Virulence factor landscape of a Staphylococcus aureus sequence type 45 strain, MCRF184

Area of Science:

• Microbiology
• Genomics
• Infectious Diseases

Background:

• Describes the methicillin-sensitive Staphylococcus aureus (MSSA) ST45 strain MCRF184, identified as the cause of severe necrotizing fasciitis in a diabetic patient.
• Highlights the presence of three genomic islands (νSaα, νSaβ, νSaγ) and two phage-related regions in the MCRF184 genome.
• Notes the absence of SCCmec genes and the presence of a putative efflux pump and mobilization genes in a specific genomic region.

Purpose of the Study:

• To characterize the virulence factors of the ST45 MSSA strain MCRF184.
• To investigate the genomic features contributing to the severe necrotizing fasciitis observed.
• To compare the genetic makeup of MCRF184 with previously sequenced Staphylococcus aureus strains.

Main Methods:

• Whole-genome sequencing of the MCRF184 strain.
• Bioinformatic analysis to identify genomic islands, phage-related regions, and open reading frames (ORFs).
• Identification and characterization of specific virulence factors, including phenol soluble modulins (PSMs).

Main Results:

• The MCRF184 genome contains a type III νSaα island, a truncated νSaβ island with an enterotoxin gene cluster (egc), and a νSaγ island with α-toxin.
• Phage-related regions include phage φSa3 with immune evasion cluster (IEC) genes and an incomplete, distinct phage.
• Identified phenol soluble modulins (PSMs) α1-α4 and β1-β2 as key virulence factors; ten ORFs were novel.

Conclusions:

• The MCRF184 strain possesses a unique combination of virulence factors and genomic features.
• These factors, including novel ORFs and specific toxins, contribute to its high virulence.
• The study concludes that MCRF184 is a highly virulent Staphylococcus aureus strain with significant pathogenic potential.