Treatment of Mycoplasma hominis Infections
Doxycycline is the first-line treatment for Mycoplasma hominis infections, with tetracyclines remaining the most effective and clinically proven option for both genital and extragenous infections. 1, 2, 3
First-Line Treatment
- Doxycycline is the preferred tetracycline due to superior activity and tolerability, with MIC90 of 0.064 μg/ml against M. hominis isolates 3
- Standard dosing: 100 mg orally twice daily for 10-14 days 2
- Tetracycline resistance occurs in approximately 8% of isolates, but doxycycline remains the drug of first choice overall 1, 3
Alternative Treatment Options
When tetracyclines fail or are contraindicated:
- Clindamycin is the established alternative to tetracyclines for extragenital M. hominis infections 2
- Josamycin (a macrolide) shows activity against M. hominis and is particularly useful for pregnant women and neonates when tetracyclines are contraindicated 1
- Fluoroquinolones have limited efficacy: levofloxacin (MIC90 0.19 μg/ml) is more active than ciprofloxacin (MIC90 0.5 μg/ml), but both are significantly less effective than doxycycline 3
Critical Resistance Patterns
- M. hominis is innately resistant to all macrolides except josamycin, with MIC ≥256 μg/ml for erythromycin, azithromycin, and clarithromycin 3
- Beta-lactam antibiotics, aminoglycosides, sulfonamides, and chloramphenicol are completely ineffective and should never be used 2, 4
- Cross-resistance exists between tetracyclines when the tetM gene is acquired 4
Treatment Duration and Monitoring
- 10-14 days of antibiotic therapy is recommended for extragenital infections based on clinical experience 2
- Genital tract infections may require similar duration, though optimal length is not definitively established 2
- Bloodstream invasion with metastatic spread to CNS or joints requires mandatory treatment with effective antibiotics 2
Special Clinical Scenarios
- Postpartum fever and febrile abortion: M. hominis bacteremia in these settings is often transient and self-limiting, generally not requiring treatment unless systemic complications develop 2
- Urologic trauma or disease with bacteremia: requires active antibiotic treatment due to risk of metastatic infection 2
- Pregnancy: josamycin is the preferred alternative when tetracyclines are contraindicated 1
Common Pitfalls to Avoid
- Do not empirically use azithromycin or other common macrolides (except josamycin) as M. hominis has intrinsic high-level resistance 3
- Do not use fluoroquinolones as first-line agents—they have significantly inferior activity compared to tetracyclines 3
- Do not assume susceptibility patterns from other mycoplasma species (M. pneumoniae, M. genitalium) apply to M. hominis—resistance profiles differ substantially 4, 5
- Perform local susceptibility testing when available, as geographic variation in resistance patterns exists 1