Routine culturing for Clostridium difficile?

MICROBIOTA INSIGHTS IN CLOSTRIDIUM DIFFICILE INFECTION AND INFLAMMATORY BOWEL DISEASE

Inflammatory bowel disease (IBD) is characterized by chronic intestinal inflammation that includes Crohn´s disease (CD) and ulcerative colitis (UC). Although the etiology is still unknown, some specific factors have been directly related to IBD, including genetic factors, abnormal intestinal immunity, and/or gut microbiota modifications. Recent findings highlight the primary role of the gut microbiota closely associated with a persistent inappropriate inflammatory response. This gut environment of dysbiosis in a susceptible IBD host can increasingly worsen and lead to colonization and infection with some opportunistic pathogens, especially Clostridium difficile. C. difficile is an intestinal pathogen considered the main cause of antibiotic-associated diarrhea and colitis and an important complication of IBD, which can trigger or worsen an IBD flare. Recent findings have highlighted the loss of bacterial cooperation in the gut ecosystem, as well as the pronounced intestinal dysbiosis, in patients suffering from IBD and concomitant C. difficile infection (CDI). The results of intestinal microbiota studies are still limited and often difficult to compare because of the variety of disease conditions. However, these data provide important clues regarding the main modifications and interrelations in the complicated gut ecosystem to better understand both diseases and to take advantage of the development of new therapeutic strategies. In this review, we analyze in depth the gut microbiota changes associated with both forms of IBD and CDI and their similarity with the dysbiosis that occurs in CDI. We also discuss the metabolic pathways that favor the proliferation or decrease in several important taxa directly related to the disease.

Enteric infection in relapse of inflammatory bowel disease: importance of microbiological examination of stool

OBJECTIVE

Previous reports have suggested that diarrhoeal relapses of inflammatory bowel disease (IBD) may be associated or confused with enteric infection, and that treatment of such infections with appropriate antibiotics may be beneficial. To re-evaluate the suggestion that enteric infection is rare and microbiological testing of stool not routinely necessary in patients presenting with relapse of IBD, we have reviewed the incidence of concurrent infection in patients presenting in relapse over a recent 5-year period.

METHODS

Stool microbiology results relating to relapses of IBD during the period 1997-2001 were obtained retrospectively. Relapse was confirmed by standard clinical, sigmoidoscopic and laboratory criteria.

RESULTS

During the period 1997-2001 there were 237 relapses in 213 patients. Enteric infection was found in 25 (10.5%) relapses in 24 patients; in seven patients, infection was associated with the initial presentation of their IBD. Clostridium difficile toxin was detected in 13 (5.5%) instances; the 12 other infections (5% relapses) were Campylobacter spp. (five), Entamoeba histolytica (three), Salmonella spp. (one), Plesiomonas shigelloides (one), Strongyloides stercoralis (one) and Blastocystis hominis (one). There was a significant association between infection and the need for hospital admission. Of the 13 relapses associated with C. difficile, ten were in outpatients, seven patients had undergone previous antibiotic treatment, and four patients were presenting with IBD for the first time. All relapses resolved satisfactorily after treatment with antibiotics with or without corticosteroids.

CONCLUSIONS

The high prevalence of enteric infections, of which C. difficile was the most common, indicates that all patients presenting with relapse of IBD should have stool examined microbiologically.

Clostridium difficile-associated diarrhea: epidemiological data from Western Australia associated with a modified antibiotic policy

The incidence of Clostridium difficile-associated diarrhea (CDAD) has increased dramatically in hospitals worldwide during the past 2 decades. In Western Australia, this increase was most obvious during the 1980s, when there was also an increase in the use of third-generation cephalosporin antibiotics. A study of the epidemiology of CDAD and the use of third-generation cephalosporins during 1993-2000 was undertaken. From 1993 through 1998, the incidence of CDAD remained relatively stable (2-3 cases per 1000 discharges annually). Then, a significant decrease in the incidence occurred, from 2.09 cases per 1000 discharges (95% confidence interval [CI], 1.71-2.47) in 1998 to 0.87 cases per 1000 discharges (95% CI, 0.63-1.11) in 1999 (P<.0001); this decrease persisted into 2000. A decrease in third-generation cephalosporin use occurred during the period of the study because of changes in the prescribing policy. These findings suggest that a reduction in the use of third-generation cephalosporins can reduce the occurrence of CDAD.

