Applied and Environmental Microbiology, August 2000, p. 3330-3336, Vol. 66, No. 8
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Copyright © 2000, American Society for Microbiology. All rights reserved.
Dental Caries Research Group, Guy's, King's, and St. Thomas' Dental Institute, London SE5 9RW,1 and Unilever Research, Port Sunlight, Wirral L63 3JW,2 England
Received 3 April 2000/Accepted 31 May 2000
The genotypic heterogeneity of Streptococcus oralis
isolated from the oral cavity was investigated using repetitive
extragenic palindromic PCR. Unrelated subjects harbored unique
genotypes, with numerous genotypes being isolated from an individual.
S. oralis is the predominant aciduric bacterium isolated
from noncarious tooth sites. Genotypic comparison of the aciduric
populations isolated at pH 5.2 with those isolated from
mitis-salivarius agar (MSA) (pH 7.0) indicated that the aciduric
populations were genotypically distinct in the majority of subjects
(
2 = 13.09; P = 0.0031). Neither
the aciduric nor the MSA-isolated strains were stable, with no strains
isolated at baseline being isolated 4 or 12 weeks later in the majority
of subjects. The basis of this instability is unknown but is similar to
that reported for Streptococcus mitis. Examination of
S. oralis strains isolated from cohabiting couples
demonstrated that in three of five couples, genotypically identical
strains were isolated from both partners and this was confirmed by
using Salmonella enteritidis repetitive element PCR and
enterobacterial PCR typing. These data provide further evidence of the
physiological and genotypic heterogeneity of non-mutans streptococci.
The demonstration of distinct aciduric populations of S. oralis implies that the role of these and other non-mutans
streptococci in the caries process requires reevaluation.
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