Pseudomonas aeruginosa and the oropharyngeal ecosystem of tube-fed patients

Abstract

We evaluated whether elderly patients fed with nasogastric tubes (NGT) are predisposed to Pseudomonas aeruginosa colonization in the oropharynx. Fifty-three patients on NGT feeding and 50 orally fed controls with similar clinical characteristics were studied. The tongue dorsum was swabbed and cultured. P. aeruginosa was isolated in 18 (34%) of the NGT-fed group but in no controls (p<0.001). Other gram-negative bacteria were cultured from 34 (64%) of NGT-fed patients as compared with 4 (8%) of controls (p<0.001). Antibiotic susceptibility of the oropharyngeal P. aeruginosa isolates was compared with that of isolates from sputum cultures obtained from our hospital's bacteriologic laboratory. The oropharyngeal isolates showed a higher rate of resistance; differences were significant for amikacin (p<0.03). Scanning electron microscope studies showed a biofilm containing P. aeruginosa organisms. The pulsed-field gel electrophoresis profile of these organisms was similar to that of P. aeruginosa isolates from the oropharynx. NGT-fed patients may serve as vectors of resistant P. aeruginosa strains.

Figure 1

Nasogastric tube embedded in the nasopharynx. 1, nasogastric tube; 2, dorsum of tongue.

Figure 2

Representative biofilms on nasogastric tubes showing bacterial organisms with typical form of Pseudomonas aeruginosa. Scanning electronic microscope. A, scale bar, 1 µm; B, scale bar, 10 µm.

Figure 3

Pulsed-field gel electrophoresis of three pairs of Pseudomonas aeruginosa isolates obtained from three patients from nasogastric tubes (lanes 2, 4, 6) and from oropharynx (lanes 3, 5, 7). Lane 1 shows the λ marker size (New England Biolabs, Eldan, Rosh Ha’ain, Israel).