Mycoplasma hominis: what a positive result means

Mycoplasma hominis is a bacterium that sits in the normal genital flora of many people without symptoms. It is not classed as an STI. In 2018 the European STI Guidelines Editorial Board even advised against routine testing for it, because a positive result without symptoms means very little (Horner, 2018).

People still get that result, and it still gives them a fright.

That happens because the name mycoplasma calls up mycoplasma genitalium, which is an entirely different bacterium. Below we set out the difference and explain where Mycoplasma hominis does belong.

Is mycoplasma hominis an STI?

No, not in the usual sense. The bacterium can pass on through sexual contact, but it is found just as readily in people without symptoms and without recent risk. That is why it is not on the list of infections routinely tested for in the Netherlands, and why the RIVM does not track it in STI surveillance.

The confusion lives in the name.

Mycoplasma genitalium is an established STI and has its own European guideline, including its own treatment advice (Jensen, 2022). Mycoplasma hominis has neither. Two bacteria, the same first name, a completely different status. Anyone reading only "mycoplasma" on a test page cannot tell which of the two is meant.

So where does mycoplasma hominis belong?

More often with disturbed vaginal flora than with an STI. Mycoplasma hominis is regularly found alongside bacterial vaginosis, where the normal lactic acid bacteria drop in number and other bacteria get room. There the bacterium is more of a passenger than the driver.

That makes it a familiar pattern, not a mystery.

It closely resembles the debate around gardnerella, which we covered in is gardnerella an STI. There too the bacterium follows a disturbed balance, rather than being something you "catch" from a partner the way chlamydia works.

If your symptoms are discharge with an unusual smell, read bacterial vaginosis symptoms. If you are unsure between bacterial vaginosis, candida and trichomonas, our comparison of the three sets them side by side.

What does a positive mycoplasma hominis result mean?

Usually it means the bacterium is present. Without symptoms that is not in itself a reason for treatment. The position of the European STI Guidelines Editorial Board is that untargeted testing for this bacterium mainly produces results nobody can interpret well (Horner, 2018).

With symptoms it sits differently, but even then the question is: is this bacterium the cause?

Picture two women aged 27 getting the same positive result from a broad panel. One has had discharge with an unusual smell for 6 weeks. The other has no complaints at all.

For the first, the result belongs in a bigger story about vaginal flora. For the second it says almost nothing, and we've come to see that as the most important sentence in this article.

Research into urethritis in men shows that several causes are often involved at once, and that in a share of cases no known cause is found at all (Jordan, 2020). So a positive Mycoplasma hominis on that list does not automatically mean you have found the cause.

That weighing up belongs with a doctor. We cannot interpret a result for you and will not try.

Is mycoplasma hominis treated?

Only where there are symptoms and other, more likely causes have been ruled out. In people without symptoms, treating is generally not on the table. The Dutch GP standard on the STI consultation describes which causes are tested for as standard in Dutch primary care, and Mycoplasma hominis is not among them.

The same objection applies as with ureaplasma.

Antibiotics without a clear indication contribute to resistance. With mycoplasma genitalium that became plainly visible, and that story is in mycoplasma genitalium treatment. A course "just to be safe" is therefore not a neutral choice here.

What is better to rule out first?

The causes that produce symptoms most often and have a clear treatment route. Those are chlamydia and gonorrhoea, and in women trichomonas alongside them. They sit in virtually every STI panel, and a negative result on those meaningfully changes the conversation with your GP.

That part you can do with us.

A test for chlamydia, gonorrhoea and trichomonas works without an appointment and without anything reaching your GP records. What we do not do is test for Mycoplasma hominis or ureaplasma, for exactly the reasons in this article.

Thuisarts.nl, the patient platform of the Dutch College of General Practitioners, explains how to raise discharge-related symptoms.

Further reading

For the overview of all causes of urethral symptoms: urethritis. For the bacterium with the same debate around it: ureaplasma urealyticum.

And for the bacterium that is an STI but sits outside a standard panel: mycoplasma genitalium.

References

• Horner P, et al. Should we be testing for urogenital Mycoplasma hominis, Ureaplasma parvum and Ureaplasma urealyticum in men and women? A position statement from the European STI Guidelines Editorial Board. Journal of the European Academy of Dermatology and Venereology, 2018. PMID 29924422.
• Jensen JS, et al. 2021 European guideline on the management of Mycoplasma genitalium infections. Journal of the European Academy of Dermatology and Venereology, 2022. PMID 35182080.
• Jordan SJ, et al. Aetiology and prevalence of mixed-infections and mono-infections in non-gonococcal urethritis in men: a case-control study. Sexually Transmitted Infections, 2020. PMID 31515293.
• NHG-Standaard Het soa-consult, Dutch College of General Practitioners. Accessed July 2026.
• RIVM, Sexually transmitted infections in the Netherlands, annual report. Accessed July 2026.
• Thuisarts.nl, Vaginal discharge. Accessed July 2026.

Every test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.