Macrolide resistance in group A beta haemolytic Streptococcus isolated from outpatient children in Latvia.

Group A streptococci (GAS) are responsible for up to 30% of cases of pharyngitis in children, and such children do not benefit from treatment with antibiotics. During the last decade, increased resistance to macrolides has emerged as a critical issue in the treatment of GAS pharyngitis. The objective of this study was to determine the antimicrobial resistance of group A beta haemolytic Streptococcus isolated from outpatient children. From 2002 to 2006, 96 GAS strains were obtained from the pharynx of outpatients having symptoms of acute pharyngitis. Antibiotic resistance was determined by disc susceptibility tests according to CLSI standards. The presence of ermA, ermB and mefA was established by the amplification of streptococcal DNA with specific primers. Antimicrobial susceptibility tests revealed that all the strains tested were sensitive to vancomycin, linezolid, penicillin and ceftriaxone. Simultaneously, high levels of resistance to macrolides were evident; 78% of the isolates were resistant to clindamycin and erythromycin. No significant change in the yearly or seasonal incidence of resistance was observed. We describe high antimicrobial resistance of GAS to macrolides in outpatient children (78%), which can be explained by the frequent use of macrolides in the treatment of such individuals. Therefore, macrolides should not be the first drug of choice.