الفهرس 
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Abstract
S. pyogenes is an important public health concern and have a significant direct socioeconomic impact. It is a major cause of mobidity and mortality. Erythromycin is an effective macrolide antibiotic for treating GAS infections. However, GAS macrolide resistance has been increased. So determining erythromycin resistance phenotypes seems to be a useful tool in eradicating GAS infection.
The main known mechanisms of macrolide resistance in S. pyogenes are macrolide specific efflux mechanism (M phenotype), encoded by the macrolide efflux protein A (mef A) gene, as well as the modification of the ribosomal target by a methylase enzyme. Methylation results in resistance to macrolide, lincosamide, and streptogramin B (MLS) antibiotics. Methylase can be expressed either constitutively (cMLS phenotype) or inducibly (iMLS phenotype).
The current study included (100) swabs taken from either ear or throat of both males and females at different age groups who were attended to Outpatient Clinic of Otorhinolaryngology, Faculty of Medicine, BeniSueif University.
The study showed a high resistance 83.3% (35/ 42) towards erythromycin, which was alarmingly high and 31% (13/ 42) towards resistance clindamycin.
By performing the double disk diffusion test on all isolates resistant to erythromycin and susceptible to clindamycinm, no cases showed a positive D zone test (iMLSB phenotype) and all 22 isolates (52.3%) showed negative D zone test (M phenotype) .
The overall MIC range of erythromycin resistant isolates was 1-≥64 μg/ml. large number of strains with M phenotype expressed low-level macrolide resistance (MIC was 1-4μg/ml), while cMLSB isolates showed a high level of erythromycin resistance (MIC was ≥64 μg/ml) with significant P- value 0.0001. Our results confirmed a strong correlation between the M phenotype and the mef A gene in GAS with P –value 0.001.
Although the prevalence of the recognized phenotypes of erythromycin-resistant S. pyogenes may vary from area to area and over time, macrolides appear to remain a useful and adequate remedy for the treatment of S. pyogenes infections. Since changes of resistance rates and their mechanisms can occur rapidly, concomitant monitoring of the antibiotic consumption and emergence of resistance is advisable with evaluation of potential risk factor.