Association Between Early Childhood Caries and Colonization with Streptococcus mutans Genotypes From Mothers

PURPOSE

The purpose of this study was to evaluate Streptococcus mutans genotypes (GT) between mother and child (M-C) in a high caries risk cohort to explore the association with early childhood caries (ECC).

METHODS

Sixty-nine infants (each approximately one year old) had periodic oral examinations (dmfs) and microbial samples collected from dental plaque, saliva, and other oral surfaces. Their mothers had an examination and plaque collected. S mutans isolates were genotyped using repetitive extragenic palindromic-PCR (rep-PCR). Statistical analyses were conducted for associations of S mutans in M-C dyads with caries outcomes.

RESULTS

Twenty-seven S mutans genotypes (GT) from 3,414 isolates were identified. M-C were categorized as GT match (n equals 40) or no-match (n equals 29). When modeling the severity of ECC at 36 months (approximately four years old), the estimated dmfs in the match group was 2.61 times that of the no-match group (P=.014).

CONCLUSIONS

Colonization of children with Streptococcus mutans genotypes that matched with mothers was shown to be highly associated with early childhood caries. Although the data suggest vertical transmission of S mutans in 40 of 69 children that shared GT with their mother, it is possible that other individuals transmitted the S mutans. Nonetheless, these findings support the importance of the mother's oral microbial status as a contributing influence to their children's oral health.

Isolation of Raoultella planticola from refillable antimicrobial liquid soap dispensers in a dental setting

BACKGROUND

Liquid antimicrobial soaps are commonly used in the dental health care setting for hand washing to minimize the potential spread of infectious agents to health care workers and patients. The purpose of the current study was to evaluate possible bacterial contamination of antimicrobial liquid soap dispensers located in 2 institutional comprehensive dental care clinics.

METHODS

Fourteen soap dispensers and 16 original stock containers were sampled. A 1-milliliter aliquot was diluted in 10 mL of phosphate buffer (Tween-80; Acros). Serial dilutions were plated in duplicate on neutralizing agar and incubated for 7 days. Molecular identification was performed using 500 base pair comparisons of 16S ribosomal ribonucleic acid sequencing. Taq polymerase chain reaction was performed with sequence-specific primers for Raoultella species.

RESULTS

Bacterial growth was observed at 18 hours for 57% (8 of 14) of soap dispenser samples. Bacterial densities ranged from 4 × 10(2) to 6 × 10(9) colony-forming units per milliliter. Original commercial containers exhibited no growth. Isolates were identified as Raoultella (Klebsiella) planticola.

CONCLUSIONS

This is the first study to the authors' knowledge indicating recovery of R. planticola from antimicrobial liquid soap dispensers. R. planticola is a recognized environmental opportunistic pathogen that potentially poses a health concern.

PRACTICAL IMPLICATIONS

These findings indicate compliance problems with infection prevention recommendations and support the US Centers for Disease Control and Prevention's recommendation that dispensers should not be topped off. High bacterial loads of R. planticola are inconsistent with infection control practices and are a concern because transmission and possible infection to the health care worker or the patient may occur.

The pH of beverages in the United States

BACKGROUND

Dental erosion is the chemical dissolution of tooth structure in the absence of bacteria when the environment is acidic (pH < 4.0). Research indicates that low pH is the primary determinant of a beverage's erosive potential. In addition, citrate chelation of calcium ions may contribute to erosion at higher pH. The authors of this study determined the erosive potential measured by the pH of commercially available beverages in the United States.

METHODS

The authors purchased 379 beverages from stores in Birmingham, Alabama, and categorized them (for example, juices, sodas, flavored waters, teas, and energy drinks) and assessed their pH. They used a pH meter to measure the pH of each beverage in triplicate immediately after it was opened at a temperature of 25°C. The authors recorded the pH data as mean (standard deviation).

RESULTS

Most (93%, 354 of 379) beverages had a pH of less than 4.0, and 7% (25 of 379) had a pH of 4.0 or more. Relative beverage erosivity zones based on studies of apatite solubility in acid indicated that 39% (149 of 379) of the beverages tested in this study were considered extremely erosive (pH < 3.0), 54% (205 of 379) were considered erosive (pH 3.0 to 3.99), and 7% (25 of 379) were considered minimally erosive (pH ≥ 4.0).

CONCLUSIONS

This comprehensive pH assessment of commercially available beverages in the United States found that most are potentially erosive to the dentition.

PRACTICAL IMPLICATIONS

This study's findings provide dental clinicians and auxiliaries with information regarding the erosive potential of commercially available beverages. Specific dietary recommendations for the prevention of dental erosion may now be developed based on the patient's history of beverage consumption.

Mutans streptococci enumeration and genotype selection using different bacitracin-containing media

The primary etiological agents associated with dental caries include the mutans streptococci (MS) comprised of Streptococcus mutans and Streptococcus sobrinus. The effective cultivation and isolation of MS are necessary for the study of MS, including their proper clinical assessment in the epidemiological study of dental caries. Several selective media have been developed for the isolation, enumeration, and characterization of MS. However, inhibition of MS may occur, reducing counts and perhaps limiting selection of some strains. The purpose of this study was to compare five culture media containing bacitracin recommended for the isolation of MS. Five commonly used bacitracin-containing media (MSB, MSKB, GTSB, TYS20B, and TYCSB) used for MS isolation were quantitatively evaluated. Standard plate counts were performed in duplicate for 2 prototype MS strains (S. mutans UA159 and S. sobrinus 6715) and for MS isolates from clinical saliva samples obtained from 16 children (approximate age 5years) to determine total plate counts, and total S. mutans counts. Selected isolates (n=249) from all five media for 5 saliva samples were further confirmed as S. mutans with real-time PCR then subsequently evaluated qualitatively with rep-PCR for genotype determination. All media resulted in variable enumeration with no significant difference in MS counts. MS prototype strains grew well on all five media; clinical isolates demonstrated more variability in counts but no overall significant differences were found. MSB demonstrated comparable ability to grow S. mutans but allowed for more non-S. mutans growth. All 5 media identified a consistent predominant genotype by rep-PCR. Recovery of minor genotypes was not inhibited by media type.

