Morphology: No cell wall (intrinsic resistance to all β-lactams). Pleomorphic; smallest free-living bacteria. Does not Gram-stain.
Typical drugs
- #1Azithromycin— First-line in CAP combination + monotherapy in young healthy outpatients with mild atypical syndrome.
- #2Doxycycline— Equivalent atypical coverage; preferred in macrolide-resistant areas / children >8 yrs.
- #3Levofloxacin— Respiratory FQ — covers atypicals + typicals as monotherapy.
- #4Moxifloxacin
Empiric therapy when resistant
If macrolide-resistant suspected (recent travel from Asia, treatment failure on azithromycin × 48–72h): switch to doxycycline or respiratory fluoroquinolone (levofloxacin / moxifloxacin).
Resistance mechanisms
Target alteration
23S rRNA point mutations (A2058G, A2059G) reduce macrolide binding
Example: Macrolide-resistant Mycoplasma — rising in Asia (>80% in some regions) and emerging in US (~10–15%).
Resistance notes
Macrolide resistance epidemic in East Asia; rising in US. β-lactams INHERENTLY ineffective (no cell wall) — never use amoxicillin or ceftriaxone for known Mycoplasma.
Common syndromes
Pearls
"Walking pneumonia" — young adults, school-age children; subacute dry cough, low-grade fever, headache, myalgias. Extrapulmonary manifestations: cold-agglutinin hemolytic anemia, Mycoplasma-induced rash and mucositis (MIRM / Stevens-Johnson-like), encephalitis / transverse myelitis, bullous myringitis (rare classic finding). Cold agglutinin test can be done at bedside with a tube of EDTA in ice water. β-lactams useless — must remember if patient "failed amox."
References
- IDSA/ATS Community-Acquired Pneumonia in Adults (2019)