Exploration of Erythromycin Ribosomal Methylase Genotypes Among D+ Methicillin-resistant Staphylococcus aureus Strains in Sokoto, Nigeria

Abstract

Introduction: Antibiotics are lifesaving compounds that have been successful for decades. However, many pathogenic bacteria are becoming resistant to them. Cross-resistance of the macrolide-lincosamide-streptogramin B (MLSB) antibiotic classes is a major cause of increased morbidity. This study appraises the phenotypic and genotypic distribution of inducible clindamycin resistance among methicillin-resistant Staphylococcus aureus (MRSA) isolates. Materials and Methods: Erythromycin-induced resistance to clindamycin antibiotics among MRSA isolates was verified phenotypically using the Double-disk diffusion test (D-test) and genotypically by the polymerase chain reaction. Results: All MRSA isolates were resistant to erythromycin. The prevalence of iMLSB (iMLSB: inducible macrolide-lincosamide-streptogramin B) phenotype was 23.7% (9/38), macrolide streptogramin (MS) phenotype 47.4% (18/38), and cMLSB (cMLS: constitutive macrolide-lincosamide-streptogramin) phenotype 28.9% (11/38) of the isolates. The nine isolates with the iMLSB phenotype were tested for the presence of the erythromycin ribosomal methylase (erm) gene. The ermA gene was detected in five (55.6%) isolates, the ermB gene in two (22.2%) isolates, and the ermC gene in two (22.2%) isolates. Conclusion: The erm-positive isolates expressed the iMLSB phenotype, and the ermA gene was predominant. We showed that the cMLSB phenotype was prevalent among the MRSA isolates, signifying the possibility of achieving a good therapeutic outcome when clindamycin is used. The observed distribution of the erm gene explored here gives credence to the adequacy of the D-test in monitoring and testing for potential clindamycin treatment failures.

Keywords

• orsa
• cefoxitine-resistant staphylococcus aureus
• linezolid
• molecular epidemiology
• oxacillin-resistant staphylococcus aureus