title: Survey of strain distribution and antibiotic resistance pattern of group B streptococci (Streptococcus agalactiae) isolated from clinical specimens.
abstract: OBJECTIVE
  The aims of the present study were to determine the antibiotic susceptibility profils with particular emphasis on susceptible or resistant strains to macrolides and lincosamids antibiotics and to determine possible antibiotic resistance mechanisms occurring in group B streptococci (GBS) strains using PCR assay and disk diffusion method.
  
  
  METHODS
  A total of 62 clinical GBS strains were investigated. Antibacterial susceptibility testing was performed using the disk diffusion method and inducible resistance test for clindamycin by standard double disk diffusion or D-zone test for all isolates to differentiate macrolide resistance phenotype (M), constitutive macrolide-lincosamide-streptogramin B phenotype (cMLSB) and induced macrolide-lincosamide-streptogramin B phenotype (iMLSB). In addition, minimum inhibitory concentrations (MIC) of penicillin were determined for all isolates. Finally, possible existence of antibiotic resistance genes for erythromycin (ermTR, ermB and mefA/E) and for clindamycin (linB) were examined among isolates using PCR assay.
  
  
  RESULTS
  All 62 isolates were susceptible to penicillin, ampicillin, linezolid, cefazoline and vancomycin. However, 93.5% (n=58) of isolates showed an increased MIC to penicillin. The overall rate of erythromycin resistance was 35.5% (n=22). All erythromycin-resistant isolates displayed the M phenotype (100%, n=22). All three erythromycin resistance genes (i.e. ermTR, ermB and mefA/E) were found in erythromycin-resistant isolates.
  
  
  CONCLUSIONS
  It was concluded that prescribing antibiotic without antibacterial susceptibility tests should be prevented because of the high prevalence of erythromycin-resistant GBS strains and the fact that erythromycin-resistant GBS strains has shown an increased MIC to penicillin, as the drug of choice for treating GBS infections.
authors.affiliation: Department of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Seyed Masoud
authors.initials: SM
authors.lastname: Mousavi
authors.affiliation: Department of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Mona
authors.initials: M
authors.lastname: Nasaj
authors.affiliation: Department of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Seyed Mostafa
authors.initials: SM
authors.lastname: Hosseini
authors.affiliation: Department of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran; Brucellosis Research Center, Hamadan University of Medical Sciences, Hamadan, Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Arabestani
keywords: Streptococcus agalactiae; antibiotic susceptibility; capsular genotyping; group B streptococci; macrolide-lincosamide-streptogramin B; polymerase chain reaction