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# Mycoplasma (pathogen, not a drug) ## Overview *Mycoplasma* is a genus of bacteria that lack a cell wall; therefore, **β-lactam antibiotics (penicillins, cephalosporins, carbapenems) and glycopeptides are ineffective**. Treatment depends on the species and infection: - *Mycoplasma pneumoniae*: respiratory infection, including atypical pneumonia. - *Mycoplasma genitalium*: sexually transmitted urethritis, cervicitis, and pelvic inflammatory disease (PID). - *Mycoplasma hominis* and *Ureaplasma* species: treatment is usually reserved for selected invasive or clearly symptomatic infections because colonization is common. Testing and local resistance patterns are important, particularly for *M. genitalium*. ## Primary Indications Antibiotic treatment may be indicated for: - Confirmed or strongly suspected *M. pneumoniae* pneumonia or significant respiratory disease. - Confirmed symptomatic *M. genitalium* infection. - Selected invasive infections caused by *M. hominis* or *Ureaplasma*, guided by susceptibility testing and infectious-disease consultation. Do **not** treat asymptomatic colonization routinely. ## Adult Dosing ### *Mycoplasma pneumoniae* respiratory infection Usual options, depending on illness severity and local resistance: - **Azithromycin:** 500 mg orally on day 1, then 250 mg once daily on days 2–5. - Alternative: 500 mg orally once daily for 3 days. - **Doxycycline:** 100 mg orally or IV every 12 hours for 5–7 days. - Often preferred when macrolide resistance is suspected and the patient is an appropriate candidate. - **Levofloxacin:** 500–750 mg orally or IV once daily for 5–7 days, generally reserved for adults when alternatives are unsuitable. - **Moxifloxacin:** 400 mg orally or IV once daily for 5–7 days; reserve for selected adults because of fluoroquinolone toxicity. Duration should follow the clinical syndrome and local protocol. Severe pneumonia may require hospitalization and broader empiric therapy for typical bacterial pathogens. ### *Mycoplasma genitalium* Use resistance-guided therapy when available: - **If macrolide-sensitive:** doxycycline 100 mg orally twice daily for 7 days, followed by azithromycin 1 g orally once, then 500 mg once daily for 3 additional days - Total azithromycin dose: 2.5 g. - **If macrolide resistance is detected or suspected:** doxycycline 100 mg orally twice daily for 7 days, followed by moxifloxacin 400 mg orally once daily for 7 days. - **If resistance testing is unavailable:** doxycycline 100 mg twice daily for 7 days, followed by moxifloxacin 400 mg once daily for 7 days is commonly recommended where appropriate. Avoid azithromycin 1 g single-dose monotherapy because of high resistance and treatment failure risk. For PID involving *M. genitalium*, use a complete PID regimen and consult current guidelines; moxifloxacin may be needed for 14 days in selected cases. ### *Mycoplasma hominis* or *Ureaplasma* Treatment is infection- and susceptibility-specific. Potential active agents include: - **Doxycycline:** 100 mg orally or IV every 12 hours. - **Clindamycin:** may be active against *M. hominis*; dose depends on infection site and severity. - **Fluoroquinolones:** may be active, but susceptibility is variable. Macrolides are generally unreliable for *M. hominis*. Seek specialist advice for invasive disease. ## Pediatric Dosing ### *M. pneumoniae* For children with clinically significant infection: - **Azithromycin:** 10 mg/kg orally on day 1, then 5 mg/kg once daily on days 2–5. - Maximum: 500 mg on day 1; 250 mg/day on days 2–5. - Alternative 3-day regimen: 10 mg/kg once daily for 3 days; maximum 500 mg/day. - **Doxycycline:** 2.2 mg/kg orally or IV every 12 hours. - Maximum: 100 mg per dose. - Short courses are generally considered acceptable in children, including younger children, when clinically indicated; follow local pediatric guidance. - **Levofloxacin:** 8–10 mg/kg orally or IV every 12–24 hours, depending on age and indication. - Maximum: 750 mg/day. - Reserve for situations where benefits outweigh musculoskeletal and other fluoroquinolone risks; specialist guidance is recommended. ### *M. genitalium* There are **limited pediatric data**. Obtain specialist advice, particularly for children and adolescents. - Doxycycline and moxifloxacin dosing may be weight-based, but treatment should follow current sexually transmitted infection guidance and local protocols. - Moxifloxacin is generally avoided in children unless no suitable alternatives exist and specialist benefits outweigh risks. - Evaluate for sexual abuse in prepubertal children with a sexually transmitted *M. genitalium* infection, according to local safeguarding requirements. ## Dose