Oral colonization by respiratory pathogens in patients receiving intensive care

Abstract

OBJECTIVES: An observational study was conducted to examine respiratory pathogen colonization of different surfaces in the oral cavity, as well as extra-oral sites, in mechanically ventilated patients receiving intensive care. METHODS: Swab samples of the tongue dorsum, throat, anterior nares, and supragingival plaque were obtained within 48 hours of intubation. Sampling was continued bi-weekly thereafter until extubation, discharge, or death. Weekly tracheal aspirate samples were also obtained. Samples were cultured to identify aerobic and facultatively anaerobic Gram negative bacteria (AGNB), Staphylococcus aureus, and yeasts. All patients received a daily oral cleaning with cotton tipped applicators soaked in a 0.2% chlorhexidine solution. RESULTS: Samples were obtained from 55 patients at baseline. Among the five sampled sites, the dorsal tongue surface was found to have the highest prevalence (54.5%) and levels (6.5x106cfu/ml) of AGNB at baseline. The dorsal tongue surface also harbored the highest levels of yeast (6.0x104 cfu/ml), while yeast prevalence (50.0%) was greatest in supragingival plaque. No significant differences in S. aureus viable counts or prevalence were found. Generalized estimating equations analyses showed that both yeast viable counts and prevalence had increased significantly at the second sampling time point (time effect p=0.006), while no significant differences were observed for AGNB or S. aureus. CONCLUSIONS: Despite the traditional assertion that the anterior nares are the primary reservoir of S. aureus, the results of this study suggest that the oral cavity may be an equally important reservoir of this pathogen in mechanically ventilated patients. Oral respiratory pathogens remain prevalent despite daily application of chlorhexidine in the short term. The dorsal tongue surface is likely to be an important reservoir of oral respiratory pathogens, and increased consideration of this site is warranted in the development oral hygiene protocols for these patient groups..