Mycoplasma genitalium

What is a Mycoplasma genitalium infection?

Mycoplasma genitalium (Mgen) is a sexually transmitted infection (STI) which causes few, and often no, symptoms. It is sometimes described as a 'new' STI - it was discovered in 1981.

At that time it was unclear that it was sexually transmitted and no reliable test had been developed to detect it. A reliable test that hospital labs can use has been available since 2017.

Mgen is caused by a tiny bacterium called Mycoplasma genitalium. It infects the urogenital tract, which means the vagina, womb (uterus) and Fallopian tubes and urethra in women, and the urethra and epididymis (sperm-carrying tube) in men.

To read more about other STIs, see the separate leaflet called Sexually Transmitted Infections.

How common is Mycoplasma genitalium infection?

Mycoplasma genitalium is thought to infect one to two in every 100 adults aged 16-44 years in the UK who are sexually active. However, relatively few studies have looked at how common this infection is. Some experts think Mgen may already infect around 2% of Europeans and 3% of the world's population.

The infection rate for mycoplasma genitalium is highest in those who have multiple sexual partners or do not practise safe sex (this is true for all STIs). It is also more common in those who smoke (which we know makes people more susceptible to many infections) and those of Afro-Caribbean ethnicity. (In the United States it is least common in people of Hispanic ethnicity, then people who are white and then most common in African-Americans.

Mycoplasma genitalium symptoms

The infection most often has no symptoms. It is thought that seven to eight out of every ten affected men, and five to seven out of every ten affected women do not have symptoms.

However, in male patients with nongonococcal urethritis and female patients with pelvic inflammatory disease, Mgen is a common cause.

Where Mgen causes symptoms, they are thought to typically appear 1-3 weeks after initial infection. They include:

Mycoplasma genitalium in men

• Urethritis (inflammation and swelling of the tube that carries urine from the bladder to outside).

• Pain on passing water.

• Pain on ejaculation.

• Watery or cloudy discharge from the tip of the penis.

• Inflammation of the back passage (proctitis).

• Inflammation of the foreskin and penis.

Mycoplasma genitalium in women

• Urethritis (pain on urination, soreness in the external genitalia).

• Increased or altered vaginal discharge.

• Bleeding between periods.

• Cervicitis (inflammation of the cervix) causing pain on intercourse and discharge or bleeding after intercourse.

• Lower tummy (abdominal) pain.

Is Mycoplasma genitalium the same as chlamydia?

Mycoplasma genitalium symptoms are very similar to infection with chlamydia, but it is caused by a different germ (bacterium). Many cases in the past have probably been treated as if they were chlamydia; this may have led to Mgen 'learning' about antibiotics and developing resistance, since treatment for chlamydia does not completely eradicate mycoplasma genitalium.

It is possible to have both infections. Mgen appears to be less common than chlamydia. It also appears to be slightly less easily transmitted than chlamydia.

See the separate leaflet called Chlamydia for more information.

How do you test for Mycoplasma genitalium?

Urethritis is inflammation of the urethra, which is the tube that carries urine out from the bladder. Urethritis is most commonly caused by infection and is the most common condition diagnosed and treated among men in genitourinary medicine (GUM) clinics or sexual health clinics in the UK.

Urethritis is known to be an STI. Some years ago, when testing was not available for chlamydia or for Mgen (and they were not known as major causes of urethritis), cases of urethritis were divided into two terms.

They were referred to as 'gonococcal urethritis' and 'non-gonococcal urethritis' (NGU) - sometimes also called 'nonspecific urethritis' (NSU). When a test for chlamydia was developed it became clear that many, but not all, cases of NGU were due to chlamydia.

However, significant numbers of cases did not test positive for either gonococcus or chlamydia. It now seems likely that many - if not most - of these are due to Mgen. The most common cause of NGU is still chlamydia; in the UK, Mgen is now believed to be more common than gonorrhoea.

To read more about these infections, see the separate leaflets called Gonorrhoea, Urethritis and Urethral Discharge in Men and Non-gonococcal Urethritis.

How is mycoplasma genitalium transmitted?

Mycoplasma genitalium is caught from sex with an infected person. It is transmitted through genital to genital contact such as vaginal or anal sex. Transmission may occur even without penetration.

Can I catch Mycoplasma genitalium from oral sex?

