Distribution of Staphylococcal Cassette Chromosome mec Types and Correlation with Comorbidity and Infection Type in Patients with MRSA Bacteremia

Jiun-Ling Wang,Yee-Chun Chen,Shey-Ying Chen,Jann-Tay Wang,Shan-Chwen Chang,Frank R Deleo

doi:10.1371/journal.pone.0009489

Abstract

BackgroundMolecular epidemiological definitions that are based on staphylococcal cassette chromosome mec (SCCmec) typing and phylogenetic analysis of methicillin-resistant Staphylococcus aureus (MRSA) isolates are considered a reliable way to distinguish between healthcare-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA). However, there is little information regarding the clinical features and outcomes of bacteremia patients with MRSA carrying different SCCmec types.MethodsFrom January 1 through December 31, 2006, we recorded the demographic data and outcomes of 159 consecutive adult MRSA bacteremia patients from whom isolates for SCCmec analysis were collected. All participants were patients at a tertiary care center in Taiwan.Principal FindingsThe following SCCmec types were identified in MRSA isolates: 30 SCCmec II (18.9%), 87 SCCmec III (54.7%), 22 SCCmec IV (13.8%), and 20 SCCmec V (12.6%). The time from admission to the first MRSA-positive blood culture for patients infected with isolates with the SCCmec III element (mean/median, 50.7/26 days) was significantly longer than for patients infected with isolates carrying SCCmec IV or V (mean/median, 6.7/3 days for SCCmec IV; 11.1/10.5 days for SCCmec V) (P<0.05). In univariate analysis, community onset, soft tissue infection, and deep-seated infection were predictors for SCCmec IV/V. In multivariate analysis, length of stay before index culture, diabetes mellitus, and being bedridden were independent risk factors associated with SCCmec II/III.ConclusionsThese findings are in agreement with previous studies of the genetic characteristics of CA-MRSA. MRSA bacteremia with SCCmec II/III isolates occurred more among patients with serious comorbidities and prolonged hospitalization. Community onset, skin and soft tissue infection, and deep-seated infection best predicted SCCmec IV/V MRSA bacteremia.

Highlights

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has been isolated mainly from skin or soft tissue infections [1,2], severe invasive infections caused by CAMRSA strains, such as pyomyositis, osteomyelitis, necrotizing fasciitis, severe pneumonia, and sepsis, have been reported [3,4,5,6,7]
In their study of community-associated MRSA (CA-MRSA) strains defined by antibiogram phenotype, Popovich et al concluded that demographic data and risk factors could not reliably distinguish patients infected with CA-MRSA strains from those infected with healthcare-associated MRSA (HA-MRSA) strains [9]
Risk Factors, and Clinical Features During the study period, there were 159 consecutive adult patients with MRSA bacteremia from whom isolates were collected for microbiological analysis (101 men, 63.5%; 58 women, 36.5%)

Summary

Introduction

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has been isolated mainly from skin or soft tissue infections [1,2], severe invasive infections caused by CAMRSA strains, such as pyomyositis, osteomyelitis, necrotizing fasciitis, severe pneumonia, and sepsis, have been reported [3,4,5,6,7]. Molecular epidemiological definitions, based on staphylococcal cassette chromosome mec (SCCmec) typing and phylogenetic analysis of MRSA isolates, are considered the most reliable way to distinguish between HA-MRSA and CA-MRSA [17]. In a study of MRSA bacteremia by Seybold et al, CA-MRSA strains (as defined by PFGE) were associated with injection drug use and with skin and soft tissue infection [8]. Molecular epidemiological definitions that are based on staphylococcal cassette chromosome mec (SCCmec) typing and phylogenetic analysis of methicillin-resistant Staphylococcus aureus (MRSA) isolates are considered a reliable way to distinguish between healthcare-associated MRSA (HA-MRSA) and community-associated MRSA (CA-MRSA). There is little information regarding the clinical features and outcomes of bacteremia patients with MRSA carrying different SCCmec types

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Conclusion