Tag Archives: Urethra

Microbiology

Male circumcision may protect against HPV infection in males and females

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Dr. Sanchari Sinha Dutta, Ph.D.By Dr. Sanchari Sinha Dutta, Ph.D.Apr 10 2023Reviewed by Lily Ramsey, LLM

A systematic review and meta-analysis published in the Clinical Microbiology and Infection Journal highlights the protective effect of male circumcision on the prevalence, incidence, and clearance of human papillomavirus (HPV) infection in males and their female sexual partners.

Study: Association between male circumcision and human papillomavirus infection in males and females: a systematic review, meta-analysis, and meta-regression. Image Credit: KTStockphotos/Shutterstock.com

Study: Association between male circumcision and human papillomavirus infection in males and females: a systematic review, meta-analysis, and meta-regression. Image Credit: KTStockphotos/Shutterstock.com

Background

Human papillomavirus (HPV) is the most common sexually transmitted infection globally. While low-risk HPV types are associated with genital warts, high-risk HPV types are considered major causative factors for cervical cancer.   

Male circumcision is known to have protective effects against many sexually transmitted infections and sexual activity-related conditions.

Many studies have found a link between male circumcision and reduced risk of human immunodeficiency virus (HIV) infection, herpes simplex virus type 2 infection, syphilis, genital ulcer, chancroid, and candidiasis.

In this systematic review, scientists have provided a detailed overview of the association between male circumcision and the risk of HPV infection in males and their female sexual partners. The review also explores whether the protective effects of circumcision vary between different penile sites.

Study design

The scientists searched various scientific documentation databases and included observational and experimental studies reporting the effect of male circumcision on the prevalence, incidence, and clearance of HPV infection in males and their female sexual partners.

Regarding study definitions, prevalence refers to the presence of an HPV infection at any timepoints; incidence refers to the presence of an HPV infection absent at a previous time point; and clearance refers to the absence of a previously-present HPV infection.

For the risk of bias assessment, the Newcastle-Ottawa scale and the Cochrane risk-of-bias tool were used for observational studies and randomized trials, respectively.  

Important observations

The initial screening of databases led to the identification of 1,409 studies, of which 32 studies, including 25 unique study populations, were finally included in the systematic review and meta-analysis. These studies were published between 2002 and 2022.

Among selected studies, 17 were cross-sectional, ten compared two groups cross-sectionally, and five were randomized clinical trials.

In these studies, samples for HPV infection detection and genotyping were collected from different sites in males, including the urethra, foreskin, glans and/or corona, shaft, scrotum, and perianal area. In females, the samples were taken from the cervix and vagina.     

Prevalence of HPV infection

The prevalence of HPV infection among all participants at baseline ranged from 8.7% to 69.8%. 21 studies reported the association between circumcision and HPV infection prevalence in males.

According to the study estimates, circumcision significantly reduced the risk of HPV infections at both glans and shaft. The highest protective effect of circumcision was observed at the glans, irrespective of the viral types (low-risk and high-risk HPV types).

Incidence of HPV infection

The association between circumcision and HPV infection incidence in males was reported by nine studies. Similar to the prevalence findings, circumcision significantly reduced the risk of incident HPV infection at the glans. This association remained unchanged when stratified by low-risk and high-risk HPV types.

Clearance of HPV infection

The association between circumcision and HPV infection clearance in males was reported by seven studies.

In these studies, circumcision significantly increased both the rate and risk of HPV infection clearance at the glans. This occurred irrespective of the types of HPV (low-risk or high-risk).

HPV infection outcomes in females

A total of six studies investigated the association between male circumcision and HPV infection outcomes in female partners of circumcised males. In these studies, circumcision significantly reduced the risk of prevalent high-risk HPV infections and the incidence rate of high-risk HPV infections in female partners.

A similar but non-significant trend was also reported for prevalent infections and the incidence rate of low-risk HPV infections.

Significance

This systematic review and meta-analysis indicate that male circumcision has significant protective effects against the prevalence, incidence, and clearance of HPV infections at the glans penis.

Circumcision also protects female partners of circumcised males against contracting HPV infection.

As mentioned in the article, circumcision is believed to protect against sexually transmitted infections by changing keratinization and the local immune environment of the penis.

The current systematic review suggests that male circumcision might act as a potential preventive intervention, especially in regions where HPV-related cancers are highly prevalent, and anti-HPV vaccination is not available.

Journal reference:
Microbiology

Vaginal sex can shape the composition of urethral microbiome in healthy men

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Reviewed by Emily Henderson, B.Sc.Mar 21 2023

Contrary to common beliefs, your urine is not germ free. In fact, a new study shows that the urethra of healthy men is teeming with microbial life and that a specific activity-;vaginal sex-;can shape its composition. The research, published March 24 in the journal Cell Reports Medicine, provides a healthy baseline for clinicians and scientists to contrast between healthy and diseased states of the urethra, an entrance to the urinary and reproductive systems.

We know where bugs in the gut come from; they primarily come from our surroundings through fecal-oral transfer. But where does genital microbiology come from?”

David Nelson, co-senior author, microbiologist at Indiana University

To flush out the answer, the team of microbiologists, statisticians, and physicians sequenced the penile urethra swabs of 110 healthy adult men. These participants had no urethral symptoms or sexually transmitted infections (STIs) and no inflammation of the urethra. DNA sequencing results revealed that two types of bacterial communities call the penile urethra home-;one native to the organ, the other from a foreign source.

“It is important to set this baseline,” says co-senior author Qunfeng Dong, a bioinformatician at Loyola University Chicago. “Only by understanding what health is can we define what diseases are.”

The researchers found that most of the healthy men had a simple, sparse community of oxygen-loving bacteria in the urethra. In addition, these bacteria probably live close to the urethral opening at the tip of the penis, where there is ample oxygen. The consistent findings of these bacteria suggest that they are the core community that supports penile urethra health.

But some of the men also had a more complex secondary group of bacteria that are often found in the vagina and can disturb the healthy bacterial ecosystem of the vagina. The team speculates that these bacteria reside deeper in the penile urethra because they thrive in oxygen-scarce settings. Only men who reported having vaginal sex carry these bacteria, hinting at the microbes’ origins.

Delving into the participant’s sexual history, the team found a close link between this second bacterial community and vaginal sex but not other sexual behaviors, such as oral sex and anal sex. They also found evidence that vaginal sex has lasting effects. Vagina-associated bacteria remained detectable in the participants for at least two months after vaginal sex, indicating that sexual exposure to the vagina can reshape the male urinary-tract microbiome.

“In our study, one behavior explains 10% of the overall bacterial variation,” says Nelson, when discussing the influence of vaginal sex. “The fact that a specific behavior is such a strong determinant is just profound.”

Although current findings from the study show that vaginal bacteria can spread to the penile urethra, the team’s next plan is to test whether the reverse is true. Using the newly established baseline, the researchers also hope to offer new insights into bacteria’s role in urinary- and reproductive-tract diseases, including unexplained urethral inflammation and STIs.

“STIs really impact people who are socioeconomically disadvantaged; they disproportionately impact women and minorities,” says Nelson. “It’s a part of health care that’s overlooked because of stigma. I think our study has a potential to dramatically change how we handle STI diagnosis and management in a positive way.”

This work was supported by the National Institute of Allergy and Infectious Diseases.

Source:

Cell Press

Journal reference:

Toh, E., et al. (2023). Sexual behavior shapes male genitourinary microbiome composition. Cell Reports Medicine. doi.org/10.1016/j.xcrm.2023.100981