histologic criteria in rectal biopsy that help differentiate acute self-limited colitis from idiopathic inflammatory bowel disease.

Pseudomembranous colitis: causes and cures.

Clostridium difficile is the most common nosocomial pathogen of the gastrointestinal tract and has increased in frequency over time. Typical symptoms of C. difficile infection include diarrhea, which is usually nonbloody, or colitis associated with severe abdominal pain, fever and/or gross or occult blood in the stools. Pseudomembranous colitis (PMC), the severest form of this disease, occurs as a result of a severe inflammatory response to the C. difficile toxins. This review focuses on PMC, as this severe form is associated with the greatest medical concern. Diagnosis rests on detection of C. difficile in the stool, either by culture, tissue culture assay for cytotoxin B or detection of antigens in the stool by rapid enzyme immunoassays. Oral therapy with metronidazole 250 mg 4 times a day for 10 days is the recommended first-line therapy. Vancomycin is also effective, but its use must be limited to decrease the development of vancomycin-resistant organisms such as enterococci. Vancomycin (125-500 mg 4 times a day for 10 days) should be limited to those who cannot tolerate or have not responded to metronidazole, or when metronidazole use is contraindicated, as in the first trimester of pregnancy. A therapeutic response within a few days is usual. Recurrence of symptoms after antibiotics occurs in 20% of cases and is associated with persistence of C. difficile in the stools. Further recurrences then become more likely. Therapy with antibiotics in a pulsed or tapered regimen is often effective as are efforts to normalize the fecal flora. The yeast Saccharomyces boulardii has been proven in controlled trials to reduce recurrences when given as an adjunct to antibiotic therapy. Careful hand washing and environmental decontamination are necessary to prevent epidemics.