A 24-year-old man with community-acquired pneumonia shows no improvement after 5 days of intravenous ceftriaxone. Sputum PCR is positive for Mycoplasma pneumoniae. The failure of ceftriaxone is explained by which property of this organism?
- A Absence of a peptidoglycan cell wall ✓
- B Production of beta-lactamase
- C Intracellular persistence within macrophages
- D Alteration of ribosomal binding sites
Correct answer: A. Absence of a peptidoglycan cell wall
Explanation
Mycoplasma pneumoniae is the smallest free-living bacterium and uniquely lacks a peptidoglycan cell wall, being bounded only by a sterol-containing membrane. Beta-lactam antibiotics act on cell wall synthesis and are therefore inherently ineffective, independent of any resistance enzyme. Macrolides, tetracyclines, and fluoroquinolones, which act on protein synthesis or DNA replication, are the drugs of choice. Ribosomal alteration causes macrolide resistance, not beta-lactam failure.
Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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