In vitro activity of 19 antimicrobial agents against enterococci from healthy subjects and hospitalized patients and use of an ace gene probe from Enterococcus faecalis for species identification

We tested 165 enterococcal isolates, biased toward vancomycin resistant (VR ) isolates, collected during recent years from fecal samples of healthy sub jects and clinical specimens of hospitalized patients (mostly from United S tates and some from Europe) for susceptibility to 19 antimicrobials, Nosoco mial isolates, whether VR or not, were more often highly resistant to amino glycosides and clindamycin than fecal isolates from healthy community volun teers and more often resistant to erythromycin, chloramphenicol, trimethopr im, levofloxacin and, for E, faecium, ampicillin (93 vs, 0%). Resistance ra tes were similar between nosocomial and community-fecal isolates for minocy cline, rifampin and quinupristin-dalfopristin (Q-D), None of the 165 entero cocci tested hybridized with aph(2 ' ')-Ic and aph(2 ' ')-Id probes for rec ently described gentamicin resistance genes and 37 of the 39 isolates with high level resistance (HLR) to gentamicin hybridized with an intragenic aac (6 ' )aph(2 ' ') probe. Of the two newer drugs tested, daptomycin MIC(90)s were 0.25 mug/mL for E. faecalis and 1 mug/mL for E. faecium, regardless of their vancomycin resistance level or source. For Q-D, none of 28 E. faeciu m from community based healthy subjects in the USA and 7 of 66 E, faecium f rom hospitalized patients in the United States were resistant. Among these 7 Q-D-r United States isolates and 7 Q-D-r isolates from Europe (MICs of Q- D of 4-8 mug/mL), none hybridized with vat(D) (formerly satA) and vat(E) (f ormerly satG) DNA probes, indicating the involvement of other mechanism/s o f resistance in these isolates. We also demonstrated that an intragenic pro be of the gene ace from E. faecalis showed specific hybridizations to all E . faecalis isolates, suggesting the usefulness of this gene for identificat ion of this species.