The epidemiology of Staphylococcus aureus carriage in patients attending inner city sexually transmitted infections and community clinics in Calgary, Canada

PLoS One. 2017 May 25;12(5):e0178557. doi: 10.1371/journal.pone.0178557. eCollection 2017.


Background: Although 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.

Methods: We 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.

Results: The 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.

Conclusion: There 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.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Canada
  • Community-Acquired Infections / microbiology*
  • Cross-Sectional Studies
  • Female
  • Humans
  • Male
  • Methicillin Resistance / genetics
  • Methicillin-Resistant Staphylococcus aureus / genetics
  • Methicillin-Resistant Staphylococcus aureus / pathogenicity
  • Microbial Sensitivity Tests / methods
  • Middle Aged
  • Molecular Epidemiology / methods
  • Molecular Typing
  • Sexually Transmitted Diseases / embryology*
  • Sexually Transmitted Diseases / microbiology*
  • Staphylococcal Infections / epidemiology*
  • Staphylococcal Infections / microbiology*
  • Staphylococcus aureus / genetics*
  • Staphylococcus aureus / pathogenicity
  • Virulence Factors / genetics
  • Young Adult


  • Virulence Factors

Grant support

This work received support from the University of Calgary Multipurpose Research and Education Fund, Grant number 753315. The recipient of the grant is JC.