Characterization of Clinical Strains of Enterohemorrhagic E. Coli (EHEC)

APPROACH: Clinical EHEC strains, obtained from patients at Inova Fairfax Hospital, will be characterized using PCR and DNA-sequencing techniques previously developed by USDA scientists. Laboratory experiments will be conducted to determine mortality rates for clinical EHEC strains; strains will be incubated in surface waters from different sources and at different temperatures.
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PROGRESS: 2004/10 TO 2009/10<BR>
Progress Report:<BR> Approach: Clinical EHEC strains, obtained from patients at Inova Fairfax Hospital, will be characterized using PCR and DNA-sequencing techniques previously developed by USDA scientists. Laboratory experiments will be conducted to determine mortality rates for clinical EHEC strains; strains will be incubated in surface waters from different sources and at different temperatures. <BR>Significant Activities that Support Special Target Populations: Water-borne and food-borne enterohemorrhagic E. coli (EHEC) pose a serious threat to public health, causing an estimated 100,000 infections in the U.S. annually. Recent outbreaks of E. coli O157:H7 associated with leafy vegetables (e.g. spinach) illustrate the vulnerability of the food supply to EHEC contamination. Consequently, rapid identification of EHEC infections is critical not only for patient care, but also to allow public health and regulatory agencies to identify, and remove, the source of contamination as quickly as possible. However, the current system for identifying outbreaks is neither rapid nor sensitive. A minimum of two weeks is required to identify an incipient EHEC outbreak (CDC website). In the case of fresh produce, since most produce is consumed within a two period, identification of produce-borne outbreaks requires preliminary characterization of EHEC strains by clinical labs and timely communication. Polymerase chain reaction (PCR) assays are available that can rapidly identify EHEC strains and allow for preliminary strain characterization; however, these assays have not been widely adopted by clinical labs. In conjunction Inova Fairfax Hospital, EHEC strains from human stool specimens were analyzed using PCR to confirm identification and to provide a preliminary PCR profile. We were able to detect a small cluster of cases presumptively caused by the same non-O157 EHEC strain during the summer of 2006. These results indicate that PCR protocols are suitable for use in clinical labs, and if used routinely, would allow for a higher rate of diagnosis and more rapid identification of outbreaks. A jointly authored poster was presented at the 2007 annual meetings of the American Society for Microbiology. A manuscript entitled 'A multiple protocol to improve diagnosis and isolation of Shiga toxin-producing Escherichia coli (STEC) from human stool specimens' was published in the journal Diagnostic Microbiology & Infectious Disease. Meetings are held quarterly to discuss results with frequent email communication in the interim.