Antimicrobial susceptibility of porcine brachyspira hyodysenteriae isolates from Switzerland

[摘要] The anaerobic spirochaete Brachyspira (B.) hyodysenteriae is the causative agent of swine dysentery (SD), a severe mucohaemorrhagic diarrheal disease in pigs worldwide. Currently, no data for antimicrobial susceptibility of B. hyodysenteriae from Switzerland are available and though antimicrobial treatment is the main therapy, no standardised methods for antimicrobial susceptibility testing are established. Therefore, a broth microdilution test was performed for 30 Swiss porcine field isolates and evaluated for its suitability in diagnostics. For the pleuromutilins, tiamulin and valnemulin, a good reproducibility in testing and susceptibility at low concentrations could be observed. The reproducibility for doxycycline was acceptable. A part of the isolates showed reduced susceptibility. For lincomycin and the macrolides, tylosin and tylvalosin, reproducibility was influenced by the occurrence of so-called skips. Furthermore, reduced susceptibility for lincomycin and resistance for tylosin could be detected. Sequencing of the 23S rDNA revealed, that a point mutation is responsible for resistance and a possible explanation for the skipped wells. In a European comparison Switzerland is still in a favourable situation. However, accurate determination of minimal inhibitory concentrations is questionable, and a classification of isolates into susceptible and resistant isolates is difficult due to the lack of unambiguous classification criteria.

[发布机构] University of Zurich

[效力级别] 570 Life sciences

[关键词] Institute of Veterinary Bacteriology;570 Life sciences;biology