Qualitative cultures in ventilator-associated pneumonia – can they be used with confidence?

The sensitivity and specificity of the radiographic and clinical evidence used to diagnose ventilator-associated pneumonia vary depending on the number of clinical criteria present. Bacteriological confirmation that rules out other diseases can be achieved by quantitative or qualitative cultures of tracheal aspirate. The rate of tracheal colonization in ventilated patients reduces the usefulness of qualitative cultures, but the absence of multiresistant micro-organisms in cultures from patients on prior antibiotics or a sterile culture in patients without prior antimicrobials may provide sufficient justification to stop or de-escalate antibiotics. However, more accurate guidance regarding whether antibiotics are unnecessary and should be stopped is provided by quantitative culture.