title: Antibiotic susceptibility of periodontal Streptococcus constellatus and Streptococcus intermedius clinical isolates.
abstract: BACKGROUND
  Streptococcus constellatus and Streptococcus intermedius in subgingival dental plaque biofilms may contribute to forms of periodontitis that resist treatment with conventional mechanical root debridement/surgical procedures and may additionally participate in some extraoral infections. Because systemic antibiotics are often used in these clinical situations, and little is known of the antibiotic susceptibility of subgingival isolates of these two bacterial species, this study determined the in vitro susceptibility to six antibiotics of fresh S. constellatus and S. intermedius clinical isolates from human periodontitis lesions.
  
  
  METHODS
  A total of 33 S. constellatus and 17 S. intermedius subgingival strains, each recovered from separate patients with severe chronic periodontitis (n = 50) before treatment, were subjected to antibiotic gradient strip susceptibility testing with amoxicillin, azithromycin, clindamycin, ciprofloxacin, and doxycycline on blood-supplemented Mueller-Hinton agar and to the inhibitory effects of metronidazole at 16 mg/L in an enriched Brucella blood agar dilution assay. Clinical and Laboratory Standards Institute and European Committee on Antimicrobial Susceptibility Testing interpretative standards were used to assess the results.
  
  
  RESULTS
  Clindamycin was the most active antibiotic against S. constellatus (minimum inhibitory concentration at 90% [MIC90] 0.25 mg/L), and amoxicillin was most active against S. intermedius (MIC90 0.125 mg/L). A total of 30% of the S. constellatus and S. intermedius clinical isolates were resistant in vitro to doxycycline, 98% were only intermediate in susceptibility to ciprofloxacin, and 90% were resistant to metronidazole at 16 mg/L.
  
  
  CONCLUSIONS
  Subgingival S. constellatus and S. intermedius exhibited variable antibiotic susceptibility profiles, potentially complicating empirical selection of periodontitis antibiotic therapy in patients who are species positive.
authors.affiliation: Department of Periodontology and Oral Implantology, and Oral Microbiology Testing Service Laboratory, Temple University School of Dentistry, Philadelphia, PA.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Rams
authors.forename: Diane
authors.initials: D
authors.lastname: Feik
authors.forename: Joel E
authors.initials: JE
authors.lastname: Mortensen
authors.forename: John E
authors.initials: JE
authors.lastname: Degener
authors.forename: Arie J
authors.initials: AJ
authors.lastname: van Winkelhoff
mesh_terms: D000328:Adult; D000368:Aged; D000658:Amoxicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017963:Azithromycin / Q000494:pharmacology; D001431:Bacteriological Techniques; D055113:Chronic Periodontitis / Q000382:microbiology*; D002939:Ciprofloxacin / Q000494:pharmacology; D002981:Clindamycin / Q000494:pharmacology; D004318:Doxycycline / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D005260:Female; D006801:Humans; D008297:Male; D008795:Metronidazole / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D010403:Penicillin Resistance; D013291:Streptococcus / Q000145:classification / Q000187:drug effects*; D034367:Streptococcus intermedius / Q000187:drug effects*; D013753:Tetracycline Resistance
chemical_list: D000900:Anti-Bacterial Agents; D008795:Metronidazole; D002981:Clindamycin; D002939:Ciprofloxacin; D000658:Amoxicillin; D017963:Azithromycin; D004318:Doxycycline
keywords: Anti-infective agents; Streptococcus; chronic periodontitis; drug resistance; in vitro; periodontal pocket