Role of acrAB in antibiotic resistance of Haemophilus parasuis serovar 4

Haemophilus parasuis infection is responsible for important economic losses to the pig industry. The increasing emergence of resistance to multiple antibiotics is of concern and to study the role of the acrRAB operon in H. parasuis drug resistance, acrB or acrR mutants were generated from H. parasuis serovar 4 clinical strains. The susceptibilities of the clinical strains and their acrB/acrR mutants to a number of antibiotics were determined. The acrB mutants were more susceptible to novobiocin, erythromycin, clarithromycin, and azithromycin. In the acrR mutant of H. parasuis, acrB was up-regulated, as determined by quantitative reverse transcriptase polymerase chain reaction. The results of this study indicated that the efflux pump AcrB may play a role in multidrug resistance of H. parasuis.