Adjustments - **Renal impairment:** - Azithromycin and doxycycline generally require no renal dose adjustment. - Levofloxacin requires dose adjustment when creatinine clearance is <50 mL/min. - Moxifloxacin generally requires no renal adjustment. - **Hepatic impairment:** use azithromycin cautiously in significant liver disease; monitor for hepatotoxicity. - **Pregnancy:** - Avoid doxycycline and fluoroquinolones when suitable alternatives exist. - Azithromycin is commonly used for *M. pneumoniae*. - Treatment of *M. genitalium* during pregnancy requires specialist-guided therapy; moxifloxacin is not appropriate. - **Obesity, critical illness, and severe pneumonia:** follow institutional pharmacokinetic and IV dosing protocols. ## Contraindications Contraindications vary by agent: - **Azithromycin:** serious macrolide allergy; caution with prior cholestatic jaundice or hepatic dysfunction associated with azithromycin. - **Doxycycline:** hypersensitivity; avoid or use specialist guidance in pregnancy, breastfeeding, and young children when alternatives are suitable. - **Levofloxacin/moxifloxacin:** fluoroquinolone hypersensitivity; avoid concomitant use with selected QT-prolonging drugs when possible. Use cautiously with a history of tendon disorders, aortic aneurysm risk, peripheral neuropathy, myasthenia gravis, or significant CNS disease. - **All agents:** consider local susceptibility data and infection site. ## Adverse Effects - **Azithromycin:** nausea, diarrhea, abdominal pain, hepatotoxicity, QT prolongation, rare severe allergic reactions. - **Doxycycline:** nausea, esophagitis, photosensitivity, headache, pill injury. Take with adequate water and remain upright for at least 30 minutes. - **Levofloxacin/moxifloxacin:** tendinitis or tendon rupture, peripheral neuropathy, CNS effects, dysglycemia, QT prolongation, aortic complications, *Clostridioides difficile* infection, and severe allergic reactions. - **Treatment failure:** particularly common with *M. genitalium* because of macrolide resistance. ## Key Drug Interactions - **QT prolongation:** azithromycin, levofloxacin, and moxifloxacin may interact additively with antiarrhythmics and other QT-prolonging drugs. - **Doxycycline and polyvalent cations:** separate from calcium, magnesium, aluminum, iron, and zinc products by at least 2 hours before or 4–6 hours after, depending on product instructions. - **Doxycycline:** may have reduced absorption with antacids and may increase anticoagulant effect of warfarin. - **Fluoroquinolones and cations:** separate oral doses from antacids, iron, calcium, magnesium, and zinc. - **Fluoroquinolones and corticosteroids:** increased tendon injury risk. - **Azithromycin:** may increase exposure to certain drugs via P-glycoprotein or other mechanisms; review the full medication list. ## Monitoring - Confirm the organism and infection site when feasible. - Review local macrolide and fluoroquinolone resistance data. - Assess clinical response within 48–72 hours for respiratory infection. - Monitor hepatic function if prolonged therapy, liver disease, or hepatotoxic medications are present. - Consider ECG and electrolyte assessment when using QT-prolonging drugs in high-risk patients. - Monitor for severe diarrhea, tendon pain, neuropathy, severe rash, or allergic reactions. - For *M. genitalium*, perform a test of cure when recommended by current local guidelines, especially after alternative or resistance-guided therapy. - Test and treat sexual partners according to current STI guidance; avoid sexual activity until treatment is completed and partners have been managed. ## Clinical Pearls - **β-lactams do not treat Mycoplasma** because these organisms lack a peptidoglycan cell wall. - A positive respiratory PCR may represent infection, but treatment should be based on the clinical syndrome rather than detection alone. - Macrolide-resistant *M. pneumoniae* is geographically variable. - For *M. genitalium*, **do not use azithromycin 1 g alone** unless specifically directed by an up-to-date local protocol. - Resistance-guided treatment is preferred for *M. genitalium*. - Doxycycline reduces organism burden in *M. genitalium* but has a substantial microbiologic failure rate when used alone. - Fluoroquinolones should be reserved for appropriate cases because of potentially serious adverse effects. - Exact regimen and duration depend on species, site of infection, susceptibility results, pregnancy status, age, renal function, and local guidelines. *Educational information only; it is not a substitute for patient-specific diagnosis or prescribing. Verify current local guidelines, susceptibility data, product labeling, and specialist recommendations before treatment.*