New chlamydia hypothesis highlights importance of early screening

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New insights on chlamydia’s link to cancer and ectopic pregnancy risk could lead to preventative treatments for chlamydia-induced disease.

Researchers have discovered a new possible explanation for why chlamydia could increase the risk of developing cancer or having an ectopic pregnancy. The findings from the review, carried out by the University of Bristol and University of Edinburgh, also offer a potential explanation for how pelvic inflammatory disease could be triggered in some women.

The review has been published in the Journal of Infectious Diseases.

Researchers analysed evidence from lab-based studies, animal models, and clinical studies on the role of chlamydia in diseases of the reproductive tract. The findings of the analysis showed that chlamydia induces a particular type of change in reproductive tract cells known as ‘epithelial to mesenchymal transition’ (EMT), which can lead to inflammation and cell growth. From this, the researchers determined that this chlamydia-triggered cell change contributes to the development of further disease.

The researchers’ analysis of the findings suggests that chlamydia induces a particular type of change in reproductive tract cells known as epithelial to mesenchymal transition (EMT), which can lead to inflammation and cell growth. Their hypothesis is that this chlamydia-triggered cell change contributes to the development of further disease.

Chlamydia is the most common bacterial sexually transmitted infection worldwide. If left untreated, it can cause pelvic inflammatory disease, ectopic pregnancy, tubal factor infertility, and chronic pelvic pain due to tubal scarring.

Insights for disease prevention

Dr Paddy Horner, from the NIHR Health Protection Research Unit in Behavioural Science and Evaluation at University of Bristol, who led the review, said: “Chlamydia is a bacterial infection that stimulates EMT, which may persist after the chlamydia infection has cleared.

“We think that the association of chlamydia with ovarian and cervical cancer could be explained by the persistence of EMT changes in combination with DNA damage caused by chlamydia following chlamydia infection.

“Also, we know that EMT cells impair the integrity of the lining of the infected reproductive tract cell, making it more susceptible to invasion by other bacteria. This increases the risk of pelvic inflammatory disease from those invading bacteria.Dis

“Furthermore, epithelial (barrier) cells in the fallopian tube that have previously been infected with chlamydia have more receptors on their surface, which are associated with an increased risk of ectopic pregnancy. There is evidence that these cell surface receptor changes could be caused by EMT.

“If our hypothesis about the role of EMT following chlamydia infection in women is correct, it could help explain some of the recent epidemiological observations about chlamydia and reproductive disease which are difficult to account for using current concepts about the immune response to chlamydia.

“It would also support the English National Chlamydia Screening Programme’s shift to earlier testing of women, as the shorter the duration of infection, the lower the risk of developing EMT changes. Further down the line, this could lead to the development of new tests for identifying women at increased risk of ovarian cancer and ectopic pregnancy and interventions that could reduce these risks.

“Obviously a lot more research is needed before we can be sure that our hypothesis is correct, but the evidence from this review suggests that further research in this area would be fruitful and could have important benefits both for patients and in the prevention of chlamydia-induced disease in the long-term.”

The importance of early chlamydia detection

Munira Oza, Director of the Ectopic Pregnancy Trust, said: “This analysis helps to further our understanding of one of the possible risk factors for ectopic pregnancy and we would welcome more research in this area.

“It also highlights the importance of the change of focus of the National Chlamydia Screening Programme to opportunistically making proactive offers of a chlamydia test to young people without symptoms to reduce the risk of reproductive harm.

“With early detection through the screening programme and much-needed education to reduce the stigma of chlamydia, we hope that many women and families might be spared the health risks and heartache of ectopic pregnancy. We encourage young women to screen when given the opportunity.”


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