Prevalence of shiga-toxin producing E. coli on cattle farms located in the Arkansas Delta region

The objective of this study was to determine the prevalence of E. coli STEC on small (30- 40 head) cattle farms in the Arkansas Delta. Samples were collected between 6 September and 25 November 2012 (average air temperature = 16.9°C) from 180 randomly selected beef cows located on 18 farms in five counties (Clay, Craighead, Greene, Poinsett and St. Francis). Samples collected included: 30 rectal swabs from ten cows per farm (3 samples from each cow), three soil samples, three water samples, and when available, three feed samples. The rectal swabs were transferred to 5 ml sterile modified Trypticase Soy Broth (mTSB; containing novobiocin) tubes. Five grams of feed or soil were transferred to sterile stomacher bags containing 45 ml of buffered peptone water (BPW). An aliquot (1 ml) of each soil, water or feed sample was transferred to 5-ml sterile mTSB tubes. After incubation, a loopful of culture from each mTSB tubes were streaked on a cefixime and tellurite MacConkey Sorbitol Agar, (CT-SMAC) and a CT- Rainbow O157 agar plate and incubated for 18-20 hours at 35°C. Each plate was then scored for the presence of E. coli O157 and non-O157 STEC by colony appearance. Non-O157 STEC colonies were confirmed as E. coli by routine biochemical tests. The E. coli O157 colonies were confirmed by Latex Agglutination assays for the O157 antigen.;Among the 18 farms, differences (P ≈ 0) existed in the proportion of fecal samples that tested positive for both O157 STEC and non-O157. Sixty-one percent and 100% of the farms had cattle that tested positive for O157 STEC and non-O157 STEC, respectively. Differences (P ≈ 0) in the proportion of positives were also observed in environmental samples for non-O157 STEC; however, no differences (P=0.973) were observed for environmental samples that were positive for O157 STEC.;Differences (P ≈ 0) were observed for in the proportion of fecal samples that tested positive for both O157 STEC and non-O157 STEC between counties. The proportion of environmental samples that tested positive for O157 STEC (P ≈ 0) and non-O157 STEC (P = 0.012) were also different among the counties studied.;In this study, the prevalence rates of E. coli STEC on small cattle farms in the Arkansas Delta were relatively high. Further work is needed to determine risk factors, concerning the public that may be associated with high prevalence rates for both O157 and non-O157 STEC.