The best antibiotic for a mycoplasma infection depends on which species you’re dealing with. For respiratory infections caused by Mycoplasma pneumoniae, azithromycin is the most commonly prescribed first-line treatment. For the sexually transmitted infection caused by Mycoplasma genitalium, treatment now follows a two-stage approach starting with doxycycline, then adding a second antibiotic based on resistance testing. The answer also shifts depending on where you live, because antibiotic resistance rates vary dramatically by region.
Mycoplasma Pneumoniae: Respiratory Infections
Azithromycin is the go-to antibiotic for mycoplasma pneumonia, sometimes called “walking pneumonia.” The standard course is five days: a larger dose on day one, followed by a smaller dose each day for the remaining four days. Most people start feeling better within two to three days of starting treatment, though a lingering cough can stick around for weeks after the course is finished.
Doxycycline is the main alternative and is typically prescribed for 7 to 14 days. Fluoroquinolones like moxifloxacin also work well against M. pneumoniae and follow a similar 7- to 14-day course. These options become important when azithromycin isn’t effective, which brings us to the growing problem of resistance.
Why Azithromycin Doesn’t Always Work
Macrolide resistance in M. pneumoniae varies enormously by geography. In the United States, fewer than 10% of strains are resistant overall, though some areas in the South and East have seen rates above 20% during outbreaks. In Europe, resistance averages around 5%. But in parts of Asia the picture is very different: China’s resistance rate sits around 80%, and Japan’s exceeds 50%. The global average is roughly 28%.
If you’re in a region with low resistance, azithromycin remains an excellent first choice. In areas with high resistance, or if your symptoms aren’t improving after a few days on azithromycin, doxycycline or a fluoroquinolone is the usual next step. For children under eight, who generally shouldn’t take doxycycline, and for pregnant individuals, azithromycin remains the preferred option regardless of regional resistance patterns.
A Newer Option for Resistant Strains
Lefamulin is a newer antibiotic that works through a different mechanism, blocking bacterial protein production in a way that sidesteps existing resistance. In lab testing, it showed extremely potent activity against both macrolide-susceptible and macrolide-resistant M. pneumoniae strains, outperforming azithromycin, doxycycline, and moxifloxacin against resistant isolates. In clinical trials for community-acquired pneumonia, lefamulin matched moxifloxacin’s success rate (about 89% vs. 91%). It’s not a routine first-line pick, but it represents a meaningful backup when standard antibiotics fail.
Mycoplasma Genitalium: A Different Approach
Treating M. genitalium, the sexually transmitted species, is more complicated. A single antibiotic often isn’t enough. Current CDC guidelines recommend a two-stage treatment: you start with doxycycline for seven days to reduce the bacterial load, then switch to a second antibiotic to clear the remaining infection. Which second antibiotic you get depends on whether your strain is resistant to macrolides.
Ideally, your provider will order a macrolide resistance test before choosing that second drug. When resistance-guided therapy is used, cure rates exceed 90%. Here’s how the two paths break down:
- Macrolide-sensitive strains: Seven days of doxycycline, followed by high-dose azithromycin over four days.
- Macrolide-resistant strains: Seven days of doxycycline, followed by seven days of moxifloxacin.
When resistance testing isn’t available, guidelines default to the more aggressive path: doxycycline followed by moxifloxacin. This avoids the risk of treatment failure from unknowingly prescribing azithromycin against a resistant strain.
Why Resistance Testing Matters for M. Genitalium
Doxycycline alone has a poor cure rate against M. genitalium when used as the sole treatment. It works well as a “pre-treatment” to knock down the number of bacteria, but it rarely eliminates the infection by itself. That’s why the two-stage approach exists. The resistance test determines whether azithromycin can finish the job or whether you need moxifloxacin instead.
This matters because moxifloxacin, while effective, is a more powerful fluoroquinolone with a broader side effect profile. Using it only when truly needed helps preserve it as an option and reduces unnecessary risk. If your provider has access to resistance testing, the tailored approach gives you the best chance of clearing the infection in one round of treatment.
Treatment During Pregnancy
Pregnancy limits your options significantly. Doxycycline and moxifloxacin are both generally avoided during pregnancy. For M. genitalium, international guidelines consistently recommend azithromycin as the first-line treatment for pregnant individuals, whether or not resistance status is known. Safety data for azithromycin in pregnancy is reassuring. For macrolide-resistant infections during pregnancy, however, there’s no well-established safe alternative, and treatment decisions become more individualized.
For M. pneumoniae, azithromycin is also the standard choice during pregnancy, since it falls into a safer category than the tetracycline and fluoroquinolone alternatives.
What to Expect During Treatment
Regardless of which antibiotic you’re prescribed, symptom improvement for respiratory mycoplasma typically begins within two to three days. Full recovery from a respiratory infection can take several weeks, and a persistent cough after finishing antibiotics is normal, not a sign of treatment failure.
For M. genitalium, the total treatment course runs about two weeks when you add the doxycycline and follow-up antibiotic together. A test of cure is usually recommended a few weeks after finishing treatment to confirm the infection has cleared, since symptoms alone aren’t a reliable indicator.