Abstract
We tested 165 enterococcal isolates, biased toward vancomycin resistant (VR) isolates, collected during recent years from fecal samples of healthy subjects and clinical specimens of hospitalized patients
(mostly from United States and some from Europe) for susceptibility to 19 antimicrobials. Nosocomial isolates, whether VR or not, were more often highly resistant to aminoglycosides and clindamycin than
fecal isolates from healthy community volunteers and more often resistant to erythromycin, chloramphenicol, trimethoprim, levofloxacin and, for
E. faecium
, ampicillin (93 vs. 0%). Resistance rates
were similar between nosocomial and community-fecal isolates for minocycline, rifampin and quinupristin-dalfopristin (Q-D). None of the 165 enterococci tested hybridized with
aph(2″)-Ic
and
aph(2″)-Id
probes for recently 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 µg/mL for
E. faecalis
and 1 µg/mL for
E. faecium
, regardless of their vancomycin resistance level or
source. For Q-D, none of 28
E. faecium
from community based healthy subjects in the USA and 7 of 66
E. faecium
from 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 µg/mL), none hybridized with
vat
(D) (formerly
satA
) and
vat
(E) (formerly
satG
) DNA probes, indicating the involvement of other mechanism/s of resistance in these isolates. We also demonstrated that an intragenic probe of the gene
ace
from
E. faecalis
showed
specific hybridizations to all
E. faecalis
isolates, suggesting the usefulness of this gene for identification of this species.