Comparative Efficacy of Erthromycin and other Macrolides on Streptococcal Species Isolated From Clinical Specimens

Abstract

This study was designed to investigate the in vitro activity of Erythromycin compared with Azithromycin and Clarithromycin against 50 strains of streptococcal species isolated from patients present with different diseases during the period between April to August 2003. The results showed that Erythromycin has zones diameter of > 19 mm and MIC of < 0.5μg/ml against susceptible strains of S. pyogenes and < 11 mm, and MIC > 4 μg/ml for resistant strains. Zones diameter > 20 mm and MIC < 0.5 μg/ml against susceptible strains of S. agalactiae; 14 mm, 1 μg/ml against intermediate susceptible strains; < 12 mm and > 2 μg/ml for resistant strains. Zones diameter > 19 mm and MIC < 0.5 μg/ml against susceptible strains of V. streptococci; and < 3 mm, with MIC of > 16 μg/ml for resistant strains. The zone diameter of > 18 mm and MIC < 0.5 μg/ml was recorded for susceptible strains of S. pneumoniae; while 17mm, 1μg/ml for intermediate susceptible strain; and > 10 mm, > 4 μg/ml for resistant strains. All strains of Enterococcus faecalis were resistant to these antibiotics with MIC > 16 μg/ml. The results also showed that 7 strains of S. pyogenes out of 10 were sensitive to these antibiotics and 3 strains resistant. Seven strains of S. agalactiae were susceptible to Erythromycin and Azithromycin, but 8 strains were susceptible to Clarithromycin; one strain was intermediate susceptible to Erythromycin and Azithromycin; 2 strains were resistant to these antibiotics. Two, 1 and 7, strains of V. streptococci were resistant, intermediate susceptible and susceptible respectively to these antibiotic. Three strains of S. pneumoniae were resistant but 1 and 6, strains were intermediate and susceptible to Erythromycin and Azithromycin respectively and 7 strains were susceptible to Clarithromycin. The comparison indicated that Clarithromycin more active than Erythromycin and Azithromycin, also Erythromycin more active than Azithromycin.