Determination of resistance and virulence genes inEnterococcus faecalisandE. faeciumstrains isolated from poultry and their genotypic characterization by ADSRRS-fingerprinting

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Abstract

The aim of this study was to determine the antimicrobial resistance of E. faecalis and E. faecium strains isolated from poultry and to carry out genotypic characterization thereof with the ADSRRS-fingerprinting method (amplification of DNA fragments surrounding rare restriction sites) and analysis of the genetic relatedness between the isolates with different resistance and virulence determinants. Samples were collected from 70 4-week-old chickens and tested for Enterococcus. Minimum inhibitory concentrations of 11 antimicrobials were determined using the broth microdilution method. Detection of antibiotic resistance and virulence genes was performed using PCR, and molecular analysis was carried out using the ADSRRS-fingerprinting method. The highest percentage of strains was resistant to tetracycline (60.5%) and erythromycin (54.4%), and a large number exhibited high-level resistance to both kanamycin (42.1%) and streptomycin (34.2%). Among 8 genes encoding AME, the tested strains showed mainly the presence of [aph(3′)-IIIa], [ant(6)-Ia], [aac(6′)-Ie-aph(2′′)-Ia], and [ant(9)-Ia] genes. Phenotypic resistance to erythromycin was encoded in 98.4% strains by the ermB gene. Genotypic resistance to tetracycline in E. faecium was associated with the presence of tetM and tetL (respectively, in 95.5 and 57.7% of the isolates); in contrast, E. faecalis strains were characterized mainly by the presence of tetO (83.3%). The virulence profile was homogenous for all E. faecium strains and included only efaAfm and ccf genes. All E. faecalis strains exhibited efaAfs, gelE, and genes encoding sex pheromones. The strains tested exhibited 34 genotypic profiles. Comparative analysis of phenotypic and genotypic resistance and virulence profiles and confrontation thereof with the genotypes of the strains tested showed that strains assigned to a particular genotype have an identical phenotypic resistance profile and a panel of resistance and virulence genes. The results of this study confirm that poultry can be a reservoir of resistant E. faecium and E. faecalis strains with multiple combinations of resistance and virulence genes, whose specific panel determines not only phenotypic characteristics but also has a strong correlation with the genotypic profiles of the strains.

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