Potential effect of topical antibiotics administration in the oral cavity on the reduced number of bacteria entering the lower respiratory tract after oral cancer surgery.

Background/purpose: One of the causes of ventilator-associated pneumonia (VAP) is aspiration of oropharyngeal fluid containing pathogenic microorganisms into the lower respiratory tract. In this study, we aimed to investigate whether antibiotic ointment applied to the oral cavity can reduce the number of bacteria in the fluid on the cuff of a tracheal cannula. Materials and methods: Tetracycline ointment was applied intraorally once to a patient under endotracheal intubation by postoperative tracheostomy for oral cancer. The tetracycline concentrations in the oropharyngeal fluid and fluid on the cuff of tracheal cannula were determined by bioassay, and the total viable bacterial count was determined by delayed real-time polymerase chain reaction developed by the authors from before to 6 h after application. Results: A total of seven patients were enrolled. Very high antibiotic concentrations were maintained, ranging from 481 μg/ml to 2060 μg/ml in oropharyngeal fluid and from 267 μg/ml to 858 μg/ml in fluid on the cuff from 1 h to 6 h after application. Compared to the pre-application results, the inhibition rates of viable bacteria were 80.0-97.7% for oropharyngeal fluid and 47.6%-91.9% for fluid on the cuff at 1-6 h after application, indicating that antibiotic ointment can inhibit bacteria entering the lower respiratory tract for a long period of time in intubated patients. Conclusion: Oral application of antibiotic ointment reduced the number of bacteria entering the lower respiratory tract, suggesting that it may be useful in the prevention or treatment of VAP.