Definition
Healthcare-associated pneumonia can be defined as pneumonia in a patient with at least one of the following risk factors:

hospitalization in an acute care hospital for two or more days in the last 90 days;
residence in a nursing home or long-term care facility in the last 30 days
receiving outpatient intravenous therapy (like antibiotics or chemotherapy) within the past 30 days
receiving home wound care within the past 30 days
attending a hospital clinic or dialysis center in the last 30 days
having a family member with known multi-drug resistant pathogens

Causes
In some studies, the bacteria found in patients with HCAP were more similar to HAP than to CAP; compared to CAP, they could have higher rates of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa, and less Streptococcus pneumoniae and Haemophilus influenzae. In European and Asian studies, the etiology of HCAP was similar to that of CAP, and rates of multi drug resistant pathogens such as Staphylococcus aureus and Pseudomonas aeruginosa were not as high as seen in North American studies. It is well known that nursing home residents have high rates of colonization with MRSA. However, not all studies have found high rates of S. aureus and gram-negative bacteria. One factor responsible for these differences is the reliance on sputum samples and the strictness of the criteria to discriminate
between colonising or disease-causing bacteria. Moreover, sputum samples might be less frequently obtained in the elderly. Aspiration (both of microscopic drops and macroscopic amounts of nose and throat secretions) is thought to be the most important cause of HCAP.
Morrow L. Critical Decisions for the Treatment of Health-care-Associated Pneumonia in the ICU. External links
Hospital-Acquired, Health Care Associated, and Ventilator-Associated Pneumonia from the Cleveland Clinic
Cecil Textbook of Medicine