Comparison of various culture methods for isolation of group B streptococcus from intrapartum vaginal colonization.

AIMS: Group B Streptococcus (GBS) is one of the most common causes of neonatal sepsis throughout the world. Reports of vaginal colonization of GBS in India are few and variable. A study was conducted on pregnant women in a tertiary care hospital to compare various methods for isolation of GBS, to study the prevalence of GBS in pregnant women in third trimester, and to determine risk factors for GBS colonization. SETTINGS AND DESIGN: Observational descriptive study. MATERIALS AND METHODS: High vaginal swabs from 150 pregnant women in their third trimester were used to compare three methods for isolation of GBS viz. direct culture on 5% Sheep Blood agar, direct culture on selective Columbia Blood Agar and culture in LIM enrichment broth with subsequent culture on 5% Sheep Blood agar. A history of associated risk factors was also taken. STATISTICAL ANALYSIS USED: Statistical analysis was performed by Chi-square test. RESULTS: Isolation was best from LIM enrichment broth with subsequent culture on 5% Sheep Blood Agar. Prevalence of GBS colonization by using culture method was 12.67%. Most frequently associated risk factor was intrapartum fever (42.11%). CONCLUSIONS: Standard Culture Method using LIM enrichment should be adopted as standard practice for isolation of GBS from vaginal swabs.