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Applied and Environmental Microbiology, August 2000, p. 3330-3336, Vol. 66, No. 8
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
( The initiation of dental caries is
associated with the ability of dental plaque to produce acid from
ingested foods on a caries-prone tooth surface. At caries-prone sites,
smooth tooth surfaces, interproximal sites, pits and fissures where
plaque accumulates (1, 3, 10), and certainly within carious
lesions, the local pH is acidic, and the bacteria present in these
sites must be aciduric, exhibiting an ability to replicate in the
prevailing or transient acidic environment. Dental plaque contains many
species of acidogenic and aciduric microorganisms. The acidogenic
bacteria most closely associated with the dental caries process are
mutans streptococci (Streptococcus mutans and
Streptococcus sobrinus), lactobacilli, and perhaps
Actinomyces spp. There has been considerable discussion as
to the role of other bacteria, in particular the role of the non-mutans
streptococci (NMS), in the initiation and progression of dental caries.
In an attempt to obtain understanding of the potential pathogenic role
of these, van Houte and colleagues studied the acidogenicity of NMS
isolated from sound and carious tooth sites (29, 35, 36). In
these studies, the NMS were heterogeneous with respect to
acidogenicity. Thus, from infected dentine within carious lesions and
from plaque on sound surfaces in the mouths of caries-active subjects,
NMS which were more acidogenic than NMS were isolated from sound tooth
surfaces in caries-free subjects. The clonality of these strains has
not been reported nor was the aciduricity of the isolates investigated.
However, this was the first detailed and focused report of
heterogeneity amongst individual NMS species of a determinant expected
to be a significant feature of any microorganism involved in the
initiation of dental caries. The acidogenic NMS were also more numerous
than mutans streptococci, and it was proposed that these organisms may
play a significant role in the caries process.
The aciduricity of bacteria isolated from the dental plaque biofilm has
been investigated in a number of studies with a variety of in vitro
techniques, primarily by determining the ability of isolates to
metabolize carbohydrates and survive at acidic pH levels (11, 12,
15, 18, 23, 31, 32). These studies have demonstrated that
lactobacilli and mutans streptococci are the most aciduric dental
plaque bacteria, while NMS and Actinomyces spp. are less
aciduric. However, the strains tested in those experiments were all
isolated from conventional selective and nonselective culture media,
which may have influenced the phenotypes of the strains isolated and
subsequently examined. The predominant aciduric component of dental
plaque has not been extensively investigated. In a preliminary report,
we indicated that the predominant aciduric bacteria isolated from
dental plaque taken from noncarious surfaces were NMS, with
Streptococcus oralis, Streptococcus
parasanguinis, and Streptococcus intermedius being the
most frequently isolated (8). In this paper, we extend these
observations and report the genotypic characterization of aciduric
S. oralis strains from saliva and interproximal dental
plaque samples. Representatives of the aciduric isolates from each
subject were genotyped by using repetitive extragenic palindromic PCR
(REP-PCR [2]) and were compared to those isolated from
conventional culture media (pH 7.0). The stability of the S. oralis populations was assessed over periods of up to 12 weeks,
and the transmissibility of strains was determined by comparing the
S. oralis genotypes in the plaque flora of cohabiting couples.
Isolation of S. oralis from saliva and interproximal
plaque by using MSA and aciduric media.
Paraffin wax
(Ivoclar-Vivadent, Schaan, Liechtenstein)-stimulated saliva was
collected from volunteers and decimally diluted in fastidious anaerobe
broth (LabM; Salford, Lancs, England), and 100-µl aliquots were
plated onto mitis salivarius agar (MSA) (Becton-Dickinson, Oxford,
England) supplemented with 0.1% potassium tellurite (Becton-Dickinson)
for the isolation of viridans streptococci. Interproximal dental plaque
was collected from a single caries-free site in each subject. The
plaque samples were collected by using sterile wooden toothpicks, and
each sample was placed in 1 ml of sterile PBSTC (1.58 g of
K2HPO4 · 3H2O, 0.34 g
of KH2PO4, 8 g of NaCl, 1.0 g of
sodium thioglycollate, and 0.001 g of cetyltrimethylammonium bromide
per liter of distilled water). The samples were dispersed by vortexing
with sterile glass beads (BDH), decimally diluted in PBSTC, and plated
onto MSA. The MSA plates were incubated anaerobically at 37°C for 3 days.
