Molecular characterization of Enterococcus spp. from honey bees in Türkiye: antimicrobial resistance and virulence gene profiles

Abstract

The genus Enterococcus consists of Gram-positive, non-spore-forming, catalase-negative, facultative anaerobic bacteria that can occur both as single or diplococci and in chains. Commensal microorganisms of the gastrointestinal tract of humans and animals, including this genus, acquire high antimicrobial resistance and virulence genes and can turn into opportunistic pathogens. In this study, 42 Enterococcus spp. were isolated and identified by conventional and molecular (ddl gene sequence) methods from honey bee specimens in Türkiye. Of the isolates, 37 (88%) were identified as E. faecalis and five (12%) as E. faecium. Antimicrobial resistance profiles against nine antibiotics were determined by the disk diffusion method. Antibiotic resistance genes and eight different virulence genes were characterized by molecular methods. Of the 42 isolates, 24 (57%) were resistant to erythromycin, six (14%) were resistant to streptomycin, three (7%) were resistant to tetracycline, and two (2%) were resistant to ciprofloxacin. ermB resistance gene was detected in 16 (80%) of 24 erythromycin-resistant E. faecalis isolates and in 100% of four E. faecium isolates. The tetM gene was identified in three tetracycline-resistant strains. “ant(6)-Ia”, “aac(6’)-le-aph(2’’)-Ia” and “acc(6)-Ii” gene co-existence were determined in 6 strains, one of which was E. faecium. Only two of 8 virulence genes (esp and hyl genes) were not detected in any strain, while the gene encoding the sex pheromones determinant and gelatinase protein was detected in 95% of the strains. Antibiotic resistance, resistance, and virulence genes in Enterococcus species isolated from honey bees could pose potential risks to bee health.