The effect of intrapartum penicillin on vaginal group B streptococcus colony counts

• Published in: American journal of obstetrics and gynecology Vol. 197; no. 6; pp. 583.e1 - 583.e4
• Main Authors: McNanley, Anna R., MD, Glantz, J. Christopher, MD, MPH, Hardy, Dwight J., PhD, Vicino, David, BS
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA Mosby, Inc 01.12.2007; Elsevier
• Subjects: Anti-Bacterial Agents - administration & dosage; Antibacterial agents; Antibiotics. Antiinfectious agents. Antiparasitic agents; Bacterial diseases; Biological and medical sciences; Colony Count, Microbial; Delivery. Postpartum. Lactation; Female; group B streptococcus; Gynecology. Andrology. Obstetrics; Human bacterial diseases; Humans; Infectious diseases; intrapartum; Medical sciences; Obstetrics and Gynecology; Penicillin G - administration & dosage; penicillin-G; Pharmacology. Drug treatments; Pregnancy; Staphylococcal infections, streptococcal infections, pneumococcal infections; Streptococcal Infections - drug therapy; Streptococcus agalactiae - drug effects; Streptococcus agalactiae - isolation & purification; Time Factors; vaginal colonization; Vaginosis, Bacterial - drug therapy; group B streptococcus; penicillin-G; vaginal colonization; intrapartum; β-Lactams; Gynecology; Vagina; Obstetrics; Infection; Penicillin derivatives; Numeration; Streptococcaceae; Antibiotic; Streptococcus; Streptococcal infection; Penicillin; Bacteriosis; Bacteria; Micrococcales; Delivery; Antibacterial agent
• ISSN: 0002-9378; 1097-6868
• DOI: 10.1016/j.ajog.2007.08.045

Objective The objective of the study was to determine the temporal relationship between intrapartum penicillin-G (PCN-G) and vaginal group B streptococcus (GBS) counts. Study Design In 50 women with GBS-positive antenatal cultures, intrapartum cultures were collected just before the first PCN-G dose and every 2 hours × 4 or until delivery. Colony counts were quantified using serial dilution. Results were standardized as percent of initial colony count and analyzed using sequential Wilcoxon tests. Results Of 50 subjects with GBS-positive antepartum cultures, 35 (70%) had positive intrapartum vaginal cultures, of which 27 received intrapartum PCN-G. Degree of vaginal colonization varied greatly between subjects, and counts (percents) were not normally distributed. From the T0 (time = zero) colony count standardized to 100%, counts fell rapidly to means ± SE and medians of 18.2 ± -7.5% and 0.5% at T2 ( P < .0001), 2.5 ± 1.7% and 0.02% at T4 ( P = .006), and less than 0.2% and 0.0% at T6 and 8 ( P = .07 and P = .46, respectively). Conclusion Vaginal GBS colony counts fall rapidly after intrapartum PCN-G administration, which may partly explain the effectiveness of chemoprophylaxis.