Frequency of genes encoding erythromycin ribosomal methylases among clinical isolates with different D-phenotypes in Tehran, Iran.

BACKGROUND AND OBJECTIVES

Macrolide, lincosamide and streptogramin type B (MLSB) antibiotics are important in the treatment of infections and existence of isolates with ability to resist against MLSB antibiotics is worrisome.

MATERIALS AND METHODS

In this cross sectional study, 101 isolates were collected from patients of five selected hospitals in Tehran over a period of five months. Disk diffusion tests and differentiation between constitutive and inducible resistances were carried out by D-test. The presence of and genes were detected using PCR or multiplex PCR.

RESULTS

Out of 101 isolates, 58 (57.4%) were methicillin resistant and 57 (56.4%) expressed resistance to erythromycin. The prevalence of constitutive MLSB (cMLSB), inducible MLSB (iMLSB) and MS (Negative) phenotype in all erythromycin resistant isolates were 71.9, 26.3 and 1.7%, respectively. Out of all the erythromycin resistant isolates, 57.8% harbored both and genes which possessed constitutive resistance. 8.7% of the isolates contained gene alone which possessed inducible resistance with D phenotype and 5.2% of isolates just contained gene which had inducible resistance with D phenotype. gene was detected in 3.5% of the erythromycin resistant isolates with constitutive resistance. None of the genes were detected among MS phenotypes.

CONCLUSION

In this study, most of isolates carried both and genes and there was a significant relationship ( value ≤ 0.05) between different resistance phenotypes and genes.