Prevalence of and Risk Factors for Colonization by Methicillin-Resistant Staphylococcus aureus among Adults in Community Settings in Taiwan

Abstract

In order to determine the prevalence of methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) colonization among adults in community settings in Taiwan and identify its risk factors, we conducted the present study. For a 3-month period, we enrolled all adults who attended mandatory health examinations at three medical centers and signed the informed consent. Nasal swabs were taken for the isolation of S. aureus. For each MRSA isolate, we performed multilocus sequence typing, identification of the staphylococcal cassette chromosome mec, tests for the presence of the Panton-Valentine leukocidin gene, and tests for drug susceptibilities. Risk factors for MRSA colonization were determined. The results indicated that the MRSA colonization rate among adults in the community settings in Taiwan was 3.8% (119/3,098). Most MRSA isolates belonged to sequence type 59 (84.0%). Independent risk factors for MRSA colonization included the presence of household members less than 7 years old (P < 0.0001) and the use of antibiotics within the past year (P ‫؍‬ 0.0031). Smoking appeared to be protective against MRSA colonization (P < 0.0001).Before the late 1990s, nearly all methicillin (meticillin)-resistant Staphylococcus aureus (MRSA) infections occurred in patients with specific risk factors who were in health care facilities (31). However, the emergence of MRSA infections among previously healthy persons in community settings (without exposure to health care facilities) was noted thereafter (6, 31). Therefore, MRSA infections are now classified as health care-associated MRSA (HA-MRSA) infections and community-associated MRSA (CA-MRSA) infections (38).Strains responsible for CA-MRSA infections differ from those for HA-MRSA infections in several phenotypic and genetic features (1, 28). CA-MRSA strains carry type IV or V staphylococcal cassette chromosome mec (SCCmec) elements, are usually Panton-Valentine leukocidin (PVL) producing, and are not multidrug resistant; HA-MRSA strains carry type I, II, or III SCCmec elements, are usually not PVL producing, and are multidrug resistant (15,22,28).Initially, CA-MRSA infections were mostly reported in young children (36). However, as CA-MRSA infections became more common, infections were reported among people of all ages and contributed to the increase of communityassociated S. aureus infections with significance (25,29,36). MRSA colonization is an important risk factor for subsequent MRSA infection (30), so several studies in the United States have characterized the MRSA colonization rate in a community setting (13,16). These studies demonstrated that the nasal colonization rates among healthy children increased from In Taiwan, MRSA strains of sequence type 59 (ST59), determined by multilocus sequence typing (MLST) and carrying type IV or V SCCmec elements, were recently found to be the major strains of CA-MRSA (5, 7, 27). Other studies demonstrated that these CA-MRSA strains were responsible for the rapid increase in the number of CA-MRSA infections among children and adults ...

Factors Associated with Nasal Colonization of Methicillin-Resistant Staphylococcus aureus among Healthy Children in Taiwan

“…In the same study, the PFGE C/SCCmec IV/PVL Ϫ clone was responsible for only 8.8% of the clinical isolates. The discrepancy of clonal distributions in clinical and colonizing isolates was also identified in other studies (6,37). The finding suggested greater virulence of the clone positive for PVL than of its sister clone negative for PVL.…”

“…In contrast to the data from the meta-analysis, results from this study indicated a strikingly high incidence of MRSA carriage (7.8%) among healthy Taiwanese children from 2005 to 2008, with rates ranging from 6.2% to 9.5% in different geographic areas. The carriage rate in children reported here was also significantly higher than in the Taiwanese adult populations surveyed during the same period (3.8%; P Ͻ 0.0001) (37). This observation may suggest unique epidemiology for MRSA in Taiwanese children or, more likely, a universal increase in MRSA carriage in the past decade.…”

“…The carriage of MRSA with CA genotypes was significantly higher among children than among adults (25). Furthermore, living with young children was associated with increased risk of MRSA colonization in adults (37). When combined, these observations strongly suggested young children were the major reservoir of MRSA in the community and were the main population responsible for the accelerated transmission of CA-MRSA.…”

Longitudinal Analysis of Methicillin-Resistant and Methicillin-Susceptible Staphylococcus aureus Carriage in Healthy Adolescents

“…This finding was unexpected and can be misleading due to the relatively small number of MRSA carriers in the current study and the fact that the MRSA strains were frequently predominantly limited clones in a defined environment (21,22). Indeed, previous molecular epidemiology studies of CA-MRSA indicated that a prevalent clone, ST59, was circulating in Taiwan and accounted for Ͼ80% of MRSA carriage isolates in both pediatric and adult populations (7,9). The majority of nasal MRSA isolates in the current study were also of the ST59 clone (equivalent to spa type t437).…”

“…In Taiwan, MRSA has accounted for Ͼ50% of childhood CA infections since 2005 (8). Carriage of MRSA in the nose was identified in 7.8% and 3.7% of the pediatric and adult populations in Taiwan, respectively (7,9). The individuals with an increased risk of MRSA carriage included very young children (2 to 6 months old), those living in a crowded environment (i.e., with greater number of siblings, attending day care), adults with household members Ͻ7 years old, or those who received antibiotic treatment in the preceding year.…”