title: Detection of antibiotic resistance genes in samples from acute and chronic endodontic infections and after treatment.
abstract: OBJECTIVE
  The purpose of this study was twofold: survey samples from acute and chronic endodontic infections for the presence of genes encoding resistance to beta-lactams, tetracycline and erythromycin, and evaluate the ability of treatment to eliminate these genes from root canals.
  
  
  METHODS
  DNA extracts from samples of abscess aspirates (n=25) and root canals of teeth with asymptomatic apical periodontitis (n=24) were used as template for direct detection of the genes blaTEM, cfxA, tetM, tetQ, tetW, and ermC using real-time polymerase chain reaction (PCR). Bacterial presence was determined using PCR with universal bacterial primers. Root canals of the asymptomatic cases were also sampled and evaluated after chemomechanical procedures using NiTi instruments with 2.5% NaOCl irrigation.
  
  
  RESULTS
  All abscess and initial root canal samples were positive for bacteria. At least one of the target resistance genes was found in 36% of the abscess samples and 67% of the asymptomatic cases. The most prevalent genes in abscesses were blaTEM (24%) and ermC (24%), while tetM (42%) and tetW (29%) prevailed in asymptomatic cases. The blaTEM gene was significantly associated with acute cases (p=0.02). Conversely, tetM was significantly more prevalent in asymptomatic cases (p=0.008). Treatment eliminated resistance genes from most cases.
  
  
  CONCLUSIONS
  Acute and chronic endodontic infections harboured resistance genes for 3 classes of widely used antibiotics. In most cases, treatment was effective in eliminating these genes, but there were a few cases in which they persisted. The implications of persistence are unknown. Direct detection of resistance genes in abscesses may be a potential method for rapid diagnosis and establishment of proactive antimicrobial therapy.
authors.affiliation: Department of Endodontics and Molecular Microbiology Laboratory, Faculty of Dentistry, Estácio de Sá University, Rio de Janeiro, RJ, Brazil.
authors.forename: Isabela N
authors.initials: IN
authors.lastname: Rôças
authors.forename: José F
authors.initials: JF
authors.lastname: Siqueira
mesh_terms: D000328:Adult; D001424:Bacterial Infections / Q000235:genetics*; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D004352:Drug Resistance, Microbial / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010482:Periapical Abscess / Q000382:microbiology*; D010485:Periapical Periodontitis / Q000235:genetics*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D012390:Root Canal Therapy / Q000009:adverse effects*
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S
keywords: Acute apical abscess; Antibiotic resistance genes; Asymptomatic apical periodontitis; Endodontic treatment