AUTHOR=Schindler Yulia , Rahav Galia , Nissan Israel , Treygerman Orit , Prajgrod George , Attia Bracha Zukerman , Raz Ronit , Valenci Gal Zizelski , Tekes-Manova Dorit , Maor Yasmin 

TITLE=Group B streptococcus virulence factors associated with different clinical syndromes: Asymptomatic carriage in pregnant women and early-onset disease in the newborn

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1093288

DOI=10.3389/fmicb.2023.1093288

ISSN=1664-302X

ABSTRACT=<sec><title>Background</title><p>Group B streptococcus (GBS) harbors many virulence factors but there is limited data regarding their importance in colonization in pregnancy and early-onset disease (EOD) in the newborn. We hypothesized that colonization and EOD are associated with different distribution and expression of virulence factors.</p></sec><sec><title>Methods</title><p>We studied 36 GBS EOD and 234 GBS isolates collected during routine screening. Virulence genes (pilus-like structures-<italic>PI-1, PI-2a, PI-2b</italic>; <italic>rib</italic> and <italic>hvgA</italic>) presence and expression were identified by PCR and qRT-PCR. Whole genome sequencing (WGS) and comparative genomic analyses were used to compare coding sequences (CDSs) of colonizing and EOD isolates.</p></sec><sec><title>Results</title><p>Serotype III (ST17) was significantly associated with EOD and serotype VI (ST1) with colonization. <italic>hvgA</italic> and <italic>rib</italic> genes were more prevalent among EOD isolates (58.3 and 77.8%, respectively; <italic>p</italic> &lt; 0.01). The pilus loci <italic>PI-2b</italic> and <italic>PI-2a</italic> were more prevalent among EOD isolates (61.1%, <italic>p</italic> &lt; 0.01), while the pilus loci <italic>PI-2a</italic> and <italic>PI-1</italic> among colonizing isolates (89.7 and 93.1% vs. 55.6 and 69.4%, <italic>p</italic> &lt; 0.01). qRT PCR analysis revealed that <italic>hvgA</italic> was barely expressed in colonizing isolates, even though the gene was detected. Expression of the <italic>rib</italic> gene and <italic>PI-2b</italic> was two-fold higher in EOD isolates compared to colonizing isolates. Transcription of <italic>PI-2a</italic> was three-fold higher in colonizing isolates compared to EOD isolates. ST17 isolates (associated with EOD) had a smaller genome size compared ST1 and the genome was more conserved relative to the reference strain and ST17 isolates. In a multivariate logistic regression analysis virulence factors independently associated with EOD were serotype 3, and <italic>PI-1</italic> and <italic>PI-2a</italic> was protective.</p></sec><sec><title>Conclusion</title><p>There was a significant difference in the distribution of <italic>hvg A</italic>, <italic>rib</italic>, and <italic>PI</italic> genes among EOD (serotype III/ST17) and colonizing (serotype VI/ST1) isolates suggesting an association between invasive disease and these virulence factors. Further study is needed to understand the contribution of these genes to GBS virulence.</p></sec>