Circumcision Alters the Penis Microbiome

Diminished bacterial diversity and abundance may help explain why circumcision is associated with reduced HIV infection.

By | April 18, 2013

CDC, C. GOLDSMITHA circumcised penis is less hospitable to anaerobic bacteria than an uncircumcised one, research published in mBio earlier this week found. The study suggests that changes in the penis’s microbial composition could explain why circumcision reduces men’s risk of contracting HIV.

Researchers compared 79 men from Rakai, Uganda, who volunteered to be circumcised, with 77 uncircumcised controls from the same community, measuring the microbial diversity of both groups’ penises before the circumcisions and a year after the procedures. (The control group also volunteered to be circumcised but was randomly assigned to undergo the procedure after the study was over.)

While microbial populations on all the men’s penises shifted over time, the men who had been circumcised showed a more pronounced change. Circumcision “selected for bacteria capable of surviving in the aerated circumcised microenvironment,” the researchers wrote in the paper. Prevalence and diversity of 12 taxa of anaerobic bacteria decreased most dramatically.

According to previous research, circumcision reduces men’s HIV risk by 50 to 60 percent, and the authors of the new study argued that this reduction could in part be explained by the decline in penis microbes. They hypothesized that the bacteria living under the foreskin may cause minor inflammatory immune responses. Inflammation caused by bacteria could stimulate Langerhans cells to present HIV particles to CD4+ T cells. Since HIV uses these cells to replicate, the authors reasoned, this immune response could increase the likelihood that HIV will take hold in the body. The researchers plan to test this hypothesis in further work, according to LiveScience.

“As a society, we’ve gotten used to thinking about alterations to the microbiome as having negative outcomes,” coauthor Lance Price, who researches microbial pathogens at the George Washington University School of Public Health, told the Los Angeles Times. “We think about the person who takes antibiotics in the hospital and ends up with an infection in their gut because we’ve knocked out the natural microbiota. But here’s a situation where we’re flipping that notion on its head. The disturbance of the microbiome could have a positive effect.”

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Avatar of: brinxster


Posts: 1

April 18, 2013



We have millions of boys across the world who are forced to have their genitals mutilated against their free will. So it's of upmost importance to note that no matter what the pros or cons of circumcision are, it must be a choice the male himself decides for himself. 

He, himself can weigh all the pros & cons, such as a 75% loss of sexual sensitivity and fourfold increased risk of erectile dysfunction, and decide if those pros are worth sacrificing a great deal of sensitivity for. In most cases though, when Human Rights are respected and he has that choice for himself he simply opts to use condoms instead of amputating a part of his genitals. 


Avatar of: Jackieno


Posts: 1

April 18, 2013

This article is wrong and the study misses the main point. Cut men get different INVASIVE bacteria. Whereas natural men have NATURAL bacteria. It has been observed that natural boys have the same bacteria as natural girls and that cut boys have different (invasive) bacteria. These folks are taking a primitive approach. The fact is that you change the natural flora, you cause problems.

BTW, It has become evident that in the actual populations men that have parts of their genitals cut off are getting HIV at the same or higher rate than men that have their natural genitals. For example The HIV prevalence rate among circumcised males between the ages of 15 and 49 in Zimbabwe is higher than that of the uncircumcised males "after the circumcision drive." In Uganda the HIV rate continues to rise after the the circumcision drive. IN US population studies, circumcision has not shown ANY benefit for HIV or STDS.

The often cited studies probably just show that men that had their genitals wounded (and cannot have sex for some time) and/or have received condoms and safe sex advice get HIV at a lower rate than men not wounded and/or that have not gotten condoms and safe sex advice. In any event, the 1.3% risk change (almost 60 %relative risk change) claimed is barely statistically significant.

This is a terrible waste of resources and may lead to less use of condoms and more HIV in Africa. It will certainly lead to more sexual dysfunction as these men age -- who supplies the VIAGRA?

Avatar of: mikerol


Posts: 1

April 18, 2013


A wash cloth before and after sex or a good blow job from a clean mouth are equally effective and leave the pleasure zones intact!  

 Making it a taboo to compare male with female sexual mutilation is the biggest scandal of the controversy. In both instances the most sensitive and most erogenous zone of the human body is amputated and severely damaged. In both instances, what counts primarily is the cutting of human sexuality. The imposition of control by the patriarchy.  A good look at a book on embryology will show the development of the nerves and tissue and how they are the same.

