Hospital-acquired pneumonia

Definition and types. Hospital-acquired (nosocomial) pneumonia is pneumonia developing 48 hours or more after hospital admission and not incubating at the time of admission. Ventilator-associated pneumonia (VAP) arises more than 48 hours after endotracheal intubation. Early-onset (within 4 days) tends to involve community-type organisms; late-onset (day 5 onward) involves multidrug-resistant organisms.

Why it is severe in older patients. Nosocomial respiratory infections are often severe because of resistance of the causative bacteria to antibiotics and because of the vulnerability of patients already weakened by the illness that brought them to hospital. Additional geriatric contributors: immobility and supine posture, dysphagia and silent aspiration, sedatives, nasogastric tubes, delirium, malnutrition and poor oral hygiene.

Organisms. S. aureus (including MRSA), Pseudomonas aeruginosa and enteric Gram-negative bacteria predominate, frequently with antibiotic resistance. Pneumonia in patients recently treated with antibiotics is often due to complex, resistant or polymicrobial flora. In Indian hospitals, Acinetobacter baumannii, Klebsiella pneumoniae with carbapenem resistance and ESBL producers are major concerns.

Clinical features and diagnosis. New or worsening infiltrate on chest radiograph plus at least two of — fever or hypothermia, leucocytosis or leucopenia, purulent secretions, worsening oxygenation. In the old, delirium or unexplained deterioration may be the only clue. Obtain lower respiratory tract samples (deep tracheal aspirate, or bronchoalveolar lavage in the ventilated) before starting antibiotics, plus blood cultures. Differentiate from atelectasis, pulmonary embolism, pulmonary oedema, ARDS and drug-induced lung injury.

Treatment. Start prompt empirical broad-spectrum therapy guided by local antibiogram, prior antibiotic exposure and risk factors for MDR organisms (recent IV antibiotics within 90 days, prolonged stay, septic shock, ARDS, renal replacement therapy). Typical empirical cover: an antipseudomonal β-lactam (piperacillin-tazobactam, cefepime or meropenem) ± MRSA cover (vancomycin or linezolid) ± a second antipseudomonal agent in septic shock. De-escalate at 48–72 hours on culture results and treat for 7 days in most patients. Adjust doses for renal function and monitor for nephrotoxicity, C. difficile and delirium.

Prevention (highly examinable). Hand hygiene; semi-recumbent positioning at 30–45°; daily sedation interruption and assessment of readiness to extubate; subglottic secretion drainage; oral care with chlorhexidine and regular dental hygiene; early mobilisation and chest physiotherapy; avoid unnecessary nasogastric tubes, sedatives and acid suppression; swallow screening after stroke; and antimicrobial stewardship with isolation of colonised patients.

IDSA guidance on antimicrobial-resistant Gram-negative infections (updated 2023–2024) now defines preferred agents for resistant hospital-acquired and ventilator-associated pneumonia: ceftazidime-avibactam, ceftolozane-tazobactam or imipenem-relebactam for difficult-to-treat Pseudomonas; ceftazidime-avibactam or meropenem-vaborbactam for KPC-producing carbapenem-resistant Enterobacterales; ceftazidime-avibactam plus aztreonam for metallo-β-lactamase producers; and cefiderocol or sulbactam-durlobactam for carbapenem-resistant Acinetobacter. The parallel message is shorter courses — 7 days is sufficient for most HAP/VAP, with de-escalation guided by culture and clinical response.