Why Should Both Sexual Partners Test for Macrolide Resistance if One Partner Has an Ongoing Mgen Infection?

Introduction

Receiving a diagnosis of Mycoplasma genitalium (Mgen) can raise understandable questions — particularly when it comes to a partner's health. When one partner has an ongoing Mgen infection, there are important reasons why both individuals may benefit from testing, including testing for macrolide resistance. Understanding why this matters can help both partners make informed decisions about their sexual health.

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 Macrolide Resistance in Mgen, and Why Does It Matter?

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If one partner has a Mycoplasma genitalium infection, both partners may carry the same strain — including any antibiotic resistance it has developed. Macrolide resistance in Mgen means that commonly used antibiotics may be less effective. Testing both partners for macrolide resistance helps ensure the most appropriate management pathway is identified for each individual.

Key points to be aware of:

• Mgen can be passed between sexual partners
• Resistant strains can be transmitted alongside the infection itself
• Both partners may carry the same resistant strain without knowing
• Testing helps identify whether macrolide resistance is present
• Results may guide decisions around further clinical management
• Symptoms can vary significantly between individuals — or be absent entirely

Macrolide resistance testing alone cannot confirm whether treatment will be successful. Results should always be discussed with an appropriate healthcare provider.

When Could Mgen Be Linked to Macrolide Resistance?

Macrolide resistance in Mycoplasma genitalium has become increasingly common in the UK. Macrolides — a class of antibiotics that includes azithromycin — have historically been used in the management of Mgen. However, over time, resistance mutations have developed in many circulating strains.

When a person has an ongoing Mgen infection that has not resolved following antibiotic use, macrolide resistance is one possibility that may be considered. If that strain is then transmitted to a partner, the partner may also carry a macrolide-resistant form of the infection — even if they have never taken antibiotics themselves.

Understanding Mycoplasma Genitalium

Mycoplasma genitalium is a small bacterial infection that can affect the urogenital tract in both men and women. It is sexually transmissible and can be passed through vaginal, anal, or, less commonly, oral sexual contact. Many people with Mgen experience no symptoms at all, which makes ongoing transmission between partners a real consideration.

In cases where symptoms do occur, they may include:

• Unusual discharge
• Discomfort or burning during urination
• Pelvic discomfort (in some cases)
• Urethral irritation in men

It is important to note that these symptoms can have several possible causes and do not automatically indicate Mgen or any other STI. Testing may help clarify the cause.

Why Is Macrolide Resistance Testing Important for Both Partners?

The Risk of Re-infection

One of the most clinically relevant reasons for both partners to undergo macrolide resistance testing is the risk of re-infection. If one partner is managing an ongoing Mgen infection and their partner remains untested, there is a possibility that the infection continues to be passed back and forth — sometimes referred to as a "ping-pong" pattern of re-infection.

If a resistant strain is involved, this cycle becomes more complex, as the same resistance profile may be present in both individuals.

Resistant Strains Can Be Transmitted

Macrolide resistance in Mgen is determined by specific genetic mutations within the bacteria. If a person carries a strain with these mutations, that resistant strain can be transmitted to a sexual partner through unprotected sexual contact — just as the infection itself can.

This means a partner who has never previously been treated for Mgen could potentially carry a macrolide-resistant strain simply because they acquired it from an infected partner. Testing is the only way to determine whether this has occurred.

Informing Clinical Management

Testing both partners for Mgen, along with macrolide resistance profiling, can provide important information that may help inform decisions about clinical management. Without knowing whether a resistant strain is present in both partners, it may be more difficult for a treating clinician to identify the most appropriate course of action.

Our clinic provides Mycoplasma genitalium testing as part of our confidential private STI testing services.

How Does Macrolide Resistance Testing Work?

Macrolide resistance testing for Mgen is typically performed using a urine sample or a swab (urethral, vaginal, or cervical depending on anatomy and exposure). The sample is sent to a laboratory, where it is analysed not only for the presence of Mgen but also for genetic mutations associated with macrolide resistance.

Results are returned confidentially and, where appropriate, patients are advised to discuss them with a relevant healthcare provider who can advise on next steps.

Other STIs to Consider Alongside Mgen Testing

If one or both partners are being tested for Mgen and macrolide resistance, it may also be a sensible opportunity to consider testing for other sexually transmitted infections. Many STIs can be present without causing obvious symptoms, and co-infections are not uncommon.

Depending on individual circumstances and exposure history, a full STI screen may be worth considering. This could include testing for infections such as chlamydia, gonorrhoea, and others. Our clinic offers a range of private STI testing options, including a chlamydia test and gonorrhoea test, which can be arranged alongside Mgen testing where appropriate.

When STI Testing May Be Sensible

Testing for Mgen and macrolide resistance may be worth considering in the following situations:

• One partner has a confirmed or suspected Mgen infection
• Previous treatment for Mgen does not appear to have resolved the infection
• There has been unprotected sexual contact with a known or suspected Mgen-positive partner
• Symptoms have persisted despite prior clinical management
• Either partner has a new or concurrent sexual partner

Frequently Asked Questions

Can I have a macrolide-resistant Mgen infection without ever having taken antibiotics?

Yes. Macrolide-resistant strains of Mgen can be acquired through sexual contact with a person who carries a resistant strain, regardless of your own antibiotic history.

Does macrolide resistance mean the infection cannot be treated?

Not necessarily. Macrolide resistance indicates that one class of antibiotics may be less effective. A relevant healthcare provider can advise on alternative management options based on your test results.

Should both partners test even if one has no symptoms?

In many cases, Mgen causes no noticeable symptoms. Because the infection can be present without symptoms, testing may still be relevant even in the absence of obvious signs.

How soon after possible exposure should testing be done?

If you are concerned about a possible Mgen exposure, it is generally advisable not to delay testing unnecessarily. Your testing provider can advise on appropriate timing based on your circumstances.

What happens if my test result is positive for macrolide resistance?

A positive result for macrolide resistance does not mean treatment is impossible. The result should be discussed with a qualified healthcare provider who can advise on the most appropriate next steps for your individual situation.

Is Mgen testing the same as a standard STI screen?

Not always. Mgen is not routinely included in all standard STI screens. It is worth confirming with your testing provider that Mgen and macrolide resistance testing are specifically included.

When to Seek Medical Advice

If you or your partner are experiencing severe pelvic pain, high fever, significant urethral discharge, or symptoms that are worsening or not improving, consultation with an appropriate healthcare service is advised. These situations may require clinical assessment beyond private testing services.

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 a possible Mgen infection, macrolide resistance, or any other aspect of your sexual health, confidential STI testing appointments are available at our UK clinic. Testing decisions depend on symptoms, exposure history, and individual risk factors. Our team can help you understand your options and advise on appropriate next steps.

Visit STI Clinic UK to find out more about our testing services.

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.