GASTRIC AND PHARYNGEAL FLORA IN NOSOCOMIAL PNEUMONIA ACQUIRED DURING MECHANICAL VENTILATION

We studied the interrelations between gastric, pharyngeal, proximal, a nd distal airway bacterial flora in ventilator-associated pneumonia (V AP) on 36 patients with nosocomial pneumonia acquired during mechanica l ventilation (MV) and 27 mechanically ventilated control subjects wit hout pulmonary infection. Gastric, pharyngeal, and endotracheal (EA) s ampling for quantitative cultures were performed upon all patients, as well as fiberoptic bronchoscopy with protected specimen brush (PSB) s ampling. Mean bacterial and fungi colony counts were significantly inc reased in pharyngeal, EA, and PSB samples in patients with VAP compare d with control subjects. The overall increase in colonization was due to gram-positive cocci in all samples. In addition, gram-negative baci lli and fungi mean counts increased significantly in PSB pneumonia sam ples versus control samples. However, mean gastric colonization was si milar in both patients with VAP and control subjects. In the former gr oup there was an increase in coincident microorganisms isolated from g astric, pharyngeal, and EA samples in relation to PSB samples compared with control samples. Among the different quantitative cultures analy zed, only those obtained from EA significantly correlated with PSB cul tures in patients with pneumonia (r = 0.67, p = 0.001). In summary, th e present study shows that the coincidence between microorganisms isol ated in PSB cultures and those from gastric and oropharynx increase in MV patients with pneumonia, indicating that both reservoirs play a ke y role in the pathogenesis of pneumonia. Conceivably, preventing both gastric and pharyngeal colonization may reduce the incidence of ventil ator-associated pneumonia. From all the noninvasive samples studied on ly endotracheal aspirate cultures were useful for inferring the etiolo gy of some VAP pneumonias.