Submitted to: American Journal of Veterinary Research
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/7/2010
Publication Date: 11/7/2010
Publication URL: DOI: 10.2460/ajvr.71.11.1339.
Citation: Kondo, S., Hoar, B.R., Mandrell, R.E., Atwill, E.R. 2010. Longitudinal prevalence and molecular typing of Escherichia coli O157:H7 using multiple-locus variable-number tandem-repeats analysis and pulsed field gel electrophoresis in a range cattle herd in California. American Journal of Veterinary Research. 71(11):1339-1347. Interpretive Summary: This study involved identification of seasonal pattern and risk factors for Escherichia coli O157:H7 in feces in range cattle in California and assessment of strain diversity over time using genetic fingerprinting methods.Cattle fecal samples were collected monthly froma cow-calf operation in the California Sierra Foothills over 12 months. E.coli O157:H7 was isolated and virulence factors were detected by PCR. The incidence estimate of E. coli O157:H7 was 10.5% (48/456). We determined that prevalence was lowest during the winter and the 30 day average temperature before sampling was significantly associated with fecal prevalence of E. coli O157:H7. Multiple strains were based on fingerprinting were recovered and indicated turnover of predominant types over time. Fingerprinting methodsprovide a useful tool in outbreak investigation.
Technical Abstract: Objectives –(1) Identify the seasonal pattern and risk factors for Escherichia coli O157:H7 in feces in range cattle in California, (2) Determine strain diversity and transition over time using Multi-Locus Variable-Number Tandem Repeat Analysis (MLVA) and Pulsed Field Gel Electrophoresis (PFGE) Samples– Approximately 40 freshly passed fecal samples /month were collected froma cow-calf operation in the California Sierra Foothills over 12 months. Procedures –E.coliO157:H7 was recovered from feces using immunomagnetic separation (IMS) and two selective media, CT-SMAC and NT-Rainbow. Virulence factors were detected with RT-PCR. E.coli O157:H7 positive isolates were subtyped by MLVA and PFGE. Prevalence estimates were calculated and significant risk factors determined by logistic regression. A dendrogram based on the MLVA typing was constructed. Results – Overall prevalence estimate of E. coli O157:H7 was 10.5% (48/456), with prevalence lowest during the winter. Thirty day average temperature before sampling was significantly associated with fecal prevalence of E. coli O157:H7. Nineteen MLVA types and 12 PFGE types were identified. Conclusions and clinical relevance – Our study demonstrated the seasonal pattern of E. coli O157:H7 fecal prevalence in range cattle operation in California. Subtyping using MLVA and PFGE showed a diversity of E. coli O157:H7 strains in this cow-calf operation and turnover of predominant types over time. MLVA and PFGE results were well correlated and MLVA may be a powerful tool in outbreak investigation.