Antimicrobial susceptibility of Actinobacillus pleuropneumoniae isolates from clinical outbreaks of porcine respiratory diseases.

Limited data regarding the susceptibility of Actinobacillus pleuropneumoniae to antimicrobials has been published during recent years. Accordingly, the aim of the present study was to investigate the distribution of MICs for the isolates of A. pleuropneumoniae from diseased pigs in the Czech Republic between 2007 and 2009. A total of 242 isolates were tested for susceptibility to 16 antimicrobial agents by a broth microdilution method. A low degree of resistance was observed for florfenicol (0.8%), amoxicillin and clavulanic acid (0.8%), tilmicosin (1.2%), tiamulin (1.7%) and ampicillin (3.3%), whereas resistance to tetracycline was detected more frequently, 23.9% of isolates. Interestingly, resistance to florfenicol has not yet been reported in any study investigating antimicrobial resistance of A. pleuropneumoniae. By PCR the presence of the floR gene was confirmed in all florfenicol resistant isolates.