Erythromycin Resistance Determinants in Clinical Gram Positive Cocci Isolated from Nigerian Patients

Introduction: The emergence of erythromycin resistant Gram positive cocci in various parts of the world has become worrisome in clinical settings in recent times, however there is little or no information on the determinants of erythromycin resistance from Nigeria. Aim: This study investigated the determinants of erythromycin resistance in clinical Gram positive cocci bacteria isolated from Nigerian patients. Materials and Methods: Assembly of isolates of non-duplicate staphylococci from various clinical specimens from south western and northern hospitals of Nigeria were collected. While enterococci were obtained from our culture collection which were previously collected from healthy people from community. Characterisation of 25 staphylococci and enterococci each were done using standard microbiology procedures, susceptibility pattern to erythromycin and other panel of antimicrobial agents including Minimum Inhibitory Concentrations (MICs) to erythromycin was determined. Erythromycin resistance genes were amplified using Polymerase Chain Reaction (PCR). Results: None of the strains had ermA and mefA but the strains showed heterogeneous possession of ermB, ermC, msrA and msrB genes in no particular pattern including multiple gene acquisition. MIC50 and MIC90 of staphylococci strains to erythromycin were 2 µg/mL and >64 µg/mL, respectively; wherein 7 (28%) were sensitive to erythromycin, while 11 (44%) of enterococci were sensitive to erythromycin with MIC50 and MIC90 of 1 and >64 µg/mL, respectively. One of the staphylococci isolates had inducible clindamycin resistance. Conclusion: In conclusion, high level staphylococci and enterococci resistance was found to various antibiotics with limited therapeutic option. Ribosomal methylation and efflux are the main resistant determinants found in these isolates.