Clinical prediction rules to optimize cytotoxin testing for Clostridium difficile in hospitalized patients with diarrhea

BACKGROUND

Although routine testing of hospitalized patients with diarrhea for Clostridium difficile cytotoxin has been advocated as a high-yield procedure, the rationale for this practice has been questioned. To target a low-yield subgroup for whom routine testing could be deferred, we derived a clinical decision rule for predicting results of the C difficile cytotoxin assay in hospitalized adults with diarrhea.

METHODS

We hypothesized a priori that two variables, antibiotic use (within 30 days prior to testing) and history of significant diarrhea (new onset of > 3 partially formed or watery stools per 24 hour period), would be highly predictive of cytotoxin results, and obtained these data on 480 consecutive patients who underwent diagnostic testing for C difficile at a university hospital and affiliated Veterans Affairs medical center. For more detailed modelling, we recorded symptoms, signs, comorbidity, and other potential causes of diarrhea for 68 test positive patients (cases) and 265 randomly selected test negative patients (controls) within the study cohort.

RESULTS

The overall prevalence of positive cytotoxin assays was 14%. Prior antibiotic therapy (OR = 9.0, 95% CI 2.1-38.4), significant diarrhea (OR = 2.2, 95% CI 1.1-4.7), and abdominal pain (OR = 1.9, 95% CI 0.96-3.7) were independent predictors of cytotoxin assay results. The model discriminated patients with positive and negative assays with a receiver operating characteristic (ROC) area of 0.68; observed and predicted probabilities of a positive cytotoxin assay were well correlated over the entire range of observed probabilities (r2 = 0.86). A decision rule (defined as positive if prior antibiotic use and either significant diarrhea or abdominal pain are present) demonstrated sensitivity and specificity of 86 and 45%. When applied to the entire dataset (N = 480), a simplified a priori rule, defined as positive if both prior antibiotic use and history of significant diarrhea are present, demonstrated sensitivity, specificity, positive and negative predictive value of 80, 45, 18 and 94%, respectively (6% of those predicted to be cytotoxin-negative actually tested positive). Use of this rule would have averted 39% of cytotoxin assays in our study population.

CONCLUSIONS

Patients without prior antibiotic use and either significant diarrhea or abdominal pain are unlikely to have positive C difficile cytotoxin assay results, and may not routinely require cytotoxin testing.

Evaluation of an enzyme immunoassay kit for the detection of Clostridium difficile enterotoxin

The Premier Clostridium difficile toxin A enzyme immunoassay (EIA) kit was evaluated for the detection of C. difficile enterotoxin in fecal samples. A total of 314 samples was tested by culture, cytotoxin detection and EIA kit. Compared to a combined culture/cytotoxin result the Premier EIA kit had a sensitivity of 88.3%, a specificity of 100%, a predictive value positive of 100% and a predictive value negative of 87.4%. Test results were available within 3 hrs providing a rapid and reliable means of detecting C. difficile enterotoxin.

