New Markers Could Predict Risk of Severe Chlamydia Infection

Chlamydia trachomatis is a common sexually transmitted infection that can cause pelvic inflammatory disease, infertility, and other reproductive complications when it spreads to the upper genital tract. Currently, ascension into the uterus and endometrium can only be confirmed through an invasive endometrial biopsy. Researchers have now identified biological markers that may pave the way for new diagnostics to predict a woman’s risk of severe infection without the need for such procedures.

A collaborative team from North Carolina State University (Raleigh, NC, USA) and the UNC School of Medicine (Chapel Hill, NC, USA) analyzed cervicovaginal microbiome (CVM) samples from 246 women in a high-risk cohort for chlamydia. Using 16S ribosomal RNA (rRNA) gene-based high-throughput amplicon sequencing, they tagged and quantified bacteria present in the samples. Participants were classified into three groups—CT negative, CT positive, and CT ascended—to assess differences in microbiome composition.

Image: New diagnostics could predict a woman’s risk of a common sexually transmitted infection (Photo courtesy of 123RF)

The sequencing analysis revealed that higher amounts of certain bacterial species, such as Hemophilus haemolyticus, Sutterella stercoricanis, and Actinobaculum massiliense, were predictive of ascended infections. These microbes also correlated with seven cytokines previously linked to chlamydia spread. Notably, the study found that the bacterial load of chlamydia itself was the strongest predictor of ascension.

The findings, published in Infection and Immunity, indicate that specific microbial and immune profiles could be developed into biomarkers to identify women at high risk for upper genital tract infection. Such diagnostics could enable earlier intervention, potentially preventing severe reproductive outcomes. Future studies will focus on understanding how these microbes influence immune responses to control chlamydia levels and disease progression.

"We knew that some bacterial species make a woman more susceptible to CT infection, while ‘good’ bacteria such as lactobacillus seem to make it harder to become infected," said Catherine O’Connell, professor of pediatrics, UNC School of Medicine, and co-project leader. “This work shows that other bacteria present may be keeping host immunity alert and responsive, making it harder for infecting chlamydia to grow abundantly. It shows that there is potential for developing biomarkers to identify women at high risk for ascended CT.”