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

Abstract

Methicillin-resistant Staphylococcus aureus (MRSA) has been identified as a major cause of communityassociated (CA) S. aureus infections in the past decade. The main reservoir in the community for MRSA and the factors contributing to its worldwide spread remain poorly defined. Between July 2005 and June 2008, a total of 6,057 healthy children 2 to 60 months of age were screened for carriage of S. aureus and Streptococcus pneumoniae in Taiwan. The prevalence and epidemiological factors influencing MRSA carriage were determined. MRSA strains were tested for antimicrobial susceptibility and underwent molecular characterization. The overall prevalences of MRSA and S. aureus carriage were 7.8% and 23.2%, respectively. A majority (88%) of MRSA isolates belonged to a common Asian-Pacific CA-MRSA lineage, multilocus sequence type 59, and were resistant to multiple non-beta-lactam antibiotics. The carriage rate of MRSA was higher among subjects 2 to 6 months old (P < 0.0001), residing in northern Taiwan (P ‫؍‬ 0.0003), and enrolled later in the study (P < 0.0001). MRSA colonization was associated with the number of children in the family (adjusted odds ratio [aOR], 1.114; 95% confidence interval [CI], 1.002 to 1.240; P ‫؍‬ 0.0463) and day care attendance (aOR, 1.530; 95% CI, 1.201 to 1.949; P ‫؍‬ 0.0006). Breast feeding (P < 0.0001) and colonization with S. pneumoniae (P ‫؍‬ 0.0170) were protective against MRSA colonization. We concluded that epidemic CA-MRSA strains increasingly colonized Taiwanese children between 2005 and 2008. The carriage rate varied significantly across different demographical features. Crowding was an independent environmental risk factor that might accelerate CA-MRSA transmission in the community.

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).…”

“…The higher incidence of S. aureus colonization in males than in females has been identified in several studies, including a population-based study involving 9,622 persons aged Ն1 year old in the United States (28). Intriguingly, we did not recognize such an association in the surveillance study in Taiwanese children aged 2 to 60 months (7). The female sex hormones, particularly estrogen, which have a potent immune-modulating effect, may modify the host innate immunity and have an impact on S. aureus colonization.…”

“…In 1 large-scale surveillance study, we investigated the epidemiological factors associated with MRSA colonization among 6,057 healthy children (7). Young children (i.e., age 2 to 6 months old) and children who spent much time in a crowded environment (i.e., with a greater number of children in the family, or attending day care) had a significantly higher risk of MRSA colonization.…”

“…MRSA has been the dominant cause of community-associated (CA) skin and soft tissue infections in many regions of the world (6,7). The long-term carriage pattern of CA-MRSA in healthy hosts is less commonly reported and may be distinct from currently known patterns, which are mostly derived from observations on MSSA.…”

“…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.…”