Clostridium difficile-associated diarrhoea: epidemiological data from Western Australia

The incidence of Clostridium difficile-associated diarrhoea (CDAD) was investigated retrospectively at a 690-bed teaching hospital for the period 1983-92. Our aims were to determine: (i) the distribution by age and sex of patients with CDAD, (ii) the possibility of a seasonal trend and, (iii) the influence of infection control procedures, contamination of the hospital environment and the use of third-generation cephalosporins. The laboratory diagnosis of CDAD was based on demonstration of the organism by stool culture and/or detection of specific cytotoxin in stool filtrates. C. difficile was detected in 917 patients who were being investigated for diarrhoeal illness. Yearly isolations varied from a low of 49 in 1983 to a high of 120 in 1990 (Chi square for linear trend 128.8; P < 0.005). Most patients were elderly, with 63% aged 60 years or more; the majority (59%) were female. The relationship between culture of C. difficile and detection of cytotoxin in faecal extracts was also examined. Sixty percent of a sample of 132 isolates from patients in whom faecal cytotoxin was not detected produced cytotoxin in vitro, suggesting that culture is a more sensitive indicator of infection with C. difficile than cytotoxin detection. When the total number of faecal specimens received in the laboratory was used as a denominator there was an increase in the number of incident cases of CDAD between 1983 and 1990, apart from 1986. When occupied bed days was used as the denominator a similar trend was observed with a peak in 1990.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective criteria for the microbiological examination of faecal specimens

To assess the effectiveness of predetermined investigation criteria for the examination of faecal samples from inpatients, cultured stool specimens were prospectively examined for Salmonella spp, Shigella spp, Campylobacter spp and Clostridium difficile, and screened microscopically for intestinal parasites. Out of a total of 505 specimens, 421 (83%) fulfilled the criteria for examination for C difficile, 254 (50%) for Salmonella spp, Shigella spp, and Campylobacter spp, and 87 (17%) for intestinal parasites. Isolation rates for these organisms in those groups of patients where examination was indicated were 22.5% for C difficile and 9.1% for Salmonella spp, Shigella spp, and Campylobacter spp; the detection rate for parasites was 3.5%. In those patients where the criteria did not suggest investigation, the isolation or detection rates were 3.6% for C difficile, 0% for Salmonella spp, Shigella spp, and Campylobacter spp, and 1.7% for intestinal parasites, suggesting that the use of predetermined investigation criteria was effective.

Gastrointestinal carriage of Clostridium difficile in cats and dogs attending veterinary clinics

Cats and dogs being treated at two veterinary clinics were investigated for gastrointestinal carriage of Clostridium difficile using selective solid and enrichment media. Thirty-two (39.5%) of 81 stool samples yielded C. difficile. There were significant differences in isolation rates between clinics, 61.0% of animals being positive at one clinic compared to 17.5% at the other (Chi-square, P less than 0.005). Of 29 animals receiving antibiotics, 15 (52.0%) harboured C. difficile while 11 (23.9%) of 46 animals not receiving antibiotics were positive (Chi-square, P less than 0.01). There was no difference in carriage rate between cats (38.1%) and dogs (40.0%). The environment at both veterinary clinics was surveyed for the presence of C. difficile. Fifteen of 20 sites at one clinic were positive compared to 6 of 14 sites at the other clinic. Both cytotoxigenic and noncytotoxigenic isolates of C. difficile were recovered from animals and environmental sites. These findings suggest that household pets may be a potentially significant reservoir of infection with C. difficile.

Relapse versus reinfection with Clostridium difficile

Relapse of Clostridium difficile-associated diarrhoea occurs in 15-20% of patients; however, whether relapse is due to an endogenous source of the organism or reinfection from the environment remains unclear. Restriction enzyme analysis (REA) of chromosomal DNA was used to type multiple isolates from ten patients who had experienced apparent relapses. More than half the relapses were due to infection with a new strain of C. difficile. The remaining patients were infected with the same strain, but whether this strain was acquired from the environment or from endogenous sources could not be determined. Relapses with a different strain of C. difficile could occur if an individual harboured more than one strain in their gastrointestinal tract. To investigate this possibility ten other patients were assessed for carriage of multiple strains. Ten colonies from a primary culture plate from each patient were typed by REA and tested for their ability to produce cytotoxin. All isolates from the same patient were identical by both methods, indicating that multiple carriage of strains may be a rare event.

