Bacterial infections in men are a common cause of infertility. Scarring at the site of Infection can cause infertility if scarring blocks the tubes within the testis, epididymis or ejaculatory ducts. The immune response itself can cause the production of chemical byproducts which can be toxic to sperm.

Features of Infections that Cause Male Infertility

Bacterial Infection of the reproductive tract organs can impair the production of sperm or cause scarring and blockage of the tubules that transport sperm, causing infertility. Bacteria can infect various organs of the male reproductive tract including the testis (causing orchitis), the epididymis (causing epididimitis) and the prostate (causing prostatitis). Infection of the testis can shut down the production of sperm by blocking the tiny testicular tubules in which sperm are produced called seminiferous tubules. Freshly produced sperm are temporarily stored in the epididymis, an organ alongside the testis consisting of coiled sperm ducts in which sperm undergo final maturation as they slowly move through the sperm ducts. Infections in the epididymis may interfere with the proper maturation of sperm and can block sperm transport. Because the prostate produces a large portion of the fluid in the ejaculate, infection in the prostate may block the release of fluid from the prostate, reducing the volume of ejaculate.

Effects of Immune Response on Fertility

In response to an infection, white blood cells flood the infection site. Having an excess of white blood cells in the semen can cause fertility problems too, because white blood cells involved in inflammatory process release reactive oxygen species (ROS). ROS are free radicals which are toxic to semen. Sperm plasma membranes can be damaged if they are exposed to high levels of ROS, affecting the sperm's ability to fertilize an egg. Furthermore, ROS in semen can cause sperm DNA damage resulting in fertilization failure. Cytokines, chemical messengers produced as part of the inflammatory response have also been implicated in disrupting normal sperm production. Another part of the immune response that may cause infertility is the production of antibodies to fight the bacterial infection. Sometimes anti-sperm antibodies are also produced which can cause sperm cells to stick together in large clumps, making them useless for fertilization.

Identification of Bacterial Infection

Finding bacteria in the semen is relatively common and is not enough to diagnose infection because bacteria can appear in the semen due to contamination of the sample during collection. Bacteria present on the skin such as staphylococcus and streptococcus are common sources of contamination. Semen may become contaminated with bacteria if the man has a urinary tract infection. E.coli from the gastrointestinal tract may also contaminate semen in the ejaculate. The World Health Organization (WHO) defines infection of the semen as the presence of greater than 1000 bacteria per ml (about a teaspoon) of semen. The presence of very high numbers of white blood cells in the semen (greater than one million per ml) can also signal that an infection is present. To diagnose infection, a sample of semen is cultured in the lab to see which bacteria actually grow out in colonies on culture plates.

Treatment

Depending on the type of bacteria, antibiotics can be prescribed to kill the bacteria. If the infection has already caused inflammation and scarring of the tubes, antibiotic treatment alone will likely not be enough to restore fertility. Surgery may be needed to unblock the tubes. If the blocked tubes are the very small seminiferous tubules of the testis or the epididymis, surgery may not be possible to reopen the tubes. Assisted Reproductive Technology (ART) treatments such as in vitro fertilization (IVF) may be necessary if blockages are so severe that rare or no sperm are present in the ejaculate. If sperm is still being produced, just not transported, it is possible to recover sperm from the epididymis or testis by surgical methods. Because the quantity of sperm recovered by surgical means is very small and the sperm are relatively immature compared to ejaculated sperm, intracytoplasmic sperm injection (ICSI) may be the only treatment option.

Prevention

Some common bacteria that infect men and cause infertility are the bacteria that cause gonorrhea (Neisseria gonorrhea), syphilis (Treponema pallidium), and chlamydia (Chlamydia trachomatis). These three diseases are all sexually transmitted diseases. The risk of infection by these bacteria can be reduced by using condoms during sexual intercourse.