Antibiotic susceptibility profiles of oral pathogens

Periodontitis is a bacterial disease that can be treated with systemic antibiotics. The aim of this study was to establish the antibiotic susceptibility profiles of five periodontal pathogens to six commonly used antibiotics in periodontics. A total of 247 periodontal bacterial isolates were tested for susceptibility to the six antibiotics using the Etest method. MIC(50) and MIC(90) values (minimum inhibitory concentrations for 50% and 90% of the organisms, respectively) were calculated. Both European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Clinical and Laboratory Standards Institute (CLSI) breakpoints were used in the study to interpret results. β-Lactamase production was tested when amoxicillin resistance was found. MIC(90) values of the anaerobic bacteria were all well below breakpoint values, except for three isolates of Prevotella intermedia and one isolate of Fusobacterium nucleatum that were resistant to amoxicillin (CLSI breakpoints); these isolates were β-lactamase-positive. Two isolates of the capnophilic Aggregatibacter actinomycetemcomitans appeared to be amoxicillin-resistant but failed to show β-lactamase activity. Comparison with a previous study from The Netherlands showed minor differences in susceptibility profiles, but the MIC(90) values of A. actinomycetemcomitans for amoxicillin, clindamycin, azithromycin and tetracycline were higher. Geographical differences in the susceptibility profiles of Porphyromonas gingivalis and A. actinomycetemcomitans between European countries were noted. Comparison of European susceptibility profiles with that of a South American country (Colombia) revealed a much higher resistance in the latter. Owing to these differences in susceptibility profiles, it is of concern to regularly perform surveillance studies on antibiotic resistance.