Purpose: The presence of antibiotic resistance genes in endodontic microorganisms may render the infection resistant to common antibiotics, particularly during regenerative procedures when total microbial elimination is sought. The aims of this project were to use molecular methods to identify selected antibiotics resistance genes in primary and persistent endodontic infections and determine the effectiveness of contemporary endodontic procedures in eliminating bacteria with these genes.
Methods: Fifty teeth from patients with primary or persistent infections were included. The root canals were aseptically accessed and sampled prior to endodontic procedures as well as following contemporary chemomechanical preparation and medication with calcium hydroxide. DNA extraction, PCR amplification and gel electrophoresis were performed for the following antibiotics resistance genes: blaTEM-1, cfxA, blaZ, tetM, tetW, tetQ, vanA, vanD, and vanE.
Results: Five specimens were excluded for lack of bacterial DNA (3), unavailability of a second specimen (1); or being from an old incomplete treatment (1), leaving 30 primary and 15 persistent endodontic infections. There was an overall reduction in prevalence of the genes in the pre-operative and pre-obturation specimens (p=0.006). The respective changes in individual genes were: blaTEM-1: 32% and 9% (p=0.05), cfxA: 11% and 0% (p=0.02), blaZ: 2% and 0%, tetM: 21% and 21%, tetW: 19% and 2% (p=0.07), and tetQ: 9% and 0% (p=0.04). No specimens contained vanA, vanD, or vanE. Primary infections were more likely to have the resistance genes studied (72% vs. 60%) but this was not statistically significant, except for blaTEM-1 which was more prevalent in primary infections (p=0.04).
Conclusion: We conclude that blaTEM-1 was more prevalent in primary than persistent infections, that vancomycin resistance is not present and that the prevalent antibiotic resistance genes are generally reduced with treatment except for tetM. (Supported by a Grant DE015320-01-A1 from NIDCR and a Grant from the AAE Foundation.)