Mycoplasma infections are treated with specific classes of antibiotics: macrolides, tetracyclines, and fluoroquinolones. Common antibiotics like penicillin and amoxicillin do not work against mycoplasma because these bacteria lack a cell wall, which is the exact structure those drugs target. The right antibiotic depends on which type of mycoplasma you have and where the infection is in your body.
Why Common Antibiotics Don’t Work
Most bacteria are surrounded by a rigid cell wall. Penicillin and related antibiotics (the beta-lactam family) kill bacteria by breaking apart that wall. Mycoplasma species are unusual: they have no cell wall at all. This makes them naturally immune to some of the most commonly prescribed antibiotics, including penicillin, amoxicillin, and cephalosporins. If you were given one of these drugs and your symptoms didn’t improve, this is likely why.
Instead, effective treatments target other parts of the bacteria, mainly the machinery it uses to build proteins or copy its DNA. That’s why doctors turn to three specific antibiotic classes for mycoplasma infections.
Treating Mycoplasma Pneumoniae (Walking Pneumonia)
Mycoplasma pneumoniae causes a common respiratory infection sometimes called “walking pneumonia.” Many cases are mild enough that people recover without antibiotics at all, but when treatment is needed, macrolides are the go-to choice. Azithromycin is the most widely prescribed, partly because its shorter course (typically three to five days) is easy to complete.
For older children and adults, tetracyclines like doxycycline are an effective alternative. A large network analysis of over 6,000 patients published in The Lancet’s eClinicalMedicine found that minocycline (another tetracycline) actually showed the most favorable outcomes across several measures, including clinical response, time to symptom improvement, and cough resolution. For children under eight, moxifloxacin (a fluoroquinolone) appeared most effective in the same analysis.
Fluoroquinolones like levofloxacin and moxifloxacin are generally reserved as second-line options. The Infectious Diseases Society of America supports both, along with doxycycline, as alternatives when macrolides fail or aren’t appropriate.
Macrolide Resistance
One concern is that some strains of M. pneumoniae no longer respond to macrolides like azithromycin. In the United States, resistance rates have been relatively low. A CDC-tracked study in Ohio found an average macrolide resistance rate of about 2.4% between September 2023 and September 2024, with monthly fluctuations between 0% and 8.7%. Resistance rates tend to mirror how frequently azithromycin is prescribed in a given area. In parts of East Asia, resistance rates are dramatically higher, sometimes exceeding 80%. If a macrolide isn’t working after a few days, your doctor will typically switch to doxycycline or a fluoroquinolone.
Treating Mycoplasma Genitalium
Mycoplasma genitalium is a sexually transmitted infection that can cause urethritis, cervicitis, and pelvic inflammatory disease. Treatment is more complex than for respiratory mycoplasma because antibiotic resistance is far more common with this species, and a two-stage approach is now standard.
The CDC recommends starting with a seven-day course of doxycycline. Doxycycline alone rarely clears M. genitalium completely, but it reduces the bacterial load and makes the second antibiotic more effective. What comes next depends on whether the bacteria are resistant to macrolides:
- Macrolide-sensitive infections: After the initial week of doxycycline, a four-day course of azithromycin follows (a larger dose on day one, then smaller doses for three more days).
- Macrolide-resistant infections (or resistance unknown): The doxycycline is followed by seven days of moxifloxacin instead.
In persistent cases where M. genitalium is still detected after initial treatment, a 14-day course of moxifloxacin has been effective at eradicating the bacteria. Because treatment failure is a real possibility, a follow-up test (called a test of cure) is recommended 21 days after finishing the full antibiotic course. This confirms the infection is actually gone.
Treating Mycoplasma Hominis and Ureaplasma
Mycoplasma hominis and ureaplasma species are found in the urogenital tract and can sometimes cause infections, particularly after surgery, during pregnancy, or in newborns. These species behave differently from both M. pneumoniae and M. genitalium when it comes to antibiotic susceptibility.
M. hominis is naturally resistant to common macrolides like erythromycin and azithromycin. Doxycycline is effective for most strains, though roughly 10 to 13% of M. hominis isolates show tetracycline resistance. Clindamycin turns out to be the most potent agent against M. hominis specifically. Certain fluoroquinolones also work: ofloxacin shows over 95% susceptibility, while ciprofloxacin is only moderately active at about 70%.
Ureaplasma species are generally more susceptible across the board. Tetracycline resistance in ureaplasma isolates runs only about 1 to 3%, making doxycycline a reliable first option.
Treatment During Pregnancy
Pregnancy significantly narrows the antibiotic options. Tetracyclines like doxycycline are off-limits because they can affect fetal bone and tooth development. Fluoroquinolones like moxifloxacin are also generally avoided. That leaves azithromycin as the primary safe option. International guidelines consistently recommend azithromycin as first-line treatment for mycoplasma genitalium infections during pregnancy, with generally reassuring safety data for both the mother and baby.
Where things get difficult is macrolide-resistant infections in pregnant patients. There is no clear consensus on a safe and effective backup drug, and guidelines vary on whether pristinamycin (a less common antibiotic) is appropriate in this situation. This is one of the trickier scenarios in mycoplasma treatment and typically requires specialist input.
Children and Mycoplasma Treatment
For respiratory mycoplasma in children, macrolides remain the first choice. Azithromycin is the most commonly used because it’s available in liquid form and requires only a short course. Tetracyclines like doxycycline are options for older children but have traditionally been avoided in kids under eight due to concerns about tooth discoloration, though recent guidance has become more flexible on short courses.
When macrolides fail in younger children, moxifloxacin has shown the best results in clinical analyses, though fluoroquinolones in children are used cautiously and typically only when other options haven’t worked. For children over eight with macrolide-resistant infections, minocycline appears to be the most effective alternative based on current evidence.
What to Expect During Treatment
Most antibiotic courses for mycoplasma run between 5 and 14 days, depending on the species and location of infection. Respiratory infections often start to improve within a few days of starting the right antibiotic, though a lingering cough can persist for weeks even after the bacteria are cleared. Urogenital infections require the full multi-stage course, and skipping the second antibiotic or stopping early increases the risk of treatment failure and resistance.
If your symptoms aren’t improving after several days on an antibiotic, it likely means either the strain is resistant to that particular drug or the diagnosis needs a second look. Resistance testing, when available, can guide a more targeted switch. For M. genitalium in particular, testing for macrolide resistance before choosing the second-stage antibiotic can make the difference between clearing the infection on the first attempt and needing repeated courses.