Contrasting Pediatric and Adult Methicillin-resistantStaphylococcus aureusIsolates

Michael Z David,Susan E Crawford,Daniel C Kim,Susan Boyle-Vavra,Robert S Daum,Mark A Hostetler

doi:10.3201/eid1204.050960

Abstract

We performed a prospective study of all inpatient and outpatient methicillin-resistant Staphylococcus aureus (MRSA) isolates identified at the University of Chicago Hospitals from November 2003 through November 2004. Differences in resistance to non-beta-lactam antimicrobial drugs were determined after stratification of the 578 MRSA isolates into 4 groups by patient age (pediatric vs. adult) and onset location (community vs. hospital). Non-beta-lactam resistance was significantly greater among the 288 adult than the 177 pediatric community-associated isolates for erythromycin (93.2 vs. 87.0%, p = 0.03), clindamycin (51.8 vs. 7.3%, p<0.001), ciprofloxacin (62.1 vs. 10.7%, p<0.001), gentamicin (11.1 vs. 1.1%, p<0.001), and tetracycline (19.9 vs. 6.4%, p<0.001). In contrast, hospital-associated MRSA isolates from children and adults had similar rates of non-beta-lactam antimicrobial drug resistance. In our region, clindamycin is an appropriate empiric therapy of community-associated MRSA infection in children but should be used with caution in adults.

Highlights

The definition of CA-methicillin-resistant Staphylococcus aureus (MRSA) has not been standardized
Of the adult MRSA isolates, 27.9% were cultured from outpatients; of the pediatric MRSA isolates, 57.2% were cultured from outpatients
When community association or onset was defined by using the temporal criterion of procuring isolates

Summary

Introduction

The definition of CA-MRSA has not been standardized. No single definition would likely suffice for all purposes. We previously noted that CA-MRSA isolates often lacked resistance to multiple non–β-lactam antimicrobial drugs when compared with HA-MRSA strains [5,6]. This phenomenon has been documented in adults [4,7] and children [8,9,10]. Few data exist that compare antimicrobial drug resistance profiles of adult and pediatric MRSA infection isolates stratified by site of onset (hospital vs community). Using the temporal definition of CA-MRSA, we examined the hypothesis that these 2 groups may be infected by MRSA strains with different rates of resistance to non–β-lactam antimicrobial drugs when the isolates had onset in the community.

Methods

Results

Conclusion