ARS | Publication request: Outbreak Investigation: STEC O157

Submitted to: Medical Laboratory Observer
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 28, 2010
Publication Date: March 18, 2010
Repository URL: http://hdl.handle.net/10113/44290
Citation: Durso, L., Maguire, H., Cronquist, A., Bono, J.L. 2010. Outbreak Investigation: STEC O157. Medical Laboratory Observer [serial online]. Available: www.mlo-online.com.

Interpretive Summary: The standard microbiological methods used to isolate Shiga-toxigenic Escherichia coli O157:H7 (STEC O157) from human stool are frequently inadequate for isolation of this same organism from environmental samples. This is because STEC O157 can make people very sick and they will shed large numbers of STEC O157 in their feces. In contrast, STEC O157 does not usually make cattle sick, and when the bacteria are present in cattle feces, it is usually present in very small numbers compared to all of the other fecal bacteria. Thus, microbiological methods that are sufficient for culture of STEC O157 from clinically ill humans result in overgrowth of all the other bacteria from animal feces or environmental samples. This paper describes effective laboratory isolation methods for STEC O157 that will increase the ability of public health laboratories to isolate STEC O157 from environmental samples collected as part of a human outbreak investigation.

Technical Abstract: The standard microbiological methods used to isolate Escherichia coli O157:H7 from human stool are frequently inadequate for isolation of this same organism from environmental samples. This paper describes the laboratory isolation of this pathogen from four environmental samples collected as part of a human outbreak investigation at a livestock show.