Expression of GBS virulence genes,Hy1B and Cy1E in high vaginal swabs of symptomatic pregnant women of < 37 weeks gestational age at Hospital Tengku Ampuan Afzan (HTAA),Kuantan

Abstract

Maternal vaginal group B streptococcal (GBS) colonization is considered to be a risk factor for preterm delivery and consequent neonatal GBS infections such as early onset and late onset neonatal infections. To reduce the burden of GBS infection among mothers and neonates, Centre for Disease Control (CDC) had established guidelines which involved screening of pregnant mothers in 35th-37th week of gestational age. Despite adherence to the guideline, the incidence of late onset neonatal infection remains unchanged. Nowadays, it has become more apparent that maternal immunization should be considered a valid preventative strategy. Conjugated-capsular polysaccharide vaccines is one of the vaccine candidate explored by researchers. However, these vaccines tend to switch capsular serotypes, making this type of vaccine futile. Thus, other GBS virulence factors should be investigated as an alternative vaccine candidate. This study is a laboratory-based follow-up study, to investigate the association between the maternal characteristics of the GBS positive pregnant women with preterm delivery, and also to explore the relationship between the expression of HylB gene which encodes the hyaluronidase toxin, and CylE gene which encodes the β-hemolysin in symptomatic pregnant women of <37 weeks of gestational age at Hospital Tengku Ampuan Afzan (HTAA), and preterm delivery. Maternal characteristics such as socio demographic details and obstetric history of the pregnant women were enquired. A total of 82 bacterial isolates were obtained from high vaginal swabs of symptomatic pregnant women collected during the period from 1st January 2020 to 18th March 2020. Out of the 82, 40 were found to be GBS positive. The 40 GBS isolates were processed for RNA extraction and sent for qPCR. ∆∆Ct method was used to calculate the relative mRNA expression level of HylB and CylE genes in the isolates. The GBS-positive women were followed up after their estimated date of delivery to enquire about their delivery outcomes. Out of the 40 women, 22 (55%) had preterm delivery and 18 had term delivery (45%). Additionally, the study showed that the maternal characteristics were not found to be confounding factors in causing preterm delivery. Symptomatic pregnant women especially preterm labour women who had preterm delivery were demonstrated with elevated HylB gene, in comparison to preterm labour women with term delivery. Meanwhile, CylE gene was induced in symptomatic pregnant women including preterm labour and PPROM who delivered prematurely when compared to those who delivered at term. This provides evidence that both HylB and CylE genes could be considered as potential alternative candidates for exploratory and pre-clinical stages of vaccine development.