Detección de Enterococcus resistentes a altos niveles de aminoglucósidos y resistentes a glucopéptidos en Lactuca sativa (lechuga)

Abstract

The aim of this study was to assess the presence of enterococci highly resistant to aminoglycosides and glycopeptides in foods eaten uncooked, in order to evaluate their role as reservoirs of antimicrobial resistance. We isolated 92 strains of enterococci from 79 samples of lettuce grown on farms near the city of Corrientes (Argentina). Enterococci were identified by standard methods. Antimicrobial susceptibility was determined by growth in azide dextrose broth supplemented with 500 microg/ml of gentamicin and 2,000 microg/ml of streptomycin, and by disk diffusion technique using disks with high levels of aminoglycosides, vancomycin and teicoplanin, in Müller Hinton agar. The most frequently detected species was E. faecium (32.61%), followed by E. faecalis (21.74%), E. gallinarum (13.04%), E. casseliflavus and E. mundtii (7.60%), E. hirae, (6.52%), E. durans (4.35%), E. raffinossus and E. saccharolyticus (2.17%), E. avium and E. malodoratus (1.10%). High-level resistance to streptomycin and gentamicin was found in 2 strains of E. Faecium. Resistance to streptomycin alone was observed in 2 strains of E. faecium, in 3 of E. hirae and in 1 of E. mundtii. Resistance only to gentamicin was not observed in any strain. None of the isolates showed glycopeptide resistance, except the intrinsically resistant species (E. gallinarum and E. casseliflavus). These results confirm the presence of enterococci within the community having susceptibility profiles similar to those of strains found in hospitals.