BACKGROUND & OBJECTIVES: Streptococcus pyogenes (group A Streptococcus - GAS) is 
an important human pathogen which causes a variety of diseases, including 
tonsillopharyngitis, scarlet fever and rheumatic fever. It is important to 
understand the changes in epidemiology of the diseases caused by the pathogen 
for improved control of such infections. Hence, the aim of the present study was 
to carry out an epidemiological analysis of GAS infections in Serbia in a 9-yr 
period (1991-1999) and evaluation of susceptibility of GAS isolates obtained 
during the same period to penicillin and erythromycin.
METHODS: Occurrence of tonsillopharyngitis, scarlatina and rheumatic fever was 
analyzed and GAS carrier status in healthy children was examined over a 9-yr 
period from 1991 to 1999. Susceptibility to penicillin and erythromycin was 
determined for 1657 GAS isolates obtained from patients diagnosed with 
pharyngitis or scarlet fever and 512 isolates from healthy carriers. M-type 
antigen was also determined in these isolates.
RESULTS: The average incidences of tonsillopharyngitis and scarlet fever were 
76.2 and 30.8 per cent respectively. A total of 166 cases of rheumatic fever 
were registered. Per cent of carriers varied from 5.5 to 11.4 per cent over the 
study period. Predominating M serotypes among GAS isolates tested were M1, M3, 
M4, M6, M11, M12 and M18, depending on the source of clinical material and 
period of isolation. Antimicrobial susceptibility testing showed susceptibility 
to penicillin in all isolates tested and resistance to erythromycin in 2.41 per 
cent of the isolates.
INTERPRETATION & CONCLUSION: Although the fluctuations in incidence were noted 
during the nine-year period, the incidence of streptococcal tonsillopharyngitis 
is low but with a steady raise in Serbia. No significant changes in the 
incidence of scarlet fever and rheumatic fever were noted. Susceptibility to 
penicillin remained unchanged, but the number or erythromycin resistant strains 
have increased.