Rapid automated microscopy for microbiological surveillance of ventilator-associated pneumonia

Am J Respir Crit Care Med. 2015 Mar 1;191(5):566-73. doi: 10.1164/rccm.201408-1468OC.


Rationale: Diagnosis of ventilator-associated pneumonia (VAP) is imprecise.

Objectives: To (1) determine whether alternate-day surveillance mini-bronchoalveolar lavage (mini-BAL) in ventilated adults could reduce time to initiation of targeted treatment and (2) evaluate the potential for automated microscopy to reduce analysis time.

Methods: Adult intensive care unit patients who were anticipated to require ventilation for at least a further 48 hours were included. Mini-BALs were processed for identification, quantitation, and antibiotic susceptibility, using (1) clinical culture (50 ± 7 h) and (2) automated microscopy (∼5 h plus offline analysis).

Measurements and main results: Seventy-seven mini-BALs were performed in 33 patients. One patient (3%) was clinically diagnosed with VAP. Of 73 paired samples, culture identified 7 containing pneumonia panel bacteria (>10(4) colony-forming units/ml) from five patients (15%) (4 Staphylococcus aureus [3 methicillin-resistant S. aureus], 2 Stenotrophomonas maltophilia, 1 Klebsiella pneumoniae) and resulted in antimicrobial changes/additions to two of five (40%) of those patients. Microscopy identified 7 of 7 microbiologically positive organisms and 64 of 66 negative samples compared with culture. Antimicrobial responses were concordant in four of five comparisons. Antimicrobial changes/additions would have occurred in three of seven microscopy-positive patients (43%) had those results been clinically available in 5 hours, including one patient diagnosed later with VAP despite negative mini-BAL cultures.

Conclusions: Microbiological surveillance detected infection in patients at risk for VAP independent of clinical signs, resulting in changes to antimicrobial therapy. Automated microscopy was 100% sensitive and 97% specific for high-risk pneumonia organisms compared with clinical culturing. Rapid microscopy-based surveillance may be informative for treatment and antimicrobial stewardship in patients at risk for VAP.

Keywords: microbiological techniques; nosocomial infections; ventilator-associated pneumonia.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Automation
  • Bacteriological Techniques / methods
  • Bronchoalveolar Lavage / methods
  • Bronchoalveolar Lavage Fluid / microbiology*
  • Female
  • Humans
  • Male
  • Microscopy / methods
  • Middle Aged
  • Pneumonia, Ventilator-Associated / diagnosis*
  • Pneumonia, Ventilator-Associated / microbiology
  • Sensitivity and Specificity