Risk factors associated with methicillin resistance among Staphylococcus aureus infections in veterans.
BACKGROUND
Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging concern in infectious disease practice. Although MRSA infections occur in a wide variety of anatomic sites, the majority of studies considering the risk factors for methicillin resistance among S. aureus infections have focused on MRSA bacteremia.


OBJECTIVE
To describe risk factors associated with methicillin resistance among S. aureus infections at different anatomic sites.


METHODS
We collected information on the demographic and clinical characteristics of patients examined at the Atlanta Veterans Affairs Medical Center with S. aureus infections during the period from June 2007 through May 2008. We used multivariate logistic regression to describe factors significantly associated with methicillin resistance.


RESULTS
There were 568 cases of S. aureus infection among 528 patients. We identified 352 cases (62%) of MRSA infection and 216 cases (38%) of methicillin-sensitive S. aureus infection. The adjusted odds of methicillin resistance were higher among infections that occurred among patients who had a prior history of MRSA infection (odds ratio [OR], 3.9 [95% confidence interval {CI}, 2.3-6.4]) or resided in a long-term care facility during the past 12 months (OR, 2.0 [95% CI, 1.0-4.0]) but were lower for infections that occurred among patients who had undergone a biopsy procedure during the past 12 months (OR, 0.7 [95% CI, 0.6-0.9]). Most cases of infection were community-onset infections (523 [92%] of 568 cases), and about one-half (278 [49%]) were not healthcare associated.


CONCLUSIONS
Compared with previous studies of methicillin resistance among patients with S. aureus bacteremia, we found similar factors to be associated with methicillin resistance among S. aureus isolates recovered from more diverse anatomic sites of infection. Of note, nearly one-half of our cases of MRSA infection were not healthcare associated.
McCarthy
Natalie L
NL
Rollins School of Public Health, Emory University, Atlanta, Georgia, USA.
Sullivan
Patrick S
PS
Gaynes
Robert
R
Rimland
David
D
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents; D001900:Boston; D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology; D005260:Female; D006787:Hospitals, Veterans; D006801:Humans; D008297:Male; D016106:Methicillin Resistance; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D008875:Middle Aged; D009666:Nose / Q000382:microbiology; D009960:Oropharynx / Q000382:microbiology; D015995:Prevalence; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology; D014728:Veterans; D055815:Young Adult
D000900:Anti-Bacterial Agents