title: The marine environment as a reservoir of enterococci carrying resistance and virulence genes strongly associated with clinical strains.
abstract: To gain insights into the relationships and the genetic exchange among environmental and clinical enterococci, 59 strains (29 from marine aquaculture sites and 30 from clinical settings) resistant to tetracycline, erythromycin, ampicillin and/or gentamicin were analysed for the antibiotic resistance tet(M), tet(L), tet(O), erm(A), erm(B), mef blaZ, aac(6')-Ie aph(2″)-Ia and virulence gelE, cylB, efaA and esp genes, and for the copper resistance gene tcrB. Antibiotic resistance and virulence genes were detected more frequently in clinical than in environmental enterococci; the opposite was true for copper resistance. Conjugation experiments demonstrated the transfer of antibiotic resistance genes from marine to clinical enterococci in interspecific mating and the uncommon joint transfer of tet(L) and erm(B). Enterobacterial repetitive intergenic consensus polymerase chain reaction typing evidenced a cluster (90% similarity) encompassing strains carrying multiple antibiotic resistance genes from both sets; the others marine isolates exhibited polyclonality and bore tcrB. Our results demonstrate that antibiotic-resistant marine enterococci bear antibiotic resistance genes transferable to humans and suggest that copper resistance, not observed among clinical strains, may be useful for survival in the environment, whereas virulence genes likely confer no advantage to enterococcal populations adapted to a lifestyle outside the host.
authors.affiliation: Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Di Cesare
authors.forename: Sonia
authors.initials: S
authors.lastname: Pasquaroli
authors.forename: Carla
authors.initials: C
authors.lastname: Vignaroli
authors.forename: Paolo
authors.initials: P
authors.lastname: Paroncini
authors.forename: Gian Marco
authors.initials: GM
authors.lastname: Luna
authors.forename: Esther
authors.initials: E
authors.lastname: Manso
authors.forename: Francesca
authors.initials: F
authors.lastname: Biavasco
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004197:Disease Reservoirs / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D016983:Enterococcus / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D016908:Gram-Positive Bacterial Infections / Q000382:microbiology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010802:Phylogeny; D012623:Seawater / Q000382:microbiology*; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D037521:Virulence Factors