Reduced susceptibility to amoxicillin of oral streptococci following amoxicillin exposure

As antibiotic pressure often triggers bacterial resistance, the use of short-duration therapies is increasingly recommended. The objective of the present study was to evaluate both the clinical efficiency and the impact on oral streptococci of a 3 day versus a 7 day amoxicillin therapy for odontogenic infection requiring tooth extraction. On day 0, patients were randomly assigned to a 3 day or 7 day amoxicillin treatment. The tooth was extracted on day 2 and the post-operative follow-up was carried out on day 9. Oral flora was collected on days 0, 9 and 30, and the susceptibility of the streptococci to amoxicillin was determined. The results showed that treatment with amoxicillin for 3 or 7 days had a similar clinical efficiency, and also induced similar selection of oral streptococci with reduced susceptibility to amoxicillin, suggesting that the selection of strains with reduced susceptibility to amoxicillin is a rapid phenomenon, appearing even with short-duration therapies.