Affiliation:
1. Focus Bio-Inova, Inc., Herndon, Virginia
2. Pfizer Inc., Pfizer Global Pharmaceuticals, New York, New York
Abstract
ABSTRACT
Since the approval of linezolid in 2000, sporadic reports of resistance have been given and a greater understanding of the underlying mechanisms of resistance has been gained. However, since these developments, an updated status of the in vitro activity of linezolid against gram-positive organisms from the United States has not been reported. The LEADER 2004 surveillance initiative was undertaken to obtain current and representative data on the activity of linezolid against key species, including isolates with significant resistance phenotypes. Organisms were isolated during 2004 and included 2,872
Staphylococcus aureus
, 496 coagulase-negative staphylococcus (CNS), 428
Enterococcus faecalis
, 196
Enterococcus faecium
, and 422
Streptococcus pneumoniae
isolates. All
S. aureus
isolates (54.2% oxacillin resistant) were susceptible to linezolid (MIC
90
= 2 μg/ml); MIC distributions were consistent, regardless of oxacillin or multidrug resistance status. For CNS, one nonsusceptible isolate was encountered (
Staphylococcus epidermidis
; MIC = 32 μg/ml), but overall, the MIC
90
(1 μg/ml) was lower than that obtained with
S. aureus
. For
E. faecalis
and
E. faecium
, 99.5% and 96.4% of isolates, respectively, were linezolid susceptible. Both species had an MIC
90
of 2 μg/ml, and MIC distributions did not vary with the vancomycin susceptibility status of the populations analyzed. Linezolid nonsusceptibility was not encountered among the
S. pneumoniae
isolates. These findings indicate that linezolid nonsusceptibility has remained rare among staphylococci and uncommon and sporadic among enterococci. Nonetheless, careful and ongoing monitoring of the in vitro effectiveness of linezolid will be needed so that any changes to the current status may be detected as soon as possible.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Pharmacology (medical),Pharmacology
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