Group B Streptococcus Colonising the Genital Tract of Pregnant Women from Dibrugarh, Assam: Circulating Serotypes, Susceptibility Pattern and Phylogenetic Analysis

Abstract

Introduction: Maternal genitalia colonising bacteria i.e., Group B Streptococcus (GBS) well known as Streptococcus agalactiae is responsible for serious health complications in newborns like sepsis, meningitis and pneumonitis. Centre for Disease Control and Prevention (CDC) recommends a thorough culture based screening in 35-37 weeks gestation mothers for further therapeutic steps. Previously no study was carried out on the occurrence of GBS among pregnant mothers in Assam with phylogenetic analysis. Aim: To bring the scenario of GBS infection in antepartum women by targeting the capsular serotypes with their antibiogram profile and to bring the phylogenetic relationship of the prevailing GBS isolates found in Dibrugarh district, Assam, India. Materials and Methods: This was a hospital based observational study which was carried out in District Urban Health Centre, Assam, India. Lower vaginal swabs without using speculum were collected from the enrolled late trimester pregnant women. Socio-demographic data were collected with their consent. Out of the total enrolled participants (n=345), GBS was isolated in 52 samples. These were inspected by culture techniques and further confirmed using molecular methods. Serotyping was carried out by employing multiplex PCR. Antibiotic susceptibility test was conducted as per Clinical and Laboratory Standards Institute (CLSI) guidelines and phylogenetic tree was reconstructed. Data analysis was done using Statistical Package for the Social Sciences (SPSS) version 16.0. Results: This study showed a GBS carriage rate of 15.1% in the colonising participating women. No significant association with any of the demographic and clinical factors was found. Serotype Ia (42.1%) was the ruling one followed by VI (31.6%), II (15.8%) and VII (10.5%). While 36.7% of the GBS isolates were grouped into not typeable. Serotypes Ia showed resistant towards cefotaxime, erythromycin and clindamycin and serotype II towards vancomycin. Phylogenetic evaluation showed the presence of four distinct clusters viz., I, II, III and IV with unique evolutionary trends in human GBS population in the study site. Conclusion: So far in Assam, this study reports for the first time on GBS prevailing rate in late trimester mothers which may be helpful in declining the rate of adverse neonatal outcomes with on time maternal therapeutic administration by real time monitoring of antibiogram profiling. This study also paves a way of designing Capsular Polysaccharide (CPS) based vaccines for immunising the expectant mothers to prevent adverse outcomes of the newborns.

Keywords

• antibiotic susceptibility test
• phylogenesis
• streptococcus agalactiae
• urinary tract infections