title: Characterization of antibiotic resistant enterococci isolated from untreated waters for human consumption in Portugal.
abstract: Untreated drinking water is frequently overlooked as a source of antibiotic resistance in developed countries. To gain further insight on this topic, we isolated the indicator bacteria Enterococcus spp. from water samples collected in wells, fountains and natural springs supplying different communities across Portugal, and characterized their antibiotic resistance profile with both phenotypic and genetic approaches. We found various rates of resistance to seven antibiotic families. Over 50% of the isolates were resistant to at least ciprofloxacin, tetracyclines or quinupristin-dalfopristin and 57% were multidrug resistant to ≥3 antibiotics from different families. Multiple enterococcal species (E. faecalis, E. faecium, E. hirae, E. casseliflavus and other Enterococcus spp) from different water samples harbored genes encoding resistance to tetracyclines, erythromycin or gentamicin [tet(M)-46%, tet(L)-14%, tet(S)-5%, erm(B)-22%, aac(6´)-Ie-aph(2″)-12%] and putative virulence factors [gel-28%, asa1-16%]. The present study positions untreated drinking water within the spectrum of ecological niches that may be reservoirs of or vehicles for antibiotic resistant enterococci/genes. These findings are worthy of attention as spread of antibiotic resistant enterococci to humans and animals through water ingestion cannot be dismissed.
authors.affiliation: CEBIMED, Faculdade de Ciências da Saúde, Universidade Fernando Pessoa, Rua Carlos da Maia 256, 4200-150 Porto, Portugal.
authors.forename: Ana S
authors.initials: AS
authors.lastname: Macedo
authors.forename: Ana R
authors.initials: AR
authors.lastname: Freitas
authors.forename: Cristina
authors.initials: C
authors.lastname: Abreu
authors.forename: Elisabete
authors.initials: E
authors.lastname: Machado
authors.forename: Luísa
authors.initials: L
authors.lastname: Peixe
authors.forename: João C
authors.initials: JC
authors.lastname: Sousa
authors.forename: Carla
authors.initials: C
authors.lastname: Novais
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D017931:DNA Primers; D004197:Disease Reservoirs; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D016983:Enterococcus / Q000145:classification / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D008826:Microbial Sensitivity Tests; D011174:Portugal; D037521:Virulence Factors / Q000235:genetics; D014871:Water Microbiology; D014881:Water Supply
chemical_list: D000900:Anti-Bacterial Agents; D017931:DNA Primers; D037521:Virulence Factors