Recent trends in antimicrobial susceptibility and the presence of the tetracycline resistance gene in Actinobacillus pleuropneumoniae isolates in Japan

Abstract

A total of 101 Actinobacillus pleuropneumoniae isolates from diseased pigs taken from across Japan during 2002 to 2005 were examined for antimicrobial susceptibility. All isolates were susceptible to ceftiofur, erythromycin, florfenicol and enrofloxacin. Antimicrobial-resistant isolates to oxytetracycline (OTC) (27.7%), dihydrostreptomycin (10.9%), thiamphenicol (10.9%), kanamycin (5.9%), trimethoprim (4.0%) and ampicillin (2.0%) were recognized. OTC-resistant isolates taken from 1986 to 2005 were examined for the tetracycline resistance gene. In OTC-resistant isolates, tetB has been the most frequently isolated gene in Japan. It is likely that the dissemination of tetB has contributed to the increased OTC resistance of A. pleuropneumoniae in Japan.