Enterococci from ready‐to‐eat food – horizontal gene transfer of antibiotic resistance genes and genotypic characterization by PCR melting profile

BACKGROUND The aim of this study was to evaluate the possibility of the horizontal transfer of genes encoding resistance to aminoglycosides ( aac (6′)‐Ie‐ aph (2″)‐Ia, aph (2″)‐Ib, aph (2″)‐Ic, aph (2″)‐Id, ant (4′)‐Ia and ant (6′)‐Ia), tetracyclines ( tet M, tet L, tet K, tet O and tet W), and macrolides ( erm A, erm B, erm C, msr C, mef AB) in Enterococcus strains isolated from ready‐to‐eat dishes purchased in bars and restaurants in Olsztyn, Poland. RESULTS It was found that 74% of tested strains were able to conjugal transfer at least one of the antibiotic resistance genes. Transfer of resistance to tetracyclines in strains was observed with a frequency ranging from 1.3 × 10 −6 to 8.7 × 10 −7 transconjugants/donor. The int gene and the tet M gene were transferred simultaneously, which indicated that a transposon of the Tn 916 /Tn 1545 also participated in the conjugation process. The frequency of transferring genes of resistance to macrolides ranged from 3.2 × 10 −6 to 2.4 × 10 −8 transconjugants/donor. The ermB gene was transferred the most frequently. The frequency of acquisition of genes encoding aminoglycosides in strains isolated from food ranged from 1.7 × 10 −6 to 3,2 × 10 −8 transconjugants/donor. Transfer of the aac(6′)‐Ie‐aph(2″) gene was the most frequent. In all reactions, the clonal character of transconjugants and recipients was confirmed by the polymerase chain reaction melting profile (PCR MP) method, which is an alternative to the pulsed field gel electrophoresis (PFGE) method. CONCLUSION The findings of this study indicate that Enterococcus isolated from ready‐to‐eat food is able to horizontally transfer genes encoding various antibiotic resistance mechanisms.