Macrolide resistance trends in beta-hemolytic streptococci in a tertiary Korean hospital.
OBJECTIVE
Erythromycin-resistant beta-hemolytic streptococci (BHS) has recently emerged and quickly spread between and within countries throughout the world. In this study, we evaluate the antimicrobial susceptibility patterns and erythromycin resistance mechanisms of BHS during 2003-2004.


METHODS
The MICs of seven antimicrobials were determined for 204 clinical isolates of BHS from 2003 to 2004. Resistance mechanisms of erythromycin-resistant BHS were studied by the double disk test as well as by polymerase chain reaction (PCR).


RESULTS
Compared with our previous study, resistance among Streptococcus pyogenes isolates to a variety of drugs decreased strikingly: from 25.7% to 4.8% in erythromycin; 15.8% to 0% in clindamycin; and 47.1% to 19.0% in tetracycline. The prevalent phenotypes and genotypes of macrolide-lincosamide-streptograminB (MLSB) resistance in Streptococcus pyogenes isolates have been changed from the constitutive MLSB phenotype carrying erm(B) to the M phenotype with mef(A) gene. In contrast with Streptococcus pyogenes, resistance rates to erythromycin (36.7%), clindamycin (43.1%), and tetracycline (95.4%) in Streptococcus agalactiae isolates did not show decreasing trends. Among the Streptococcus dysgalactiae subsp. equisimilis isolates (Lancefield group C, G), resistance rates to erythromycin, clindamycin, tetracycline and chloramphenicol were observed to be 9.4%, 3.1%, 68.8%, and 9.4%, respectively.


CONCLUSIONS
Continual monitoring of antimicrobial resistance among large-colony-forming BHS is needed to provide the medical community with current data regarding the resistance mechanisms that are most common to their local or regional environments.
Uh
Young
Y
Department of Laboratory Medicine, Yonsei University Wonju College of Medicine, Ilsan-dong 162, Wonju, Gangwon-do, Korea. u931018@yonsei.ac.kr
Hwang
Gyu Yel
GY
Jang
In Ho
IH
Cho
Hyun Mi
HM
Noh
Song Mi
SM
Kim
Hyo Youl
HY
Kwon
Ohgun
O
Yoon
Kap Jun
KJ
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D004917:Erythromycin / Q000494:pharmacology*; D005798:Genes, Bacterial; D005838:Genotype; D006761:Hospitals; D006801:Humans; D015994:Incidence; D007723:Korea; D008826:Microbial Sensitivity Tests; D013291:Streptococcus / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D013292:Streptococcus agalactiae / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D013297:Streptococcus pyogenes / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; D004917:Erythromycin