Oral microflora and selection of resistance after a single dose of amoxicillin

The study aimed to determine the effects of a single-dose antibiotic prophylaxis on normal oral microflora. A single dose of 2 g amoxicillinwas given to 29 healthy volunteers. Saliva was collected before antibiotic administration (day 1), and again on days 2, 5, 10, 17 and 24 and subjected to culturing and antibiotic sensitivity analysis. Twenty-one per cent (6/29) of the individuals carried penicillin-V-and amoxicillin-resistant viridans streptococci before antibiotic administration. After a single dose of amoxicillin there was a significant reduction in Streptococcus salivarius on days 2 and 5, a significant reduction in other viridans streptococci on day 2 and the proportion of viridans streptococci with reduced susceptibility to amoxicillin was significantly increased on days 2 and 5. A single dose of amoxicillin can cause an ecological disturbance and induce selection of resistant strains in the oral microflora. D. Khalil, CMI 2016;22:949.e1-949.e4 (C) 2016 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.