tions and may constitute “reservoirs of resistance” (18). The existence of a biofilm in such a reservoir would facil- itate antibiotic resistance (19). A similar effect was report- ed with polyvinyl chloride endotracheal tubes (20). The increased resistance rate of oropharyngeal P. aeruginosa isolates to relevant antibiotics in our study as compared with the isolates from sputum is in agreement with this observation. The epidemiologic importance of a human reservoir of P. aeruginosa is not limited to the patient. NGT-fed patients are often transferred to general hospitals and may possibly serve as vectors of resistant organisms to other medical settings (emergency departments, surgical, ortho- pedic, urologic wards, and intensive care units). One limitation of our study is that it was performed at a single facility. However, each of the four wards that partic- ipated is located in a pavilion separated by 50 m to 100 m from another. Moreover, the factors involved in the oropharyngeal ecosystem colonization by P. eruginosa dis- RESEARCH Figure 1. Nasogastric tube embedded in the nasopharynx. 1, naso- gastric tube; 2, dorsum of tongue. Discussion NGT-fed elderly patients may constitute a human reser- voir of P. aeruginosa. Determination of the antibiotic sus- ceptibility of these P. aeruginosa isolates showed that they had a higher rate of resistance to most antibiotics than to P. aeruginosa isolates from sputum obtained from hospital- ized patients with bronchopulmonary infections during the same period. This difference reached statistical signifi- cance for amikacin. Early studies had reported on the propensity of gram-negative bacteria to colonize elderly patients’ oropharynges (10–13). Our recently published study (2) and the present one are the only reports docu- menting the colonization of the oropharynx in NGT-fed patients by pathogenic florae. Two factors may explain the high prevalence of P. aeruginosa in the NGT-fed patients. One is the lack of mechanical clearance of the mouth provided by chewing and swallowing, an important mechanism in preventing gram-negative bacteria from colonizing the oropharynx of the elderly (14). The other factor is P. aeruginosa’s known ability to adhere and form biofilm on plastic tubes, includ- ing those made of polyvinyl chloride (15,16). The biofilms formed on NGTs probably play a major role in the persist- ence of its colonization of the oropharynges of these patients and interfere with its eradication by antibiotics. The clinical implications of such a reservoir are far reaching. An opportunistic organism such as P. aeruginosa in the oropharynx constitutes a threat to NGT-fed patients, who are at risk for aspiration pneumonia and systemic infections (17). Moreover, these elderly NGT-fed patients, most of whom reside in long-term-care facilities, are under “antibiotic pressure” because of frequent clinical infec- 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. 958 Emerging Infectious Diseases • Vol. 9, No. 8, August 2003