Critical Care Medicine

Answer 1 Haemophilus influenzae. Although Streptococcus pneumoniae and H. influenzae may be recovered during the first few days of a patient’s stay in the intensive care unit, they are rarely isolated thereafter. Staphylococcus aureus is the pathogen most frequently isolated from lower respiratory tract samples of patients with ventilator-associated pneumonia (VAP). Other commonly isolated pathogens include Pseudomonas aeruginosa, Enterobacter species, Klebsiella species, Acinetobacter baumannii, Proteus species, and Escherichia coli. Prevotella melaninogenica is among the most common anaerobic organisms isolated. Although anaerobic bacteria are frequently isolated from the oropharynx, and microaspiration has been demonstrated to be the predominant mechanism of VAP, the role of anaerobic bacteria in VAP is unclear, with many studies reporting a low incidence of anaerobic bacteria in VAP. Isolation of anaerobic bacteria requires adequate transport conditions and specific growth media. With these measures, anaerobic bacteria have been isolated in up to 25% of patients with VAP. SUGGESTED READING 1. Bonten MJ, Gaillard CA, Wouters EF, et al. Problems in diagnosing nosocomial pneumonia in mechanically ventilated patients: a review. Crit Care Med 1994;22:1683-91. 2. Chiles C, Ravin CE. Radiographic recognition of pneumothorax in the intensive care unit. Crit Care Med 1986;14:677-80. 3. Lamm WJ, Graham MM, Albert RK. Mechanism by which the prone position improves oxygenation in acute lung injury. Am J Respir Crit Care Med 1994;150:184-93. 4. Pappert D, Rossaint R, Slama K, et al. Influence of positioning on ventilation-perfusion relationships in severe adult respiratory distress syndrome. Chest 1994;106:1511-6. 5. Tuxen DV. Detrimental effects of positive end-expiratory pressure during controlled mechanical ventilation of patients with severe airflow obstruction. Am Rev Respir Dis 1989;140:5-9. 6. Tuxen DV, Williams TJ, Scheinkestel CD, et al. Use of a measurement of pulmonary hyperinflation to control the level of mechanical ventilation in patients with acute severe asthma. Am Rev Respir Dis 1992;146(5 Pt 1):1136-42. Click here to return to the questions

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