Study of antimicrobial susceptibility to respiratory pathogens in pigs

The antimicrobial susceptibility of common respiratory pathogens of pigs including Actinobacillus (Haemophilus) pleuropneumoniae, Pasteurella multocida, Streptococcus suis, and Trueperella (Arcanobacterium) pyogenes – was studied in the samples isolated from industrial pig farms located in east and central province of Ukraine. The study was carried out with analysis the results of surveillance the microbial strains susceptibility in the 620 animals with signs of respiratory pathology. The samples were isolated and tested during 2023-2024 at the Research Center for Biosafety and Environmental Control of Agricultural and Industrial Complex Resources. To determine the sensitivity of bacteria to antibiotics, the Kirby-Bauer agar diffusion method was used. Resistance was determined against to particular antibiotic groups, the application of which is regulated by the government requirements of Ukraine. In order to identify differences in the prevalence of resistant strains to individual antibiotics dependent on the year of the study, the results were statistically analyzed with using the χ 2 criterion. The dynamics of the spread of resistance to individual antimicrobial drugs were identified. The most effective category D drugs that are allowed to be used for the treatment of animals on the first day of infection caused by the studied bacteria are drugs containing Amoxicillin. However, resistance to Amoxicillin in A. pleuropneumoniae isolates increased from 12% in 2023 to 18% in 2024. The consequence of the requirements breach for the rational use of antimicrobial drugs was the resistance generation in respect to category B antimicrobial drugs, which are allowed to be used for the treatment of productive animals only in the absence of effective drugs of categories C or D. Fluoroquinolone-resistant strains of S. suis were detected in 6%, and A. pleuropneumoniae in 9-18% of samples, respectively in 2024. Among the studied isolates of P. multocida and T. pyogenes, there is no observed the resistance against fluoroquinolones. The introduction of regular monitoring of antibiotic resistance will allow selecting the most effective antimicrobial treatment regimen for respiratory pathology in pigs and will contribute to the implementation of the requirements of the “One Health” concept in respect with agricultural production.