title: Penicillin susceptibility and macrolide-lincosamide-streptogramin B resistance in group B Streptococcus isolates from a Canadian hospital.
abstract: BACKGROUND
  Intrapartum antibiotic prophylaxis (IAP) is recommended for pregnant women who test positive for group B Streptococcus (GBS) in their genitourinary tract to prevent GBS-induced neonatal sepsis. Penicillin G is used as the primary antibiotic, and clindamycin or erythromycin as the secondary, if allergies exist. Decreased susceptibility to penicillin G has occasionally been reported; however, clindamycin and erythromycin resistance is on the rise and is causing concern over the use of clindamycin and erythromycin IAP.
  
  
  METHODS
  Antibiotic resistance was characterized phenotypically using a D-Test for erythromycin and clindamycin, while an E-Test (E-strip) was used for penicillin G. GBS was isolated from vaginal-rectal swabs and serologically confirmed using Prolex (Pro-Lab Diagnostics, Canada) streptococcal grouping reagents. Susceptibility testing of isolates was performed according to the Clinical Laboratory Standards Institute guidelines.
  
  
  RESULTS
  All 158 isolates were penicillin G sensitive. Inducible macrolide-lincosamide-streptogramin B (MLSB) resistance was observed in 13.9% of isolates. Constitutive MLSB resistance was observed in 12.7% of isolates. M phenotype resistance was observed in 6.3% of isolates. In total, erythromycin resistance was present in 32.9% of the GBS isolates, while clindamycin resistance was present in 26.6%.
  
  
  CONCLUSIONS
  The sampled GBS population showed no sign of reduced penicillin susceptibility, with all being well under susceptible minimum inhibitory concentration values. These data are congruent with the large body of evidence showing that penicillin G remains the most reliable clinical antibiotic for IAP. Clindamycin and erythromycin resistance was higher than expected, contributing to a growing body of evidence that suggests the re-evaluation of clindamycin and erythromycin IAP is warranted.
authors.affiliation: Department of Biological Science, Faculty of Science, Thompson Rivers University, Kamloops.
authors.forename: Kevin
authors.initials: K
authors.lastname: Sherman
authors.forename: Sue
authors.initials: S
authors.lastname: Whitehead
authors.forename: Edith
authors.initials: E
authors.lastname: Blondel-Hill
authors.forename: Ken
authors.initials: K
authors.lastname: Wagner
authors.forename: Naowarat
authors.initials: N
authors.lastname: Cheeptham
keywords: Clindamycin; Erythromycin; Group B Streptococcus; Macrolide-lincosamide-streptogramin B resistance; Penicillin resistance; Regional hospital