Antibiotic Resistance in Primary and Persistent Endodontic Infections

Introduction: The presence of antibiotic resistance genes in endodontic microorganisms might render the infection resistant to common antibiotics. The aims of this project were to identify selected antibiotic resistance genes in primary and persistent endodontic infections and to determine the effectiveness of contemporary endodontic procedures in eliminating bacteria with these genes. Methods: In patients undergoing primary endodontic treatment or retreatment, the root canals were aseptically accessed and sampled before endodontic procedures as well as after contemporary chemomechanical preparation and medication with calcium hydroxide. Identification of the following antibiotic resistance genes was performed by using polymerase chain reaction: bla(TEM-1), cfxA, blaZ, tetM, tetW, tetQ, vanA, vanD, and vanE. Limited phenotypic identification and antibiotic susceptibility verification were also performed. Results: Overall, there were 45 specimens available for analysis, 30 from primary and 15 from persistent endodontic infections. In preoperative specimens, only bla(TEM-1) was significantly more prevalent in primary versus persistent infections (P = .04). After contemporary treatment procedures, there was an overall reduction in prevalence of these genes (P < .001). bla(TEM-1)., and tetW were significantly reduced (P < .05), cfxA, blaZ, and tetQ were eliminated, but there was no change in tetM. No specimens contained vanA, vanD, or vanE. Antibiotic susceptibility testing showed significant differences among the antibiotics (P < .001) and general concordance with the gene findings. Conclusions: bla(TEM-1) was more prevalent in primary than persistent infections. Vancomycin resistance was not present. The genes identified were reduced with treatment except for tetM. Genetic testing might be useful as a screening tool for antibiotic resistance. (J Endod 2011;37:1337-1344)