Why is a Macrolide Resistance Test vital if your Mycoplasma Genitalium PCR test comes back positive?

Receiving a positive Mycoplasma genitalium PCR test result can feel unsettling. It is entirely understandable to have questions about what happens next and what the result means for your health. One of the most clinically important steps following a positive PCR result is understanding whether a macrolide resistance test is also needed — and why this additional testing can be essential to your care pathway.

Our clinic provides confidential STI testing services. We do not provide GP services or dermatology consultations, but we can advise on appropriate next steps if further medical care is needed.

What is a Macrolide Resistance Test — and Why Does It Matter?

A macrolide resistance test analyses a positive Mycoplasma genitalium sample to determine whether the infection carries genetic mutations that make it resistant to macrolide antibiotics — the class of antibiotics most commonly used as a first-line treatment option.

Without this test, there is a significant risk that an inappropriate antibiotic may be prescribed, leading to treatment failure and potentially contributing to further antibiotic resistance. In short, knowing whether resistance is present helps direct healthcare professionals towards the most effective treatment approach for each individual.

Quick summary: why macrolide resistance testing matters

• Mycoplasma genitalium is increasingly resistant to standard antibiotic treatment
• A PCR test confirms infection is present, but not how it should be treated
• A macrolide resistance test identifies specific genetic mutations in the bacteria
• Treatment without resistance information risks failure and worsening resistance
• Resistance-guided treatment improves outcomes and reduces unnecessary antibiotic use

Symptoms alone and even a PCR positive result cannot determine the most appropriate treatment pathway. A macrolide resistance test provides the additional information needed to guide clinical decisions.

When Could a Positive Mycoplasma Genitalium PCR Result Be Complicated by Resistance?

Macrolide resistance in Mycoplasma genitalium is not a rare occurrence. Studies suggest resistance rates in the UK and globally have risen significantly in recent years, with some estimates indicating resistance in over 40% of cases in certain populations. This means that for a considerable number of people who test positive, standard macrolide treatment may not be effective without first knowing the resistance profile of their infection.

This is particularly relevant if you have previously been treated for Mycoplasma genitalium, have had treatment that did not appear to clear the infection, or if your testing was prompted by symptoms that have persisted despite prior antibiotic use.

Understanding Mycoplasma Genitalium

Mycoplasma genitalium is a sexually transmitted bacterial infection. It is relatively small in terms of its genetic make-up but can cause a range of symptoms — or, in some cases, no noticeable symptoms at all. It is thought to be more common than once recognised, partly because routine testing for it has only become more widespread in recent years.

Possible symptoms can include:

• Urethral discharge or discomfort when urinating
• Pelvic pain or discomfort in some individuals
• Vaginal discharge or changes
• Rectal discomfort in some cases

It is important to note that many conditions can produce similar symptoms. Symptoms such as discharge or discomfort do not automatically indicate a Mycoplasma genitalium infection, and testing is the only way to clarify the cause.

How Does the Macrolide Resistance Test Work?

Once a Mycoplasma genitalium PCR test returns a positive result, the same sample — or a new sample — can be analysed further. The resistance test uses molecular techniques to identify specific mutations in the 23S rRNA gene, which are associated with resistance to macrolide antibiotics such as azithromycin.

This is a laboratory-based test and does not require an additional clinical visit in most cases, as the resistance analysis can often be performed on the original sample. Results are typically reported alongside guidance for the prescribing clinician, allowing treatment to be tailored accordingly.

Why Antibiotic Resistance in Mycoplasma Genitalium Is a Growing Concern

Mycoplasma genitalium has demonstrated a troubling capacity to develop resistance, particularly to macrolide antibiotics. This is partly because the organism has limited genetic complexity, meaning mutations that confer resistance can spread relatively easily within the bacterial population when antibiotics are used.

The consequence of treating macrolide-resistant Mycoplasma genitalium with a macrolide antibiotic is that the infection is unlikely to clear, and the resistance may be reinforced. This is why clinical guidelines increasingly recommend that macrolide resistance testing should accompany a positive PCR result wherever possible, before any treatment decision is made.

For a broader understanding of STI testing and what is available, you may find it helpful to explore our full STI screen options.

