Macrolide-lincosamide-streptogramin B resistance phenotypes and genotypes among Staphylococcus aureus clinical...

Area of Science:

• Microbiology
• Molecular Biology
• Infectious Diseases

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) are significant pathogens.
• Macrolide-lincosamide-streptogramin B (MLS(B)) resistance is a growing concern in staphylococcal infections.
• Understanding resistance mechanisms is crucial for effective treatment strategies.

Purpose of the Study:

• To investigate the macrolide-lincosamide-streptogramin B (MLS(B)) resistance phenotypes and genotypes in MRSA and MSSA isolates.
• To compare the prevalence of different resistance mechanisms between MRSA and MSSA.
• To explore potential reasons for observed resistance patterns in Japan.

Main Methods:

• Phenotypic characterization of MLS(B) resistance in 269 MRSA and 434 MSSA isolates.
• Genotypic analysis to identify resistance genes, specifically erm(A) and erm(C).
• Statistical analysis to compare resistance prevalence between bacterial types and with international data.

Main Results:

• The constitutive MLS(B) resistance phenotype and the erm(A) gene were predominant in erythromycin-resistant MRSA (61.3%).
• The inducible MLS(B) resistance phenotype and the erm(C) gene were more prevalent in erythromycin-resistant MSSA (94.0%).
• A higher incidence of the MLS(B) inducible phenotype was observed compared to other countries.

Conclusions:

• Distinct genotypic and phenotypic resistance patterns exist for MLS(B) in MRSA and MSSA.
• The erm(A) gene is associated with constitutive resistance in MRSA, while erm(C) is linked to inducible resistance in MSSA.
• The high prevalence of inducible MLS(B) resistance in Japan may be influenced by antibiotic usage guidelines.