The antibiotic treatment of severe community-acquired pneumonia admitted to the critical care unit

Community-acquired pneumonias (CAP) are still caused by Streptococcus pneum oniae, Hemophilus influenzae, or Moraxella catarrhalis. Legionella and Chla mydia pneumoniae have been defined as important atypical pathogens causing CAP. Klebsiella causes CAP primarily in patients with chronic alcoholism or in chronic care facilities. Normal hosts do not present with 'unusual path ogens" e.g., Staphylococcus aureus or Pseudomonas aeruginosa. The clinical severity of a bacterial pneumonia has important prognostic implications and predicts admission to intensive care units, duration of therapy, and compl ications. The factors that determine the severity of a CAP are less related to the pathogen than the underlying cardiopulmonary status of the patient as well as the patient's humoral immunity. Relatively avirulent pathogens m ay result in severe CAP in patients with diminished/absent splenic function or significant cardiopulmonary disease. A critical concept is to appreciat e that the selection of antimicrobial therapy is not dependent on co-morbid ities since the antimicrobial therapy is directed against the pathogen and not the co-morbidities. Therefore the treatment of CAP, whether moderate or severe is with the same antibiotic at the same dose. Many antibiotic regim ens are equally efficacious in the treatment of CAP. The most cost effectiv e optimal regimen covers both typical and atypical pathogens, e.g., levoflo xacin, and is currently the preferred antibiotic approach to moderate or se vere CAP in the CCU.