Antimicrobial resistance of actinobacillus pleuropneumoniae field isolates in autonomus province of vojvodina, republic of serbia

Actinobacillus pluropneumoniae (APP) is one of the most important bacterial respiratory pathogens in swine. It is the only etiological agent of porcine pleuropneumoniae (PPP) or appears as a secondary bacterial infection of the swine's respiratory disease complex (PRDC). Antibiotics are still the most effective measure for reducing mortality and severity of clinical symptoms in most parts of the world. Nevertheless, in recent years, resistance to certain antibiotics such as tetracycline, penicillin, aminoglycosides and others has been increasing. The aim of this study was to examine the resistance of A. pleuropneumoniae isolates in the area of AP Vojvodina. The samples were collected from dead pigs' lung tissue from 14 farms. Bacterial strains were isolated on agar with 5% sheep blood and Staphylococcus aureus culture as a source of factor V and for subculture chocolate agar enriched with 10 mg/L NAD was included as well. After the examination of morphological and cultural characteristics, biochemical identification was performed using standard bacteriological tests. APP was confirmed by PCR. A total of 35 bacterial isolates were tested on antimicrobial resistance using the disc diffusion method with 11 antibiotics. Antibiotics from the group: aminoglycosides, sulfonamides, fluoroquinolones, phenicols, tetracyclines and beta-lactam antibiotics were used. The isolates collected in the area of AP Vojvodina, from 2015 to 2022, retained high sensitivity to florfenicol, cephalosporins and fluoroquinolones. However, increasing antibiotic resistance was observed for penicillin, tetracycline and all tested aminoglycosides.