title: Antimicrobial susceptibility patterns and macrolide resistance genes of viridans group streptococci from blood cultures in Korea.
abstract: 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.
authors.affiliation: Department of Laboratory Medicine, Yonsei University Wonju College of Medicine, Ilsan-dong 162, Wonju, Kangwon-do, South Korea. u931018@wonju.yonsei.ac.kr
authors.forename: Young
authors.initials: Y
authors.lastname: Uh
authors.forename: Dong Hoon
authors.initials: DH
authors.lastname: Shin
authors.forename: In Ho
authors.initials: IH
authors.lastname: Jang
authors.forename: Gyu Yel
authors.initials: GY
authors.lastname: Hwang
authors.forename: Mi Kyung
authors.initials: MK
authors.lastname: Lee
authors.forename: Kap Jun
authors.initials: KJ
authors.lastname: Yoon
authors.forename: Hyo Youl
authors.initials: HY
authors.lastname: Kim
mesh_terms: 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*
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides; D004917:Erythromycin