Enterococcus cecorum (E. cecorum) is often associated with bacterial chondronecrosis with osteomyelitis (BCO) in broilers. Prophylactic treatment with antimicrobials is common in poultry industry, and in case of outbreaks antimicrobial treatment is needed. In this study, the minimal inhibitory concentrations (MIC) and epidemiological cutoff (ECOFF) values for ten antimicrobials were determined in a collection of E. cecorum strains. Whole genome sequencing data were analyzed for a selection of E. cecorum strains to identify resistance determinants involved in the observed phenotypes. Wild type and non-wild type isolates were observed for investigated antimicrobial agents. Several antimicrobial resistance genes (ARGs) were detected in the isolates, linking phenotypes with genotypes for resistance to vancomycin, tetracycline, lincomycin, spectinomycin, and tylosin. All detected resistance genes were located on mobile genetic elements (MGEs). Point Mutations (PMs) were found in isolates with a non-wild type phenotype for enrofloxacin and ampicillin/ceftiofur. Isolates showing non-wild type phenotypes for enrofloxacin had PMs within the gyrA, gyrB, and parC genes, while five amino acid changes in PBP2x superfamily proteins were observed in non-wildtype phenotypes for tested beta-lactam antibiotics. This study is one of the first that describes the genetic landscape of ARGs within MGEs in Enterococcus cecorum, in association with phenotypical resistance determination.
Less...