Characteristics of Virulent ST5-SCC

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Epidemiology

Background:

• Hospital-acquired infections (HAIs) pose a significant threat to patient safety, particularly in surgical settings.
• Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of HAIs, necessitating investigations into its transmission dynamics.
• Understanding the molecular epidemiology of MRSA outbreaks is crucial for implementing effective control measures.

Purpose of the Study:

• To investigate the transmission pathway of Methicillin-resistant Staphylococcus aureus (MRSA) prevalence in a pancreatic surgery ward.
• To identify the specific MRSA clone responsible for infections in the ward.
• To determine the genetic characteristics, including resistance and virulence factors, of the circulating MRSA strains.

Main Methods:

• Molecular epidemiology techniques including Pulse Field Gel Electrophoresis (PFGE), Multilocus Sequence Typing (MLST), and SCCmec typing were employed.
• Whole-genome sequencing was performed on MRSA isolates.
• Polymerase Chain Reaction (PCR) was used to detect specific resistance and virulence genes. Bacterial identification and antibiotic susceptibility testing (AST) were conducted using the Vitek 2 Compact System.

Main Results:

• Twenty MRSA strains were isolated from January to May 2020, with 19 belonging to PFGE pattern A.
• All patient and environmental isolates were identified as sequence type ST5-SCCmec II-spa type t311.
• The MRSA clone carried multiple resistance genes (e.g., mecA, blaZ) and virulence genes (e.g., tst, hlg, hla).
• Patients with MRSA infections frequently had fever and had undergone recent surgery or invasive procedures.

Conclusions:

• A specific MRSA clone (ST5-MRSA-II-t311) was confirmed to be prevalent in the pancreatic surgery ward.
• MRSA is identified as a significant risk factor for post-surgical nosocomial infections.
• Enhanced hand hygiene practices and continuous environmental surveillance are critical for preventing MRSA transmission in healthcare settings.