Final answer:
The most common cause of post-operative pneumonia or pneumonia acquired in a hospital/ICU setting is healthcare-associated pneumonia (HCAP).
Step-by-step explanation:
The most common cause of post-operative pneumonia or pneumonia acquired in a hospital/ICU setting is healthcare-associated pneumonia (HCAP).
Common bacteria that are responsible for HCAP include Klebsiella pneumoniae, Staphylococcus aureus, and species of Escherichia, Proteus, and Serratia.
Patients who are at risk include the elderly, those with preexisting lung conditions, and those who are immunocompromised.
Invasive medical devices like catheters and ventilators can also introduce pneumonia-causing pathogens into the body.