title: Incidence and antimicrobial susceptibility of Porphyromonas gingivalis isolated from mixed endodontic infections.
abstract: OBJECTIVE
  To investigate the prevalence of Porphyromonas gingivalis in root canals of infected teeth with periapical abscesses and to investigate the antimicrobial susceptibility of this species to some frequently prescribed antibiotics.
  
  
  METHODS
  Samples were obtained from 70 root canals of abscessed teeth. Microbial sampling, isolation and bacterial identification were accomplished using appropriate culture methods for anaerobic species. The antimicrobial susceptibility of the 20 strains of P. gingivalis isolated was determined by using the E-test. The antimicrobial agents tested were amoxicillin, amoxicillin + clavulanate, azythromycin, benzylpenicillin, cephaclor, clindamycin, erythromycin, metronidazole and tetracycline.
  
  
  RESULTS
  A total of 352 individual strains, belonging to 69 different species, were isolated. Eighty three percent of the strains were strict anaerobes and 47.5% of the isolated bacteria were Gram-negative. Porphyromonas gingivalis was found in 20 root canals and was most frequently found in symptomatic cases. Statistically, the presence of P. gingivalis was related to purulent exudates and pain on palpation (both P < 0.05). All P. gingivalis strains were sensitive to amoxicillin, amoxicillin + clavulanate, cephaclor, clindamycin, benzylpenicyllin, metronidazole and tetracycline. The lowest range of minimum inhibitory concentration (MIC) (0.026-0.125 microg mL(-1)) was observed against amoxicillin + clavulanate and clindamycin. The lowest MIC 90 was observed against clindamycin (0.064 microg mL(-1)). One strain was resistant to erythromycin and eight strains were resistant to azythromycin.
  
  
  CONCLUSIONS
  Porphyromonas gingivalis pathogen is isolated with frequency from root canals of infected teeth with periapical abscesses. Amoxicillin, as well as amoxicillin-clavulanic acid and benzylpenicillin were effective against P. gingivalis.
authors.affiliation: Endodontic Department, Piracicaba Dental School, State University of Campinas, UNICAMP, Piracicaba, SP, Brazil.
authors.forename: R C
authors.initials: RC
authors.lastname: Jacinto
authors.forename: B P F A
authors.initials: BP
authors.lastname: Gomes
authors.forename: H N
authors.initials: HN
authors.lastname: Shah
authors.forename: C C
authors.initials: CC
authors.lastname: Ferraz
authors.forename: A A
authors.initials: AA
authors.lastname: Zaia
authors.forename: F J
authors.initials: FJ
authors.lastname: Souza-Filho
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D002417:Cattle; D002648:Child; D003786:Dental Pulp Cavity / Q000382:microbiology*; D005260:Female; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests / Q000379:methods; D008875:Middle Aged; D010482:Periapical Abscess / Q000382:microbiology*; D016966:Porphyromonas gingivalis / Q000187:drug effects*; D015995:Prevalence; D011671:Pulpitis / Q000382:microbiology
chemical_list: D000890:Anti-Infective Agents