Genomic characterisation of perinatal Western Australian Streptococcus agalactiae isolates

Abstract

As a leading cause of neonatal sepsis, Streptococcus agalactiae, commonly known as Group B Streptococcus, is a major neonatal pathogen. Current global screening practices employ risk- or culture-based protocols for detection of these organisms. In Western Australia (WA), universal culture-based screening is provided, with subsequent intrapartum antibiotic prophylaxis for all S. agalactiae-positive women during labour. Widespread antibiotic exposure is not ideal and this is one of the factors driving development of vaccines against S. agalactiae. Vaccine candidates have focused on the capsule, surface proteins and pilus types, however, capsule serotypes are known to vary geographically. The aim of this study was to use genome sequencing to gain an understanding of the circulating genotypes in WA, and to assess variations in the associated gene pools. We sequenced 141 antenatal carriage (vaginal/rectal) isolates and 10 neonatal invasive disease isolates from WA. Based on the global PubMLST database, the 151 strains were characterised into 30 sequence types, with clustering of these mainly into clonal complexes 1, 12, 17, 19 and 23. Of the genes encoding eleven surface proteins that were analysed, the most prevalent were fbp, lmb and scpB which were present in ≥ 98% of isolates. A cluster of non-haemolytic isolates, one of which was a neonatal invasive disease isolate, appeared to lack the entire cyl locus. Admixture analysis of population structure revealed evidence of genetic transfer among the WA isolates across structural groups. When compared against the PubMLST S. agalactiae data, WA isolates showed high levels of strain diversity with minimal apparent clustering. This is the first whole genome sequence study of WA S. agalactiae isolates and also represents the first addition of Australian isolate data to PubMLST. This report provides insight into the distribution and diversity of vaccine targets of S. agalactiae within Western Australia, indicating that the most appropriate capsular vaccine for this population would be the proposed pentavalent (Cps Ia, Ib, II, III and V) preparation, whilst vaccines targeting surface proteins should ideally utilise Fbp, Lmb and/or ScpB.

Molecular Epidemiology of Group B Streptococcus Colonization in Egyptian Women

“…The overrepresentation of ST-1 with asymptomatic carriage [ 5 , 9 , 37 ], as well as the association of ST-1 with serotype V has been well-documented [ 8 , 38 , 39 , 40 , 41 , 42 ]. In contrast to data from Australia [ 43 ], ST-1 is a single dominant ST of serotype V in GBS strains from the US [ 44 ]. Similarly, in our study, CC1 appeared to be largely limited to ST-1, with ST-1 serotype V representing almost two-thirds of all CC1 strains.…”

“…All except one ST-569 strains were isolated from pregnant women. While rarely reported elsewhere [ 38 , 43 , 68 ], ST-569 was the second most predominant ST in Ethiopia [ 69 ]. Moreover, we found one isolate of ST-486 serotype Ia, which according to the public MLST database [ 22 ], has not been detected outside of Africa.…”

Host range, morphological and genomic characterisation of bacteriophages with activity against clinical Streptococcus agalactiae isolates

“…All of the carriage S. agalactiae isolates were serotyped via multiplex assay to detect serotypes Ia, Ib and III [19] and remaining serotypes were determined by standard PCR and gel electrophoresis [20]. In addition to serotyping, 42 of the 246 carriage isolates, 10 of the 10 neonatal invasive isolates and 14 of the 15 reference isolates had whole genome sequence data available [21].…”

Genomic epidemiology of group B streptococci spanning 10 years in an Irish maternity hospital, 2008–2017

“…In the present study, we demonstrated A global meningitis genome partnership, with contributions from high, middle and low income countries, has been proposed to aid the WHO defeating meningitis roadmap (63). For GBS, WGS has been central in population surveillance and elucidating the population structure and evolution (15,37,49,64). The publicly available genome sequences and metadata presented here will provide a baseline for monitoring the genomic epidemiology of infant and maternal GBS in Ireland.…”