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Genotypic Heterogeneity of Streptococcus
oralis and Distinct Aciduric Subpopulations in Human Dental
Plaque
ABSTRACT
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
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.
INTRODUCTION
Top
Abstract
Introduction
Materials and Methods
Results
Discussion
References
MATERIALS AND METHODS
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Abstract
Introduction
Materials and Methods
Results
Discussion
References
-D-N-acetylneuraminic
acid (Sigma, Poole, Dorset, England) in 50 mM
N-tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid (TES)
buffer, pH 7.5] in a flat-bottomed microtiter tray. The enzyme assays
were incubated aerobically at 37°C for 3 h, and an increase in
fluorescence, demonstrating sialidase activity, was measured by using a
fluorimeter (Perkin-Elmer, Beaconsfield, Hants, England) at emission
and excitation wavelengths of 380 and 460 nm, respectively. The
remainder of the cultures were supplemented with glycerol to final
concentrations of approximately 50% (vol/vol), and the microtiter
plates were stored at 
80°C.
-fucosidase,
-N-acetylgalactosaminidase, and
-N-acetylglucosaminidase by using the appropriate
fluorogenic substrate as previously described (4). Those
strains which were negative for -fucosidase, positive for the two
hexosaminidase activities, and positive for sialidase activity were
identified as S. oralis, and the identification was
confirmed by using further physiological tests, including fermentation
of a range of carbohydrates and hydrolysis of arginine and esculin
(4).
Aciduric S. oralis strains were also isolated from each
interproximal plaque sample. This isolation procedure employed was the
most probable number (MPN) technique. The predominant aciduric bacteria
in each sample capable of growth and proliferation in acidic media were
isolated by using brain heart infusion (BHI) (Oxoid) adjusted to pH 5.2 by using citric acid and Na2HPO4 at final
concentrations of 13 and 26 mM, respectively. Each plaque sample was
decimally diluted in PBSTC to give a dilution series from
10
1 to 108, and 12 replicates of each
dilution, 15 µl of plaque dilution in PBSTC, and 135 µl of acidic
BHI were set up in sterile flat-bottomed microtiter trays and incubated
anaerobically for 5 days. The terminal pH of wells exhibiting growth
was measured and found to be ±0.05 pH units of the original pH of the
medium. Terminal wells, the lowest dilutions exhibiting bacterial
growth were subcultured onto Columbia agar (Oxoid) supplemented with
5% (vol/vol) horse blood and were incubated anaerobically for 48 h. The colonies were examined by gram-staining, and those that appeared
as gram-positive cocci were identified. Aciduric S. oralis
strains were isolated from each subject, and these were stored in
glycerol broth at 80°C until required for subsequent genotypic
analysis (2). For the majority of the investigations, the
MPN method was used as a convenient multiwell procedure for the
isolation of aciduric S. oralis strains from samples, but
the MPN method was used to quantitate the proportion of S. oralis in 18 interproximal samples. From these samples, the number
of aciduric S. oralis strains as a percentage of the total
bacterial count determined using the MPN method with BHI at pH 7.0 was
calculated, and the proportion of S. oralis strains isolated
from MSA was expressed as a percentage of the total bacterial count on
nonselective media (9).
Genotyping of S. oralis. Individual S. oralis strains were genotyped by using repetitive extragenic palindromic-PCR (REP-PCR) which, as previously described, results in amplicon patterns which are unique for each independent isolate of S. oralis and all other species of viridans streptococci (2). For confirmatory purposes, enterobacterial PCR (ERIC-PCR) and Salmonella enteritidis repetitive element PCR (SERE-PCR) were also used as previously described (2).
