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Date of Award
Biochemistry and Molecular Biology
Bacterial Vaginosis (BV) is a condition where a healthy vaginal microbiome predominantly consisting of Lactobacilli species has been replaced by commensal species, including Gardnerella vaginalis which can colonize healthy women. Full genome sequencing of G. vaginalis strains in previous studies revealed significant differences between BV and non-BV isolates. To test whether there are distinct pathogenic and commensal lineages within this species, this study aimed to isolate BV and non-BV associated G. vaginalis strains and correlate whether genotypic differences can reliably be used as markers to define BV and non-BV clinical categories.
qPCR assays developed for the chaperonin-60 (Cpn60) gene, lytic transglycosylase gene, and 8 previously indicated marker genes (Balashov et al. 2014) enumerated titers, frequency, and possibly elude to their clinical relevance in uncultured specimens from over 80 BV and 25 non-BV patient multi-visit samples defined for their clinical state. Our results indicated that the Cpn60 region serves to screen for the distinct main clade groups in G.vaginalis species whereas other gene assays indicated subgroups within clades exist with uneven distribution in clinical categories.
Our results emphasize 6 clade genotypes exist (Clades1/2/3/4a/4b/5). Clade1 and Clade2 and Clade4a associated to BV patients particularly Acute BV occurring in higher frequency and titers. Clade1, Clade2 (Cpn60 Fingerprint2) and Clade2 (Cpn60 Fingerprint6) strains were shown in-vitro to have high to moderate susceptibility to metronidazole, with 74%, 74% and 50% respectively lying below the threshold value of 32 µg/mL invitro. LacZ, a gene in Clade1 strains particularly marked strains with high susceptibility to the drug. Clade3 (74%), Clade5 (89%) and Clade4 (94%) contained higher to moderate resistant strains above threshold value. Clade4a with unchanging titers occurred least likely in non-BV patients. Clade3 and Clade5 were shown to occur in insignificantly indifferent titers and frequency between Acute, Remission and non-BV samples, however, a subset of Clade3 strains containing lytic transglycoslase and thioredoxin associated highly with the acute BV state. Clade3 presence pre-treatment associated with long-term reoccurrence of BV in patients. Post-treatment Clade1 and Clade3 presence associated with long-term reoccurrence of BV whereas Clade2 associated with a refractory response upon treatment.
The next step to study is whether certain combinations of G.vaginalis genotypes and their associated phenotypes with probable interspecies relationships, are particular to clinical outcomes such as patients who remain in remission, those that reoccur in the short-term, reoccur in the long-term or immediately fail to respond to treatment. Assessment of patient genotypes may prove useful for diagnosing high-risk patients who could benefit from intervention.
Siddiqui, Ruqaiya, "Characterizing Gardnerella Vaginalis In Bacterial Vaginosis" (2018). Wayne State University Theses. 807.