Infection and Drug Resistance (Dec 2023)

Molecular Characteristics, Antimicrobial Susceptibility, Biofilm-Forming Ability of Clinically Invasive Staphylococcus aureus Isolates

  • Wang W,
  • Zhong Q,
  • Cheng K,
  • Tan L,
  • Huang X

Journal volume & issue
Vol. Volume 16
pp. 7671 – 7681

Abstract

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Weiguo Wang, Qiuxaing Zhong, Ke Cheng, Lili Tan, Xincheng Huang Department of Clinical Laboratory, The First Hospital of Nanchang, Nanchang, Jiangxi, People’s Republic of ChinaCorrespondence: Xincheng Huang, Email [email protected]: This study aimed to investigate the molecular characteristics, antimicrobial resistance, and biofilm-forming ability of Staphylococcus aureus isolates from invasive infections.Methods: A total of 92 non-repetitive S. aureus isolates from invasive infections were analyzed by Multi-locus Sequence Typing (MLST), spa typing, and chromosomal cassette mec (SCCmec) typing. Antibiotic susceptibility testing was performed using the disk diffusion and agar dilution methods. Biofilm-forming ability was assessed using crystal violet assay. The presence and expression of biofilm-associated genes were examined using PCR and RT-qPCR.Results: Among the 55 Methicillin-resistant S. aureus (MRSA) and 41 Methicillin-sensitive S. aureus (MSSA) isolates, ST59 (43.6%) predominated in MRSA, while ST7 (39.0%) was most common in MSSA. As expected, MRSA exhibited higher antibiotic resistance rates compared to MSSA isolates. Biofilm formation assays revealed that the majority of isolates (88.5%) produced biofilms, with 26.0% classified as strong producers (OD570 ≥ 1.0) and 62.5% as weak producers (0.2 ≤ OD570< 1.0). MSSA exhibited a higher biofilm-forming ability than MRSA (P < 0.01), with variations across clones. Notably, ST7 isolates displayed greater biofilm-forming ability than other sequence types (ST59, ST5, and ST239). RT-qPCR results revealed that ST7 isolates exhibited higher expression levels of icaA compared to other sequence types.Conclusion: This study revealed significant molecular heterogeneity among invasive S. aureus isolates, with ST59 and ST7 as dominant clones. The strong biofilm-forming capacity of ST7 merits concern given its rising prevalence regionally. Continuous surveillance of emerging successful lineages is critical to help guide infection control strategies against invasive S. aureus infections.Keywords: Staphylococcus aureus, invasive infection, biofilm, ST7

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