Molecular epidemiology and virulence factors of methicillin‐resistant Staphylococcus aureus isolated from patients with bacteremia

Abstract

Background The various virulence factors of methicillin‐resistant Staphylococcus aureus bacteremia (MRSAB) are associated with a high mortality rate worldwide. Further studies are warranted to confirm the significant relationship between the strains and virulence genes. Here, we prospectively investigated the molecular characteristics underlying the genotypes and virulence factors of MRSA isolated from patients with bacteremia. Methods We collected 59 MRSA isolates from adult patients with bacteremia. Antimicrobial susceptibility results were obtained with the Vitek2 automated system. Genotypes were identified with multi‐locus sequence typing (MLST) and pulse‐field gel electrophoresis (PFGE), and 21 virulence genes were detected with polymerase chain reaction (PCR). Results The 59 MRSA isolates mainly comprised ST5 (n = 31, 52.5%) and ST72 (n = 22, 37.2%). Most ST5 isolates and all ST72 isolates were clustered into one and two PFGE groups, respectively. The mean number of virulence genes was higher in ST5 than in ST72. Sel was more frequently detected in ST5 than in ST72, whereas sec and sed were found only in ST5. ST5 had significantly higher resistance against many antibiotics than ST72. Conclusion Most MRSA isolates causing bacteremia were ST5 (CC5) and ST72 (CC8), and those belonging to the same STs were divided into only a few PFGE groups. ST5 was associated with higher antibiotic resistance and staphylococcal superantigen toxin genes, than ST72, which may be related to its higher virulence.

Short communication: First detection of Panton-Valentine leukocidin–positive methicillin-resistant Staphylococcus aureus ST30 in raw milk taken from dairy cows with mastitis in South Korea

“…It has been reported that MRSA strains differed in their carriage of enterotoxin and leucotoxin encoding genes. Consistent with previous reports (Song et al, 2016;Kim et al, 2020), the majority (92.9%) of ST72 MRSA strains carried identical staphylococcal enterotoxin and leukotoxin encoding genes: seg, sei, sem, sen, seo, and LukED; only LukED was predominant in the ST188 MRSA strains. We also found that the majority of ST30-IV MRSA isolates carried sei (100%) and LukED (87.5%) genes.…”

Prevalence and Characteristics of Antimicrobial-Resistant Staphylococcus aureus and Methicillin-Resistant Staphylococcus aureus from Retail Meat in Korea

“…However, all strains of ST72 showed susceptibility to tetracycline. Several studies ( Kim et al, 2020 ; Lim et al, 2012 ; Park et al, 2007 ) also reported that the ST72 type isolates were susceptible to tetracycline. ST72 is the most reported type in Korea, and is widely prevalent in clinical environment, livestock products, and soil ( Ko et al, 2011 ; Lim et al, 2010 ).…”

Relationship between mortality and molecular epidemiology of methicillin-resistant Staphylococcus aureus bacteremia

“…In addition, in recent years, the existence or absence of the lukF-PV gene has made no difference in virulence; thus, we suggest that there are pathogenic factors other than the lukF-PV gene [52]. High drug resistance was strongly associated with the virulence factors of S. aureus [53]. The POT index -106-137-80 was the most frequently isolated and is the most frequently isolated and commonly reported in hospitals in Japan [54,55].…”