The presence of bacteria in semen is considered normal in most cases, as cultures are naturally found inside the urinary and genital tracts. In some cases this healthy bacteria can grow out of control, leading to an infection. An infection inside of the penis or prostate may lead to high levels of bacteria in semen. Having sex with an infected partner could also lead to an infection in the genital or urinary tract, although this is less likely to occur.
All healthy males have some level of bacteria in their semen. These normally occurring flora colonize in the reproductive and urinary tracts and typically do not cause any harm. In males who aren't circumcised, bacteria may also colonize behind the foreskin. Overgrowth of this bacteria can be prevented through proper hygiene. Those who do not wash behind their foreskins correctly could wind up with a urinary tract infection or more than average bacteria in their semen.
Colonization of bacteria is not considered an infection. An infection is typically related to additional symptoms, such as urinary frequency or urgency. Other signs of an infection include fever, pus or blood coming from the penis, unusual discharge, or pain. Sometimes there is no known cause of infection. Normal bacteria can grow more rapidly than usual for any number of reasons, including hormonal issues, unusual stress, or another illness.
Large amounts of bacteria in semen may also be caused by infection through sex with an infected partner. Women with a bacterial vaginal infection can spread harmful bacteria through intercourse. This is not considered the same as sexually transmitted diseases, which are mostly caused by viruses. When this does occur, men will typically notice symptoms of an infection. A doctor is generally the one who detects bacteria in semen.
Prostate swelling can also lead to infection because the swollen prostate gland doesn't allow the bladder to empty completely. Bacteria is then allowed to grow inside the bladder, and can then migrate into the genital tract. This condition is much more common in older men because they are prone to enlarged prostates.
In most cases, treatment for large quantities of bacteria in semen includes the use of antibiotic medication. The exact type of medication used will depend on the type of bacteria present. In rare cases, an uncircumcised male may have his foreskin removed due to recurrent infection if bacteria stems from an overgrowth beneath the foreskin itself. This is uncommon in males who practice proper hygiene. Men with enlarged prostates are often given medication to bring down swelling and underlying prostate conditions can also be treated.