Visualization of amplicons. The amplification products of REP-PCR and ERIC-PCR were analyzed by using 2% Metaphor agarose (Flowgen, Staffordshire, England) containing 0.5 µg of ethidium bromide per ml and were separated electrophoretically on 20- by 25-cm gels at 140 V for 3 h in Tris-borate-EDTA buffer. SERE-PCR products (15 µl) were resolved on 0.8% agarose (Sigma) containing 0.5 µg of ethidium bromide per ml by electrophoretic separation at 140 V for 3 h. To all samples, 3 µl of tracking dye (0.25% bromophenol blue, 0.25% xylene cyanol FF, 30% glycerol) was added, and molecular size marker (pGEM DNA Markers; Promega, Southampton, England) were included on all gels, in three to four separate lanes, to facilitate comparison of tracks between gels. Gels were examined on a transilluminator and were photographed by using Polaroid type 665 positive-negative film (Sigma).
Computer-assisted analysis of the DNA patterns.
All of the
patterns of the isolates from an individual were compared by using
GelCompar version 4.0 (Applied Maths, Kortrijk, Belgium). The
individual bands in each of the patterns produced by the different PCR
methods were analyzed by applying the Dice coefficient to the peaks.
For clustering, the unweighted pair group method using mathematical
averages (UPGMA) was used, and a band position tolerance of 1.5% was
used for comparison of the DNA patterns. The analysis of the patterns
was undertaken in accordance with the instructions of the manufacturer.
Differences in the frequency of recovery of genotypes were compared
statistically using the 2 test (Fisher's exact test).
Genotypic heterogeneity of S. oralis isolated from individuals. Interproximal plaque samples were taken from 15 subjects, and S. oralis strains were isolated from each sample by using MSA and the multiwell method as described above. The genotypes present in each subject, isolated on each medium, were compared by cluster analysis, and the similarity of the strains from the two culture conditions in each subject was determined.
Stability of S. oralis genotypes. The stability of the S. oralis populations in individual mouths was determined in two experiments. In the first, an oral rinse was obtained from each of five unrelated adults on three separate occasions: at baseline and 4 and 12 weeks later. The S. oralis component of the flora was isolated from each of the oral rinses by using MSA only. S. oralis isolates present in each sample were identified, and individual strains were genotyped by using REP-PCR. The genotypes of these populations were compared by cluster analysis, and the stability of the population present at baseline was determined over the 12-week period.
In the second experiment, to assess the stability of the aciduric S. oralis population in interproximal plaque, samples were taken from 10 adult subjects on two separate occasions 4 weeks apart. The predominant aciduric bacteria in each sample were isolated using the multiwell method as described above. The strains, primarily viridans streptococci, isolated in this way were identified. Those isolates identified as S. oralis were genotyped by using the REP-PCR method described above. The stability of the aciduric S. oralis populations in each subject was evaluated by cluster analysis.Transmission of S. oralis between subjects. Interproximal plaque samples were taken from five cohabiting couples at the same time, and the S. oralis populations were isolated from each sample by using both the multiwell and MSA methods. The genotypes of S. oralis in each sample were determined, and the genotypes of each couple were compared by using cluster analysis in order to ascertain the presence of strains, which were apparently indistinguishable from each other, in the interproximal samples of each couple. The presence of such strains would indicate transmission of S. oralis between couples.
When strains were isolated from couples which were indistinguishable by REP-PCR, these strains were subjected to additional strain genotyping by using SERE-PCR and ERIC-PCR methods. This was undertaken since strains which are different by REP-PCR are clearly different, but strains which exhibit the same pattern by only one typing method may be shown to be different when subjected to other typing systems. Therefore, indistinguishable strains should yield similar, but different, band patterns when examined with other typing methods.| |
RESULTS |
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Abstract
Introduction
Materials and Methods
Results
Discussion
References
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Genotypic heterogeneity of S. oralis within
individuals.
