Have Methicillin Resistant Staphylococcus aureus clinical isolates to be also resistant to Streptogramins?

Document Type : Original Article


1 Microbiology Department, Medical Research Institute, Alexandria University, Alexandria, Egypt

2 Faculty of Pharmacy, Alexandria University, Alexandria, Egypt


Background: Methicillin Resistant Staphylococcus aureus (MRSA) is a significant pathogen causing high morbidity and mortality. The extensive misuse of antibiotics has led to the willing of using older compounds like macrolide, lincosamides, and streptogramin (MLS) antimicrobials family. This study aimed to detect phenotypic and molecular characterization of macrolide, lincosamides, and streptogramins resistance in MRSA clinical isolates.
Methods: Antimicrobial susceptibility testing of 50 MRSA clinical isolates to MLS agents and quinupristin-dalfopristin (Q -D) was performed using disk diffusion method. Besides, polymerase chain reaction was conducted for amplification of genes related to streptogramins resistance (ermA, ermB, ermC, msrA, vatA, vatB, vatC, vgaA and vgbA).
Results: MLSB resistance phenotypes detected were cMLSB 9(18%), iMLSB 5(10%), MSB 8(16%), and 3(6%) isolates were LSA phenotype. No resistance to Q-D was detected in any of the tested isolates .The most prevalent MLSB resistance genes were ermC in the cMLSB and msrA in the MSB. The 3 (6%) LSA phenotype isolates expected to be SA resistant, and the 22(44%) isolates expected to be SB resistant, were sensitive to Q-D. Genes related to Q-D resistance (vatA, vatB, vatC, vgaA and vgbA genes) were not detected confirming the susceptibility of all the tested isolates to Q-D by disk diffusion method. .
Conclusion: Accurate identification of phenotypic and genotypic MLSB resistance is a crucial approach to decrease the antibiotic resistance rates. The study revealed a high prevalence of the cMLSB phenotype and the most prevalent resistance determinants was ermC.


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