Abstract
Escherichia coli serotype O157:H7 is a recently recognized human pathogen associated with hemorrhagic colitis. Unlike most E. coli strains, E. coli O157: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 O157:H7 in stool cultures was determined in comparison with MacConkey agar. The relative frequency of non-sorbitol-fermenting (NSF) organisms other than E. coli O157: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 O157:H7 was isolated from 18 stools, all of which were from patients with bloody diarrhea. In every instance, the growth of E. coli O157: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 O157:H7 was indistinguishable from fecal flora. SMAC medium permitted ready recognition of E. coli O157:H7 in stool cultures. Detection of E. coli O157:H7 on SMAC medium 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 O157:H7, and we recommend routine use of SMAC medium especially for culturing bloody stools.
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- Karmali M. A., Petric M., Lim C., Fleming P. C., Arbus G. S., Lior H. The association between idiopathic hemolytic uremic syndrome and infection by verotoxin-producing Escherichia coli. J Infect Dis. 1985 May;151(5):775–782. doi: 10.1093/infdis/151.5.775. [DOI] [PubMed] [Google Scholar]
- Karmali M. A., Steele B. T., Petric M., Lim C. Sporadic cases of haemolytic-uraemic syndrome associated with faecal cytotoxin and cytotoxin-producing Escherichia coli in stools. Lancet. 1983 Mar 19;1(8325):619–620. doi: 10.1016/s0140-6736(83)91795-6. [DOI] [PubMed] [Google Scholar]
- Pai C. H., Gordon R., Sims H. V., Bryan L. E. Sporadic cases of hemorrhagic colitis associated with Escherichia coli O157:H7. Clinical, epidemiologic, and bacteriologic features. Ann Intern Med. 1984 Dec;101(6):738–742. doi: 10.7326/0003-4819-101-6-738. [DOI] [PubMed] [Google Scholar]
- RAPPAPORT F., HENIG E. Media for the isolation and differentiation of pathogenic Esch. coli (serotypes O 111 and O 55). J Clin Pathol. 1952 Nov;5(4):361–362. doi: 10.1136/jcp.5.4.361. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ratnam S., March S. B. Sporadic occurrence of hemorrhagic colitis associated with Escherichia coli O157:H7 in Newfoundland. CMAJ. 1986 Jan 1;134(1):43-5, 49. [PMC free article] [PubMed] [Google Scholar]
- Remis R. S., MacDonald K. L., Riley L. W., Puhr N. D., Wells J. G., Davis B. R., Blake P. A., Cohen M. L. Sporadic cases of hemorrhagic colitis associated with Escherichia coli O157:H7. Ann Intern Med. 1984 Nov;101(5):624–626. doi: 10.7326/0003-4819-101-5-624. [DOI] [PubMed] [Google Scholar]
- Riley L. W., Remis R. S., Helgerson S. D., McGee H. B., Wells J. G., Davis B. R., Hebert R. J., Olcott E. S., Johnson L. M., Hargrett N. T. Hemorrhagic colitis associated with a rare Escherichia coli serotype. N Engl J Med. 1983 Mar 24;308(12):681–685. doi: 10.1056/NEJM198303243081203. [DOI] [PubMed] [Google Scholar]
- Wells J. G., Davis B. R., Wachsmuth I. K., Riley L. W., Remis R. S., Sokolow R., Morris G. K. Laboratory investigation of hemorrhagic colitis outbreaks associated with a rare Escherichia coli serotype. J Clin Microbiol. 1983 Sep;18(3):512–520. doi: 10.1128/jcm.18.3.512-520.1983. [DOI] [PMC free article] [PubMed] [Google Scholar]