Selective and differential medium for isolation of Clostridium difficile

Pseudomembranous colitis after treatment with metronidazole

Images

Selective medium for isolation of Clostridium botulinum from human feces

A selective medium, Clostridium botulinum isolation (CBI) agar, was developed for the isolation of C. botulinum from human feces. This medium contains cycloserine (250 microgram/ml), sulfamethoxazole (76 microgram/ml), and trimethoprim (4 microgram/ml) as selective inhibitory agents. Qualitative tests indicated complete recovery of C. botulinum types A, B, F, and G on CBI medium. It was more difficult to recognize type G colonies on the medium because of their lack of lipase activity. Except for a few species of Clostridium, the growth of other obligate anaerobes and of the facultative anaerobes tested on CBI medium was suppressed. Quantitative studies of C. botulinum on the selective medium yielded counts comparable to those obtained on egg yolk agar control plates. Isolation of C. botulinum types A, B, and F from seeded fecal specimens was easily achieved with CBI medium. The use of CBI agar should aid the rapid isolation of C. botulinum from fecal specimens associated with foodborne and infant botulism.

Spectrum of antibiotic-associated diarrhoea

In an attempt to find the extent to which Clostridium difficile could be implicated as the cause of antibiotic-associated diarrhoea, the stools of 53 patients who had diarrhoea after a course of antibiotics were investigated for the presence of C. difficile toxin. Ten of the patients (19%) were found to be positive, but the stools of four out of 53 patients without diarrhoea after a course of antibiotics were also found to contain C. difficile toxin (7.5%). The titre of toxin in patients both with and without diarrhoea fell within the same range (up to 10(-5)). Neither the organism nor its toxin was found in the stool of 26 patients with ulcerative colitis, eight with Crohn's disease, 49 with non-specific diarrhoea, and 27 normal controls. We conclude that, while C. difficile is responsible for a proportion of cases of antibiotic-associated diarrhoea, the concentration of toxin is not the sole factor affecting the severity of this disorder.

Clostridium difficile in relation to enteric bacterial pathogens

All feces samples (n = 2,390) sent to the Bacteriological Laboratory, Göteborg, Sweden over 43 days were, in addition to the standard procedure, cultivated to detect Clostridium difficile by using a special selective medium. C. difficile was found in 81 of the 2,390 samples (3%). These 81 samples represented 56 patients. Fifty of the 56 patients had diarrhea. In 20 of the 56 patients (36%), Salmonella, Campylobacter, or Yersinia were also found. Of the 2,390 samples 252 (11%) from 132 patients revealed positive isolations of Salmonella, Shigella, Campylobacter, or Yersinia in comparison to 3% for C. difficile alone. This result suggests that C. difficile can easily be isolated with proper techniques. Concomitant isolations of more than one bacterial pathogen in cases of gastroenteritis were often found for C. difficile. The theory presented here is that any change of the normal bacterial fecal flora due to such causes as antimicrobial treatment or enteric infections like Salmonella increases the possibilities of isolating C. difficile. The causative significance of C. difficile might in most cases be doubtful. The majority of cases with diarrhea and C. difficile were self-healing and not severe. Only 2 cases of 56 had severe diarrhea with extended engagement of the colonic mucous membrane, but with no signs of pseudomembranes.

Antimicrobial agent-associated colitis and diarrhea

Although antimicrobial agent-associated colitis has been recognized as a clinicopathologic entity for years, the cause of this disease has been determined only recently. Virtually all cases of pseudomembranous colitis and some cases of antimicrobial agent-associated nonspecific colitis or diarrhea have been shown to be caused by a toxin of Clostridium difficile. Methods for cultivating C difficile from feces and for detecting the toxin have been developed. Oral administration of vancomycin has proved to be effective for the treatment of C difficile-induced colitis, although isolated instances of relapse after treatment have been documented.The discovery of C difficile as a human intestinal pathogen has provided an explanation for some, but not all cases of antimicrobial agent-associated diarrhea. The epidemiology, pathogenesis and means of prevention of C difficile toxin-induced diarrhea remain to be determined.

