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MRSA in Tibet: high prevalence driven by the epidemic clone CC59-ST59-SCCmec IV-t437 and insights from whole-genome analysis
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DOI：10.3389/fmicb.2026.1889907.png)
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Abstract
En 中文
ObjectivesMethicillin-resistant Staphylococcus aureus (MRSA) poses a serious public health burden in Tibet; where genome-informed epidemiological data remain limited. This study aimed to characterize the molecular epidemiology of MRSA among Tibetans and explore factors associated with its elevated prevalence.MethodsWe analyzed 115 non-duplicate MRSA isolates from Tibetans; comprising 51 hospital-associated MRSA (HA-MRSA) from clinical infections and 64 community-colonizing MRSA (CA-MRSA). CA-MRSA isolates were obtained from nasal swabs of hospitalized patients within 24 h of admission (to exclude nosocomial acquisition) and from their family members between June and December 2023. All isolates underwent antimicrobial susceptibility testing and whole-genome sequencing (WGS)-based typing [sequence type (ST); spa; SCCmec]. We performed core-genome single nucleotide polymorphism (cgSNP) phylogeny and profiled resistance and virulence determinants.ResultsThe MRSA nasal colonization rate was 10.53%. The clone CC59-ST59-SCCmec IV-t437 predominated; accounting for 59.4% of CA-MRSA and 39.2% of HA-MRSA. Phylogenetic analysis revealed a distinct Tibetan MRSA cluster with limited genetic relatedness to strains from other Chinese provinces. cgSNP analysis identified seven CA-MRSA transmission clusters defined by ≤25 cgSNP differences; approximating the ≤25 wgSNP threshold. a finding corroborated by epidemiological links to shared households or hospital exposure. While ST59 conserved core virulence determinants (capsule biosynthesis; iron acquisition); ST22 uniquely harbored the egc cluster and was uniformly positive for the lukS-PV/lukF-PVloci. No significant virulence differences were observed between HA-MRSA and CA-MRSA within the same ST. All isolates remained susceptible to vancomycin and linezolid; exhibiting concordant resistance profiles across both settings.ConclusionCC59-ST59-SCCmec IV-t437 is the predominant MRSA lineage in Tibet and shows substantial clonal overlap between HA-MRSA and CA-MRSA. These results support the use of whole-genome sequencing to guide empirical therapy and highlight the need for continued surveillance and targeted infection control in this high-burden region.
Keywords:
molecular epidemiology
virulence
whole-genome sequencing
CA-MRSA
Tibetans
HA-MRSA
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