title: Biocide and antibiotic resistance of Enterococcus faecalis and Enterococcus faecium isolated from the swine meat chain.
abstract: In this study nine strains of Enterococcus faecalis and 12 strains of Enterococcus faecium, isolated from different sample types in the swine meat chain and previously characterized for the presence of antibiotic resistance genes, were examined for phenotypic tolerance to seven biocides (chlorexidine, benzalkonium chloride, triclosan, sodium hypochlorite, 2-propanol, formaldehyde and hydrogen peroxide) and resistance to nine antibiotics (ampicillin, vancomycin, gentamicin, kanamycin, streptomycin, erythromycin, clindamycin, tetracycline and chloramphenicol). Moreover, the presence of efflux system encoding genes qacA/B, qacC, qacE, qacEΔ1, emeA, and stress response genes, sigV and gsp65, involved in the tolerance to biocides, was analysed. Most strains were not tolerant to the biocides, but showed minimum inhibitory concentrations (MICs) higher than the recommended cut-off values for all the antibiotics tested, except for vancomycin and chloramphenicol. Only weak correlations, if any, were found between biocide and antibiotic resistance data. One E. faecalis strain was tolerant to triclosan and one E. faecium strain, with higher tolerance to chlorexidine than the other strains tested, was found to carry a qacA/B gene. Our results indicated that phenotypic resistance to antibiotics is very frequent in enterococcal isolates from the swine meat chain, but phenotypic tolerance to biocides is not common. On the other hand, the gene qacA/B was found for the first time in the species E. faecium, an indication of the necessity to adopt measures suitable to control the spread of biocide resistance determinants among enterococci.
authors.affiliation: Dipartimento di Biotecnologie, Università degli Studi di Verona, Strada Le Grazie 15, 37134, Verona, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Rizzotti
authors.affiliation: Dipartimento di Biotecnologie, Università degli Studi di Verona, Strada Le Grazie 15, 37134, Verona, Italy. Electronic address: franca.rossi@univr.it.
authors.forename: Franca
authors.initials: F
authors.lastname: Rossi
authors.affiliation: Dipartimento di Biotecnologie, Università degli Studi di Verona, Strada Le Grazie 15, 37134, Verona, Italy.
authors.forename: Sandra
authors.initials: S
authors.lastname: Torriani
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D004202:Disinfectants / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D013293:Enterococcus faecalis / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D016984:Enterococcus faecium / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D004917:Erythromycin / Q000494:pharmacology; D005798:Genes, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics; D008826:Microbial Sensitivity Tests; D000069466:Red Meat / Q000382:microbiology*; D012808:Sigma Factor / Q000235:genetics; D013552:Swine; D013752:Tetracycline / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004202:Disinfectants; C445688:EmeA protein, Enterococcus faecalis; C422481:Gsp65 protein, Enterococcus faecalis; D006360:Heat-Shock Proteins; D026901:Membrane Transport Proteins; C496836:SigV protein, Enterococcus faecalis; D012808:Sigma Factor; D004917:Erythromycin; D013752:Tetracycline
keywords: Biocide tolerance; Enterococci; Stress response genes; qac genes