Antibiotic susceptibility and PCR-RFLP patterns of Bordetella bronchiseptica strains isolated from pigs and other hosts in Hungary

Bordetella bronchiseptica (Bb) is involved in the aetiology of atrophic rhinitis of swine and causes remarkable economic losses for pig production. Antibiotic treatment is widely used for the treatment of bacterial infections, nevertheless, little is known about the antibiotic resistance of the B. bronchiseptica strains circulating in Hungary. Our aim was to fill this gap by a retrospective analysis of strains originated from pigs. Furthermore, we determined the PCR-RFLP patterns of some strains and compared to those of strains from other host species.

Antibiotic susceptibility of 15 Hungarian strains was determined by Kirby-Bauer disk diffusion method. Plasmid isolation was performed with QIAprep Spin Miniprep Kit. PCR-RFLP: 43 Bb isolates from pigs, 38 from dogs, 4 from cats were analysed on fimA by HincII and SalI, on flaA by BglI, HincII and MspI, and on cyaA by NarI and SalI.

All strains were susceptible to colistin and amphenicols, but a high levels of resistance were detected to a number of other antibiotics (penicillin, vancomycin, lincomycin and ceftiofur). The resistance to ampicillin, neomycin, tilmicosin and flumequine varied widely among the strains. All but five of the strains were susceptible to sulphonamides while only one isolate was resistant against tetracycline and nalidixic acid, respectively. Four out of 15 strains presented plasmids. The PCR-RFLP of fimA resulted uniform bands in all strains examined. By PCR-RFLP of flaA, the isolates from pigs in Hungary were uniform and differed from strains originated from the other hosts, while the isolates from pigs from other countries represented three types (A, B and C). Most strains of porcine origin (93%) belonged to the type B. The PCR RFLP of cyaA of strains from pigs proved to be uniform (pattern A), only one foreign porcine isolate belonged to type D.

The practice of antibiotic therapy in livestock farms might affects the rate of resistance against antibiotics. However, our study revealed no correlation between the antibiotic resistance patterns and the origin of the strains. Signs of general antibiotic resistance spreading were not detected. The present results point to a possible connection between Bb flaA PCR-RFLP profiles and hosts. In a certain geographical region, signs of host adaptation were recognizable.

Disclosure of Interest: None Declared.