It is not yet clear whether it can be easily transmitted through oral sex but it is thought possible.

Will a condom protect me from Mycoplasma genitalium?

Yes, whilst condoms do not provide perfect protection, male or female condom use provides a very high level of protection against Mycoplasma genitalium since it greatly reduces direct contact between genital tissues, particularly the penis.

What are the complications of Mycoplasma genitalium infection?

The complications of a Mycoplasma genitalium infection result mainly from the way the immune system reacts to the germ (bacterium).

However, the bacterium itself appears to be directly harmful to the Fallopian tube lining.

The main complications are similar to those of chlamydia:

• Pelvic inflammatory disease: this is infection and inflammation in the womb (uterus) and Fallopian tubes. Symptoms may include abdominal pain and pain on intercourse, a raised temperature, and becoming significantly unwell. Infection of the Fallopian tubes may cause them to become scarred and blocked, leading to tubal infertility.

• Sexually acquired reactive arthritis (SARA) can occur as a reaction to urethritis in men and women.

• Epididymo-orchitis may occur in men - this is painful swelling and infection of the testicle (testis) and a tube called the epididymis. There has been a suggestion that Mgen may have a role in male infertility. This has not yet been proved.

• If someone has other STIs like HIV, having Mgen as well makes them more likely to pass on those other infections.

What are the risks of Mycoplasma genitalium in pregnancy?

Mycoplasma genitalium is linked to preterm birth and miscarriage.

It is thought possible that Mycoplasma genitalium can be passed to the baby at the time of vaginal delivery. It is not clear whether Mgen can be passed to the baby whilst in the womb (uterus) and it is also unclear whether this causes harm to the baby.

If diagnosed with Mycoplasma genitalium during pregnancy it is important to inform the midwife and/or obstetrician of the diagnosis. It is also vitally important that you inform the clinic which is treating the Mgen if there is any chance of pregnancy as not all antibiotics used for Mgen are safe for use in pregnancy.

Can I tell whether my partner has Mycoplasma genitalium?

It is impossible to tell whether someone has Mycoplasma genitalium - they may not even know themselves since the infection normally causes no symptoms (it is asymptomatic).

Testing for Mycoplasma genitalium

Mycoplasma genitalium can be detected by laboratory tests performed on vaginal swabs (from women) and 'first void' urine samples from men.

The germ (bacterium) is not easy to detect or isolate, and a special test called a nucleic acid detection test is used.

Laboratories also test Mgen for antibiotic resistance in order to determine which treatment to use.

People who should be tested for Mycoplasma genitalium

Tests should be performed for:

• Any men or women with symptoms that could be due to Mycoplasma genitalium.

• All men with non-gonococcal urethritis.

• All women with pelvic inflammatory disease.

• Current sexual partners of persons infected with Mgen.

Sexual partners who test positive but have no symptoms should be treated for Mycoplasma genitalium. It is not yet clear if Mgen is harmful to them, but treating them prevents them from passing Mgen back to the affected patient or on to others.

Mycoplasma genitalium treatment

Mycoplasma genitalium treatment is changing, as the germ (bacterium) is rapidly becoming resistant to the usual treatments. The mainstay of treatment used to be a single dose of an antibiotic, azithromycin. However, longer courses of treatment are usually now needed.

Newer medicines like pristinamycin, solithromycin and sitafloxacin are being tried. However, widespread use of these newer medicines - particularly if patients don't complete the course, so that their Mgen is not completely eradicated - will lead to further drug resistance.

Current sexual partners should be given the same treatment regime as the patient.

Current recommended treatments in the UK

• Doxycycline 100 mg twice daily for seven days; or

• Azithromycin 1 g as a single dose, then 500 mg daily for two more days; or

• Moxifloxacin 400 mg daily for 10 days. This is currently reserved for cases known to be resistant to azithromycin. Resistance to moxifloxacin is already problematic in Asia.

If these are not effective, alternatives are:

• Doxycycline 100 mg twice daily for seven days, followed by pristinamycin 1 g four times daily for 10 days.

• Pristinamycin 1 g four times daily for 10 days.

• Doxycycline 100 mg twice daily for 14 days.

• Minocycline 100 mg twice daily for 14 days.

