Abstract
Nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA) plays an important role in the epidemiology and pathogenesis of disease. Situations of close-quarter contact in groups are generally regarded as a risk factor for community-acquired MRSA strains due to transmission via fomites and person-to-person contact. With these criteria for risk, homeless individuals using shelter facilities, including showers and toilets, should be considered high risk for colonization and infection. The aim of this study was to determine the prevalence of nasal colonization of MRSA in a homeless population compared to established rates of colonization within the public and a control group of subjects from a neighboring medical school campus, and to analyze phylogenetic diversity among the MRSA strains. Nasal samples were taken from the study population of 332 adult participants and analyzed. In addition, participants were surveyed about various lifestyle factors in order to elucidate potential patterns of behavior associated with MRSA colonization. Homeless and control groups both had higher prevalence of MRSA (9.8 and 10.6%, respectively), when compared to the general population reported by previous studies (1.8%). However, the control group had a similar MRSA rate compared to health-care workers (4.6%), while the homeless population had an increased prevalence. Risk factors identified in this study included male gender, age over 50 years, and use of antibiotics within the past 3 months. Phylogenetic relationships between nine of the positive samples from the homeless population were analyzed, showing eight of the nine samples had a high degree of relatedness between the spaA genes of the MRSA strains. This indicates that the same MRSA strain might be transmitted from person-to-person among homeless population. These findings increase our understanding of key differences in MRSA characteristics within homeless populations, as well as risks for MRSA associated with being homeless, such as age and gender, which may then be a useful tool in guiding more effective prevention, treatment, and health care for homeless individuals.
Highlights
Nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA) plays an important role in the epidemiology and pathogenesis of disease [1]
Using a total of 285 samples from the homeless population and the 47 samples from the control population, it was determined by chi-squared analysis that both the homeless population (p < 0.001) and the control group (p < 0.01) had an increased prevalence of MRSA colonization compared to the general population (Table 1) as reported by Dulon et al in a 2014 study [23]
Given the crowded conditions of shelters and lifestyle factors associated with homelessness, homeless individuals appear to be at a higher risk for MRSA colonization than the general population (Table 1)
Summary
Nasal colonization of methicillin-resistant Staphylococcus aureus (MRSA) plays an important role in the epidemiology and pathogenesis of disease [1]. MRSA is a group of virulent strains of S. aureus that are resistant to treatment with beta-lactam antibiotic medicines. These strains were first reported in the United Kingdom in 1961 and appeared in the United States in 1981 [2, 3]. It is estimated that 53 million people worldwide and 2.5 million Americans are carriers of MRSA [3], meaning MRSA colonizes the natural microbiota of these individuals. MRSA colonization is considered a risk for MRSA infection [4], since carrying the bacteria increases risk of infection as well as subsequent symptoms of infection, if predisposing events such as an open wound or immunosuppression exist. While the clinical presentation of MRSA is identical to that of methicillin-sensitive S. aureus, drug resistance may present additional challenges in treatment and management [2, 3]
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