Most nosocomial respiratory infections are caused by so-called microaspiration of upper airway secretions, through inapparent aspiration, into the lower respiratory tract. Also, "macroaspirations" of esophageal or gastric material is known to result in<unk> . Since it results from aspiration either type is called aspiration pneumonia. Although gram-negative bacilli are a common cause they are rarely found in the respiratory tract of people without pneumonia, which has led to speculation of the mouth and throat as origin of the infection.
Hospital-acquired pneumonia
Community-acquired pneumonia
Ventilator-associated pneumonia
Idiopathic pneumonia syndrome
Pneumococcal pneumonia
Bacterial pneumonia
Hantavirus pulmonary syndrome
Aspiration pneumonia