Genomic and phenotypic characterisation of invasive neonatal and colonising group B Streptococcus isolates from Slovenia, 2001\u20132018

Tina Perme,Magnus Unemo,Samo Jeverica,Alojz Ihan,Miha Lučovnik,Maja Bombek Ihan,Štefan Grosek,Lilijana Kornhauser Cerar,Jana Lozar Krivec,Andrej Rojnik,Daniel Golparian,Petja Fister

doi:10.1186/s12879-020-05599-y

Abstract

BackgroundGroup B Streptococcus (GBS) is the leading cause of invasive neonatal disease in the industrialized world. We aimed to genomically and phenotypically characterise invasive GBS isolates in Slovenia from 2001 to 2018 and contemporary colonising GBS isolates from screening cultures in 2018.MethodsGBS isolates from 101 patients (invasive isolates) and 70 pregnant women (colonising isolates) were analysed. Basic clinical characteristics of the patients were collected from medical records. Antimicrobial susceptibility and phenotypic capsular serotype were determined. Whole-genome sequencing was performed to assign multilocus sequence types (STs), clonal complexes (CCs), pathogenicity/virulence factors, including capsular genotypes, and genome-based phylogeny.ResultsAmong invasive neonatal disease patients, 42.6% (n = 43) were females, 41.5% (n = 39/94) were from preterm deliveries (< 37 weeks gestation), and 41.6% (n = 42) had early-onset disease (EOD). All isolates were susceptible to benzylpenicillin with low minimum inhibitory concentrations (MICs; ≤0.125 mg/L). Overall, 7 serotypes were identified (Ia, Ib, II-V and VIII); serotype III being the most prevalent (59.6%). Twenty-eight MLST STs were detected that clustered into 6 CCs. CC-17 was the most common CC overall (53.2%), as well as among invasive (67.3%) and non-invasive (32.9%) isolates (p < 0.001). CC-17 was more common among patients with late-onset disease (LOD) (81.4%) compared to EOD (47.6%) (p < 0.001). The prevalence of other CCs was 12.9% (CC-23), 11.1% (CC-12), 10.5% (CC-1), 8.2% (CC-19), and 1.8% (CC-498). Of all isolates, 2.3% were singletons.ConclusionsA high prevalence of hypervirulent CC-17 isolates, with low genomic diversity and characteristic profile of pathogenicity/virulence factors, was detected among invasive neonatal and colonising GBS isolates from pregnant women in Slovenia. This is the first genomic characterisation of GBS isolates in Slovenia and provides valuable microbiological and genomic baseline data regarding the invasive and colonising GBS population nationally. Continuous genomic surveillance of GBS infections is crucial to analyse the impact of IND prevention strategies on the population structure of GBS locally, nationally, and internationally.

Highlights

Group B Streptococcus (GBS) is the leading cause of invasive neonatal disease in the industrialized world
Continuous genomic surveillance of GBS infections is crucial to analyse the impact of invasive neonatal disease (IND) prevention strategies on the population structure of GBS locally, nationally, and internationally
IND is divided into early-onset disease (EOD), occurring within the first week postpartum, and late-onset disease (LOD), affecting infants aged > 1 week, mostly up to 90 days [2]

Summary

Introduction

Group B Streptococcus (GBS) is the leading cause of invasive neonatal disease in the industrialized world. Group B Streptococcus (GBS; Streptococcus agalactiae) is the leading cause of invasive neonatal disease (IND) in industrialized world [1]. EOD can be prevented using intrapartum antibiotic prophylaxis This is most effective when administered based on universal screening of GBS colonisation during the late third trimester of pregnancy or intrapartum [2]. In Slovenia, a less effective risk-based approach is predominantly used, which results in lower coverage of subsequent prophylaxis. This is likely the main reason for the high incidence of IND in Slovenia, estimated at 0.72/1000 live births, 0.53/1000 for EOD [3]

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