Diversity of enterococcal species and characterization of high-level aminoglycoside resistant enterococci of samples of wastewater and surface water in Tunisia

Resumen

One hundred-fourteen samples of wastewater (n = 64) and surface-water (n = 50) were inoculated in Slanetz-Bartley agar plates supplemented or not with gentamicin (SB-Gen and SB plates, respectively) for enterococci recovery Enterococci were obtained from 75% of tested samples in SB media (72% in wastewater; 78% in surface-water), and 85 enterococcal isolates (one/positive-sample) were obtained Enterococcus faecium was the most prevalent species (63.5%), followed by Enterococcus faecalis (20%), Enterococcus hirae (9.4%), Enterococcus casseliflavus (4.7%), and Enterococcus gallinarum/ Enterococcus durans (2.4%) Antibiotic resistance detected among these enterococci was as follows [percentage/detected gene (number isolates)]: kanamycin [29%/ aph(3')-IIIa (n = 22)], streptomycin [8%/ ant(6)-Ia (n = 4)], erythromycin [44%/ erm(B) (n = 34)], tetracycline [18%/ tet(M) (n = 6)/ tet(M)- tet(L) (n = 9)], chloramphenicol [2%/ cat(A) (n = 1)], ciprofloxacin [7%] and trimethoprim-sulfamethoxazole [94%] High-level-gentamicin resistant (HLR-G) enterococci were recovered from 15 samples in SB-Gen or SB plates [12/64 samples of wastewater (19%) and 3/50 samples of surface-water (6%)]; HLR-G isolates were identified as E faecium (n = 7), E faecalis (n = 6), and E casseliflavus (n = 2) These HLR-G enterococci carried the aac(6')-Ie- aph(2″)-Ia and erm(B) genes, in addition to aph(3')-IIIa (n = 10), ant(6)-Ia (n = 9), tet(M) (n = 13), tet(L) (n = 8) and cat(A) genes (n = 2) Three HLR-G enterococci carried the esp virulence gene Sequence-types detected among HLR-G enterococci were as follows: E faecalis (ST480, ST314, ST202, ST55, and the new ones ST531 and ST532) and E faecium (ST327, ST12, ST296, and the new ones ST985 and ST986) Thirty-two different PFGE patterns were detected among 36 high-level-aminoglycoside-resistant enterococci recovered in water samples Diverse genetic lineages of HLR-G enterococci were detected in wastewater and surface-water in Tunisia Water can represent an important source for the dissemination of these antibiotic resistant microorganisms to other environments •E faecium was the most prevalent species, followed by E faecalis.•HLR-G enterococci were recovered in wastewater (19%) and surface-water (6%) samples.•Diverse genetic lineages of HLR-G enterococci were detected in water in Tunisia.•esp gene, putative marker of clinical enterococci, was detected in three isolates.•Wastewater and surface-water could contribute to the spreading of HLR-G enterococci © 2015 Elsevier B.V..