Mycoplasma (pathogen, Not A Drug)

# Mycoplasma (pathogen, Not A Drug) ## Overview *Mycoplasma pneumoniae* is a common cause of atypical community-acquired pneumonia (CAP) and tracheobronchitis. These organisms lack a cell wall, rendering beta-lactam antibiotics (penicillins, cephalosporins) completely ineffective. Treatment typically targets protein synthesis inhibition. ## Primary Indications * Community-Acquired Pneumonia (CAP) * Tracheobronchitis * Extrapulmonary manifestations (e.g., hemolytic anemia, dermatologic involvement) ## Adult Dosing Treatment duration typically ranges from 5 to 14 days based on clinical response. * **Macrolides:** Azithromycin 500 mg PO on Day 1, then 250 mg PO daily for 4 days. (Note: Increasing macrolide resistance is reported globally). * **Tetracyclines:** Doxycycline 100 mg PO/IV twice daily. * **Fluoroquinolones:** Levofloxacin 500 mg PO/IV daily or Moxifloxacin 400 mg PO/IV daily. ## Pediatric Dosing Dosing depends on local resistance patterns and patient age. Tetracyclines were historically avoided in young children due to dental staining, but the American Academy of Pediatrics (AAP) now considers short courses of doxycycline acceptable. * **Azithromycin:** 10 mg/kg (max 500 mg) on Day 1, then 5 mg/kg (max 250 mg) daily for 4 days. * **Doxycycline:** 2.2 mg/kg per dose twice daily (max 100 mg/dose). * **Levofloxacin:** Reserved for cases where macrolides/tetracyclines are contraindicated or resistant strains are suspected. Dosage varies by age/weight (consult institutional pediatric formulary). ## Dose Adjustments * **Renal/Hepatic:** Macrolides and tetracyclines generally do not require dose adjustments. Fluoroquinolone dosing must be adjusted for significant renal impairment (CrCl <50 mL/min). ## Contraindications * **Macrolides:** Known hypersensitivity, history of cholestatic jaundice, or hepatic dysfunction. Use caution in patients with QTc prolongation. * **Tetracyclines:** Known hypersensitivity; caution in severe hepatic impairment. * **Fluoroquinolones:** Known hypersensitivity; caution in patients with history of tendonitis, myasthenia gravis, or risk factors for QTc prolongation. ## Adverse Effects * **Macrolides:** GI upset (nausea, diarrhea), QTc prolongation, transient hearing loss (high doses). * **Tetracyclines:** Photosensitivity, esophageal ulceration (if taken without water), GI distress. * **Fluoroquinolones:** Tendonitis/tendon rupture, CNS effects (dizziness, confusion), dysglycemia, peripheral neuropathy. ## Key Drug Interactions * **Macrolides/Fluoroquinolones:** Risk of additive QTc prolongation with other QT-prolonging agents (e.g., ondansetron, amiodarone). * **Tetracyclines:** Reduced absorption when taken with multivalent cations (calcium, iron, magnesium, aluminum, sucralfate). Space doses by 2 hours. * **General:** Macrolides (especially clarithromycin/erythromycin, less so azithromycin) and fluoroquinolones may interact with warfarin (monitor INR). ## Monitoring * **Clinical:** Resolution of fever, cough, and respiratory effort. * **Laboratory:** If using fluoroquinolones for extended courses, monitor electrolytes (Mg/K) and glucose in high-risk patients. * **Safety:** Monitor for signs of *C. difficile* infection and, with fluoroquinolones, sudden joint/tendon pain. ## Clinical Pearls * **Beta-lactam failure:** If a patient is not responding to standard CAP therapy (e.g., amoxicillin or ceftriaxone), *Mycoplasma* or *Chlamydophila* should be suspected. * **Resistance:** Macrolide-resistant *M. pneumoniae* is increasing. If the patient fails to respond to azithromycin within 48–72 hours, switch to a tetracycline or fluoroquinolone. * **Clinical Diagnosis:** Diagnosis is often clinical or via PCR; serology is often delayed and less useful for acute management. *** *Disclaimer: This information is for educational purposes only. Clinical practice guidelines vary by institution and region. Always verify dosages, contraindications, and drug-drug interactions through current, localized prescribing information (e.g., Lexicomp, UpToDate) and institutional protocols before prescribing.*