Epidemiology of and Risk Factors for Methicillin Resistance in Community-acquired and Nosocomial Staphylococcus aureus Bacteremia

Kim, Ui Seok; Bang, Ji Hwan; Kim, Hong Bin; Park, Sang Won; Oh, Myoung Don; Song, Yeong Wook; Kim, Cheol Ho; Kim, Eui Chong; Choe, Kang Won

Abstract

BACKGROUND: Strains of methicillin-resistant Staphylococcus aureus (MRSA) have emerged as important pathogens affecting primarily hospitalized patients. However, some investigators reported an increase in the frequency of community-acquired MRSA infections among persons who did not appear to have any of the recognized risk factors associated with nosocomial acquisition of MRSA. We designed this study to assess the proportion of MRSA in S. aureus bacteremia in the community and risk factors for MRSA bacteremia.
METHODS
We reviewed the medical records of 334 cases during 1991~1992 and 1996~1997 and 93 cases in the emergency room of the Seoul National University Hospital during 1993~1995, in which S. aureus was isolated from blood samples. We retrospectively analyzed 210 cases (154 and 56 cases, respectively), which satisfied the definition of clinically significant bacteremia and of which medical records were available.
RESULTS
Of 154 bacteremia cases reviewed, 32 (20.8%) were community-acquired and 122 (79.2%) were nosocomial during 1991~1992 and 1996~1997. MRSA occupied 18.8% (6 of 32) in community- acquired S. aureus bacteremia and 44.3% (54 of 122) in our hospital cases. We could not find a statistically significant increase in the rate of methicillin resistance in the community and our hospital. All of 15 cases classified as community-acquired MRSA bacteremia during 1991~1997 had more than one predisposing risk factor for MRSA infection. Nosocomial MRSA bacteremia were more frequently observed among the patients treated in the intensive care unit. (32.4% vs 10.2%, P=0.001).
CONCLUSION
MRSA bacteremia occupied 18.8% of community-acquired S. aureus bacteremia. All cases with community-acquired MRSA bacteremia had more than one predisposing risk factor for MRSA infection. We did not observe a statistically significant increase in the proportion of MRSA bacteremia in S. aureus bacteremia.