Background: Pneumonia in hospitalized patients-community-acquired (CAP) or nosocomial (NAP)-remains an important cause of morbidity and mortality. Because of the substantial mortality, particularly among the elderly or in patients with specific underlying diseases, it is essential that initial antimicrobial therapy covers the most likely causative organism(s).
Risk stratification: Elderly patients are prone to be colonized with enteric gramnegative rods, especially patients with immunosuppression, prolonged hospital stay, and concomitant medical illnesses. An increasing incidence of gramnegative rod pneumonia and polymicrobial pneumonia including anaerobic bacteria due to aspiration is observed in community-, nursing home- and hospital-acquired lower respiratory tract infections. The spectrum of causative pathogens in elderly CAP patients with underlying diseases is similar to the spectrum in patients with hospital-acquired nosocomial pneumonia "early onset" (before day 5 of hospitalization).
Therapeutic management: Several retrospective studies have shown the importance of the early, adequate initial empirical antibiotic treatment for a favorable clinical outcome and initial adequate and/or effective antimicrobial therapy initiated before definitive etiologic diagnosis is associated with an improved outcome. In addition to the expected pathogens and patient-specific risk factors, the local resistance pattern has to be considered. Especially in elderly patients with underlying diseases, concomitant medication is often mandatory; therefore, initial antimicrobial treatment should also have to take the risk of potential interactions and contraindications into account.