Mycoplasma genitalium is treated with a two-stage course of antibiotics, typically lasting 14 days total. Because this bacterium has developed high rates of resistance to common antibiotics, treatment follows a sequential approach: one antibiotic to weaken the infection, followed by a second to eliminate it. Getting the right test before starting treatment makes a significant difference in whether the antibiotics work.
Why Testing Matters Before Treatment
Mycoplasma genitalium doesn’t respond to many of the antibiotics routinely prescribed for STIs. If you’re treated based on symptoms alone, without confirming the specific infection, there’s a good chance the antibiotics won’t match the problem. The standard diagnostic tool is a nucleic acid amplification test (NAAT), which detects the bacterium’s genetic material from a urine sample or swab. For women, a vaginal swab tends to be more accurate than other specimen types.
Beyond simply confirming the infection, resistance testing has become increasingly important. Over 62% of specimens in UK surveillance data from 2023 carried mutations making them resistant to macrolide antibiotics like azithromycin. That means a one-size-fits-all prescription has a high chance of failing. If your provider can test for resistance markers before choosing an antibiotic, the odds of clearing the infection on the first attempt go up substantially.
The Standard Two-Step Antibiotic Approach
Current CDC guidelines recommend a sequential regimen rather than a single antibiotic. The first phase uses doxycycline twice daily for seven days. Doxycycline doesn’t reliably cure the infection on its own, but it reduces the bacterial load and sets the stage for the second antibiotic to finish the job. Think of it as softening the target.
The second phase depends on what resistance testing shows. If the infection is susceptible to macrolides, azithromycin follows the doxycycline course. If the infection is macrolide-resistant, or if resistance testing isn’t available, moxifloxacin once daily for seven days is the recommended follow-up. The entire treatment course runs about 14 days.
For pelvic inflammatory disease caused by this bacterium, the treatment timeline extends to 14 days of moxifloxacin alone, which has been effective at clearing the organism in that context.
The Resistance Problem
Antibiotic resistance is the central challenge with this infection, and the numbers are concerning. UK surveillance in 2023 found macrolide resistance at 62.2%, fluoroquinolone resistance (which affects moxifloxacin) at 12.1%, and dual resistance to both classes at 10.1%. These aren’t abstract lab statistics. They directly determine whether your prescription will work.
Resistance rates also vary by population. Among gay and bisexual men, macrolide resistance reached 77.4% compared to roughly 58% in heterosexual men and women. Fluoroquinolone resistance showed a similar pattern: 21.6% in men who have sex with men versus about 9.5% in other groups. People using HIV PrEP also showed higher resistance rates, likely because frequent antibiotic exposure for other STIs has given the bacterium more opportunities to develop defenses.
At the genetic level, specific mutations in the bacterium’s DNA predict treatment failure. One mutation in particular, called ParC S83, is strongly linked to moxifloxacin failure. In one study, this mutation was found in all six patients whose moxifloxacin treatment failed but in only three of 48 patients who were cured. This is why resistance-guided treatment, where the antibiotic is chosen based on the genetic profile of your specific infection, produces better outcomes than empiric prescribing.
When Standard Treatment Fails
If both macrolide and fluoroquinolone antibiotics fail, options become limited. This happens in roughly 1 in 10 cases based on dual resistance rates. Your provider may need to consult with an infectious disease specialist to find an effective regimen.
One emerging option for multi-drug resistant cases is lefamulin, a newer antibiotic that works through a different mechanism. Lab studies have shown it is highly active against mycoplasma genitalium isolates, including those resistant to both macrolides and fluoroquinolones. Importantly, combining it with doxycycline showed no harmful interactions in lab testing, with some additive benefit in certain strains. This is still early-stage evidence from laboratory studies rather than large clinical trials, but it represents a potential lifeline for cases where current options have been exhausted.
What to Expect During and After Treatment
The full antibiotic course spans about two weeks, and you should complete every dose even if symptoms improve earlier. Symptoms like urethral discharge, burning during urination, or pelvic discomfort typically begin to ease during the first week, but the infection isn’t necessarily cleared until the full course is finished.
After completing treatment, a follow-up test (called a test of cure) confirms whether the infection has been eliminated. This retest should happen at least 21 days after finishing antibiotics. Testing too early can produce a false positive because dead bacterial DNA may still be detectable. If the test comes back positive, it means the infection persists and a different antibiotic approach is needed.
Avoid sexual contact during the entire treatment period and until a negative test of cure confirms you’re clear. This prevents both reinfection and transmission.
Partner Treatment
Sexual partners need to be tested and treated as well. If only one partner is treated, reinfection is likely as soon as sexual activity resumes. Current partners and recent sexual contacts should be notified, tested with a NAAT, and treated with the same resistance-guided approach if positive. Partners should also abstain from sex until both they and the index patient have completed treatment and received a negative test of cure.
This isn’t optional or a courtesy. Untreated partners are the most common reason people cycle through repeated infections and multiple rounds of antibiotics, which in turn drives further resistance. Treating the infection as a shared problem between partners is the most reliable path to actually resolving it.