Nosocomial Pneumonia

OVERVIEW

Nosocomial or hospital-acquired pneumonia (HAP) is defined as pneumonia that is not incubating at the time of admission to hospital and develops in a patient hospitalised for >48 hours.

• common and has significant mortality
• results primarily from  micro-aspiration of oropharyngeal and upper GI bacteria

CAUSATIVE ORGANISMS

The spectrum of potential pathogens associated with HAP differs from that of community-acquired pneumonia (CAP) — reflects organisms that colonise the oropharynx of hospitalised patients

• aerobic Gram negative bacilli – ESCAPPM, Klebsiella
• Legionella
• MDR organism – MRSA, Enterobacteriaceae, Pseudomonas aeruginosa, Acinetobacter, Stenotrophomonas maltophila
• viruses – influenza, RSV, adenovirus, parainfluenza
• Aspergillus (e.g. aerosols from building works at hospital leading to contamination of air with soil)

RISK FACTORS

• intubation
• COPD
• ARDS
• low albumin
• mechanical ventilation > 3 days
• those requiring ICP monitoring
• coma or decreased LOC
• burns
• trauma
• high APACHE score
• H2 blockers or antacids
• previous antibiotics
• use drugs that are markers of severe disease (inotropes, sedation, paralysis)
• re-intubation
• bronchoscopy
• NG tube
• transport

Risk factors for Legionella

• diabetes
• immunosuppression
• high-dose corticosteroid therapy
• malignancy
• end-stage renal failure
• history of smoking
• excessive alcohol use
• known local prevalence of hospital-acquired disease

CLINICAL FEATURES

• crackles or dullness to percussion and any of the following:
• purulent sputum
• organism from blood cultures
• CXR signs: infiltrate, consolidation, cavitation, effusion
• virus in sputum
• IgM antibody +ve
• 4 fold increase in IgG titre
• histopathology +ve for pneumonia

DIAGNOSIS

Reliable diagnosis of HAP is difficult and there are no universally accepted clinical or laboratory criteria that have sufficient diagnostic sensitivity and specificity

• The presence of bacteria in expectorated sputum or endotracheal aspirate cultures usually represents colonisation only, and does not itself justify a diagnosis of HAP
• Most postoperative patients with shadowing on chest X-ray do not have pneumonia, they have atelectasis

ASSESSMENT

Clinical

• focal chest signs
• purulent sputum
• fever

Laboratory

• inflammatory marker elevation
• positive cultures (sputum or blood)
• 4 fold increase in antibody titres
• histopathology consistent with pneumonia

Radiological

• infiltrate
• consolidation
• cavitation
• pleural effusion

MANAGEMENT

Principles of antibiotic therapy

• start empirically
  -> scale back at day 2 if patient improved
• know local biograms
• failure to control –
  > re-evaluation of antibiotic therapy
• treat organism grown

Risk stratify patients:

(1) low risk of MDR organism – standard ward, < 5 days in hospital

• cover Pneumococcus and non-MDR GNBs

-> mild: augmentin or benzylpenicillin + gentamicin
-> moderate/severe: ceftriaxone or cefotaxime or tazocin or timentin

(2) high risk of MDR organism – ICU/HDU or area with known MDR problem for 5 or more days

• cover MDR organisms
• stop antibiotics for VAP at 6-8 days (evidence that longer courses lead to colonisation with MROs)
• treat Pseudomonas aeruginosa, Acinetobacter species or Stenotrophomonas maltophilia for 15 days

-> tazocin or timentin or cefepime
-> if suspected MRSA add in vancomycin (pre-existing longterm lines, prior MRSA, in hospital > 7day or recent admission <3 months)
-> add gentamicin if critically ill (ventilated) to cover MDR organisms (use ciprofloxacin if age >65y, GFR <50 or recently on gentamicin)
-> add teichoplanin if VRE colonized

References and Links

• Masterton RG, Galloway A, French G, Street M, Armstrong J, Brown E, et al. Guidelines for the management of hospital-acquired pneumonia in the UK: report of the working party on hospital-acquired pneumonia of the British Society for Antimicrobial Chemotherapy. J Antimicrob Chemother 2008;62(1):5-34. [PubMed]