Detection of enterotoxigenic Bacteroides fragilis by PCR

Strains of enterotoxigenic Bacteroides fragilis (ETBF) are associated with diarrhea in young farm animals and, at least in particular settings, in children, Enterotoxin production by ETBF is currently detected by a tissue culture assay with HT-29 cells. We hare developed a PCR assay based ore the detection of the enterotoxin gene to identify ETBF in culture and in stool samples, Overall, 113 bacterial strains were examined, including 3 B. fragilis reference strains, 75 B. fragilis isolates (comprising 40 ETBF isolates), 20 Bacteroides spp. other than B. fragilis, and 15 strains belonging to other genera, Complete agreement was found between the results of the tissue culture assay and those af the PCR For our strains, PCR was also used Bu detect ETBF directly in fecal samples. Stools from two healthy volunteers were spiked with known numbers of ETBF and were processed by three different methods. A culture method, which required inoculation of the stools on selective plates and the collection of the whole bacterial growth (''sweeps''), was Found to be the most sensitive, PCR performed with the plate sweeps yielded amplification products with a detection limit of 10(5) to 10(4) CFU/g of feces. Bg this method 18 samples of diarrheic stools (10 positive and 8 negative for ETBF) mere examined, The results of the PCR were In accordance with the culture results in all cases, The proposed PCR assay represents a diagnostic fool for the rapid identification of ETBF in culture as well as in fecal samples.