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Updated: Aug 6, 2026
04:32
Murine Oropharyngeal Aspiration Model of Ventilator-associated and Hospital-acquired Bacterial Pneumonia
Published on: June 28, 2018
Quantitative cultures for diagnosing ventilator-associated pneumonia: a critique
Shigeki Fujitani1, Victor L Yu
1Infectious Disease Section, West Los Angeles Healthcare Center, VA Greater Los Angeles Healthcare System, Los Angeles, California, USA.
Summary
Quantifying bacteria in respiratory samples lacks a standard reference, leading to diagnostic uncertainty for ventilator-associated pneumonia. Current methods are inconsistent and not evidence-based.
Area of Science:
- Critical Care Medicine
- Infectious Diseases
- Microbiology
Background:
- Diagnosing ventilator-associated pneumonia (VAP) is challenging due to the absence of a definitive reference standard.
- Invasive procedures for respiratory sample culture and bacterial quantitation are commonly used to differentiate colonization from infection.
Purpose of the Study:
- To review invasive diagnostic procedures for VAP.
- To evaluate methods of bacterial quantitation, catheter types, sample collection, and cutoff criteria used in quantitative cultures.
- To assess the standardization and evidence base of bacterial quantitation in lower respiratory tract infections.
Main Methods:
- Review of invasive sampling techniques: bronchoalveolar lavage (BAL), protected specimen brushing (PSB), nonbronchoscopic BAL, and blinded bronchial sampling.
- Analysis of bacterial quantitation methods, catheter designs, and sample processing.
- Examination of established cutoff criteria for quantitative cultures.
Main Results:
- Bacterial quantitation from lower respiratory tract samples is mathematically unstable due to variability in fluid handling and sampling area.
- Significant variability exists in methods and reference criteria across reviewed studies.
- The quantitation approach for VAP diagnosis is neither standardized nor evidence-based.
Conclusions:
- The current reliance on bacterial quantitation for diagnosing VAP is hampered by methodological inconsistencies and lack of standardization.
- Further research is needed to establish reliable and evidence-based diagnostic criteria for VAP.
- The inherent variability in quantitative methods undermines their utility in clinical decision-making for respiratory infections.
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