Identification of toxigenic Clostridium difficile by counterimmunoelectrophoresis

A counterimmunoelectrophoresis (CIE) technique which reacted positively with culture filtrates of Clostridium difficile was developed and compared with a cytotoxicity assay in human embryonic lung cell cultures. CIE, employing C. sordellii antitoxin, detected 17 of 17 C. difficile strains. Of those positive by CIE, 13 were cytotoxic in cell culture. Fourteen Clostridium species other than C. difficile, C. sordellii, and C. bifermentans were negative by CIE. C. sordellii and C. bifermentans gave positive CIE results but were not cytotoxic. Similar sensitivity of toxin detection was observed for both methods. Optimal conditions for performing CIE included use of 48-h chopped meat-glucose broth cultures as the antigen source, use of a 10x-concentrated U.S. Standard C. sordillii antitoxin, and electrophoresis for 1.5 h in 0.05 M tris(hydroxymethyl)aminomethane-barbital-sodium barbital, pH 8.8, at a constant current of 6 mA/slide. CIE appears to be a suitable alternative to the cytotoxicity assay and may serve as a means for presumptive identification of C. difficile.

[Antibiotic-associated diarrhoea and enterocolitis (author's transl)]

Many antibiotics, particularly the lincomycins, may cause diarrhoea with or without enterocolitis. The pathogenesis of antibiotic-associated diarrhoea without colitis is uncertain; colloidosmotic water binding in the colon by endogenous glycoproteins undegraded by colonic bacteria is considered. Antibiotic-associated enterocolitis is now known to be due to toxin-producing clostridia, proven for Cl. difficile. Improved methods for the detection of toxin and clostridia are presently being studied. Endoscopically, pseudomembranes are characteristic but not antibiotic-specific, they may be absent or missed diagnostically. A possible role of asymptomatic clostridia-carriers in enterocolitis clustering remains to be determined. The potentially lethal course of the disease requires rapid diagnosis and therapy, with discontinuation of the antibiotic, intensive supportive measures and, at least in severe disease, oral vancomycin.

In vitro susceptibility of Clostridium difficile isolates from patients with antibiotic-associated diarrhea or colitis

In vitro susceptibility tests were performed on 84 strains of Clostridium difficile to 11 antimicrobial agents. All isolates were from the stools of patients with antibiotic-associated diarrhea or colitis in which there was a cytopathic toxin that was neutralized by Clostridium sordellii antitoxin. Over 95% of the strains were susceptible to vancomycin, penicillin G, ampicillin, and metronidazole at concentrations of 4 microgram/ml. Susceptibility to clindamycin was variable; 60% of the strains were susceptible at 1 microgram/ml, and 9% were resistant at 128 microgram/ml. Studies of individual isolates showed that a major portion of the strains were relatively susceptible to the antimicrobial agent implicated in causing the disease.

Cultures for Clostridium difficile in stools containing a cytotoxin neutralized by Clostridium sordellii antitoxin

Stools from patients with antibiotic-associated diarrhea or colitis were cultured to detect the presence of Clostridium difficile. All specimens contained a cytotoxin which was neutralized by Clostridium sordellii antitoxin. Initial testing employed several methods with comparative merits in recovering this organism. These included the use of nonselective media, antibiotic-incorporated media, alcohol shock, and paracresol-containing broth. Optimal results were achieved with primary plating of serial dilutions onto a selective agar containing cycloserine and cefoxitin. This technique was then employed in a large number of specimens. The overall results showed that C. difficile was recovered in specimens from 71 of 73 patients. All isolates of C. difficile produced a cytotoxin which was neutralized by C. sordellii antitoxin in vitro. These results verify the utility of this medium and support the concept that C. difficile accounts for the cytotoxin found in stools in nearly all cases.