Multidrug-resistant enterococci in the hospital environment: detection of novel vancomycin-resistant E. faecium clone ST910.

Abstract

The role of the hospital environment as a reservoir of resistant bacteria in Tunisia has been poorly investigated; however, it could be responsible for the transmission of multidrug-resistant bacteria. The objective was to study the prevalence of Enterococcus in the environment of a Tunisian hospital and the antibiotic resistance phenotype/genotype in recovered isolates, with special reference to vancomycin resistance. A total of 300 samples were taken (March-June, 2013) and inoculated in Slanetz-Bartley agar plates supplemented or not supplemented with 8 µg/mL of vancomycin. Antibiotic resistance genes were tested by polymerase chain reaction (PCR). The clonal relatedness of the vanA isolates was assessed using pulsed-field gel electrophoresis (PFGE) and multilocus sequence testing (MLST). Enterococci were recovered in 33.3% of tested samples inoculated in SB medium. E faecium was the most prevalent species, followed by E. faecalis and E. casseliflavus. Antimicrobial resistance genes detected were as follows (number of isolates): erm(B) (71), tet(M) (18), aph(3')-IIIa (27), ant(6)-Ia (15), cat(A) (4), and van(C2) (6). Vancomycin-resistant-enterococci (VRE) were recovered from 14 samples (4.7%), when tested in SB-VAN. The 14 VRE (one per positive sample) were identified as E. faecium and contained the van(A),erm(B), tet(M), ant(6)-Ia, and aph(3')-IIIa genes. Thirteen of the VRE strains were ascribed by PFGE and MLST to a novel clone (new ST910), and only one VRE strain was typed as ST80 included in CC17. The emergence and spread of new clones of VRE, especially in the hospital environment in this country, could become particularly problematic.