Infectious pulmonary diseases and pneumonia are important causes of death within the group of infectious diseases in Germany. Most cases are triggered by bacteria. The morphology of the inflammation is often determined by the agent involved but several histopathological types of reaction are possible. Histology alone is only rarely able to identify the causal agent; therefore additional microbiological diagnostics are necessary in most cases. Clinically cases are classified as community-acquired and nosocomial pneumonia, pneumonia under immunosuppression and mycobacterial infections. Histologically, alveolar and interstitial as well as lobar and focal pneumonia can be differentiated. The disease mainly occurs in retired people. The prognosis is determined in particular by comorbidities. A pathogen can only be detected in approx. 32% of the cases. Pneumococci are the most common (30% of patients), which classically evoke lobar pneumonia. In approx. 10% of cases, atypical pathogens (mycoplasma, legionella, chlamydia) are detected, which cannot be detected using conventional culture methods. Respiratory viruses are found in approximately 5–10% of all CAP cases. Other bacteria such as enterobacteria and pseudomonas are rare, mostly in patients with risk factors. The main criteria for risk assessment are:

the associated clouding of consciousness, the respiratory rate (≥ 30 min), blood pressure (less than 60 mmHg diastolic or 90 mmHg systolic) and the age (≥ 65 years).

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