T Typing and Antimicrobial Susceptibility of Streptococcus pyogenes in Clinical Isolates

Kim, Yun Jeong; Kim, Seon Ju

Abstract

BACKGROUND: As invasive streptococcal infections are increasing recently and the resistance rate to either erythromycin or clindamycin is elevating, epidemiologic surveillance and appropriate guideline for antibiotic use are required. Geographical epidemiologic characteristics with T typing and antibiotic resistance rate were investigated.
METHODS
Distributions of T types according to geographical areas and sources of specimens were analyzed with 82 strains of Streptococcus pyogenes isolated from clinical samples in Seoul and Chinju. Antibiotic susceptibility test was performed for penicillin G, cephalothin, erythromycin, azithromycin, clarithromycin, clindamycin, chloramphenicol, and ofloxacin with agar dilution method. Antibiotic resistance rates were analyzed according to geographical areas, sources of specimens and T types.
RESULTS
The most common T types were T12, T1 and T28 in decreasing order. The distribution of T types between Seoul and Chinju was different. While T1, T3, and T6 were frequent in throat or other respiratory specimens, T12, T28, and B3264 were common in blood or closed pus. The resistance rate to erythromycin, azithromycin, and clarithromycin was 20%, 13% to clindamycin, and 49% to tetracycline, respectively. None of the isolates were resistant to penicillin G, cephalothin, chloramphenicol, or ofloxacin. The isolates from Chinju showed higher resistance rate than the strains from Seoul. The isolates from blood or closed pus had higher resistance rate compared to those of throat or sputum. T28 and T6 strains presented higher resistance rate than other T types.
CONCLUSIONS
As distributions of T types were variable according to geographical areas or sources of specimens, continuous microbiological and epidemiological surveillance for invasive streptococcal infections are needed. Minimizing unnecessary antibiotic use or acknowledging the severity of resistance are necessary, because the resistant proportions are increasing against macrolide, clindamycin and tetracycline.