Ten cases of antibiotic-associated colitis (AAC) were identified at a hospital in Washington, D.C., from March 17 to May 9, 1979. No geographic clustering of cases was found, nor was an association with increased use of antibiotics demonstrated. Exposure to aminoglycosides, cephalosporins, and clindamycin was associated with AAC, as was a history of enemas in the seven days before the onset of illness (P=0.045). This association was strengthened when gastrointestinal procedures-defined as (1) three or more enemas per week, (2) the insertion of a nasogastric tube for two or more days, or (3) gastrointestinal surgery-were performed within seven days of the onset of illness (P=0.007). Clostridium difficile was not isolated from the hospital environments, nursing personnel, or family members of the patients. C. difficile was isolated from stool specimens of five (36%) of 14 patients who served as controls.

We examined 45 (80%) of 56 consecutive adult patients with malignant hematologic disorders who were hospitalized during a 15-week period at Emory University Hospital, Atlanta. Stool samples for Clostridium difficile culture and cytotoxin assay were obtained on admission and then weekly during each patient's hospitalization. On admission, four patients had detectable C difficile in their stool samples, which was associated with prior antimicrobial use but not with prior cancer chemotherapy. One of the four patients with positive stool samples also had toxin present in the stool sample and was the only one with diarrhea. Eight (36%) of 22 patients hospitalized for one or more weeks had C difficile isolated from at least one stool specimen. The positive cultures showed no clustering in time, and no risk factors were identified for colonization. Only seven of 15 culture-positive stool samples and three of seven toxin-positive samples were associated with diarrhea.

Amines produced by 31 strains of the Clostridium bifermentans and C. sordellii groups were compared by examining trifluoroaceticanhydride derivatives of basic chloroform extracts from spent cultural medium by gas–liquid chromatography (g.l.c.). All of the urease-positive strains (16) exhibited an amine profile consistent with that of C. sordellii. On the other hand, 12 of 15 urease-negative strains produced amine g.l.c. patterns like that of C. bifermentans, and three strains produced amine patterns identical with that of C. sordellii. The carbohydrate composition of some of the strains was determined by g.l.c. of trimethylsilyl derivatives of acid-digested formamide extracts of whole cells. Two of the three urease-negative strains with amine profiles like C. sordellii had a carbohydrate composition similar to that of C. sordellii, and the other strain had a carbohydrate profile more like that of C. bifermentans. One known strain of C. bifermentans had a carbohydrate profile with characteristics of both C. bifermentans and C. sordellii. The results of this study point out the variability of urease production by C. sordellii and the value of gas chromatography in differentiating this organism from C. bifermentans.

Clostridiwn bifermentans can be differentiated from Clostridium sordellii by gas chromatography on the basis of amines detected after growth for 6 hr in cookedmeat medium. Products detected after exposure of resting cells to amino acids gave evidence for the probable origin of the amines.

An inoculated, irradiated beef pack (1,240 cans) study was conducted for the determination of microbiological safety for unrestricted human consumption. Each can contained a mixture of 10 6 spores of each of 10 strains of Clostridium botulinum (5 type A and 5 type B), or a total of 10 7 spores/can. The cans were irradiated to various doses (100 cans/dose) with 60 Co gamma rays at -30 � 10 C, incubated at 30 � 2 C for 6 months, and examined for swelling, toxicity, and recoverable botulinal cells. The minimal experimental sterilizing dose based on nonswollen, nontoxic sterile cans was 2.2 < experimental sterilizing dose ≤ 2.6 Mrad. Using recoverable cells as the most stringent criterion of spoilage, and assuming the conventional simple exponential (without an initial shoulder) rate of spore kill, the “12D” dose was 3.7 Mrad when estimated on the basis of a mixture of 10 strains totaling 10 7 spores/can, and 4.3 Mrad if it is assumed that each can of beef contained 10 6 spores of a single most resistant strain and all of these spores were of identical resistances. However, an analysis of the data by extreme value statistics indicated with 90% confidence that the spore death rate was not a simple exponential but might be a shifted exponential (with an initial shoulder), Weibull, lognormal, or normal, with a “12D” equivalent of about 3.0 Mrad regardless of the initial spore density per can. There was an apparent antagonism between the irradiated type A and B strains in the cans. Some of the cans contained type B toxin but did not include type B viable cells. Other cans had a mixture of type A and B toxins, but a large number of these cans did not yield recoverable type B cells. However, type A viable cells could always be demonstrated in those cans containing type A toxin.