High Prevalence of Biocide Resistance Determinants in Staphylococcus aureus Isolates from Three African Countries

Area of Science:

• Microbiology
• Antimicrobial Resistance
• Public Health

Background:

• Methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) are significant pathogens.
• Biocide resistance genes can contribute to antimicrobial resistance.
• Understanding gene prevalence in different regions is crucial for public health.

Purpose of the Study:

• To determine the prevalence of six specific biocide resistance genes in S. aureus isolates from three African countries.
• To investigate the association between biocide resistance genes and antibiotic resistance.
• To establish a new cutoff for chlorhexidine nonsusceptibility.

Main Methods:

• Analysis of 82 MRSA and 219 MSSA isolates.
• Detection of six biocide resistance genes: sepA, mepA, norA, lmrS, qacAB, and smr.
• Statistical analysis to assess gene-antibiotic resistance associations.
• Determination of a new minimum inhibitory concentration (MIC) for chlorhexidine.

Main Results:

• High prevalence of sepA (95.3%), mepA (89.4%), and norA (86.4%).
• Intermediate prevalence of lmrS (60.8%) and qacAB (40.5%).
• Low prevalence of smr (3.7%).
• Significant association observed between biocide resistance genes and antibiotic resistance.
• A new MIC cutoff of ≥1 mg/liter for chlorhexidine nonsusceptibility was defined.

Conclusions:

• Biocide resistance genes are widespread in S. aureus isolates from Africa.
• The presence of these genes is linked to antibiotic resistance, highlighting co-selection potential.
• The new chlorhexidine MIC cutoff provides a refined measure for assessing nonsusceptibility.