In the majority of the 15 subjects, the aciduric
S. oralis populations were distinct from the S. oralis population isolated by using MSA. Representative examples
of REP-PCR patterns of multiwell- and MSA-isolated S. oralis
strains for individual subjects are shown in Fig.
1. In only 4 of the 15 subjects were
S. oralis strains isolated by the MSA and multiwell methods
indistinguishable from each other by REP-PCR typing. The data are
summarized in Table 1, which shows the
number of strains examined per subject, the number of genotypes per
subject amongst those strains examined, and those genotypes recovered
from each subject on the MSA and from the aciduric medium. The null
hypothesis that each subject harbored only one S. oralis
population, i.e., that the same genotypes should be recovered from both
media, was tested, and it was found that the genotypes recovered from
the two media were significantly different (2 = 13.09; P = 0.00031). Therefore, it may be concluded
that the S. oralis populations isolated from the aciduric
media were distinct from those recovered from MSA.
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The proportion of aciduric S. oralis in interproximal plaque samples. The aciduric S. oralis isolates represented 1.9% (± 0.7%) of the MPN of bacteria in the samples isolated in BHI at pH 7.0. The MPN of bacteria at pH 5.2 represented 3.8% (± 1.2%) of the total MPN of bacteria at pH 7.0. Thus, on average, the S. oralis strains isolated in the media at pH 5.2 represented approximately 50% of the bacterial count. The S. oralis isolates recovered from the MSA plates formed 11.2% (± 3.6%) of the total count from the nonselective media.
Stability of S. oralis genotypes.
To determine the
stability of the S. oralis populations, strains were
recovered by using MSA from the saliva of five subjects sampled over a
12-week interval. There were considerable differences in the number of
genotypes of S. oralis present in the S. oralis population of each subject. When the genotypes of each subject were
compared, it was found that in only two subjects were any strains
exhibiting the same REP-PCR pattern isolated at baseline and 4 weeks
later. In no subject were strains which were identical to those
isolated in the 12-week sample isolated in the baseline or 4-week
samples (Table 2). A typical dendrogram
of these relationships is shown in Fig.
2.
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Transmission of S. oralis.
S. oralis strains were
isolated from five couples by using both MSA and the multiwell method.
In all, 40 to 62 isolates per couple were genotyped; a total of 258 isolates. On examination of the dendrograms of all strains from each
couple, it was apparent that in three couples S. oralis
strains which were indistinguishable by REP-PCR were isolated from each
member of the couple (Fig. 3). In one
couple, 3 of 16 strains from the acidic media from one partner were
identical to 10 of 16 strains from the other. In the second couple, 15 of 20 strains from the acidic medium were identical to 1 of 7 strains
from the acidic medium from the other partner, and in the third couple,
19 of 20 strains from the acidic medium were identical to 1 of 5 strains from the acidic medium from the other partner. When the
identical strains from each couple were further examined by SERE-PCR
and ERIC-PCR, it was apparent that the strains were indistinguishable
by both methods (data not shown).
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DISCUSSION |
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Materials and Methods
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Discussion
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This study has demonstrated that the S. oralis population in an individual is heterogeneous, that the aciduric S. oralis strains may be genotypically distinct from those isolated from the same plaque sample using MSA, and that the S. oralis populations are unstable but are apparently readily transmissible between cohabiting couples. In previous studies, heterogeneity in populations of other dental plaque bacteria has been reported (9, 13, 14, 16, 20-22, 33, 37). Studies of the clonality of the phylogenetically related species S. mitis biovar 1 have reported diversity similar to that found in the present study for S. oralis. Howhy and Kilian (16) identified 106 S. mitis biovar 1 isolates from amongst 250 streptococcal isolates from three members of the same family. The 106 isolates represented 24 different genotypes by restriction endonuclease analysis with 6 to 13 types being isolated from each individual. Similarly, Fitzsimmons et al. (13) isolated 101 S. mitis biovar 1 strains from 40 neonates, and when examined by ribotyping, these isolates represented 93 unique types, again demonstrating the high degree of diversity within this species. It is apparent from the data presented in this report that S. oralis populations behave in a similar manner. This high degree of genotypic diversity is not restricted to these two species of viridans streptococci, as we demonstrated in a previous study that unrelated members of each of the human species of viridans streptococci exhibited considerable diversity with either REP-PCR, ERIC-PCR, or SERE-PCR (2).
