REPRODUCIBILITY OF QUANTITATIVE CULTURES OF ENDOTRACHEAL ASPIRATES FROM MECHANICALLY VENTILATED PATIENTS

Ventilator-associated pneumonia is frequently diagnosed with quantitat ive cultures of samples obtained by bronchoscopic techniques, a method associated with high costs and potential adverse effects. Quantitativ e cultures of endotracheal aspirates are easier and cheaper to obtain, and good correlations between the results of this method and those of bronchoscopic methods have been reported. However, the reproducibilit y of quantitative cultures of endotracheal aspirates has never been de termined. We studied the quantitative analysis of endotracheal aspirat es from 21 mechanically ventilated patients taken during two study day s with 2- and 6-h intervals between samplings. In all, 140 endotrachea l aspirates were obtained. For mechanically ventilated patients, the m edian variation of quantitative culture results was 12.3% (range, 0 to 63%), corresponding to 0.7 log CFU/ml. Furthermore, variation was ind ependent of the interval of time between samplings. Persistence of sig nificant numbers of pathogens in quantitative culture results (greater than or equal to 10(5) CFU/ml) of the consecutive endotracheal aspira tes occurred in 82% of samples. We conclude that results of quantitati ve cultures from endotracheal aspirates are reproducible and may be us eful in diagnosing ventilator-associated pneumonia.