Abstract
Staphylococcus aureus (S. aureus) constantly evolves under host and environment pressures. The monitoring network is essential in assessing the epidemiology of S. aureus infections. A total of 555 S. aureus isolates were collected from five hospitals in three different geographical regions of China for the investigation of molecular characteristics, antibiotic resistance, virulence gene, and wall teichoic acid (WTA) glycosyltransferase gene profiles. 233 (42.0%) isolates were identified as MRSA, and 323 (58.2%) were defined as multidrug-resistant (MDR) isolates. MRSA prevalence showed no significant difference among the three regions. In contrast, the MDR prevalence was significantly higher in central China than that in northern China (63.5% vs. 50.8%, P < 0.05). Thirty-eight sequence types (STs) belonging to 17 clone complexes (CCs) and 126 distinct spa-types were identified. The most prevalent clone was ST59-t437 (9.7%, 54/555), followed by ST22-t309 (7.6%, 42/555) and ST5-t2460 (7.2%, 40/555). Most ST59-t437 and ST5-t2460 were MRSA isolates, whereas most ST22-t309 was MSSA isolates. The predominant clones varied in different geographical areas. The distribution of the pvl, etb, tsst, clfb, sdrC, sdrD, hlg, fnbA, and hla genes showed significant differences among different regions. We found five WTA glycosyltransferase gene profiles, with tarP-/tarS+/tarM-/tagN- being the most common combination. Remarkably, the tarP gene was identified in more CCs than just CC5 and CC398. All of 16 tarP-positive isolates also contained the tarS. Moreover, tarS was present in almost all S. aureus isolates except 10 ST630 isolates. The tagN gene was only detected in 10 of 12 ST630 S. aureus isolates without tarS. The tarM gene was absent in CC5 and CC398. In brief, there were regional differences among molecular characteristics, antibiotic resistance, and virulence gene profiles. The tarS-negative ST630 lineage carried the tagN, which was never found before, indicating that it may be capable of expressing GroP-α-GalNAc WTA and exchanging mobile genetic elements with coagulase-negative staphylococci (CoNS).
Highlights
Staphylococcus aureus (S. aureus), a Gram-positive coccus, generally colonizes on the surface of skin and mucous membranes and is thought to be one of the most significant human opportunistic pathogens in both community and hospital settings
ST5 was most prevalent (16.9%, 94/555), followed by ST59 (15.9%, 88/555), ST22 (8.5%, 47/555), ST239 (7.4%, 41/555), ST398 (7.4%, 41/555), ST188 (6.8%, 38/555), ST7 (5.9%, 33/555), and other STs accounted for 31.2%
Most ST59-t437 and ST5-t2460 were methicillin-resistant S. aureus (MRSA) isolates, whereas most ST22-t309 were methicillinsusceptible S. aureus (MSSA) isolates, suggesting that certain molecular types of S. aureus were significantly associated with methicillin-resistant status
Summary
Staphylococcus aureus (S. aureus), a Gram-positive coccus, generally colonizes on the surface of skin and mucous membranes and is thought to be one of the most significant human opportunistic pathogens in both community and hospital settings. The mortality rate of S. aureus invasive infection was extremely high (>80%) before the emergence of effective antibiotics (Peacock and Paterson, 2015). Vancomycin and linezolid generally serve as agents for therapy of invasive MRSA infections due to the side effects. It was reported that some certain molecular types of S. aureus were significantly associated with methicillin-resistant status: most ST188-t189 isolates were found to be MSSA, whereas the majority of ST59-t437 and ST5-t2460 isolates were found to be MRSA. Some certain molecular types were reported to be associated with the occurrence of complications, severity, and mortality of infection. ST121, a globally disseminated highly virulent clone, often caused longer hospitalization and prolonged antimicrobial therapy (Rao et al, 2015). It is of great significance to monitor molecular characteristics, virulence genes, and drug resistance of
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