Phenotypic and genotypic characterization of macrolide resistance in Staphylococcus aureus isolates from wound infection

Microbiologists are increasingly concerned about the rise in S. aureus MLSB (macrolide, lincosamide, streptogramin B) drug resistance. Clindamycin has been effective in treating infections by S. aureus, and the variations in clindamycin sensitivity patterns cause treatment to fail. Inducible clindamycin resistance in S. aureus is expressed via erythromycin ribosome methylase genes. In the current study, 25 S. aureus isolates were identified by conventional chemical tests and the Vitek®2 system. Specific primers were used for the amplification of Macrolide genes by PCR. Among 25 S. aureus isolates, 23(92%) isolates were methicillin resistant and 2(8%) isolates were methicilin sensitive. The 5(20%) isolates showed resistance to Erythromycin and sensitivity to Clindamycin with a positive D test which was identified as inducible MLSB, while 2(8%) isolates showed resistance criteria for both Erythromycin and Clindamycin which identity as a constitutive MLSB and 18(92%) isolates were given the sensitivity for both Erythromycin and Clindamycin. The erm resistance genes (ermA, ermB,  ermC, ermF, and ermG) were detected in 5(20%), 17(68%), 25(100%), 24(96%),11(44%) respectively. The D-test, and Vitek ®2 system should be routinely done to avoid treatment failure due to clindamycin resistance.