Effect of prophylactic administration of antibiotics on the oral microbiota

Objectives: This study was conducted to quantitatively and qualitatively evaluate the effect of antibiotics prophylaxis on the oral microbiota of mandibular impacted wisdom tooth extractions. Methods: Tongue and buccal mucosa swabs and oral rinse were collected from 10 patients. Amoxicillin 250 mg was used as antibiotics prophylaxis. The first dose was administered 1 hour before tooth extraction and then given orally three times a day until 48 hours after tooth extraction. Changes in bacterial cell counts and oral microbiota in each specimen were investigated before, 1 hour after, and 1 week after the first dose of antibiotics prophylaxis. Results: The results of bacterial cell counts determined by Ethidium bromide staining and culture method showed no significant changes before and after antibiotic administration. The results of microbiota analysis of the 16S rRNA V3 region showed changes in the oral microbiota of all 10 patients at 1 hour after antibiotic administration. After one week of treatment, the group was divided into two groups: those whose microbiota returned to their original state (4 patients) and those whose microbiota changed from the original state (6 patients). In the group whose microbiota changed before and after antibiotic administration, the proportion of obligate anaerobes was significantly higher than that before treatment, and the proportion of caries- and periodontitis-causing bacteria was also significantly higher. Conclusion: These results suggest that prophylactic administration of antibiotics may alter the microbiota and deteriorate of the oral environment, even though there is no significant change in the amount of bacteria.