Epidemiological profile of linezolid-resistant coagulase-negative staphylococci.
BACKGROUND
Surveillance studies have shown that <0.1% of coagulase-negative staphylococci are linezolid resistant; however, at our institution, 4% of such organisms were found to be resistant. We investigated the risk factors for and the epidemiological profile of linezolid-resistant coagulase-negative staphylococci.


METHODS
Susceptibility testing and pulsed-field gel electrophoresis were performed to analyze the genetic relatedness of both linezolid-resistant and linezolid-susceptible isolates. Clinical data were retrieved from medical records, and a case-case-control study was performed to identify unique risk factors for linezolid resistance.


RESULTS
Isolates recovered from 25 patients with linezolid-resistant coagulase-negative staphylococci were examined; all but 1 of the isolates were identified as Staphylococcus epidermidis, and all but 1 had a minimum inhibitory concentration of linezolid of >256 microg/mL. Pulsed-field gel electrophoresis showed that 21 (84%) of 25 linezolid-resistant isolates exhibited genetic relatedness, whereas linezolid-susceptible isolates were of diverse clones. Unique, independent predictors of linezolid resistance included receipt of linezolid in the 3 months preceding isolation of the coagulase-negative staphylococci (odds ratio, 20.6; 95% confidence interval, 5.8-73.0).


CONCLUSIONS
Linezolid-resistant coagulase-negative staphylococci have emerged at our institution and are predominately of a single clone. We believe that the most likely scenario to explain this emergence is that person-to-person spread of linezolid-resistant coagulase-negative staphylococci led to establishment of skin colonization with the strain. Subsequent use of linezolid was followed by selection of the linezolid-resistant strain, which then became the dominant skin flora. The potential for a parallel scenario involving clonal dissemination followed by selection of linezolid-resistant methicillin-resistant Staphylococcus aureus is a real possibility.
Potoski
Brian A
BA
Department of Pharmacy and Therapeutics, University of Pittsburgh Medical Center, Pittsburgh, PA, USA.
Adams
Jennifer
J
Clarke
Lloyd
L
Shutt
Kathleen
K
Linden
Peter K
PK
Baxter
Carla
C
Pasculle
A William
AW
Capitano
Blair
B
Peleg
Anton Y
AY
Szabo
Dora
D
Paterson
David L
DL
D000081:Acetamides / Q000627:therapeutic use*; D000890:Anti-Infective Agents / Q000627:therapeutic use*; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D006801:Humans; D000069349:Linezolid; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D023303:Oxazolidinones / Q000627:therapeutic use*; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology*; D013212:Staphylococcus epidermidis
D000081:Acetamides; D000890:Anti-Infective Agents; D023303:Oxazolidinones; D000069349:Linezolid