Invasive Community-Acquired Methicillin-Resistant Staphylococcus aureus: Antibiotic Resistance, Virulence and Clonal Characteristics by Whole Genome Sequencing

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Community Acquired - Methicillin Resistant Staphylococcus aureus (CA-MRSA), causes serious infections such as necrotizing pneumonia and sepsis. We evaluated SCC-mec types, clonal and virulence properties, and antibiotic resistance of invasive MRSA strains isolated in our hospital by whole genome sequencing (WGS). Five MRSA strains isolated from five patients in the adult age group, identified by MALDI-TOF MS and thought to be community-acquired by the clinician based on clinical findings and in vitro susceptibilities of the isolates, were included in the study (Table 1). Bacterial DNAs were sequenced with Illumina NovaSeq-6000. Fsa files of reading sequences were uploaded to various online databases and analyzed for SCCmec, ST and spa types, toxins, exoenzymes, and antibiotic resistance genes/mutations. All isolates were CA-MRSA, with SCCmec-type IV (n=4) and SCCmec-type V (n=1) (Table 1). Two isolates were ST-8 (USA-300), others were ST-1, ST-5 and ST-97. Panton-Valentine leukocidin was detected in one isolate (SMK-164). Virulence genes such as gamma hemolysins, enterotoxins, serine proteases, genes encoding aureolysin, staphylokinase and complement inhibitor, toxin genes, and global regulators (sae and agr) were detected (Table 1). PVL carrier isolate was also positive for staphylococcal enterotoxin O and enterotoxin P. This strain was isolated from blood and sputum of a patient with bloodstream infection and necrotizing pneumonia. Resistance genes blaZ and mecA were detected in all. One isolate carried fusC gene, the other carried fusB, mupA and msrA genes and was phenotypically resistant to mupirocin and erythromycin. Thanks to WGS, very important epidemiological clues have been obtained.

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