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Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus MRSA
Published on: February 9, 2011
Characterization of highly virulent community-associated methicillin-resistant Staphylococcus aureus ST9-SCCmec XII
Ye Jin1, Xiao Yu2, Yunbo Chen1
1State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, National Clinical Research Center for Infectious Diseases, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.
Abstract:
Previous studies have shown that livestock (LA)-MRSA ST398 evolved from a human-adapted methicillin-susceptible S. aureus (MSSA) clone. However, detailed information regarding ST9 is still unclear. Here, we characterized a community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) ST9-SCCmec XII isolate that has not been previously reported to cause serious disease in China. We obtained whole-genome sequences of one ST9-t899-XII isolate-ZY462471-from a patient with bloodstream infection without livestock contact. The antibiotic susceptibilities of ZY462471 were determined and the clinical information was extracted from medical notes and compared with twenty-seven previously sequenced genomes. Phylogenetic reconstruction was performed to investigate the probable host evolutionary origins of ZY462471, and the difference in resistome and virulence factors were investigated. Virulence assay was performed to evaluate the high virulence potential of ZY462471 and compare the virulence between the closest ST9 MSSA neighbours. Clinical data suggested that ZY462471 is a CA-MRSA. Phylogenetic analysis showed a much closer relationship of ZY462471 with human-associated MSSA ST9 isolates than other LA-MRSA ST9 isolates, suggesting that ZY462471 probably evolved from ST9 MSSA predecessors by acquiring an SCCmec cassette. Importantly, virulence assays indicated that ZY462471 was highly virulent and compared with the MSSA ST9 predecessors, ZY462471 did not show attenuated virulence. Finally, we found that ZY462471 harboured an immune evasion cluster (IEC)-carrying βC-Φ, which is typically found in human clinical S. aureus rather than LA-MRSA isolates, suggesting that ZY4762471 obtained the IEC-carrying βC-Φs from human clinical S. aureus strains. Considering its high virulence potential, this strain should be monitored to prevent more widespread dissemination.
Insights
A novel community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) ST9 strain, ZY462471, was identified in China. This highly virulent strain likely evolved from human-adapted methicillin-susceptible S. aureus (MSSA) ST9 and carries an immune evasion cluster, necessitating monitoring.
Area of Science:
- Microbiology and Infectious Diseases
- Genomics and Evolutionary Biology
- Antimicrobial Resistance
Background:
- Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) ST398 is known to evolve from human-adapted clones.
- The evolutionary origins and characteristics of ST9 strains, particularly community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) ST9, remain less understood.
- Previous research has not extensively documented severe disease caused by ST9 CA-MRSA in China.
Purpose of the Study:
- To characterize a novel CA-MRSA ST9 isolate (ZY462471) from a patient with bloodstream infection in China.
- To investigate the evolutionary origins, virulence potential, and genetic makeup of this ST9 CA-MRSA strain.
- To assess the implications of its genetic features for potential dissemination and public health.
Main Methods:
- Whole-genome sequencing of the ST9-t899-XII isolate ZY462471.
- Determination of antibiotic susceptibilities and extraction of clinical information.
- Phylogenetic analysis to infer evolutionary relationships with other S. aureus strains.
- Comparative analysis of resistome and virulence factors.
- Virulence assays to evaluate pathogenicity in vitro and in vivo.
Main Results:
- The isolate ZY462471 was identified as CA-MRSA with no reported livestock contact.
- Phylogenetic analysis revealed ZY462471 is closely related to human-associated MSSA ST9, suggesting evolution from MSSA ST9 by acquiring SCCmec.
- Virulence assays demonstrated high virulence for ZY462471, comparable to its MSSA ST9 predecessors, and it harbored an immune evasion cluster (IEC)-carrying βC-Φ, typical of human S. aureus strains.
Conclusions:
- The characterized CA-MRSA ST9 strain ZY462471 likely originated from human-adapted MSSA ST9 through SCCmec acquisition.
- This strain possesses significant virulence potential and genetic elements (IEC-carrying βC-Φ) associated with human adaptation.
- Continuous monitoring of this highly virulent CA-MRSA ST9 strain is crucial to prevent its widespread dissemination.
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