Prevalence of methicillin resistant Staphylococcus aureus in upper extremity soft tissue infections at Jackson Memorial Hospital, Miami-Dade County, Florida.

PURPOSE: Methicillin resistant Staphylococcus aureus (MRSA) has been a hospital based problem since first being reported in the 1960s. Recent increases in outpatient MRSA infections suggest that there may be increased incidence of MRSA in upper extremity soft tissue infections (UESTIs). The aim of this study is to describe the current microbial flora responsible for UESTIs at an urban, tertiary care, teaching hospital.

METHODS: A retrospective chart review was performed of all orthopaedic consultations for UESTIs from June 2006 to December 2007. The only exclusion criterion was a diagnosis of osteomyelitis. Logistic regression was used to describe the association between demographic and clinical characteristics identified on univariate analysis, and a MRSA positive culture. Odds ratios and confidence intervals are reported.

RESULTS: There were 432 orthopaedic consultations for UESTIs. Twelve cases of osteomyelitis were excluded per protocol. Therefore, 420 patients comprised our study population, ranging in age from 4 months to 95 years, (mean: 40 years), with 327 (77.9%) men and 93 (22.1%) women. Wound cultures were available in 335 of 420 patients (79.8%). Positive cultures were found in 292 patients with a 53.4% MRSA rate (156 of 292). Methicillin sensitive Staphylococcus aureus was the second most prevalent microbe, found in 73 of 292 patients (25.0%). All MRSA isolates were susceptible to gentamicin and linezolid, and 98% or more were sensitive to vancomycin, rifampin, and trimethoprim-sulfamethoxazole combination. Univariate analyses and logistic regression identified infection location proximal to the wrist (Odds Ratio = 1.81, 95% Confidence Interval = 1.06-3.09, p<0.03) and diagnosis of abscess or felon (Odds Ratio = 3.22, 95% Confidence Interval = 1.84-5.63, p<0.001) as significantly associated with a MRSA positive culture.

CONCLUSIONS: This is the largest study examining the prevalence of microbial flora in UESTIs. We found that MRSA has become the most common microbe in UESTIs comprising 53.4%, consistent with current trends at other urban medical centers.