Genomic Epidemiology of Invasive Methicillin-Resistant Staphylococcus aureus Infections Among Hospitalized Individuals in Ontario, Canada Academic Article uri icon

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  • Abstract Background Prevention and control of methicillin-resistant Staphylococcus aureus (MRSA) infections remain challenging. In-depth surveillance integrating patient and isolate data can provide evidence to better inform infection control and public health practice. Methods We analyzed MRSA cases diagnosed in 2010 (n = 212) and 2016 (n = 214) by hospitals in Ontario, Canada. Case-level clinical and demographic data were integrated with isolate characteristics, including antimicrobial resistance (AMR), classic genotyping, and whole-genome sequencing results. Results Community-associated MRSA (epidemiologically defined) increased significantly from 23.6% in 2010 to 43.0% in 2016 (P < .001). The MRSA population structure changed over time, with a 1.5× increase in clonal complex (CC)8 strains and a concomitant decrease in CC5. The clonal shift was reflected in AMR patterns, with a decrease in erythromycin (86.7% to 78.4%, P = .036) and clindamycin resistance (84.3% to 47.9%, P < .001) and a >2-fold increase in fusidic acid resistance (9.0% to 22.5%, P < .001). Isolates within both CC5 and CC8 were relatively genetically diverse. We identified 6 small genomic clusters—3 potentially related to transmission in healthcare settings. Conclusions Community-associated MRSA is increasing among hospitalized individuals in Ontario. Clonal shifting from CC5 to CC8 has impacted AMR. We identified a relatively high genetic diversity and limited genomic clustering within these dominant CCs.


  • Guthrie, Jennifer L
  • Teatero, Sarah
  • Hirai, Sotaro
  • Fortuna, Alex
  • Rosen, Daniel
  • Mallo, Gustavo V
  • Campbell, Jennifer
  • Pelude, Linda
  • Golding, George
  • Simor, Andrew E
  • Patel, Samir N
  • McGeer, Allison
  • Fittipaldi, Nahuel
  • Delport, Johan
  • Evans, Gerald
  • Hota, Susy
  • Katz, Kevin
  • Lemieux, Camille
  • Mertz, Dominik
  • Science, Michelle
  • Thampi, Nisha

publication date

  • November 13, 2020

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