Clinical significance of borderline quantitative protected brush specimen culture results.

In patients with clinical suspicion of pneumonia, quantitative cultures of protected brushing specimens (PBS) yielding ⩾ 103 CFU/ml of at least one microorganism have been found useful for differentiating airway colonization and lung infection, especially in mechanically ventilated patients. The amount of secretions collected by protected catheter brushing is small and difficult to determine accurately. Thus, the clinical significance of PBS cultures yielding organisms in concentrations ⩾ 102 but < 103 CFU/ml, in the absence of active antimicrobial treatment, is unknown. The 34 consecutive results of PBS cultures yielding organisms in concentrations ⩾ 102 but < 1033 CFU/ml in 30 patients under mechanical ventilation or weaned for ⩽4 days were prospectively studied. No patients were receiving agents active on the organism recovered. In 5 cases, the diagnosis of pneumonia was ruled out by recovery without treatment (n = 4) or negative postmortem lung cultures (n = 1). A second PBS was cultured in 29 episode...