Health experts are concerned that a little-known sexually transmitted infection is becoming resistant to antibiotics — but say a simple test can point toward effective treatment options.

Key points: Emerging sexual infection MG likened to a "superbug"

Emerging sexual infection MG likened to a "superbug" New test can help doctors choose best treatment

New test can help doctors choose best treatment Experts want infection to be reportable to health authorities

It's a bug with the unattractive name of mycoplasma genitalium, or MG for short, and many people have never heard of it.

Experts said it could cause infertility and premature birth in pregnant women.

Professor Suzanne Garland from Melbourne's Royal Women's Hospital said people infected with MG often had no symptoms.

"Young, sexually active men and women with different partners are at risk," she said.

Some men have no symptoms but can have pain when urinating. Women may also have no symptoms but some do report pain during sex or while passing urine.

And same-sex couples face the same risk factors as heterosexual couples.

Health experts say the big concern about MG is that it is becoming resistant to antibiotics.

"It's essentially acting like a superbug, with research showing at least 50 per cent of people have a drug-resistant MG, limiting their treatment options," Professor Garland said.

The good news is there is now a simple test that can screen people for the condition and which treatments are likely to work.

The new test is covered by Medicare and will be rolled out to surgeries and clinics across Australia.

Sexual health experts said it was difficult to get an accurate picture of how prevalent MG is.

"In sexual health clinics, 10-35 per cent of the people being tested have it," Professor Garland said.

To get a better picture of how prevalent MG is, health experts want MG to be made a "notifiable disease", which means laboratories need to report it to state and territory health departments.

I had never heard of this infection: patient

Chris Williams had never heard of MG before an ex-partner told him he had been diagnosed with it.

"It was concerning to me. I didn't have any symptoms and my friends didn't know about it as well," the 38-year-old said.

Chris Williams' diagnosis meant he was able to be treated effectively. ( Supplied )

He said as a gay man, he had regular tests for chlamydia, gonorrhoea, syphilis and HIV.

"I had to request a test for MG as it isn't in the usual collection of sexual tests which are commonly offered," Mr Williams said.

He took the new test and found he did have an antibiotic resistant form of MG.

"It meant they could give me one antibiotic for a week to weaken it, then a stronger one," he said.

A second test showed he was cured.

"I felt relieved," Mr Williams said.

"Despite being well-educated on sexual health, the number of unknown factors were quite scary, like, am I a carrier? Or, do I need to disclose this to sexual partners?"