Which organism is an etiologic agent of primary atypical pneumonia?

Which organism is an etiologic agent of primary atypical pneumonia?

• A. Chlamydia trachomatis
• B. Chlamydiophila psittaci
• C. Mycoplasma pneumoniae
• D. Ureaplasma urealyticum

Answer: (C)

Primary atypical pneumonia is classically caused by Mycoplasma pneumoniae. This organism is unique because it lacks a cell wall, so it doesn’t Gram-stain well and beta-lactam antibiotics aren’t effective. Clinically, it tends to cause a gradual onset with a dry, nonproductive cough and relatively mild findings—often referred to as walking pneumonia. Diagnosis is usually by serology or PCR rather than routine culture, since it requires special media for growth. Ureaplasma urealyticum and Chlamydophila psittaci can cause atypical presentations in specific contexts, and Chlamydia trachomatis is more associated with neonatal pneumonia, but Mycoplasma pneumoniae remains the classic cause of primary atypical pneumonia.

Primary atypical pneumonia is classically caused by Mycoplasma pneumoniae. This organism is unique because it lacks a cell wall, so it doesn’t Gram-stain well and beta-lactam antibiotics aren’t effective. Clinically, it tends to cause a gradual onset with a dry, nonproductive cough and relatively mild findings—often referred to as walking pneumonia. Diagnosis is usually by serology or PCR rather than routine culture, since it requires special media for growth. Ureaplasma urealyticum and Chlamydophila psittaci can cause atypical presentations in specific contexts, and Chlamydia trachomatis is more associated with neonatal pneumonia, but Mycoplasma pneumoniae remains the classic cause of primary atypical pneumonia.