TDK conference 2024

The global spread of antimicrobial resistance necessitates collaboration and joint efforts between animal and public health sectors. Among the multidrug-resistant (MDR) Escherichia coli (E. coli) strains, those producing extended-spectrum beta-lactamase (ESBL) enzymes pose a significant public health risk, particularly in nosocomial infections.

The aim of our research was to assess the presence of genes responsible for extended-spectrum beta-lactamase (ESBL) production in large-scale poultry flocks in Hungary. After sample collection and preliminary screening, we determined the minimum inhibitory concentration (MIC) of key antibiotics relevant to public health for the selected strains. The MDR strains were further analyzed for ESBL production using phenotypic expression methods, followed by next-generation sequencing.

Out of the 420 MDR strains, during the ESBL prescreening, if the MIC value for cefotaxime and cefotaxime-clavulanic acid showed at least a 3-fold reduction in MIC with the combination, the strain was presumed to be an ESBL producer. A similar approach was applied for amoxicillin and amoxicillin-clavulanic acid, where this pattern indicated potential beta-lactamase production. A total of 253 strains met these criteria, and their genetic background was mapped using next-generation sequencing.

We identified CTX-M-type genes (CTX-M-1, CTX-M-15, CTX-M-27) in 23 cases, TEM-type genes (TEM-1, TEM-12, TEM-30, TEM-32, TEM-35, TEM-79, TEM-104, TEM-122, TEM-135, and TEM-150) in 159 cases, SHV-type genes (SHV-75 and SHV-187) in 4 cases, and OXA-type genes (OXA-1, OXA-699) in 3 cases. Among the phenotypically confirmed ESBL-producing strains, we were able to identify resistance genes in 81.6% of cases. In 55.1% of the examined strains, the genes responsible for ESBL production were located on plasmids, while 18.9% of the genes were found on mobile genetic elements. Additionally, we identified 12 strains that were pan-resistant, meaning they were resistant to all the antibiotics tested.

In conclusion, the extent of the spread of genes responsible for ESBL production is alarming, especially considering the high proportion of genes carried on plasmids and mobile genetic elements, significantly increasing the likelihood of horizontal gene transfer. Our findings support the need for similar regular monitoring studies in the future.