Loo P Y, Mariana N S, Pit S, Jamal F.
Mechanism of Macrolide resistance in Malaysian isolates of group A Streptococci.
Infect Dis J Jan ;12(3):78-81.

Hundred and forty four strains of group A Streptococci isolated from various clinical sources were tested for their susceptibility to antimicrobial agents by the disc diffusion technique in accordance with the National Committee for Clinical Laboratory Standards (NCCLS). Erythromycin-resistant isolates were reconfirmed by E-test following the manufacturer`s instructions. The phenotypes of the erythromycin-resistant strains were then determined by the triple disc test. Mulitplex polymerase chain reaction (PCR) was performed for the identification of resistance genes. The overall frequency for GAS erythromycin resistance was 4.86%, mostly from throat sources (p < 0.05). All the erythromycin-resistant strains were susceptible to vancomycin, cefotaxime and cefuroxime. Tetracycline resistance was 59.72% while resistance to chloramphenicol was 0.69%. All 144 isolates were susceptible to penicillin, clindamycin and spiramycin. Minimum inhibition concentrations (MICs) of the 7 erythromycin-resistant strains ranged from 2 g/ml to 12 g/ml. All the erythromycin-resistant strains were found to be of the M phenotype possessing the mefA gene which is responsible for mediating the macrolide efflux mechanism.

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