title: Antibiotic resistance in primary and persistent endodontic infections.
abstract: BACKGROUND
  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.
authors.affiliation: Department of Endodontics, Dental School, University of Maryland, Baltimore, Maryland 21201, USA.
authors.forename: Gretchen B
authors.initials: GB
authors.lastname: Jungermann
authors.forename: Krystal
authors.initials: K
authors.lastname: Burns
authors.forename: Renu
authors.initials: R
authors.lastname: Nandakumar
authors.forename: Mostafa
authors.initials: M
authors.lastname: Tolba
authors.forename: Richard A
authors.initials: RA
authors.lastname: Venezia
authors.forename: Ashraf F
authors.initials: AF
authors.lastname: Fouad
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D004269:DNA, Bacterial / Q000235:genetics; D003788:Dental Pulp Diseases / Q000382:microbiology* / Q000628:therapy; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D010485:Periapical Periodontitis / Q000382:microbiology* / Q000628:therapy; D012388:Root Canal Irrigants / Q000627:therapeutic use; D018915:Root Canal Preparation; D013753:Tetracycline Resistance / Q000235:genetics; D020713:Vancomycin Resistance / Q000235:genetics; D055815:Young Adult; D018440:beta-Lactam Resistance / Q000235:genetics
chemical_list: D004269:DNA, Bacterial; D012388:Root Canal Irrigants