STIs That May Present With Similar Symptoms

It is worth noting that the symptoms associated with Mycoplasma genitalium can overlap with other sexually transmitted infections. Conditions such as chlamydia, gonorrhoea, and trichomoniasis may produce similar presentations, including discharge, discomfort, or pelvic symptoms.

This is one reason why a comprehensive approach to STI testing is often advisable when symptoms are present or potential exposure has occurred. A chlamydia test or gonorrhoea test may be recommended alongside Mycoplasma genitalium testing in some circumstances, depending on individual risk factors.

Symptoms vary between individuals, and many infections can be present without any noticeable signs. Testing remains the only reliable way to clarify what is or is not present.

When STI Testing May Be Sensible

Testing for Mycoplasma genitalium — and requesting macrolide resistance testing where relevant — may be worth considering in the following situations:

• You have received a positive Mycoplasma genitalium PCR result and have not yet had resistance testing
• You have experienced symptoms that have not resolved following previous treatment
• You have had a new sexual partner or unprotected sex
• A sexual partner has been diagnosed with Mycoplasma genitalium or another STI
• You are experiencing unexplained urogenital or pelvic symptoms

How STI Testing Works

STI testing is typically straightforward and discreet. Depending on the test required, samples may include:

• Urine samples — commonly used for urogenital infections
• Swab samples — taken from the urethra, vagina, cervix, rectum, or throat
• Blood samples — used for infections such as HIV, syphilis, and hepatitis

Samples are sent to an accredited laboratory for analysis. Results are returned confidentially, and our team can advise on appropriate next steps following a positive result.

For some individuals, testing for a broader range of infections — including a syphilis test — may also be appropriate depending on individual history and exposure.

Frequently Asked Questions

Does a positive Mycoplasma genitalium PCR result always mean treatment will be straightforward?

Not necessarily. While a positive PCR confirms the presence of infection, the most appropriate treatment will depend on whether macrolide resistance is present. Without resistance testing, there is a risk that first-line treatment may not be effective.

Can Mycoplasma genitalium clear without treatment?

In some cases, infections may resolve without treatment, but this is not guaranteed. Untreated infections can persist and, in some individuals, may be associated with longer-term complications. Clinical guidance on this should be sought from an appropriate healthcare provider.

Should I get tested again after treatment?

A test of cure — retesting after completing treatment — is generally recommended for Mycoplasma genitalium. This helps confirm that the infection has cleared. Your healthcare provider can advise on the appropriate timing.

What if I had no symptoms but tested positive?

Asymptomatic infections are possible and not uncommon. A positive result still warrants clinical attention and, where possible, macrolide resistance testing before treatment decisions are made.

Is Mycoplasma genitalium testing widely available?

Testing is not always included in standard sexual health screens. It is worth confirming that Mycoplasma genitalium PCR testing is specifically included when booking an STI test, and enquiring whether macrolide resistance testing is available alongside it.

How soon should testing be done after potential exposure?

Mycoplasma genitalium has an incubation period that can vary. Testing timing should be discussed with an appropriate healthcare professional or testing service to ensure accuracy.

When to Seek Medical Advice

If you are experiencing symptoms such as severe pelvic pain, significant discharge, fever, or symptoms that are worsening or not resolving, consultation with an appropriate healthcare service is advised. These symptoms may have several possible causes and warrant clinical assessment.

Similarly, if you have received a positive Mycoplasma genitalium result and have concerns about treatment or resistance, seeking guidance from a qualified healthcare professional is recommended.

If symptoms persist or worsen, consultation with an appropriate healthcare service may be advised.

Confidential STI Testing in the UK

If you are concerned about possible STI exposure, have received a positive Mycoplasma genitalium result, or have questions about whether macrolide resistance testing is appropriate in your situation, confidential STI testing appointments are available at our UK clinic. Testing decisions depend on symptoms, exposure history, and individual risk factors.

Visit STIC Clinic or explore our blog for further information on sexual health testing.

This article is for general informational purposes only and does not constitute medical advice, diagnosis, or treatment. Sexual health concerns should be assessed based on individual circumstances. If you are experiencing persistent, severe, or worsening symptoms, consultation with an appropriate healthcare service is advised. Our clinic provides private STI testing services only.