Antimicrobial susceptibility of porcine Pasteurella multocida, Streptococcus suis, and Actinobacillus pleuropneumoniae from the United States and Canada, 2001 to 2010

Objective: To provide data on the in vitro antimicrobial susceptibility of three bacterial respiratory disease pathogens isolated from swine across the United States and Canada over the period 2001 to 2010. Materials and methods: A total of 1097 Actinobacillus pleuropneumoniae, 2389 Pasteurella multocida, and 2617 Streptococcus suis isolates recovered from diseased or dead swine from North America over a 10-year period were tested for in vitro susceptibility to antimicrobial agents approved for treatment of swine respiratory disease (SRD). Clinical and Laboratory Standards Institute standardized methods were used to determine the minimum inhibitory concentrations (MICs) of ceftiofur, enrofloxacin, florfenicol, penicillin, tetracycline, tilmicosin, and tulathromycin. Results: Over the years 2001to 2010, A pleuropneumoniae and P multocida remained susceptible to ceftiofur, enrofloxacin, florfenicol, tilmicosin, and tulathromycin, and S suis remained susceptible to ceftiofur, enrofloxacin, and florfenicol. Low penicillin MIC values for P multocida and S suis and higher MIC values for A pleuropneumoniae were also seen. Most isolates of all three organisms were resistant to tetracycline over the 10 years of the survey. Implications: Monitoring antimicrobial susceptibility among swine pathogens over time provides valuable information about changes which may be occurring in the antimicrobial susceptibility of these organisms and is an important tool in effective antimicrobial therapy. Surveillance of the in vitro susceptibility of these SRD pathogens continues to be an important component in antimicrobial stewardship.