QUANTITATIVE CULTURES OF PROTECTED BRUSH SPECIMENS AND BRONCHOALVEOLAR LAVAGE IN VENTILATED PATIENTS WITHOUT SUSPECTED PNEUMONIA

Quantitative bacterial cultures of protected specimen brush (PSB) and bronchoalveolar ravage (BAL) specimens were used to assess the presenc e of distal bronchial microflora in mechanically ventilated patients w ho were not suspected of having pneumonia. A total of 54 specimens fro m 32 ICU patients were obtained. In 10 patients, only PSB specimens we re recovered, whereas in 22 patients both PSB and BAL specimens were o btained. Cultures demonstrated no growth in 10 (45%) of the 22 samples recovered by BAL and in 21 (66%) of the 32 samples recovered by the P SB method. Twenty-three specimens yielded microorganisms, but in only six patients was a significant growth in PSB and/or BAL cultures (grea ter than or equal to 10(3) and greater than or equal to 10(5) cfu/ml, respectively) detected. Four of these patients developed pneumonia on subsequent follow-up. In mechanically ventilated patients, the diagnos tic thresholds of bacterial growth in PSB and BAL cultures may be misl eading. A significant relationship was found between the ability of PS B to recover microorganisms and the duration of mechanical ventilation (p < 0.05). These findings may be a limitation present in all patient s receiving prolonged mechanical ventilation.