How long after hospital discharge is pneumonia considered hospital-acquired (HA) pneumonia?

Definition of Hospital-Acquired Pneumonia (HAP) After Hospital Discharge

Hospital-acquired pneumonia (HAP) is defined as pneumonia that occurs 48 hours or more after hospital admission and is still considered hospital-acquired for up to 14 days after hospital discharge. 1, 2

Core Diagnostic Criteria for HAP

• HAP is characterized by new or progressive lung infiltrates on chest radiography, along with clinical evidence of infectious origin, including fever, leukocytosis or leukopenia 1
• At least two of the following symptoms must be present: purulent sputum, cough or dyspnea, declining oxygenation or increased oxygen requirement 1
• By definition, HAP is not present or incubating at the time of hospital admission 3

Timing Classification of HAP

• Non-ventilator HAP occurs after 48 hours of hospital stay in non-ventilated patients 1
• Ventilator-associated pneumonia (VAP) develops in ICU patients who have been mechanically ventilated for at least 48 hours 3
• Early-onset HAP occurs within the first 5 days of hospitalization 3
• Late-onset HAP occurs after 5 days of hospitalization 3
• Post-discharge HAP can be diagnosed up to 14 days after hospital discharge 2

Risk Factors for HAP

• Mechanical ventilation for > 48 hours 4
• Residence in an ICU 4
• Duration of ICU or hospital stay (particularly prolonged stays >5 days) 3
• Severity of underlying illness and presence of comorbidities 4
• Previous antibiotic use 3
• Previous colonization with multidrug-resistant pathogens 3

Microbiology Considerations

• Early-onset HAP is typically caused by community-acquired pathogens such as methicillin-susceptible Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae 1
• Late-onset HAP is more likely to involve multidrug-resistant organisms, including Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter baumannii, and methicillin-resistant Staphylococcus aureus 1
• Nearly half of HAP cases are polymicrobial 4

Diagnostic Approach

• Microbiological confirmation is crucial for definitive diagnosis, based on qualitative or quantitative cultures of respiratory samples 1
• Blood cultures should be obtained in suspected HAP cases, especially when patients present with sepsis 5
• Semiquantitative cultures of noninvasively obtained respiratory samples are recommended over quantitative cultures of invasively obtained samples 5

Treatment Considerations for Post-Discharge HAP

• Empiric antibiotic therapy should be based on risk factors for multidrug-resistant organisms and local antibiogram data 5
• For patients with risk factors for multidrug-resistant pathogens, broader spectrum antibiotics may be necessary 3
• A 7-8 day course of antibiotics is recommended for most patients with HAP/VAP who have a good clinical response to therapy 3

Clinical Implications

• HAP significantly increases healthcare costs, with estimates ranging from $10,000 to $40,000 per case 1
• HAP is associated with increased duration of mechanical ventilation, ICU stay, and hospital length of stay 1
• The mortality rate associated with HAP is approximately 20%, with attributable mortality estimated between 5-13% 3

Remember that pneumonia developing within 14 days after hospital discharge should still be considered hospital-acquired, especially when evaluating appropriate antibiotic coverage based on likely pathogens.