Antimicrobial susceptibility patterns and macrolide resistance genes of viridans group streptococci from blood cultures in Korea.
OBJECTIVE
Our aim was to study the antimicrobial susceptibilities and macrolide resistance mechanisms of viridans group streptococci (VGS) in a Korean tertiary hospital.


METHODS
MICs of five antimicrobials were determined for 106 VGS isolated from blood cultures. The macrolide resistance mechanisms of erythromycin non-susceptible isolates were studied by the double-disc test and PCR.


RESULTS
In all, 42.4% of the isolates were susceptible to penicillin. Nine of 61 penicillin non-susceptible isolates were fully resistant (MIC >/= 4 mg/L). Rates of non-susceptibility to erythromycin, clindamycin and ceftriaxone were 33.9%, 17.9% and 9.4%, respectively. Twenty-two (61.1%) of 36 erythromycin non-susceptible isolates expressed constitutive resistance to macrolide-lincosamide-streptogramin B antibiotics (a constitutive MLS(B) phenotype); 13 isolates (36.1%) expressed an M phenotype; and one isolate, a Streptococcus bovis isolate, had an inducible MLS(B) resistance phenotype. erm(B) was found in isolates with constitutive/inducible MLS(B) phenotypes, and mef(A) in isolates with the M phenotype. In three isolates (two isolates with a constitutive MLS(B) phenotype and in one isolate with the M phenotype), none of erm(A), erm(B), erm(C) or mef(A) was detected by PCR.


CONCLUSIONS
Penicillin non-susceptible VGS were more resistant to erythromycin, clindamycin and ceftriaxone than were penicillin-susceptible isolates. A constitutive MLS(B) phenotype associated with erm(B) was the predominant mechanism of macrolide resistance among erythromycin non-susceptible isolates from this Korean hospital.
Uh
Young
Y
Department of Laboratory Medicine, Yonsei University Wonju College of Medicine, Ilsan-dong 162, Wonju, Kangwon-do, South Korea. u931018@wonju.yonsei.ac.kr
Shin
Dong Hoon
DH
Jang
In Ho
IH
Hwang
Gyu Yel
GY
Lee
Mi Kyung
MK
Yoon
Kap Jun
KJ
Kim
Hyo Youl
HY
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003428:Cross Infection / Q000382:microbiology; D024881:Drug Resistance, Bacterial; D004917:Erythromycin / Q000494:pharmacology; D005798:Genes, Bacterial / Q000235:genetics; D005838:Genotype; D006801:Humans; D007723:Korea; D018942:Macrolides / Q000494:pharmacology*; D010641:Phenotype; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013290:Streptococcal Infections / Q000097:blood / Q000382:microbiology*; D034363:Viridans Streptococci / Q000187:drug effects* / Q000235:genetics*
D000900:Anti-Bacterial Agents; D018942:Macrolides; D004917:Erythromycin