Abstract
We typed 600 methicillin-resistant Staphylococcus aureus (MRSA) isolates collected in 51 hospitals in the Rio de Janeiro, Brazil, metropolitan area during 2014–2017. We found that multiple new clonal complex (CC) 5 sequence types had replaced previously dominant MRSA lineages in hospitals. Whole-genome analysis of 208 isolates revealed an emerging sublineage of multidrug-resistant MRSA, sequence type 105, staphylococcal cassette chromosome mec II, spa t002, which we designated the Rio de Janeiro (RdJ) clone. Using molecular clock analysis, we hypothesized that this lineage began to expand in the Rio de Janeiro metropolitan area in 2009. Multivariate analysis supported an association between bloodstream infections and the CC5 lineage that includes the RdJ clone. Compared with other closely related isolates, representative isolates of the RdJ clone more effectively evaded immune function related to monocytic cells, as evidenced by decreased phagocytosis rate and increased numbers of viable unphagocytosed (free) bacteria after in vitro exposure to monocytes.
Highlights
Methicillin-resistant Staphylococcus aureus (MRSA) is characterized by the mainly clonal structure of bacterial populations and the worldwide spread of a few highly successful lineages, sequence types (STs), and clonal complexes (CCs) that cycle through waves of dominance [1,2]
All 109 strains belonging to the CC30-SCCmecIV lineage, which is related to the community-acquired methicillin-resistant Staphylococcus aureus (MRSA) USA1100/ Oceania South West Pacific clone, were susceptible to all non–β-lactams tested (Table 3)
CC5-SCCmecII was the predominant genotype in our sample, the proportions of the second and third most frequent genotypes, CC5-SCCmecIV and lukSF-PV–positive CC30-SCCmecIV, had increased from prior studies [4]
Summary
Methicillin-resistant Staphylococcus aureus (MRSA) is characterized by the mainly clonal structure of bacterial populations and the worldwide spread of a few highly successful lineages, sequence types (STs), and clonal complexes (CCs) that cycle through waves of dominance [1,2]. During the late 1990s, the Brazilian endemic clone (BEC), which belongs to the ST239(CC8)–staphylococcal cassette chromosome (SCC) mecIII lineage, comprised ≈80% of MRSA isolates in hospitals in Brazil [3]. In the 2000s, isolates of the ST1(CC1)-SCCmecIV lineage supplanted BEC in >2 hospitals in the Rio de Janeiro metropolitan area of Brazil [4]. Most studies on the molecular epidemiology of MRSA in Brazil have analyzed a small number of isolates from a limited number of hospitals [5,6,7,8,9]. We used molecular and genomic approaches to characterize 600 MRSA isolates collected from 51 hospitals in the Rio de Janeiro metropolitan area and identified a novel MRSA clone of ST105SCCmecII spa t002 (ST105-SCCmecII-t002), which we termed the Rio de Janeiro (RdJ) clone, as a predominant cause of MRSA bloodstream infections (BSIs)
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