Phenotypic and Genotypic Characterisation of Pasteurella Multocida Strains Isolated from Pigs in Poland

A total of 319 Pasteurella multocida (Pm) strains isolated from pigs in Poland were examined. Phenotypic characterisation included: biochemical tests (to determine species, subspecies, and biovar), capsular typing, and antimicrobial susceptibility. Genotypic characterisation included detection of the toxA gene by PCR. All tested Pm strains were classified as Pm subsp. multocida: 87.2% biovar 3, 10.7%-2 and 0.9%-12. One strain was classified as biovar 1. Three strains of Pm did not suit any of the biovars. Using capsular typing methods, 77% of Pm strains isolated from nasal swabs belonged to type D and 33% to type A. Among Pm strains isolated from internal organs, 59.5% belonged to type A and 40.5% to type D. All the isolates showed a high susceptibility to β-lactams: ampicillin and amoxicilin with clavulonic acid (97.8%), penicillin (86.7%), doxicilline (100%), oxytetracycline (97.8%), and tetracycline (93.2%). It was found that all strains were susceptible to norfloxacin, 97.8% to enrofloxacin, and 95.6% to SxT. 24.4% and 15.6% of the strains were resistant to linco-spectin and tiamulin, respectively. The presence of toxA gene was confirmed by PCR in 20.8% of the strains isolated from nasal swabs and 29.1% of isolates from internal organs.