Document Type

Honors Thesis

Publication Date

Spring 2019

Abstract

Streptococcus agalactiae (GBS) is a common bacterium found commensally in the vaginal mucosa of healthy adults. GBS also causes severe infection in neonates, often leading to meningitis, which can cause lifelong health consequences including impaired hearing and seizures. Infection of newborns mainly arises from a colonized mother, either before birth through ascending infection or during labor. Ascending infection, where the bacteria travel to the fetus from the vaginal mucosa, is especially concerning as it can lead to loss of pregnancy or premature birth. The most common method of neonatal GBS disease prevention is antibiotic prophylaxis during delivery, though this method is lacking in safety and application. A promising alternative target for GBS virulence attenuation involves capsular polysaccharide (CPS), which protects GBS from immune recognition and clearance. CPS is regulated by CpsA, a multifunctional protein which is implicated in transcriptional activation, and ligation of CPS to the cell wall via the LytR domain. In this study, a CpsA mutant was created with two amino acid substitutions in the LytR domain which were predicted to decrease LytR functionality. We used microscopy to determine that this mutant induced a change in chain length, as well FL-vancomycin to show that this phenotypic change was not due to a change in cell envelope structure. We measured CPS levels with an ELISA to show that this mutant causes a reduction in CPS level. Finally, we analyzed virulence in zebrafish of bacteria expressing the mutant and found that virulence was increased in WT GBS with this mutant.

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