Introduction

Nosocomial pneumonia is pneumonia acquired in the hospital (that is, manifesting at least 48 h after admission).  It is common and accounts for significant mortality and morbidity. 

Nosocomial pneumonia and ventilator-associated pneumonia (a subset of nosocomial pneumonia) are often discussed together in the literature. However, in this programme, nosocomial pneumonia and ventilator-associated pneumonia are discussed separately.

Risk factors for nosocomial pneumonia.

Aetiology of nosocomial pneumonia

A wide range of pathogens can be implicated in nosocomial pneumonia. Several factors affect the aetiology of nosocomial pneumonia.

• Time of onset after hospitalisation.
• Stress-induced flora changes.
• Antibiotic-induced flora changes.
• Exposure to contamination with nosocomial pathogens.

Nosocomial pneumonia can generally be described as ‘early nosocomial’ (appearing within five days of hospitalisation) or ‘late nosocomial’ (more than five days after hospitalisation). The organisms leading to community-acquired pneumonia, predominantly Gram-positive cocci, are seen in patients who present with pneumonia very shortly after admission to hospital (if no antibiotic therapy has so far been given) and Gram-negative bacilli predominate in patients developing pneumonia after five days of hospitalisation.

Legionella infection is possible but rare.

Diagnosis of nosocomial pneumonia

Clinical and laboratory signs allow a presumptive diagnosis of pneumonia.

Laboratory investigations

• Blood cultures.
• Sputum Gram stain and culture.
• Invasive sample collection.

Management of nosocomial pneumonia

Antibiotic treatment must be started promptly.

If the pathogen is known or suspected, antimicrobial therapy should be guided by local sensitivities; consult your microbiologist. However, in most cases empirical antibiotic treatment will be required.

Antibiotic rationale

Antibiotic choices are influenced by the following factors:

• Time of onset of the illness after admission (‘early’ or ‘late’)
• Local resistance patterns
• Severity of the pneumonia
• Underlying disease
• Recent antibiotic treatment.

Empirical therapy

Typical regimens for nosocomial pneumonia in patients previously untreated with antibiotics include:

• First-line: if cephalosporins have not been given in the last 7–10 days, an injectable cephalosporin such as cefuroxime but follow local policy on choice of cephalosporin
• Second-line: consult local treatment guidelines and/or local microbiologist.  Options include quinolones or aztreonam
• In penicillin-allergic patients: a quinolone
• If aspiration is suspected, regimens for aspiration pneumonia should be used.

Empirical therapy must cover a wide range of organisms including Pseudomonas aeruginosa and maintain high concentrations in lung parenchyma. There is controversy over the ability of monotherapy vs. combination therapy to achieve this. There have been examples of treatment-sensitive strains of Pseudomonas aeruginosa developing resistance during the course of antimicrobial therapy. In cases of suspected or confirmed Pseudomonas aeruginosa pneumonia, the antibiotics chosen should have vigorous anti-pseudomonal activity.

Possible anti-pseudomonal therapy includes:

• Combination therapy with a ureidopenicillin plus an aminoglycoside

  or

• Monotherapy with aztreonam

For nosocomial pneumonia in patients previously treated with antibiotics consult your local guidelines.