Prevalence of gram-negative rods in the normal pharyngeal flora

Abstract

We obtained throat cultures from 100 randomly selected people free from any chronic upper or lower respiratory disease who did not work in a hospital and who had not experienced any acute illness or received any antibacterial therapy in the 4 weeks preceding culture. Eighteen percent harbored either a species of Enterobacteriaceae or Pseudomonas aeruginosa in their pharynx. In all cases, colony counts were low, the majority being detected in broth media selective for Gram-negative rods. There were no clear-cut age or sex distributions of Gram-negative pharyngeal carriage. These data imply that, in at least some cases, isolation of Gram-negative rods from sputum of untreated patients may be a normal finding, and that in some patients with pulmonary infection, the pretreatment, upper respiratory tract flora may serve as the source of subsequent superinfection with Gram-negative rods.