Diarrheal disease due to Clostridium difficile in general practice

A total of 288 stool samples from patients attending their general practitioners was examined for the presence of Clostridium difficile. C. difficile or its cytotoxin was found in 16 patients (5.5%) and was the most common enteric pathogen detected. Most patients had only mild to moderate diarrhea but in the majority of patients the diarrhea was protracted. Eleven of the 16 patients had received antimicrobial agents in the 3 mths preceding onset of diarrhea and there was good circumstantial evidence that 2 other patients had also been exposed. None of the patients had a history of any inflammatory bowel disease or possible occupational exposure. The prescribing habits of general practitioners with regard to antimicrobial agents were monitored for a 1 yr period. Tetracyclines and amoxycillin accounted for approximately 25% each of all prescriptions dispensed. Ten of the 16 patients were treated with antimicrobials (mainly metronidazole) and in most cases the diarrhea resolved. We conclude that C. difficile may be a significant cause of community-acquired diarrhea.

Laboratory diagnosis of Clostridium difficile-associated diarrhoea

This paper reviews the various laboratory procedures available for the isolation and identification of Clostridium difficile and the detection of toxins produced by this organism. Laboratories should be selective in determining which patients require investigation for Clostridium difficile-associated diarrhoea. Transport and storage of stool specimens at 4 degrees C is recommended when delays in processing may occur. Tissue culture techniques are still the best method for detection of cytotoxin and a variety of cell lines can be used. Other methods for detecting cytotoxin, and methods for detecting other toxins are not sufficiently developed yet to warrant introduction into diagnostic laboratories. Culture techniques remain the most sensitive for diagnosis, particularly since the development of a variety of enrichment techniques. Cycloserine cefoxitin fructose agar is still adequate, although reduced concentrations of antimicrobial agents are necessary, and improvements, such as the addition of sodium taurocholate, increase the recovery of spores. Enrichment cultures have markedly increased isolation rates for Clostridium difficile but the significance of these isolates needs to be carefully evaluated. Until simpler and more reliable tests are available in clinical laboratories for the detection of toxins, the isolation of Clostridium difficile from patients with diarrhoeal disease should be considered paramount.

Clostridium difficile in general practice and community health

The isolation rate for Clostridium difficile in diarrhoeal stools was investigated in patients from general practice and community health centres over a 14-month period. C. difficile or its cytotoxin was detected in specimens from 89 (4.7%) of 1882 patients studied and accounted for 30.3% of all enteropathogenic micro-organisms isolated. Overall C. difficile was second only to Giardia lamblia in frequency. Recovery rates in the different groups of patients surveyed varied from 3.6 to 27.5%. The relationship between stool culture results and stool cytotoxin assay also varied considerably between groups of patients studied. Coincident infections with a variety of enteropathogenic bacteria and intestinal parasites were diagnosed in 14 of the 89 patients. It was concluded that laboratories servicing this type of practice should be aware that C. difficile may be a cause of diarrhoea. An adequate clinical history should facilitate proper processing of the specimen.

Diagnosis of Clostridium difficile-associated intestinal disease

Toxigenic Clostridium difficile is the major cause of antimicrobial agent-associated pseudomembranous colitis and is the etiological agent of approximately 30% of cases of nonspecific colitis and diarrhea (without colitis) induced by antimicrobial agents. In addition, C. difficile has been implicated in certain intestinal diseases not related to prior antimicrobial administration. C. difficile has been reported to be one of the most common enteropathogens isolated from stool specimens submitted to hospital laboratories. Thus, diagnosis of C. difficile-associated intestinal disease should now be routinely performed in diagnostic clinical laboratories. The diagnosis of C. difficile-associated intestinal disease relies on the demonstration of either the organism or the toxin(s) in stool specimens or antibody response in serum to the toxin(s). Several selective medium are available for the recovery of C. difficile from stool specimens. The toxin(s) of C. difficile can be demonstrated using a variety of techniques, including biological assays as well as immunological assays. This article will review the techniques currently available to aid in the diagnosis of C. difficile-associated intestinal disease.