Veterinary session

The spread of antimicrobial resistance has become one of the most important health issues of our time. Both human and veterinary antibiotic use contributes to the spread of resistant bacterial strains by putting selection pressure on microorganisms in our environment. Since antibiotic use in livestock farms is significant, the active substances that enter the food chain and are released into the environment are the key drivers of this process. Continued monitoring is essential because, if the trend is not reversed, within the next 30 years, the world's leading cause of death will be the number of cases of disease caused by resistant bacteria.

The aim of our study was to assess the antibacterial susceptibility of commensal Escherichia coli strains in large Hungarian flocks of domestic fowls and turkeys, with particular emphasis on the production of extended-spectrum β-lactamase (ESBL). In our laboratory studies, a total of 420 strains selected on the basis of preliminary minimum inhibitory concentration (MIC) value determinations were tested for six additional active substances of public health importance (amoxicillin, amoxicillin-clavulanic acid, cefotaxime, gentamicin, tobramycin, imipenem and aztreonam).

Our results showed that these strains showed resistance to gentamicin in 82%, tobramycin in 78%, cefotaxime in 23%, cefotaxime clavulanic acid in 8%, imipenem in 46% and aztreonam in 22%. ESBL production was suspected in 14% of the strains based on phenotypic results, which were tested according to Clinical Laboratory Standard Institute (CLSI) guidelines using cefotaxime and cefotaxime-clavulanic acid as active agents. Of the 420 strains, 99% were found to be multi-drug resistant (MDR), 112 (27%) were found to be extensively drug resistant (XDR) and 15 (4%) were found to be pan-drug resistant (PDR).

Our results are based on phenotypic studies and it is therefore essential to complement them with metagenomic studies in the future to confirm the genetic background responsible for resistance, looking for correlations between phenotypic and genotypic associations of multi-drug resistance. In conclusion, the proportion of multi-resistant strains is a cause for concern among the commensal strains in the poultry sector, which have also shown a high loss of susceptibility to critically important agents reserved for public health, and the presence of ESBL-producing strains also raises serious animal and public health concerns.