Table 33-3.

Common Causes of Severe Community-Acquired Pneumonia^*†

Streptococcus pneumoniae Enteric gram-negative bacilli Staphylococcus aureus Legionella species Mycoplasma pneumoniae Respiratory viruses Pseudomonas aeruginosa (relative frequency determined by the presence or absence of specific risk factors)

^*Severity of disease warranting treatment in an intensive care unit.

^†Organisms are listed in the general order of frequency.