Pneumonia remains a significant cause of morbidity and mortality, whether community acquired (CAP) or hospital acquired. Although many microbial pathogens may cause pneumonia, the most commonly encountered are pneumococcus; atypical organisms, such as Mycoplasma pneumoniae or Legionella; and at times Staphylococcus aureus and certain gram-negative rods. As diagnostic tests have increased in availability and sophistication, identifying multiple pathogens in the same patient is increasingly common.
Mandell LA, Waterer GW. Empirical Therapy of Community-Acquired PneumoniaAdvancing Evidence or Just More Doubt?. JAMA. 2015;314(4):396-397. doi:10.1001/jama.2015.3858