To investi
gate the antimicrobial resistance trends and the distribution of emm types of
group A streptococci (GAS), we examined 1160 clinical isolates of GAS collected between 2003 and 2006. Susceptibilities to commonly used antimicrobial a
gents were determined by Etest, and macrolide resistance
genes were detected by polymerase chain reaction (PCR). GAS isolates were typed by polymerase chain reaction PCR and sequencin
g of emm
gene. The rates of resistance to erythromycin (ERY), clindamycin, azithromycin, tetracycline, and chloramphenicol were 14.9 % , 1.4 % , 14.9 % , 18.9 % , 0.6 % , respectively. None of the isolates exhibited resistance to penicillin, ceftriaxone, linezolid, moxifloxacin, rifampicin, or vancomycin.
Macrolide resistance increased from 12.1 % in 2003 to 18.8 % in 2006 (P = 0.02). Of 173 ERY-resistant GAS isolates, 93 (53.7 % ) harbored the mefA gene, 70 (40.4 % ) the ermA, and 10 (5.8 % ) the ermB. Eighty percent of the observed emm types are covered by the proposed 26-valent GAS vaccine. Among 173 ERY-resistant isolates, the predominant emm types were 12 (19.5 % ), 77 (17.9 % ), and 4 (16.8 % ), and among 770 ERY-susceptible isolates, the predominant types were 1 (18.8 % ), 12 (17.5 % ), 28 (13.8 % ). The observed antimicrobial resistance trends and the distribution of specific emm types have implications in guiding empiric therapy and in developing vaccine strategies to prevent GAS infections.
