A patient on mechanical ventilation for 7 days develops new fever, purulent tracheal secretions, and a new right lower lobe infiltrate on chest X-ray. Quantitative BAL culture grows Acinetobacter baumannii at 10^5 CFU/mL. What is the diagnostic threshold for BAL confirming ventilator-associated pneumonia (VAP)?
- A ≥10^3 CFU/mL from BAL
- B ≥10^6 CFU/mL from BAL
- C ≥10^4 CFU/mL from BAL ✓
- D Any growth from BAL is diagnostic
Correct answer: C. ≥10^4 CFU/mL from BAL
Explanation
The standard quantitative diagnostic threshold for VAP on BAL is ≥10^4 CFU/mL; for protected specimen brush (PSB) it is ≥10^3 CFU/mL; for endotracheal aspirate it is ≥10^6 CFU/mL. These thresholds reduce false positives from upper airway colonisation. In this patient, 10^5 CFU/mL on BAL exceeds the threshold (≥10^4), confirming microbiological VAP diagnosis alongside clinical criteria.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.