Phylogenetic analysis and virulence characteristics of methicillin-resistant Staphylococcus aureus ST764-SCC mec II: an emerging hypervirulent clone ST764-t1084 in China

Abstract

Previous studies have shown that the increased prevalent ST764 clone in China, Japan, and other Asian areas. However, the knowledge of the genetic features and virulence characteristics of methicillin-resistant Staphylococcus aureus (MRSA) ST764 in China is still limited. In this study, we identified 52 ST764-SCC mec type II isolates collected from five cities in China between 2014 and 2021. Whole genome sequencing showed that the most common staphylococcal protein A ( spa ) types of ST764 in China were t002 (55.78%) and t1084 (40.38%). Virulence assays showed that ST764-t1084 isolates had high haemolytic activity and α-toxin levels. Of the critical regulatory factors affecting α-toxin production, only the SaeRS was highly expressed in ST764-t1084 isolates. Mouse abscess model indicated that the virulence of ST764-t1084 isolates was comparable to that of S. aureus USA300-LAC famous for its hypervirulence. Interestingly, ST764-t002 isolates exhibited stronger biofilm formation and cell adhesion capacities than ST764-t1084 isolates. This seems to explain why ST764-t002 subclone has become more prevalent in China in recent years. Phylogenetic analysis suggested that all ST764 isolates from China in Clade III were closely related to KUN1163 (an isolate from Japan). Notably, genomic analysis revealed that the 52 ST764 isolates did not carry arginine catabolic mobile element (ACME), which differed from ST764 isolates in Japan. Additionally, most ST764 isolates (69.23%) harboured an obvious deletion of approximately 5 kb in the SCC mec II cassette region compared to KUN1163. Our findings shed light on the potential global transmission and genotypic as well as phenotypic characteristics of ST764 lineage.

Ciprofloxacin enhances the biofilm formation of Staphylococcus aureus via an agrC-dependent mechanism

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Novel small-molecule compound YH7 inhibits the biofilm formation of Staphylococcus aureus in a sarX -dependent manner

“…Cell culture assays were conducted as previously described, with slight modifications ( 26 ). Approximately 5 × 10 5 cells were seeded in individual wells of 12-well plates.…”

Diabetic Foot Osteomyelitis Caused by Co-Infection with Methicillin-Resistant Staphylococcus aureus and Multidrug-Resistant Extended-Spectrum ß-Lactamase-Producing Escherichia coli: A Case Report

“…It has been identified in many environments throughout Japan and is spreading worldwide [5,6]. Moreover, the ST764 strain is increasing in other Asian regions, such as China and Thailand [7,8]. This proliferation may be attributed to the presence of arginine catabolic mobile element type II, which could improve the bacteria's ability to colonize the skin and mucous membrane, thereby leading to more effective transmission [8].…”

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