The instability of the S. oralis populations reported here is in contrast to the apparent population stability of S. mutans (19) and Prevotella intermedia and Prevotella nigrescens (22) populations in human dental plaque but is more like the reported instability of S. mitis biovar 1 in infants (13). The rate of genotypic change must be rapid and may be reflected in the antigenic composition of the organism, providing a mechanism with which to avoid the host's immune system and consequent elimination. It may be expected that all oral bacteria, especially those on mucosal surfaces, including those colonizing the periodontal pocket, would behave in a similar fashion; however, they do not behave in this manner, as evidenced by the reported stability of P. nigrescens and P. intermedia populations (22). Other mechanisms may underlie the rapid changes in population structure. We found that after 500 in vitro divisions there was no change in the REP-PCR pattern of recently isolated individual S. oralis strains (unpublished observations). However, more extensive growth periods, involving 10,000 replications of Escherichia coli, resulted in significant changes in genotype associated with movement of transposons within the genome (24). It would seem unlikely that this mechanism for modifying the genotypes of these streptococci is responsible for the changes observed, given the slow doubling time of bacteria in dental plaque (3) and the relatively short interval between sampling times. Both S. oralis and S. mitis are highly competent and may undergo transformation in vivo by horizontal gene transfer (25), which would be expected to produce the changes in REP-PCR patterns seen here in S. oralis. It has also been suggested that the rapid genotypic change may be related to the generation and loss of REP-PCR priming sites during DNA replication (34).
It was demonstrated in this study that S. oralis strains with the same genotype were isolated from the dental plaque of cohabiting couples. This is not unexpected, since other viridans streptococci have been shown to be transmitted between couples and between mothers and their infants (7, 13, 16, 21, 27). Transmission is presumably mediated by salivary transfer between partners. It is of note that in each of the three couples where transmission was demonstrable, the strain which appeared to have been transmitted was predominant in one of the partners. The use of the other PCR-based genotyping methods to confirm the similarity of the common genotypes provides unequivocal support for the isolation of the same strains of S. oralis from each member of these three couples, since the PCR priming sites are different for each reaction (26, 38).
We have previously reported that S. oralis is amongst the most numerous aciduric bacterial species in dental plaque (8) and that mutans streptococci are rarely isolated from among the predominant aciduric bacteria in plaque associated with caries-free tooth surfaces. In this report, we have subjected the S. oralis populations to extensive genotypic analysis, and these results considerably extend these previous observations. We have shown that aciduric S. oralis populations which are genotypically distinct from those isolated from MSA (initial pH 7.0) exist in plaque. The presence of this distinct population is unexpected, since in other studies it has been demonstrated that although NMS can survive in acidic conditions, their survival was regarded as phenotypic adaptation (32). The present data support the presence of genetically distinct aciduric S. oralis in which there may be a genetic basis to their survival and proliferation under the acidic conditions.
NMS are heterogeneous with respect to acidogenicity and, by virtue of their numerical superiority, these acidogenic NMS may play a significant role in the caries formation process (29, 35, 36). The present data may also be viewed in the same manner. The predominant aciduric bacteria isolated from caries-free tooth surfaces are not mutans streptococci but are rather S. oralis and other viridans streptococci including S. intermedius, S. parasanguinis, and Streptococcus anginosus. The role of these bacteria in the initiation of caries is not yet known, although many NMS, including S. oralis, are reported to induce caries in laboratory rats (40). The data presented here clearly indicate that S. oralis is genotypically heterogeneous with respect to aciduricity, and our previous study indicated that this species was predominant amongst the aciduric dental plaque microflora.
