Microbiologic characteristics of exfoliative toxin-producing Staphylococcus aureus

Area of Science:

• Microbiology
• Dermatology
• Infectious Diseases

Background:

• Staphylococcus aureus causes staphylococcal scalded skin syndrome (SSSS) and bullous impetigo.
• Exfoliative toxins (ETs) are key virulence factors in SSSS and bullous impetigo.
• Understanding the characteristics of ET-producing strains is crucial for effective treatment.

Purpose of the Study:

• To investigate the relationship between exfoliative toxin (ET) production, phage types, and antibiotic susceptibilities of Staphylococcus aureus strains.
• To determine the prevalence of different ET types (ET-A, ET-B) in clinical isolates.
• To assess the antibiotic resistance patterns, particularly to penicillin G, in ET-producing S. aureus.

Main Methods:

• Isolation and characterization of 74 Staphylococcus aureus strains from patients with SSSS or bullous impetigo.
• Detection of exfoliative toxin production using newborn mouse assay and latex agglutination methods.
• Phage typing of ET-producing strains to determine their group classification (Groups I, II, III).
• Determination of minimal inhibitory concentrations (MICs) for penicillin G.

Main Results:

• 61 out of 74 (82%) S. aureus isolates produced exfoliative toxins.
• ET-A was produced by 15 strains, ET-B by 32, and both by 14 strains.
• Phage Group II strains predominantly produced ET-A or both ET-A and ET-B.
• Phage Group III and mixed Group I/III strains primarily produced ET-B.
• ET-producing strains exhibited low penicillin G resistance (MIC < 2 µg/ml), unlike other pathogenic staphylococci.

Conclusions:

• A strong correlation exists between Staphylococcus aureus phage types and exfoliative toxin types.
• ET-producing strains associated with SSSS and bullous impetigo are characteristically susceptible to penicillin G.
• These findings highlight specific microbiological profiles of S. aureus strains causing these skin conditions.