Abstract

Prevalence of group B Streptococcus colonisation in mother-newborn dyads in low-income and middle-income south Asian and African countries: a prospective, observational study

Kwatra G, Izu A, Cutland C, Akaba G, Ali MM, Ahmed Z, Beck MM, Barsosio HC, Berkley JA, Chaka TE, Cossa A, Chakraborty S, Dhar N, Dorji P, Islam M, Keita AM, Mwakio S, Mwarumba S, Medugu N, Mucavele H, Mabombo V, Obaro S, Siga�que B, Sow SO, Saha SK, Santhanam S, Sharma R, Simoes EAF, Sahni RD, Tapia MD, Veeraraghavan B, Madhi SA
Lancet Microbe. 2024;5

Permenent descriptor

BACKGROUND: Rectovaginal group B Streptococcus (GBS) colonisation in pregnant individuals at the time of labour is a major risk factor for invasive GBS disease by age 7�days (early-onset disease). We aimed to investigate the prevalence of rectovaginal GBS colonisation at the time of labour among pregnant women and vertical transmission to their newborns across selected low-income and middle-income African and south Asian countries. METHODS: This prospective, observational study was undertaken at 11�maternity and obstetric care facilities based in Ethiopia, Kenya, Mozambique, Nigeria, Mali, South Africa, Bangladesh, India, and Bhutan. HIV-negative pregnant women aged 18-45�years who were in the early stages of labour and at least 37�weeks' gestation were eligible for inclusion. Lower vaginal and rectal swabs and urine were collected from the women, and swabs of the umbilicus, outer ear, axillary fold, rectum, and throat were obtained from their newborns, for GBS culture. Standardised sampling and culture using direct plating and selective media broth for detection of GBS colonisation was undertaken at the sites. Serotyping of GBS isolates was done in South Africa. The primary outcome was the prevalence of rectovaginal GBS among pregnant women, analysed in participants with available data. This study is registered with the South African National Clinical Trials Register, number DOH-27-0418-4989. FINDINGS: 6922�pregnant women were enrolled from Jan 10, 2016, to Dec 11, 2018, of whom 6514 (94�1%; 759-892�per country) were included in the analysis; data from Bhutan were not included in the study due to issues with specimen collection and processing. Overall, the prevalence of maternal GBS colonisation was 24�1% (95% CI 23�1-25�2; 1572�of 6514); it was highest in Mali (41�1% [37�7-44�6]; 314�of 764) and lowest in Ethiopia (11�6% [9�5-14�1]; 88�of 759). The�overall rate of vertical transmission of GBS from women with rectovaginal GBS colonisation was 72�3% (70�0-74�4; 1132�of 1566); it was highest in Mozambique (79�2% [73�3-84�2]; 168�of 212) and lowest in Bangladesh (55�8%, 47�5-63�8; 77�of 138). The five most common GBS colonising serotypes were Ia (37�3% [34�9-39�7]; 586�of 1572), V�(28�5% [26�3-30�8]; 448�of 1572), III (25�1% [23�0-27�3]; 394�of 1572), II (9�2% [7�8-10�7]; 144�of 1572), and Ib�(6�5% [5�4-7�8]; 102�of 1572). There was geographical variability in serotype proportion distribution; serotype VII�was the third most common serotype in India (8�6% [5�3-13�7]; 15�of 174) and serotype VI was mainly identified in Bangladesh (5�8% [3�0-11�0]; eight of 138) and India (5�7% [3�2-10�3]; ten of 174). INTERPRETATION: Our study reported a high prevalence of GBS colonisation in most settings, with some geographical variability even within African countries. Our findings suggest that serotypes not included in current multivalent capsular-polysaccharide GBS vaccines prevail in some regions, so vaccine efficacy and post-licensure effectiveness studies should assess the effect of vaccination on maternal GBS colonisation given the potential for replacement by non-vaccine serotypes. FUNDING: Bill & Melinda Gates Foundation.