Optimal Antibiotic Use in Severe Community-Acquired Pneumonia

Community-acquired pneumonia (CAP) is the main cause of death due to infectious disease in the developed countries. Although the incidence is not available in most countries, it represents more than 600,000 hospital admissions in the United States (Barlett et al. 2000) and 50,000 in the United Kingdom each year (Hirani and Macfarlane 1997). The cost is higher for nonsurvivors than for survivors (around $7,500 of an in-hospital case) (Fine et al. 1997).

Since the use of penicillin, the mortality rates of severe CAP have not decreased significantly despite advances in antimicrobial therapy and technical improvements in the ICU. Fine et al. (1997) reported that only 10% of hospitalized patients are admitted to ICU, and that the mortality rate in intubated patients reaches 40%. This mortality rate depends on the interaction between the host factors (age, comorbidities, genetic predisposition, and immunocompromise), microorganism characteristics, and optimal antibiotic use (Luján et al. 2006) (Fig. 7.1). In a recent study, Waterer et al. (2001a,b) suggest that CAP patients with septic shock appear to have different genotypes than those with hypoxemic respiratory failure without shock.

The constant increase in the number of elderly and immunocompromised patients (those receiving steroids, organ transplant recipients, HIV patients), the better survival rates of patients affected by chronic illness, and the need for appropriate empirical antibiotics administration are reasons that justify continuing research, focused on improving the diagnosis, defining risk factors that influence outcome, and assessing new therapies.