Mycoplasma: Respiratory and Genital Infections Explained

Mycoplasma is a group of very small bacteria that do not have a cell wall. Different species cause different infections and should not be treated as the same condition. Two medically important species are Mycoplasma pneumoniae, which causes respiratory tract infections, and Mycoplasma genitalium, which is a sexually transmitted infection.

Mycoplasma pneumoniae

M. pneumoniae spreads mainly through respiratory droplets during close person-to-person contact. Infection can affect the throat, windpipe and lungs. Common illnesses include pharyngitis, tracheobronchitis and pneumonia. Symptoms often develop gradually and may include cough, fever, headache, fatigue, sore throat and shortness of breath.

Most infections are mild and self-limiting, but pneumonia and other complications can occur. School-age children and younger children are commonly affected, and outbreaks can occur in schools, college residences, hospitals, long-term care facilities and other crowded settings.

Read more about Mycoplasma pneumoniae infection and Pneumonia.

Mycoplasma genitalium

M. genitalium, often called Mgen, infects the genital or urinary tract and is transmitted through sexual contact. Many infections cause no symptoms. When symptoms occur, they can include burning when urinating, genital discharge, bleeding after sex, bleeding between periods or pelvic discomfort.

Read the separate page on Mycoplasma genitalium. The existing web address uses an older label, but Mgen is a genital and urinary tract infection.

Why some antibiotics do not work

Mycoplasma bacteria lack a cell wall. This means beta-lactam antibiotics such as penicillin, which work by targeting bacterial cell walls, do not work against Mycoplasma. When antibiotics are needed, treatment depends on the species, infection site, patient factors and antibiotic resistance.

Most mild M. pneumoniae infections recover without antibiotics, while pneumonia caused by M. pneumoniae is commonly treated with an appropriate antibiotic. Antibiotic resistance can affect treatment choices, so antibiotics should be used only when medically indicated.

Testing and diagnosis

Testing depends on which infection is suspected. For respiratory disease, a healthcare professional may assess symptoms and breathing and may order chest imaging when pneumonia is suspected. Laboratory testing can use respiratory specimens, commonly collected from the nose or throat.

Mgen is diagnosed using specific laboratory testing, usually with a urine sample or genital swab. A positive test for one Mycoplasma species does not diagnose another species or an infection at a different body site.

When to seek medical care

Seek medical assessment for persistent or worsening respiratory symptoms, especially wheezing, fever or shortness of breath. Seek emergency medical care for severe breathing difficulty, blue or gray lips or skin, confusion, collapse or other rapidly worsening symptoms.

Arrange sexual health assessment for genital discharge, burning when urinating, bleeding after sex, unexplained pelvic pain or possible exposure to an STI. Severe pelvic or testicular pain, fever with significant illness, or pregnancy accompanied by pain or bleeding requires prompt medical assessment.

Prevention

Covering coughs and sneezes and washing hands regularly can reduce the spread of respiratory infections. There is currently no vaccine for M. pneumoniae.

Barrier protection such as condoms can reduce the risk of sexually transmitted infections. People diagnosed with Mgen should follow professional advice about treatment, sexual partners, follow-up testing and when sexual activity can safely resume.

Sources

Last reviewed: 4 September 2026. This page provides general health information and does not replace individual medical assessment, diagnosis or treatment.