title: A GBS culture collected shortly after GBS prophylaxis may be inaccurate.
abstract: OBJECTIVE
  To determine whether a vaginal-rectal culture obtained after antibiotic therapy has begun accurately detects pre-existing colonization with group B streptococcus (GBS).
  
  
  METHODS
  A prospective cohort study of women presenting at in labor who were known to be colonized with GBS were recruited. A GBS culture was obtained prior to administration of intravenous penicillin prophylaxis and repeated 2 hours following the first dose of penicillin. The two results were compared.
  
  
  RESULTS
  Eighty subjects were recruited. Complete results were obtained for 61 (76 %) subjects. Of these, 47 (77 %) had a GBS positive on initial culture. Persistence of GBS 2 hours after antibiotic exposure was seen in 30/47 (64 %). Conversion from GBS positive to GBS negative status was seen in 17/47 (36%).
  
  
  CONCLUSIONS
  A vaginal-rectal culture for GBS performed after antibiotic prophylaxis has commenced may not accurately reflect a patient's GBS colonization status.
authors.affiliation: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Tufts Medical Center, Boston, MA, USA. gillmackay@yahoo.co.uk
authors.forename: Gillian
authors.initials: G
authors.lastname: Mackay
authors.forename: Michael D
authors.initials: MD
authors.lastname: House
authors.forename: Evan
authors.initials: E
authors.lastname: Bloch
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Wolfberg
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000008:administration & dosage; D019072:Antibiotic Prophylaxis / Q000379:methods; D001431:Bacteriological Techniques / Q000379:methods / Q000592:standards; D004334:Drug Administration Schedule; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D010406:Penicillins / Q000008:administration & dosage*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000382:microbiology / Q000517:prevention & control*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013048:Specimen Handling / Q000379:methods; D013290:Streptococcal Infections / Q000382:microbiology / Q000517:prevention & control*; D013292:Streptococcus agalactiae / Q000302:isolation & purification*; D013997:Time Factors; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D010406:Penicillins