What is lacking in all the talk about circumcision is discussion of its archeological dimension - that it is the left over of human sacrifice. What kind of god is it that demands that of an infant? If the Bris constitutes the identity of the male, what about the identity of a Jewish girl? Or is this an entirely homosexual ceremony?

  Also, unfortunately it is / has been circumcision that has MADE for no end of anti-semitic sentiments. Freud found that it was the chief reason for unconscious anti-Semitism. And the myths surrounding it are at the core of the “blood libel.” Thus, it's time to eliminate the Brit Milah because if that is the chief reason for being anti-Semitic or anti-Abrahamic [Islam too practices the rite] then why hang on to this left-over of human sacrifice? that traumatizes the child, cutting off 5,000 nerves, that is the equivalent of female circumcision in the sense that it eliminates everything but the clitoris,and only serves the Ultra Orthodox to maintain their power? After all, reform Judaism sought to eliminate the rite in the 19th century, and Jewish identity depends on being born by a Jewish mother, or converting. Here  a link to an archive of the entire German and then some debate, note especially Michael Wolffsohn's two pieces  . Circumcision has been controversial also within Jewry forever.




Avatar of: ml66uk


Posts: 2

April 19, 2013

Female genitals are harder to clean than men's, but we don't cut parts off baby girls to make it easier.

It's illegal to cut off a girl's prepuce, or to make any incision on a girl's genitals, even if no tissue is removed. Even a pinprick is banned. Why don't boys get the same protection? Everyone should be able to decide for themselves whether or not they want parts of their genitals cut off. It's *their* body.

Male circumcision doesn't seem to help against AIDS either.  From a USAID report:
"There appears no clear pattern of association between male circumcision and HIV prevalence—in 8 of 18 countries with data, HIV prevalence is lower among circumcised men, while in the remaining 10 countries it is higher."

It's really easy to find circumcised doctors who are against circumcision, but surprisingly difficult to find male doctors in favour who weren't circumcised themselves as children.

Avatar of: Baxter Zappa

Baxter Zappa

Posts: 11

April 19, 2013

This article has stimulated a large anti-circumcision response that makes all kinds of claims, but not much evidence was cited or supplied to substantiate the claims. These comments make it sound like circumcision ruins the sex life. I know many people of all ages who are circumcised and plenty sensitive and sexual. I know people who are uncut w/ ED problems but no one who is cut w/ an ED problem. And I have heard women say that they are more likely to get UTIs from uncut men. What I said is purely anecotal, my life experience. But here is data from several real studies:

Avatar of: Hugh7


Posts: 1

May 1, 2013

This study merits a great big "SO WHAT?" It's hardly surprising if an enclosed part of the body, like between the toes, has different bacteria from an open part. The rest of the study is pure speculation piled on more speculation. But just let a story say "circumcision" and "HIV" and the media are all over it.

When are the media going to notice that it is just a tiny clique of interconnected researchers who are doing nothing but churning out articles in support of infant circumcision? In this case, the clique members are Aaron Tobian, Maria Wawer, Ronald Gray, David Serwadda and Godfrey Kigozi. Their study is of two groups of only 78 paid adult volunteers for circumcision - hardly a large or random sample of the population; each man accounts for 1.2 percentage points. They were recruited by inviting each other, so they would tend to know each other and maybe even have sexual partners in common. They are part of one of the three studies claiming to show that circumcision reduces HIV transmission (but only from women to men), that circumcision is safe, that it does no harm to sex and (not so publicised) that it does not reduce HIV transmission from men to women. (In fact they found it may INCREASE it, but that has had zero publicity.) They must be one of the most over-used experimental groups in history.

Why did they not give equivalent publicity to the letter from 38 top paediatricians - heads or spokespeople for 22 paediatric associations in 17 countries - basically the whole of Europe - pointing out that the American Academy of Pediatrics circumcision policy is culturally biased, utterly fails to show that the benefits outweigh the risks, and fails to assign any weight to the individual's right to choose the fate of his own genitals? (  They wrote because the AAP policy was being touted to promote legalising infant circumcision in Germany, contrary to its constitution.)
Or a new study showing that circumcision has no significant effect on STI transmission? (

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