Escherichia coli serotype 0157:H7 is a recently recognized human pathogen associated with hemorrhagic colitis. Unlike most E. coli strains, E. coli 0157:H7 does not ferment sorbitol. Therefore, the efficacy of MacConkey agar containing sorbitol (SMAC medium) instead of lactose as a differential medium for the detection of E. coli 0157:H7 in stool cultures was determined in comparison with MacConkey agar. The relative frequency of non-sorbitol-fermenting (NSF) organisms other than E. coli 0157:H7 in feces was low at 10 to 20% (95% confidence limits), and NSF organisms also occurred mostly in small numbers. In a field trial involving over 1,000 diarrheal stools, E. coli 0157:H7 was isolated from 18 stools, all of which were from patients with bloody diarrhea. In every instance, the growth of E. coli 0157:H7 on SMAC medium was heavy and occurred in almost pure culture as, colorless NSF colonies in contrast to fecal flora, which are mostly sorbitol fermenting and hence appear pink on this medium, whereas on MacConkey agar cultures, the growth of E. coli 0157:H7 was indistinguishable from fecal flora. SMAC medium permitted ready recognition of E. coli 0157:H7 in stool cultures. Detection of E. coli 0157:H7 on SMAC medidm had a sensitivity of 100%, a specificity of 85%, and an accuracy of 86%. SMAC medium stool culture is a simple, inexpensive, rapid, and reliable means of detecting E. coli 0157:H7, and we recommend routine use of SMAC medium especially for culturing bloody stools.

A total of 174 strains of Escherichia coli serotype 0157:H7 representing human isolates obtained from outbreaks and sporadic cases of hemorrhagic colitis, hemolytic-uremic syndrome, and nonbloody diarrheal illnesses as well as from asymptomatic carriers across Canada and the United States were examined. E. coli serotype 0157:H7 possessed distinct biochemical markers, a 100% negative reaction for P-glucuronidase and sorbitol, and a 100% positive reaction for raffinose and dulcitol; all strains otherwise were biochemically typical of E. coli. The vast majority (97%) of the strains were susceptible to commonly used antimicrobial agents. Au strains produced readily detectable levels of Verotoxin; however, with polymyxin extraction, nearly 50% of the strains showed up to a 10-fold increase in the toxin level. None were found to mediate hemagglutination of human group A erythrocytes with or without D-mannose. The majority (-70%) of the strains showed localized and diffuse adherence to HEp-2 cells and Henle 407 cells, and the adherence patterns were not very different from those observed among other E. coli strains. Twenty phage types were recognized, with phage types 1 and 2 accounting for 65% of the test strains. Plasmid analysis indicated three basic plasmid profiles: profile I was characterized by 68.7-and 4.2-megadalton (MDa) plasmids (62% of strains), profile Il was characterized by 66.2-and 1.8-MDa plasmids (20% of strains), and profile III was characterized by a 62.5-MDa plasmid (18% of strains). A small number (19%) of the strains carried at least one additional plasmid over the basic complements, and these could be considered to constitute a miscellaneous category. None of the abovedescribed characteristics of E. coli serotype 0157:H7 could be directly correlated with one another, with the nature of infection, or with the geographical distribution of strains. Escherichia coli serotype 0157:H7, initially recognized in 1982 in the United States (34, 42), has now emerged as an important enteric pathogen of considerable public health significance in Canada, the United States, and the United Kingdom, with many outbreaks and numerous sporadic cases of hemorrhagic colitis, hemolytic-uremic syndrome, and diarrheal illness occurring in nursing homes, day-care centers, schools

The value of a latex agglutination test (Escherichia coli 0157 latex test; Oxoid Ltd.) for rapid presumptive detection of E. coli serotype 0157:H7 was determined by laboratory trials and during an outbreak of hemorrhagic colitis. The latex test was found to be a simple, highly efficient and reliable test in detecting E. coli 0157:H7 with 100% sensitivity and specificity. It was also found that sorbitol-MacConkey agar cultures were not as useful for food samples as they were for fecal specimens in screening for E. coli 0157:H7, but the use of the latex screen was particularly efficient in this setting.

and the source of the infection was traced to the hotel whirlpool. Of 36 persons who used the whirlpool, 26 (72%) developed folliculitis within 1 to 5 days after exposure; the attack rate was significantly higher for children (90%) than for adults (50%). The rash characteristics were consistent with those of Pseudomonas folliculitis previously described (

Optimum relative centrifugal force (RCF) and centrifugation time to concentrate mycobacteria in clinical specimens were determined by processing split samples of sputa and urines containing mycobacteria with combinations of different RCFs and centrifugation times. Although individual test results showed considerable variation in the recovery rates of mycobacteria in the sediment, the data indicated that higher recovery rates occurred as centrifugation speed and time were increased. With a 15to 20-min centrifugation time, on the average, 67 to 71 % of mycobacteria were recovered at an RCF of 2,074 x g, and 76 to 80% were recovered at 3,005 or 3,895 x g at maximum radius. The remainder of mycobacteria was mostly recovered from the supernatant, but culturing of supernatant was not profitable. Increasing RCF had a negligible effect on acid-fast bacillus smear sensitivity. The smear sensitivity for about 25,000 clinical specimens processed with an RCF of 3,800 x g for 20 min was 71% compared with 69% as determined for over 30,000 specimens processed in a similar manner but with an RCF of 2,000 x g. An RCF of 3,000 x g applied for 15 min, or an RCF of about 2,000 to 2,500 x g applied for 20 min, is considered adequate to concentrate mycobacteria in clinical specimens.