Population genetics of group B Streptococcus from maternal carriage in an ethnically diverse community in London

Abstract

IntroductionMaternal immunization against Group B Streptococcus (GBS) has the potential to significantly reduce the burden of neonatal GBS infections. Population genetics of GBS from maternal carriage can offer key insights into vaccine target distribution.MethodsIn this study we characterized the population structure of GBS isolates from maternal carriage (n = 535) in an ethnically diverse community in London, using whole genome sequencing.ResultsThe isolates clustered into nine clonal complexes (CCs) but the majority (95%) belonged to five lineages: CC1 (26%), CC19 (26%), CC23 (20%), CC17 (13%) and CC8/10 (10%). Nine serotypes were identified, the most common were serotypes III (26%), V (21%), II (19%) and Ia (19%). Other serotypes (Ib, IV, VI, VII, IX) represented less than 10% of all isolates each. Intra-lineage serotype diversity was observed in all major CCs but was highest in CC1, which revealed nine serotypes. Nearly all isolates (99%) carried at least one of the four alpha family protein genes (alpha, alp1, alp23, and rib). All isolates were susceptible to penicillin. We found 21% and 13% of isolates to be resistant to clarithromycin and clindamycin, respectively. Prevalence of macrolide-lincosamide-streptogramin B (MLSB) resistance genes was 22% and they were most common in CC19 (37%) and CC1 (28%), and isolates with serotypes V (38%) and IV (32%). We identified some associations between maternal ethnicity and GBS population structure. Serotype Ib was significantly less common among the South Asian compared to Black women (S. Asian: 3/142, Black: 15/135, p = 0.03). There was also a significantly lower proportion of CC1 isolates among the White other (24/142) in comparison to Black (43/135) and S. Asian (44/142) women (p = 0.04). We found a significantly higher proportion of CC17 isolates among the White other compared to S. Asian women (White other: 32/142, S. Asian: 10/142, p = 0.004).ConclusionOur study showed high prevalence of GBS vaccine targets among isolates from pregnant women in London. However, the observed serotype diversity in CC1 and high prevalence of MLSB resistance genes in CC19 demonstrates presence of high risk lineages, which might act as a reservoir of non-vaccine strains and antimicrobial resistance determinants.

Capsular gene distribution and RAPD typing of Streptococcus agalactiae isolated from pregnant women

“…They found a variation in circulation of the capsular types, specially V, over time (Barros et al 2023 ). Other research conducted on 535 S. agalactiae isolates collected from pregnant women in London exhibited a that among nine serotypes identified, the most prevalent serotype was III (26%), followed by V (21%), II (19%) and Ia (19%), while the serotypes Ib, IV, VI, VII, and IX had a less than 10% prevalence (Jamrozy et al 2023 ). Also, another Iranian study carried out on 60 S. agalactiae isolates collected from women with urinary tract infection (UTI) detected the capsular serotype II as the most prevalent (66.7%), while 21.7%, 3.3%, and 1.7% of the isolates were carrying the Ib, Ia, and III capsular encoding genes, and 6.6% of the isolates were non-typeable (Gharabeigi et al 2023 ).…”

“…We detected nine clones and 53 different RAPD types of S. agalactiae with 70% similarity in the present study. Also, Jamorsy et al detected nine clone of S. agalactiae among 535 isolates collected from pregnant women in London (Jamrozy et al 2023 ). A Spanish research that used the PFGE method for typing S. agalactiae isolates, were detected 65 different patterns (Rojo-Bezares et al 2016 ).…”

“…Similarly, the rate of colonization in non-pregnant healthy adults ranged between 20 and 34% (Alzayer et al 2023 ). Babies born to colonized women may get early-onset or late-onset infections, from which 1–3% of them will develop an invasive life-threatening disease (do Nascimento et al 2019 ; Khademi and Sahebkar 2020 ; Jamrozy et al 2023 ). Recently, two new (and key) recommendations were reported for the prevention of S. agalactiae neonatal infections (NAAT and Encourage 2020 ; Puopolo et al 2019 ).…”