Cervicovaginal bacterial communities in reproductive-aged Tanzanian women with Schistosoma mansoni, Schistosoma haematobium, or without schistosome infection

Abstract

Schistosome infection is recognized as a potentially modifiable risk factor for HIV in women by the World Health Organization. Alterations in cervicovaginal bacteria have been associated with HIV acquisition and have not been studied in schistosome infection. We collected cervical swabs from Tanzanian women with and without S. mansoni and S. haematobium to determine effects on cervicovaginal microbiota. Infected women were treated, and follow-up swabs were collected after 3 months. 16S rRNA sequencing was performed on DNA extracted from swabs. We compared 39 women with S. mansoni with 52 uninfected controls, and 16 with S. haematobium with 27 controls. S. mansoni-infected women had increased abundance of Peptostreptococcus (p = 0.026) and presence of Prevotella timonesis (p = 0.048) compared to controls. High-intensity S. haematobium infection was associated with more diverse cervicovaginal bacterial communities than uninfected controls (p = 0.0159). High-intensity S. mansoni infection showed a similar trend (p = 0.154). At follow-up, we observed increased alpha diversity in S. mansoni (2.53 vs. 1.72, p = 0.022) and S. haematobium (2.05 vs. 1.12, p = 0.066) infection groups compared to controls. Modifications in cervicovaginal microbiota, particularly increased diversity and abundance of taxa associated with bacterial vaginosis and HIV (Peptostreptococcus, Prevotella), were associated with schistosome infection.

Keywords: Cervicovaginal microbiota; HIV; Microbiome; Schistosomiasis; Tanzania.

Fig. 1. Beta diversity between Schistosome infected and uninfected women at baseline and follow-up.

Principal coordinate analysis using Bray-Curtis distance metric on schistosome infected and uninfected women at baseline and 3-month follow-up. Women infected with S. haematobium at 3-month follow-up (d) are more clustered compared to uninfected women (c), or to women with S. mansoni infection at baseline (a) or 3-month follow-up (b). This indicates that infected women have cervicovaginal microbiomes that are more similar to each other than uninfected women.

Fig. 2. S. mansoni and S. haematobium alpha diversity at baseline and 3-month follow-up, by infection intensity.

Differences in alpha diversity, as shown by Shannon Diversity Index, between uninfected, low intensity infected, and high intensity infected women at baseline and 3-month follow-up from S. mansoni and S. haematobium-endemic villages. The plots display medians (dark horizontal bars) and interquartile ranges (boxes), with error bars representing 1.5 times the interquartile range or minimum/maximum values. Women with high-intensity S. mansoni infection had a trend towards increased diversity compared to uninfected women at baseline (p = 0.154). Women with high-intensity S. haematobium infection had significantly increased diversity compared to their uninfected counterparts at baseline (p = 0.016). Women with low-intensity infection S. mansoni or S. haematobium infection had increased diversity compared to their uninfected counterparts at follow-up (p = 0.022 and p = 0.066).

Fig. 3. Relative abundances of 11 most abundant cervicovaginal microbiota by genus in S. mansoni and S. haematobium groups at baseline.

Relative abundance of the 11 most abundant cervicovaginal microbiota at the genus level for uninfected, low intensity infected, and high intensity infected women with S. mansoni (upper horizontal band) and S. haematobium (lower horizontal band) at baseline. Each vertical bar represents a successfully sequenced cervicovaginal sample. Labels above each bar indicate infection status: “U” for uninfected, “L” for low-intensity infection, and “H” for high-intensity infection. Women with S. mansoni infection had increased Peptostreptococcus (shown in dark blue, p = 0.026) and women with high-intensity S. mansoni infection showed a trend toward decreased Lactobacillus (p = 0.273). No significant differences were observed in individual taxa between S. haematobium infected and uninfected women.

Fig. 4. Differences in abundance of Peptostreptococcus anaerobius between S. mansoni.

Infected and uninfected at baseline and 3-month follow-up. Differences in relative abundance of Peptostreptococcus anaerobius between S. mansoni infected and uninfected women at baseline and 3-month follow-up. The plots display medians (dark horizontal bars) and interquartile ranges (boxes), with error bars representing 1.5 times the interquartile range or maximum values. Women with S. mansoni infected had increased abundance of Peptostreptococcus anaerobius at baseline and at follow-up compared to uninfected women (p = 0.040 and p = 0.119, respectively).

Fig. 5. S. mansoni and S. haematobium microbiota by genus at 3-month follow-up.

Relative abundance of cervicovaginal microbiota at the genus level for uninfected, low intensity infected, and high intensity infected women with S. mansoni (upper band) and S. haematobium (lower band) at 3-month follow-up. Each vertical bar represents a successfully sequenced cervicovaginal sample. Labels above each bar indicate infection status: “U” for uninfected and “L” for low-intensity infection. Women with S. mansoni infection had increased Peptostreptococcus (as shown in dark blue, p = 0.049) and increased alpha diversity (p = 0.022). Women infected with S. haematobium infected also had increased alpha diversity (p = 0.017).