Our study describes the prevalence and spectrum of enterococci isolated from one-day-old chickens in the Czech Republic, their level of antimicrobial resistance, and the occurrence of multiresistance. Over a 24-month period from 1 August 2021 to 31 July 2023, a total of 464 mixed samples of one-day-old chicken organs were examined during routine inspections at 12 randomly selected poultry farms in the Czech Republic. The samples were processed via cultivation methods and suspected strains were confirmed using the MALDI-TOF Mass Spectrometry method. Antimicrobial susceptibility was determined using the MIC method for eight antimicrobials. A total of 128 isolates (prevalence of 27.6%) representing 4 species of enterococci were isolated, including Enterococcus faecalis, Enterococcus faecium, Enterococcus gallinarum, and Enterococcus hirae, with prevalence rates of 23.3%, 1.5%, 2.2%, and 0.6%, respectively. Susceptibility tests showed a high percentage of susceptible strains among E. faecalis, E. faecium, and E. gallinarum for penicillin-based antibiotics, sulfamethoxazole with trimethoprim, and florfenicol (80-100% susceptible strains). E. hirae was an exception, displaying complete resistance to enrofloxacin (0% susceptible strains) and a high degree of resistance to other tested antimicrobials (33.3% susceptible strains). Among the isolated strains, a total of 16 isolates (12.5%) showed resistance to 3 or more antimicrobials. Complete resistance to all eight antimicrobials simultaneously was observed in four isolates (3.1%). This research shows the possible sources of pathogenic enterococci and their virulence and resistance genes. The findings hold relevance for both veterinary and human medicine, contributing to a better understanding of enterococcal circulation in the human ecosystem and food chain, as well as the development of their resistance and multiresistance.

Department of Cell Biology and Genetics Faculty of Science Palacký University Olomouc 17 Listopadu 1192 779 00 Olomouc Czech Republic

Institute of Animal Protection and Welfare and Public Veterinary Medicine University of Veterinary Sciences Palackeho 1 3 612 42 Brno Czech Republic

Ptacy S R O Valasska Bystrice 194 756 27 Valašská Bystřice Czech Republic

Veterinary Research Institute Hudcova 296 70 621 00 Brno Czech Republic

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