What is the best antibiotic (abx) for Mycoplasma and Ureaplasma sexually transmitted infections (STIs)?

Best Antibiotics for Mycoplasma and Ureaplasma STIs

For Mycoplasma and Ureaplasma STIs, doxycycline 100 mg orally twice daily for 7 days is the most effective first-line treatment, with azithromycin 1 g orally as a single dose being an appropriate alternative, especially when compliance is a concern.

Treatment Recommendations by Organism

Mycoplasma genitalium

1. First-line treatment:

   • Doxycycline 100 mg orally twice daily for 7 days
   • For patients with compliance concerns: Azithromycin 1 g orally as a single dose

2. Second-line treatment (for treatment failures):

   • Moxifloxacin 400 mg orally once daily for 7-14 days 1

Ureaplasma urealyticum

1. First-line treatment:

   • Doxycycline 100 mg orally twice daily for 7 days 2
   • Azithromycin 1 g orally as a single dose 2

2. Alternative regimens:

   • Josamycin (where available) 3
   • Erythromycin base 500 mg orally four times daily for 7 days 2

Treatment Selection Considerations

• Patient compliance: Single-dose azithromycin provides better compliance through directly observed therapy and is recommended for patients with poor adherence history 2

• Pre-treatment bacterial load: Higher bacterial loads are associated with treatment failure and potential development of macrolide resistance, particularly with azithromycin 4

• Pregnancy: Azithromycin is preferred in pregnant women; doxycycline is contraindicated

• Cost considerations: Doxycycline is generally less expensive than azithromycin but requires multiple doses 2

Treatment Efficacy and Resistance Patterns

• Recent studies show increasing macrolide resistance in Mycoplasma genitalium, with moxifloxacin demonstrating superior microbiological cure rates compared to azithromycin (OR 2.79,95% CI 1.06-7.35) 1

• Clinical cure rates with azithromycin for Mycoplasma genitalium infections may be as low as 50%, while microbiological failure can occur even when clinical symptoms resolve 5

• Doxycycline remains highly effective against both Mycoplasma and Ureaplasma species with minimal resistance development 3

Follow-Up Recommendations

• Patients should abstain from sexual intercourse until therapy is completed (7 days after completion of multi-dose regimens or 7 days after single-dose therapy) 2

• Partners should be notified, examined, and treated with the same regimen as the index patient 2

• For persistent symptoms after treatment:

  1. Rule out reinfection
  2. Consider resistance testing if available
  3. Switch to second-line therapy (moxifloxacin for Mycoplasma genitalium)

Common Pitfalls and Caveats

• Discordant clinical and microbiological outcomes: Clinical cure does not always indicate microbiological cure, particularly with Mycoplasma genitalium infections 5

• Empiric treatment without testing: When possible, obtain specific diagnostic testing before treatment to guide appropriate therapy and partner management

• Inadequate partner treatment: Failure to treat partners is a common cause of reinfection and apparent treatment failure

• Overlooking resistance: In cases of treatment failure, consider antimicrobial resistance, particularly macrolide resistance in Mycoplasma genitalium