Type IV SCCmec found in decade old Brazilian MRSA isolates

Area of Science:

• Microbiology
• Infectious Diseases
• Molecular Epidemiology

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) is a significant cause of hospital-acquired infections.
• The Staphylococcal Cassette Chromosome mec (SCCmec) element, crucial for MRSA's methicillin resistance, has evolved into five main types (I-V).
• While SCCmec types I-III are typically associated with hospital-acquired MRSA (HA-MRSA), type IV is increasingly linked to community-acquired MRSA (CA-MRSA) and nosocomial infections.

Purpose of the Study:

• To investigate the prevalence and characteristics of SCCmec types in nosocomial MRSA strains collected in Brazil between 1995 and 1999.
• To determine the presence of the Panton-Valentine leukocidin (PVL) gene in these strains.
• To analyze the molecular profiles (PFGE, MLST) and antibiotic resistance patterns of different SCCmec types.

Main Methods:

• Polymerase Chain Reaction (PCR) was used to determine SCCmec complex type and detect the PVL gene.
• Pulsed-field gel electrophoresis (PFGE) and Multilocus Sequence Typing (MLST) were employed for strain typing.
• Oxacillin resistance levels were assessed for different SCCmec types.

Main Results:

• Three isolates harbored SCCmec type IVc, each with distinct PFGE and MLST profiles (ST3, ST5, ST88).
• All SCCmec type III strains belonged to MLST ST239 (Brazilian/Iberian clone).
• The PVL gene was detected only in the ST5 strain. SCCmec type IVc strains exhibited lower oxacillin resistance compared to type III strains.

Conclusions:

• SCCmec type IV MRSA clones have been circulating in Brazil for at least seven years prior to the study, potentially evading detection.
• The presence of type IVc SCCmec in nosocomial settings suggests a broader epidemiological role than previously recognized.
• Further studies are needed to understand the dissemination patterns of SCCmec type IV MRSA.