title: Acidogenicity and acid tolerance ofStreptococcus oralisandStreptococcus mitisisolated from plaque of healthy and incipient caries teeth.
abstract: BACKGROUND
  Non-mutans low pH oral streptococci are postulated to contribute to caries etiology.
  
  
  OBJECTIVE
  This study was undertaken to investigate whether the acidogenicity and acid tolerance of clinical strains ofStreptococcus oralisandStreptococcus mitiscorrelate with health or early-stage enamel caries.
  
  
  METHODS
  S. oralisandS. mitiswere isolated from plaque samples taken from the occlusal surfaces of second molars sampled at two different visits 4 years apart. All sites were sound at Visit 1; subjects were segregated into one of three groups based on the status of the site at Visit 2 and caries elsewhere in the dentition. Strains ofS. oralisandS. mitiswere evaluated for acidogenicity and acid tolerance, and the results correlated with the clinical status of the sites from which they were isolated. Mutans streptococci (MS) isolated from the plaque samples were also quantified, and the presence or absence of growth on pH 5.5 media or on media selective for bifidobacteria was recorded.
  
  
  RESULTS
  No significant positive correlations were found between the acidogenicity properties of theS. oralisandS. mitisclones and caries at either visit. Similar results were obtained for acid tolerance ofS. oralisclones but were inconclusive forS. mitisclones. A statistically significant positive correlation between MS levels and caries (or future caries) was evident at both visits, but there were no statistical correlations with the growth on pH 5.5 media or media selective for bifidobacteria.
  
  
  CONCLUSIONS
  The low pH potential likely varies considerably among oral streptococcal species and is least likely to be found among strains ofS. mitis. Accordingly, the concept and constitution of 'low pH streptococci' may need to be re-evaluated.
authors: Iowa Institute for Oral Health Research, University of Iowa College of Dentistry, Iowa City, IA, USA; jeffrey-banas@uiowa.edu.
authors: Jeffrey A
authors: JA
authors: Banas
authors: Iowa Institute for Oral Health Research, University of Iowa College of Dentistry, Iowa City, IA, USA.
authors: Min
authors: M
authors: Zhu
authors: Iowa Institute for Oral Health Research, University of Iowa College of Dentistry, Iowa City, IA, USA.
authors: Deborah V
authors: DV
authors: Dawson
authors: Iowa Institute for Oral Health Research, University of Iowa College of Dentistry, Iowa City, IA, USA.
authors: Derek R
authors: DR
authors: Blanchette
authors: Iowa Institute for Oral Health Research, University of Iowa College of Dentistry, Iowa City, IA, USA.
authors: David R
authors: DR
authors: Drake
authors: Iowa Institute for Oral Health Research, University of Iowa College of Dentistry, Iowa City, IA, USA.
authors: Hongjie
authors: H
authors: Gu
authors: Iowa Institute for Oral Health Research, University of Iowa College of Dentistry, Iowa City, IA, USA.
authors: Ryan
authors: R
authors: Frost
authors: Iowa Institute for Oral Health Research, University of Iowa College of Dentistry, Iowa City, IA, USA.
authors: Grant
authors: G
authors: McCaulley
authors: Department of Preventive and Community Dentistry, University of Iowa College of Dentistry Iowa City, IA, USA.
authors: Steven M
authors: SM
authors: Levy
keywords: acid tolerance; acidogenicity; cariogenicity; dental plaque; mutans streptococci; oral microbiota