The usefulness of phenotypic techniques for epidemiological typing Actinobacillus pleuropneumoniae strains Isolated from pigs

In this study, methods like serotyping, biochemical schemes and antibiotic susceptibility were used to analyse 70 isolates of Actinobacillus pleuropneumoniae (App). Serological identification of App strains was performed using agglutination, precipitation and coagglutination techniques. Fifteen different tests were employed for biochemical analysis. The antibiotic susceptibility pattern was analysed using 17 chemioterapeutics. The results of the serotyping techniques have shown cross-reactions-especially between serotype 2 and 6 and serotypes 1, 9 and 11. The strongest cross-reactions were observed in the agglutination test. Among 15 biochemical reactions 8 were positive for all investigated isolates. Common features for all serotypes were: NAD-dependence, CAMP reaction, hemolysis, urease production and hydrolysis of glucose, mannitol, xylose and sucrose. The results of antibiotic susceptibility have shown that all App strains are resistant to lincomycin and streptomycin. It should be stressed that an apparent difference between Polish and German strains has been observed in terms of the scope of their sensitivity/resistance to some choosen antibiotics. Generally, no significant differences were found to exist in the antibiotic sensitivity patterns among App strains. To conclude, it should be underlined that conventional methods are useful only to a limited extent as tools for an epidemiological study of App infection in swine.