This is the first report of genotypic heterogeneity amongst NMS relating to aciduricity. The significance of the aciduric S. oralis and other aciduric NMS in the caries process warrants further consideration, and it may be that the central role assigned previously to S. mutans will require reevaluation.
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ACKNOWLEDGMENTS |
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We thank the subjects who gave consent to be involved in the study.
This study was supported by Guy's, King's, and St. Thomas' Dental Institute and in part by Unilever Research, United Kingdom.
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FOOTNOTES |
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* Corresponding author. Mailing address: Department of Oral Microbiology, Dental Institute GKT, Caldecot Road, Denmark Hill, London SE5 9RW, England. Phone: 44-0171-346-3272. Fax: 44-0171-346-3073. E-mail: david.beighton{at}kcl.ac.uk.
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REFERENCES |
|---|
|
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Introduction
Materials and Methods
Results
Discussion
References
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|---|
| 1. | Alaluusua, S., and R. Malmivirta. 1994. Early plaque accumulation: a sign of caries risk in young children. Community Dent. Oral Epidemiol. 22:273-276[Medline]. |
| 2. |
Alam, S.,
S. R. Brailsford,
R. A. Whiley, and D. Beighton.
1999.
PCR-based methods for genotyping viridans group streptococci.
J. Clin. Microbiol.
37:2772-2776 |
| 3. | Beighton, D., H. Hayday, and J. Walker. 1985. The relationship between the number of the bacterium Streptococcus mutans at discrete sites on the dentition of macaque monkeys (Macaca fascicularis) and the subsequent development of dental caries. Arch. Oral Biol. 30:85-88[CrossRef][Medline]. |
| 4. |
Beighton, D.,
J. M. Hardie, and R. A. Whiley.
1991.
A scheme for the identification of viridans streptococci.
J. Med. Microbiol.
35:367-372 |
| 5. | Beighton, D., K. Smith, and H. Hayday. 1986. The growth of bacteria and the production of exoglycosidic enzymes in the dental plaque of macaque monkeys. Arch. Oral. Biol. 31:829-835[CrossRef][Medline]. |
| 6. |
Beighton, D., and R. A. Whiley.
1990.
Sialidase activity of the "Streptococcus milleri group" and other viridans group streptococci.
J. Clin. Microbiol.
28:1431-1433 |
| 7. |
Berkowitz, R. J.
1976.
Streptococcus mutans establishment and transmission in infants.
ASDC (Am. Soc. Dent. Child.) J. Dent. Child.
43:192-195.
|
| 8. | Brailsford, S. R., R. W. Byrne, S. Adams, L. Zoitopoulos, C. Allison, and D. Beighton. 1999. Investigation of the aciduric microflora of plaque. Caries Res. 33:290. |
| 9. |
Brailsford, S. R.,
H. Leftwich,
R. Tregaskis, and D. Beighton.
1999.
The predominant Actinomyces spp. isolated from infected dentine of active root caries lesions.
J. Dent. Res.
78:1525-1534 |
| 10. |
Carvalho, J. C.,
K. R. Ekstrand, and A. Thylstrup.
1989.
Dental plaque and caries on occlusal surfaces of first permanent molars in relation to stage of eruption.
