[Update pneumonia 2012].

Pneumonia is an infection of the lung parenchyma and defined as combination of a novel radiological infiltrate with typical signs and symptoms. There are 3 distinguished entities of pneumonia: community-acquired pneumonia (CAP), hospital-acquired pneumonia (HAP), and pneumonia in the immunocompromised patient. The spectrum of pathogens is increasing from CAP, mostly caused by pneumococci, over HAP (additional multi-drug resistant pathogens) to pneumonia in the immunocompromised (additional opportunistic pathogens). Therefore, each entity demands a specific diagnostic and therapeutic approach. This review compares the 3 forms of pneumonia and presents a guideline based clinical approach in the context of current studies.