[Bacterial pathogens in diarrhea: demonstration of verotoxin-producing Escherichia coli using the polymerase chain...

In 23% of 576 diarrhea patients we were able to demonstrate putative bacterial pathogens. Not included in this number is Clostridium difficile which was found in 8 of 48 (8.3%) specimens analyzed. In addition to Salmonella (8.2%), Campylobacter (6.0%), Aeromonas (2.7%), Shigella (1.9%) and Yersinia (0.8%) we identified verotoxin-producing Escherichia coli (VTEC) in 10 patients (1.9%). VTEC were found as frequently as Shigella (occurring exclusively in patients returning from the tropics) and we propose that VTEC should be routinely assayed in patients with travel-associated diarrhea as well as in those with diarrhea presumably acquired in Switzerland. Established methods for identification of E. coli O157:H7, which include screening for sorbitol-negative Enterobacteriaceae and agglutination, are laborious and insensitive (only 1 of 10 patients with proven VTEC infection positive). The other 9 patients were identified by means of the polymerase chain reaction (PCR). In 7 of these 9 patients we were able to isolate a verotoxigenic strain following a positive PCR result by screening large numbers of colonies. None of them belonged to the O157:H7 serogroup and, in addition, all were sorbitol-positive. The polymerase chain reaction as performed in this study is easy to use, is applicable to large numbers of specimens, and can be regarded as the method of choice for demonstration of VTEC in the clinical diagnostic laboratory.