title: Amoxicillin-resistant oral streptococci identified in dental plaque specimens from healthy Japanese adults.
abstract: BACKGROUND
  Infective endocarditis (IE) is known to be a life-threatening disease and invasive dental procedures are considered to be important factors. Oral amoxicillin (AMPC) is widely used for prophylaxis in patients with heart disorders who are at risk for IE. However, there is only limited information regarding the inhibition of oral bacteria by AMPC.
  
  
  RESULTS
  Dental plaque specimens were obtained from 120 healthy Japanese adult subjects, then diluted and streaked onto selective medium for oral streptococci. The minimum inhibitory concentration (MIC) of AMPC was evaluated using a macro-dilution method by Clinical Laboratory Standard Institute (2006). Seven strains with an MIC of AMPC of 16μg/mL or more were isolated from 5 subjects. The bacterial species were confirmed by sequence analysis of 16S rRNA from each strain, which demonstrated that most were Streptococcus sanguinis, followed by Streptococcus oralis. Dental plaque specimens collected from these 5 subjects again after an interval of 2-3 months possessed no strains with an MIC of AMPC of 16μg/mL or more.
  
  
  CONCLUSIONS
  These findings suggest that strains with a high MIC of AMPC are present in the oral cavities of Japanese adults, though they may be transient rather than inhabitants.
authors.affiliation: Department of Pediatric Dentistry, Osaka University Graduate School of Dentistry, Suita, Osaka, Japan.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Masuda
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Nemoto
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nakano
authors.forename: Shuhei
authors.initials: S
authors.lastname: Naka
authors.forename: Ryota
authors.initials: R
authors.lastname: Nomura
authors.forename: Takashi
authors.initials: T
authors.lastname: Ooshima
mesh_terms: D000328:Adult; D000658:Amoxicillin / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D044466:Asian People; D003773:Dental Plaque / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D004696:Endocarditis; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019533:Streptococcus oralis / Q000187:drug effects* / Q000302:isolation & purification*; D013298:Streptococcus sanguis / Q000187:drug effects* / Q000302:isolation & purification*
chemical_list: D000900:Anti-Bacterial Agents; D000658:Amoxicillin