Prognosis of recurrent bacterial vaginosis based on longitudinal changes in abundance of Lactobacillus and specific species of Gardnerella

Abstract

Refractory responses to standard-of-care oral metronidazole among recurrent bacterial vaginosis (BV) patients is not rare, and recurrence within a year is common. A better understanding of the bacterial determinants of these outcomes is essential. In this study we ask whether changes in specific species of Gardnerella are associated with poor short or long term clinical outcomes, and if and how resurgence of Lactobacillus species affects these outcomes. We quantify Lactobacillus isolates as a proportion of total vaginal bacteria using the LbRC5 qPCR assay, and 5 prevalent species of Gardnerella using primers that target species-specific polymorphisms within the cpn60 gene. The study includes 43 BV patients: 18 refractory, 16 recurrent, and 11 remission patients, sampled daily for up to two weeks post-treatment; clinical outcomes were tracked for up to 9 months. Persistently high titers of Gardnerella Gsp07 were associated with refractory responses, and persistently low abundance of Gardnerella Gsp07 and G. swidsinskii / G. leopoldii were associated with remission. Lactobacillus species abundance rose in 4–14 days after initiation of treatment in most but not all recurrent and remission patients, although increases were more sustained among remission patients. The findings suggest that Gardnerella Gsp07 and G. swidsinskii / G. leopoldii are markers of poor clinical outcome or may directly or indirectly suppress recovery of Lactobacillus species, thereby interfering with clinical recovery. Therapies that target these strains may improve patient outcome.

Association of key species of vaginal bacteria of recurrent bacterial vaginosis patients before and after oral metronidazole therapy with short- and long-term clinical outcomes

“…We sought to improve discrimination of pretreatment samples by integrating data on the proportion of total Gardnerella , identified by V4 sequences, with previous qPCR data that partially resolved Gardnerella to species levels. In our previous qPCR study [ 15 ], clade-specific primers targeting the Gardnerella cpn60 gene were able to quantify individual or subsets of genomospecies among some of the sample samples subjected to NGS sequencing in the current study. To incorporate the qPCR data into our sequencing dataset, normalized relative abundance per patient was calculated as the relative abundance by qPCR of each Gsp species relative to the total bacterial abundance, based on qPCR with broad-spectrum primers [ 15 ], times the normalized Gardnerella counts present in our sequence reads (S9 Table in S1 File ).…”

“…DNA from vaginal swabs was prepared as described [ 15 ]. Next-generation sequencing of the 16S ribosomal RNA gene, V4 region.…”

“…Associations of individual Gardnerella clades or species with BV pathogenesis have been inconsistent across different studies. However, many have observed that the presence of multiple clades is associated with BV [ 15 , 24 , 28 , 38 ].…”

“…This study focuses on recurrent BV patients as an extension of our study initially reported in 2019 in which we saw three basic responses to treatment with oral metronidazole: refractory, recurrent, and remission [ 15 , 70 ]. This qPCR-based study found that Gardnerella Gsp07 and G .…”

Astodrimer sodium and bacterial vaginosis: a mini review

“…relative to BV-associated species was linked with a higher likelihood of recurrence due to sequestration of metronidazole [ 49 ]. Conversely, another study found that persistently high titres of Gardnerella Gsp07 and/or G. swidsinskii / G. leopoldii were associated with refractory/recurrent BV [ 50 ].…”