Isolation and identification of enterococci from seawater samples: Assessment of their resistance to antibiotics and heavy metals

Abstract

A hundred Enterococcus strains were isolated from seawater samples collected from coastal areas of Istanbul. Isolates were identified to the species level using standard biochemical tests specified by Facklam and Collins. The species distribution was as follows Enterococcus faecalis (96%), Enterococcus gallinarum (3%) and Enterococcus solitarius (1%). The resistance of bacteria to both heavy metals (zinc [Zn], iron [Fe], cadmium [Cd], chrome [Cr], cobalt [Co]) and antibiotics (ampicillin 10 mu g [AP], penicillin G 10 Units [PG], gentamycin 10 mu g [GM], streptomycin 10 mu g [S], chloramphenicol 10 mu g [C], erythromycin 15 mu g [E], kanamycin 30 mu g [K], amikacin 30 mu g [AK], nalidixic acid 30 mu g [NA], and vancomycin 30 mu g [VA]) was evaluated. None of the strains was resistant to VA. It was found that among the 100 isolates, those that exhibit resistance to antibiotics, particularly NA, S and K, were also resistant all the heavy metals tested. To our knowledge this is the first report focusing on determination of resistance of environmental enterococci found in Istanbul against heavy metals and antibiotics. Thus, combined expressions of antibiotic and heavy metal resistance may help to reinforce ecological and epidemiological studies and to determine the role of these strains in antibiotic and heavy metal resistance dissemination.