Changing Pharyngeal Bacterial Flora of Hospitalized Patients

The prevalence of gram-negative bacilli among the oropharyngeal bacterial flora was low in physiologically normal subjects despite hospital exposure but rose markedly in patients with illnesses of varying severity. This increased prevalence was not correlated with antibiotic administration or inhalation therapy, was not dependent on duration of hospitalization and correlated best with the clinical severity of illness. Increased exposure to these organisms alone does not adequately explain these findings, suggesting that pharyngeal clearance mechanisms are impaired in these patients. Since most bacterial pneumonias begin with the aspiration into the lung of bacteria present in the upper respiratory tract, this alteration in the pharyngeal flora of ill patients may represent an important initial step in the pathogenesis of pneumonia due to gram-negative bacilli.