Infection with group A streptococci (GAS) causes a wide spectrum of disease in neonates and children, ranging from GAS pharyngitis to it's severe sequel – rheumatic fever (RF). The explanation for the very substantial decrease in the incidence of acute rheumatic fever in Latvia lately – 1 RF case in 2007, is unclear. It has been proposed that certain M types of group A streptococci (GAS) include strains that are particularly rheumatogenic and that others are nonrheumatogenic. Equal importance should be attributed to the appropriate and correct antimicrobial treatment of GAS. During the last ten years treatment of GAS pharyngitis has emerged as a critical issue for the increased resistance to macrolides. Correct treatment of acute GAS infection is of unanimous importance, therefore the determination of antimicrobial susceptibility of a clinical isolate is often crucial for the optimal antimicrobial therapy of infected patients.

To determine antimicrobial resistance of group A beta haemolytic Streptococcus isolated from outpatient children.

96 GAS strains isolated from pharynx of outpatients having acute pharyngitis symptoms from July 2002 to April 2006. Antimicrobial resistance of the isolates was determined as described in CLSI standarts. Antimicrobial resistance genes (ermA, ermB and mefA) were detected by amplification of streptococcal DNA with specific primers.

Antimicrobial susceptibility testing revealed that all strains tested were sensitive to vancomycin, linezolid, penicillin and ceftriaxone. Simultaneously, high level of resistance to macrolides was found – 75 isolates out of 96 (78%) were resistant to clindamycin and erythromycin. No significant change in resistance incidence was observed.

Studies on molecular basis of resistance showed that majority of strains harboured either the ermA (27), or ermB (23), or both (24). The mefA gene was detected only in one strain.

There is a high (78%) antimicrobial resistance of GAS to macrolides in outpatient children, which could be explained by frequent macrolide use in outpatient treatment, therefore they would not be the first drug of choice for treatment of tonsillitis and other S. pyogenes-related diseases.

The drug of choice remains penicillin because of its proven efficacy, safety and susceptibility, which is the drug of choice in guidelines for GAS acute pharyngitis treatment in Latvia, therefore also in prevention of rheumatic fever.