Abstract
BackgroundAlthough the nares represent the most common carriage site for traditional hospital-associated strains of Staphylococcus aureus (SA), the predominant site of carriage of SA in the community is less certain.MethodsWe conducted a cross-sectional study in 285 patients attending sexually transmitted diseases and inner-city clinics to evaluate the prevalence, body site colonisation and risk factors associated with carriage of methicillin susceptible SA (MSSA). All isolates were characterized by pulsed field gel electrophoresis, staphylococcal cassette chromosome mec, staphylococcal protein A and multilocus sequence typing.ResultsThe prevalence of colonisation with SA was 57.5% (164/285); 162 (56.8%) participants were colonized with MSSA, and 4 (1.4%) with methicillin-resistant SA (MRSA), 2 of them were co-colonised with both MRSA and MSSA. The most common sites of colonisation were the throat (73.1%), nares (65.2%) and interdigital web spaces of the hand (21.3%). Three out of 4 MRSA isolates were USA300-MRSA strains. Twelve MSSA isolates were closely related to the USA300 CA-MRSA. We identified sexual behaviours such as having more than 6 heterosexual sexual partners in the last 6 months and trimming pubic hair to be independently associated with MSSA colonisation, and more specifically practicing oral sex as a risk factor for throat colonisation.ConclusionThere is a high prevalence of MSSA carriage in this population, with a low prevalence of MRSA. The throat was the most common site of carriage and sexual behaviours were found to be risk factors for MSSA colonisation. Close strain relatedness of MSSA and USA300-MRSA isolates suggests either gain or loss of the SCCmec element, respectively.
Highlights
The prevalence of colonisation with Staphylococcus aureus (SA) was 57.5% (164/285); 162 (56.8%) participants were colonized with methicillin susceptible SA (MSSA), and 4 (1.4%) with methicillin-resistant SA (MRSA), 2 of them were co-colonised with both MRSA and MSSA
Prevalence and risk factors for Staphylococcus aureus carriage in inner city clinics in Calgary closely related to the USA300 Community-acquired strains of methicillin-resistant Staphylococcus aureus (CA-MRSA)
We identified sexual behaviours such as having more than 6 heterosexual sexual partners in the last 6 months and trimming pubic hair to be independently associated with MSSA colonisation, and practicing oral sex as a risk factor for throat colonisation
Summary
Community-acquired strains of methicillin-resistant Staphylococcus aureus (CA-MRSA) have been recognized over the last decade with increasing frequency among patients in ambulatory and hospital settings throughout Canada [1] and the United States. [2] CA-MRSA infections are defined by the lack of exposure to the hospital setting and phenotypically by the characterization of the SCCmec genotype, pulsed field electrophoresis pattern, multilocus sequence typing and the presence of Panton-Valentine leukocidin (PVL) toxin genes. [3] The dominant CA-MRSA clone in Canada has been USA-300 since it was first identified in 2004. [4] CA-MRSA has been associated with severe infections in vulnerable populations, often associated with illicit drug use, homelessness and incarceration. [5,6] The predominant site of carriage of CA-MRSA strains is unclear. Lee and colleges identified having a sexual partner with a skin infection as a risk factor for MRSA colonisation amongst HIV-positive patients [10] Diep and colleagues [11], on a population-based survey amongst men who have sex with men (MSM) in Boston and San Francisco, found a higher prevalence of CA-MRSA infections amongst MSM and up to 27% of them were infections in the genital area, suggesting close contact as risk factor for CA-MRSA infections This observation is supported by the Cook et al’s [12] findings of CA-MRSA colonisation followed by infections in the pelvic area amongst 3 heterosexual couples. The nares represent the most common carriage site for traditional hospital-associated strains of Staphylococcus aureus (SA), the predominant site of carriage of SA in the community is less certain
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