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United States Department of Agriculture

Agricultural Research Service

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Research Project: INCIDENCE & ANTIMICROBIAL RESISTANCE CHARACTERISTICS OF FOODBORNE(SALMONELLA) & COMMENSAL(E. COLI & ENTEROCOCCI) FROM THE NAHMS SWINE STUDY

Location: Bacterial Epidemiology and Antimicrobial Resistance

2013 Annual Report


1a.Objectives (from AD-416):
1. Determine the incidence of Salmonella, E. coli and enterococci in swine fecal samples in the United States.

2. Participate in the characterization of isolates at the phenotypic and genotypic level.


1b.Approach (from AD-416):
Fecal samples will be sampled using microbiological culture techniques to determine bacterial presence. Polymerase chain reaction (PCR) and Sensititre broth microdilution plates will be used to determine select antimicrobial attributes; pulsed field gel electrophoresis (PFGE) will be used to determine relatedness.


3.Progress Report:

This research is directly related to inhouse objective 2. Be a national resource of enteric bacterial isolates and resistance data for food animals from NARMS and US-VetNet.

For the period October 2, 2012 through February 19, 2013, 3,532 fecal samples were collected from pen floors of major swine producing states in the U.S., placed in whirlpak bags, placed in foam shippers with ice packs and shipped overnight to the laboratory in Athens, GA. Upon receipt samples were cultured for Salmonella using standard protocol and 475 samples were determined to be presumptive positive for Salmonella. A total of 1,252 isolates were selected and tested and 497 were isolates were presumptively identified as Salmonella, streaked to trypticase soy agar slants and shipped to the National Veterinary Services Laboratories (NVSL) in Ames, IA for confirmatory serotyping which is in progress. The NVSL will also conduct antimicrobial susceptibility testing on all of the confirmed isolates. We have completed pulsed field gel electrophoresis (PFGE) on 320 of the 497 isolates. The remaining 177 isolates will be completed by the end of the FY. Pending confirmation all PFGE data will be uploaded into the USDA VetNet database. In addition to culture for Salmonella, of the 3,532 fecal samples 1,768 samples were cultured for generic E. coli and Enterococcus species using appropriate methods. Of the 1,768 cultured for E. coli 1,734 (98.1%) were confirmed positive by indole, streaked to trypticase soy agar slants and shipped to the NVSL for antimicrobial susceptibility testing which is in progress. Of the 1,768 cultured for Enterococcus approximately 1,265 (71.5%) were confirmed positive by PCR. Approximately 66 isolates are awaiting serotype confirmation, and 19 samples are mixed serotypes; the mixed serotypes are currently being separated. Of the 1,265 confirmed serotypes, the serotype frequency in decreasing order is: Hirae (455), Faecalis (488), Faecium (195), Durans (42), Casseliflavus (3), Avium (3), and Gallinarum (1). Confirmed isolates are streaked to trypticase soy agar slants and shipped to the NVSL for antimicrobial susceptibility testing which is in progress. All data will be analyzed by APHIS and ARS scientists and manuscripts will be prepared.


Last Modified: 7/30/2014
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