In cases of pelvic inflammatory disease and epididymo-orchitis it is recommended that a 14 day course of moxifloxacin (400 mg once daily) be used.

It is recommended that a repeat test be done three weeks after finishing treatment, to make sure the infection has completely gone.

One of the main causes of medication resistance is partial treatment of infections If infections are only partially treated, a few bacteria remain - these are often the ones that were slightly better at resisting the antibiotic; these bacteria then develop a resistance mechanism which is passed on as they multiply.

Does Mycoplasma genitalium go away by itself?

It is highly unlikely that Mycoplasma genitalium ever goes away by itself.

Although immune systems are very good at fighting off some kinds of germs (bacteria), they seem to be less good at eradicating the group called Mycoplasma. These organisms are very hardy, can often infect without causing any detectable illness and hide inside the cells of bodies in order to avoid attack by the immune system.

Can I have sex whilst being treated for Mycoplasma genitalium?

It is important to refrain from intercourse until both partners have completely finished treatment. Women with pelvic inflammatory disease should refrain from intercourse until 14 days after the start of treatment or 14 days after symptoms have resolved, whichever is later.

How long have I had Mycoplasma genitalium?

Scientists are still learning about Mgen. At present, when diagnosed with Mgen, doctors have no means of determining when it was caught. It seems likely that, once caught, the infection will remain until it is treated.

It is also not known whether people who have symptoms from Mgen could previously have had silent infections. This means that a diagnosis of Mgen does not mean it has been acquired recently; it may have been present for a long time.

Can I get Mycoplasma genitalium without having sex?

Mgen is transmitted by genital-to-genital contact. It can be acquired without having full intercourse but it is an STI so transmission requires sexually intimate contact.

I am in a same-sex relationship - can I still catch Mycoplasma genitalium?

Yes, you can. Mycoplasma genitalium is transmitted by genital-to-genital contact including vaginal and anal contact and oral-to-genital contact. It is likely to be more easily transmitted in cases of genital contact, by men with symptoms of urethritis, and by women with symptoms of urethritis of pelvic inflammatory disease.

Because Mgen appears to particularly infect the urethra in men and women, male or female condom use will greatly reduce transmission between couples of any gender.

What is the outlook (prognosis) for Mycoplasma genitalium?

If Mycoplasma genitalium is eradicated with antibiotics then, as long as complications have not already developed, there is no reason to think it will cause any long-term health problems.

If (as is suspected) Mgen causes tubal damage in patients who develop pelvic inflammatory disease, then this could result in irreversible tubal damage which could affect fertility.

It is unclear whether Mgen can cause infertility in men who develop epididymo-orchitis - this is possible but research is ongoing.

If reactive arthritis develops as a consequence of Mgen then it is likely that, as for chlamydia, treatment of the Mgen will treat the arthritis, although it typically takes a few months to settle down.

Can I get tested for Mycoplasma genitalium?

At present, it is not recommended that everyone is tested for Mgen. This would involve testing millions of people in order to detect the one to three in 100 people who are thought to be positive.

This is not done because:

• It would be a hugely costly exercise, in money and manpower.

• It appears likely that it is patients who have symptoms of pelvic inflammatory disease who are most at risk of complications from Mgen.

• Treatment is currently not perfect, and if everyone is treated, then the rate at which the bacterium becomes resistant to known antibiotics will also increase rapidly.

How can I avoid catching Mycoplasma genitalium?

The fewer the sexual partners, the less likely it is to contract this infection.

Wearing a condom will help protect against Mycoplasma genitalium, and will prevent most cases of transmission.

Stopping smoking also reduces the chances of catching mycoplasma genitalium and other STIs.

When can my partner and I stop using protection?

If either or both of you have had sexual partners in the past, then it is not impossible that you have a 'silent' STI such as Mycoplasma genitalium or chlamydia.

Anyone who has had sexual partners in the past could have a "silent" STI such as Mycoplasma genitalium or chlamydia. It is therefore sensible to have tests done before having intercourse without protection. This is particularly important if:

• One of the partners has symptoms of Mycoplasma genitalium, or any other sexually transmitted condition.

• There have been symptoms in the past but they seem to have settled down without treatment.

• A previous partner has required treatment for an STI.

You may also find it helpful to read the separate leaflet called STI Tests.

Dr Mary Lowth is an author or the original author of this leaflet.