J. Dent. Res.
68:773-779 |
| 11. | Chestnutt, I. G., T. W. MacFarlane, and K. W. Stephen. 1994. An in vitro investigation of the cariogenic potential of oral streptococci. Arch. Oral Biol. 39:589-593[CrossRef][Medline]. |
| 12. | de Soet, J. J., C. van Loveren, A. J. Lammens, M. J. Pavicic, C. H. Homburg, J. M. ten Cate, and J. de Graaff. 1991. Differences in cariogenicity between fresh isolates of Streptococcus sobrinus and Streptococcus mutans. Caries Res. 25:116-122[Medline]. |
| 13. | Fitzsimmons, S., M. Evans, C. Pearce, M. J. Sheridan, R. Wientzen, G. Bowden, and M. F. Cole. 1996. Clonal diversity of Streptococcus mitis biovar 1 isolates from the oral cavity of human neonates. Clin. Diagn. Lab. Immunol. 3:517-522[Abstract]. |
| 14. | George, K. S., M. A. Reynolds, and W. A. Falkler, Jr. 1997. Arbitrarily primed polymerase chain reaction fingerprinting and clonal analysis of oral Fusobacterium nucleatum isolates. Oral Microbiol. Immunol. 12:219-226[Medline]. |
| 15. | Hamilton, I. R., and G. Svensater. 1998. Acid-regulated proteins induced by Streptococcus mutans and other oral bacteria during acid shock. Oral Microbiol. Immunol. 13:292-300[Medline]. |
| 16. | Hohwy, J., and M. Kilian. 1995. Clonal diversity of the Streptococcus mitis biovar 1 population in the human oral cavity and pharynx. Oral Microbiol. Immunol. 10:19-25[Medline]. |
| 17. |
Kawamura, Y.,
X. G. Hou,
F. Sultana,
S. Liu,
H. Yamamoto, and T. Ezaki.
1995.
Transfer of Streptococcus adjacens and Streptococcus defectivus to Abiotrophia gen. nov. as Abiotrophia adiacens comb. nov. and Abiotrophia defectiva comb. nov., respectively.
Int. J. Syst. Bacteriol.
45:798-803 |
| 18. | Kohler, B., D. Birkhed, and S. Olsson. 1995. Acid production by human strains of Streptococcus mutans and Streptococcus sobrinus. Caries Res. 29:402-406[Medline]. |
| 19. |
Kozai, K.,
D. S. Wang,
H. J. Sandham, and H. I. Phillips.
1991.
Changes in strains of mutans streptococci induced by treatment with chlorhexidine varnish.
J. Dent. Res.
70:1252-1257 |
| 20. |
Kulkarni, G. V.,
K. H. Chan, and H. J. Sandham.
1989.
An investigation into the use of restriction endonuclease analysis for the study of transmission of mutans streptococci.
J. Dent. Res.
68:1155-1161 |
| 21. |
Li, Y., and P. W. Caufield.
1995.
The fidelity of initial acquisition of mutans streptococci by infants from their mothers.
J. Dent. Res.
74:681-685 |
| 22. | Matto, J., M. Saarela, B. von Troil-Linden, E. Kononen, H. Jousimies-Somer, H. Torkko, S. Alaluusua, and S. Asikainen. 1996. Distribution and genetic analysis of oral Prevotella intermedia and Prevotella nigrescens. Oral Microbiol. Immunol. 11:96-102[Medline]. |
| 23. |
Milnes, A. R.,
G. H. Bowden, and I. R. Hamilton.
1985.
Effect of NaF and pH on the growth and glycolytic rate of recently isolated strains of oral Lactobacillus species.
J. Dent. Res.
64:401-404 |
| 24. |
Papadopoulos, D.,
D. Schneider,
J. Meier-Eiss,
W. Arber,
R. E. Lenski, and M. Blot.
1999.
Genomic evolution during a 10,000-generation experiment with bacteria.
Proc. Natl. Acad. Sci. USA
96:3807-3812 |
| 25. |
Poulsen, K.,
J. Reinholdt,
C. Jespersgaard,
K. Boye,
T. A. Brown,
M. Hauge, and M. Kilian.
1998.
A comprehensive genetic study of streptococcal immunoglobulin A1 proteases: evidence for recombination within and between species.
Infect. Immun.
66:181-190 |
| 26. |
Rajashekara, G.,
T. Koeuth,
S. Nevile,
A. Back,
K. V. Nagaraja,
J. R. Lupski, and V. Kapur.
1998.
