Evolution of Erythromycin Resistance among Streptococcus pneumoniae Isolates in Malaysia from 2005 and 2010

Objectives: This study focuses on the antibiotic susceptibility pattern and distribution of the ermB and mefA virulence genes among the Streptococcus pneumoniae due to an increase in erythromycin resistance in S. pneumoniae worldwide. Methodology: We investigated 255 clinical isolates collected from 2005-2010 to determine the serotype distribution and resistance to erythromycin in comparison to penicillin, clindamycin, clarithromycin, azithromycin, and trimethoprim sulfamethoxazole. Multiplex PCR was carried out to detect erythromycin resistance genes (ermB and mefA). Results: There were 146 (57.3%) isolates resistant to erythromycin. MIC90 for erythromycin is at >256 mg/L and MIC50 is at 16 mg/L. The ermB gene was detected in 25.3% of the erythromycin-resistant isolates and mefA gene was detected in 50.7% of the isolates. The four most common serotypes encountered are 19F, 19A, 23F and 14. The serotype distribution among the erythromycin resistant isolates was 19F (42.0%) followed by serotype 19A (11.3%), serotype 23F (9.2%) and serogroup 14 (7.0%). Conclusion: In conclusion, there is a significant rise in erythromycin resistance among the Malaysian pneumococcal isolates. The emergence of serotype 19A together with increasing prevalence of resistance to macrolide warrants for a more extensive surveillance study.