Prevalence of serotypes, production of Apx toxins, and antibiotic resistance in strains of Actinobacillus pleuropneumoniae isolated in the Czech Republic

Results of serotyping of 122 strains of Actinobacillus pleuropneumoniae isolated on 21 swine farms in the Czech Republic from January 1999 to December 2000 are presented. The highest prevalence was found for serotype 9 (n = 81, 66.4%), followed by serotype 2 (n = 19, 15.7%). Serotypes 1, 3, 5, 7, 8, 11, and 12 were identified only sporadically. Twenty-six of the isolates were tested for gene-toxic profiles and haemolytic and cytotoxic activities. The investigations confirmed the association between serotype on the one hand and Apx genotype and Apx phenotype on the other hand. Results of tests of resistance to antibiotic by the disc diffusion method have justified the apprehension of development of resistance due to long-term treatment with antibiotics. Strains with full or intermediary resistance against all the commonly used penicillinand tetracycline-type antibiotics were found. None of the strains was resistant to florfenicol, norfloxacin, or cefalotine.