SERE, a widely dispersed bacterial repetitive DNA element.
J. Med. Microbiol.
47:489-498 |
| 27. | Rogers, A. H. 1977. Evidence for the transmissibility of human dental caries. Aust. Dent. J. 22:53-66[Medline]. |
| 28. | Ruoff, K. L., R. A. Whiley, and D. Beighton. 1999. Streptococcus, p. 297-305. In P. M. Murray, E. J. Baron, M. A. Pfaller, F. C. Tenover, and R. H. Yolken (ed.), Manual of clinical microbiology. American Society for Microbiology, Washington, D.C. |
| 29. |
Sansone, C.,
J. Van Houte,
K. Joshipura,
R. Kent, and H. C. Margolis.
1993.
The association of mutans streptococci and non mutans streptococci capable of acidogenesis at a low pH with dental caries on enamel and root surfaces.
J. Dent. Res.
72:508-516 |
| 30. | Suchett-Kaye, G., D. Decoret, and O. Barsotti. 1999. Intra-familial distribution of Fusobacterium nucleatum strains in healthy families with optimal plaque control. J. Clin. Periodontol. 26:401-404[CrossRef][Medline]. |
| 31. | Svensater, G., U. B. Larsson, E. C. Greif, D. G. Cvitkovitch, and I. R. Hamilton. 1997. Acid tolerance response and survival by oral bacteria. Oral Microbiol. Immunol. 12:266-273[Medline]. |
| 32. | Takahashi, N., and T. Yamada. 1999. Acid-induced acid tolerance and acidogenicity of non-mutans streptococci. Oral Microbiol. Immunol. 14:43-48[CrossRef][Medline]. |
| 33. | Teanpaisan, R., C. W. Douglas, A. R. Eley, and T. F. Walsh. 1996. Clonality of Porphyromonas gingivalis, Prevotella intermedia and Prevotella nigrescens isolated from periodontally diseased and healthy sites. J. Periodontal Res. 31:423-432[CrossRef][Medline]. |
| 34. | van Belkum, A. 1999. The role of short sequence repeats in epidemiologic typing. Curr. Opin. Microbiol. 2:306-311[CrossRef][Medline]. |
| 35. |
van Houte, J.,
J. Lopman, and R. Kent.
1996.
The final pH of bacteria comprising the predominant flora on sound and carious human root and enamel surfaces.
J. Dent. Res.
75:1008-1014 |
| 36. |
van Houte, J.,
C. Sansone,
K. Joshipura, and R. Kent.
1991.
Mutans streptococci and non mutans streptococci acidogenic at low pH, and in vitro acidogenic potential of dental plaque in two different areas of the human dentition.
J. Dent. Res.
70:1503-1507 |
| 37. | van Steenbergen, T. J., C. J. Bosch-Tijhof, M. D. Petit, and U. Van der Velden. 1997. Intra-familial transmission and distribution of Prevotella intermedia and Prevotella nigrescens. J. Periodontal Res. 32:345-350[CrossRef][Medline]. |
| 38. |
Versalovic, J.,
T. Koeuth, and J. R. Lupski.
1991.
Distribution of repetitive DNA sequences in eubacteria and application to fingerprinting of bacterial genomes.
Nucleic Acids Res.
19:6823-6831 |
| 39. | Whiley, R. A., and D. Beighton. 1998. Current classification of the oral streptococci. Oral Microbiol. Immunol. 13:195-216[Medline]. |
| 40. | Willcox, M. D., D. B. Drucker, and R. M. Green. 1987. Relative cariogenicity and in-vivo plaque-forming ability of the bacterium Streptococcus oralis in gnotobiotic WAG/RIJ rats. Arch. Oral Biol. 32:455-457[CrossRef][Medline]. |
Applied and Environmental Microbiology, August 2000, p. 3330-3336, Vol. 66, No. 8
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