Characteristics of Streptococcus mutans genotypes and dental caries in children

This longitudinal cohort study evaluated the diversity, commonality, and stability of Streptococcus mutans genotypes associated with dental caries history. Sixty-seven 5- and 6-yr-old children, considered as being at high caries risk, had plaque collected from baseline through 36 months for S. mutans isolation and genotyping using repetitive extragenic palindromic-PCR (4,392 total isolates). Decayed, missing, or filled surfaces (dmfs (primary teeth)/DMFS (secondary teeth)) for each child were recorded at baseline. At baseline, 18 distinct genotypes were found among 911 S. mutans isolates from 67 children (diversity), and 13 genotypes were shared by at least two children (commonality). The number of genotypes per individual was positively associated with the proportion of decayed surfaces (p-ds) at baseline. Twenty-four of the 39 children who were available at follow-up visits maintained a predominant genotype for the follow-up periods (stability) and this was negatively associated with the p-ds. The observed diversity, commonality, and stability of S. mutans genotypes represent a pattern of dental caries epidemiology in this high-caries-risk community, which suggests that fewer decayed surfaces are significantly associated with lower diversity and higher stability of S. mutans genotypes.

A randomized study of sodium hypochlorite versus formocresol pulpotomy in primary molar teeth

BACKGROUND

Alternatives to vital pulpotomy treatment in primary teeth are being sought because of the high formaldehyde content of traditional formocresol (FC) pulpotomy medicaments.

AIM

The aim was to compare the clinical and radiographic success of vital pulpotomy treatment in primary molars using 3% sodium hypochlorite (NaOCl) versus a 1:5 dilution of Buckley's FC.

DESIGN

Pulpotomies were performed in primary molars of healthy children between 3 and 10 years old. Sixty-five primary teeth were randomized into two groups that were evaluated for treatment outcomes. Following treatment, the pulp chamber was filled with zinc oxide eugenol (ZnOE) and restored with a stainless steel crown cemented with glass ionomer cement. Clinical and radiographic outcomes were recorded at 6 and 12 months.

RESULTS

The control (FC) and experimental (NaOCl) groups demonstrated 100% clinical success at 6 and 12 months. The NaOCl group had 86% (19/22) radiographic success at 6 months and 80% (12/15) at 12 months. The FC group had 84% (21/25) radiographic success at 6 months and 90% (9/10) at 12 months. No significant differences were found in the radiographic outcomes between the two groups at 6 and 12 months (Fisher's exact test; P=0.574 and P=0.468, respectively).

CONCLUSION

NaOCl demonstrated clinical and radiographic success comparable to FC.

Comparative genotyping of Streptococcus mutans by repetitive extragenic palindromic polymerase chain reaction and multilocus sequence typing

The genetic diversity of Streptococcus mutans has been extensively studied using a variety of genotyping methods. Repetitive extragenic palindromic-polymerase chain reaction (rep-PCR) is a genotyping approach used for screening large numbers of bacterial isolates. This two-part study used multilocus sequence typing (MLST) analysis to evaluate genotypes previously identified as unique using rep-PCR. In part one, an isolate was selected from each of the 22 S. mutans rep-PCR genotype groups representing 8000 clinical isolates. For part two, four additional isolates were selected from the six most commonly occurring genotype groups (GG) for further analysis. Real-time PCR was performed using eight housekeeping S. mutans gene loci and the amplicons were sequenced. Sequence data analysis was performed using CLC DNA Workbench and alleles were compared with the PubMLST database for Oral Streptococcus using the Nakano scheme. Concatenated sequences were evaluated with MEGA using a minimum evolution method with bootstrap. All 22 rep-PCR genotypes were unique by MLST analysis. Within rep-PCR GGs, MLST matched rep-PCR in three groups demonstrating clonality; three groups exhibited more diversity with MLST. The discovery of three clonal groups is unique to this study and suggests that S. mutans genotypes are shared between unrelated subjects. Furthermore, MLST defined 19 new alleles and 26 new sequence types that have been confirmed and registered with PubMLST. Methods for processing were streamlined and a process for using MLST with rep-PCR is suggested. In conclusion, MLST verified that rep-PCR is a reliable and cost-effective method for screening large numbers of S. mutans strains for epidemiological study.

Real-time quantitative polymerase chain reaction for enumeration of Streptococcus mutans from oral samples

This study compared SYBR Green real-time quantitative PCR (qPCR) with standard plate counting for the enumeration of Streptococcus mutans in oral samples. Oral samples (n = 710) were collected from high-caries-risk children for quantification of S. mutans by qPCR using primer pairs. The S. mutans copy number was calculated with reference to a qPCR quantification cycle (Cq) standard curve and compared with the absorbance value at 600 nm of a standard suspension of S. mutans UA159. The S. mutans copy number results were evaluated in relation to standard plate count (SPC) results obtained from each sample following culture on Petri plates containing S. mutans selective media and reported as colony-forming units (CFUs). The mean S. mutans copy number calculated from qPCR was higher than the SPC CFUs (1.3 × 10(6) and 1.5 × 10(5) CFUs, respectively). The qPCR values were usually higher in individual samples and qPCR detected the presence of S. mutans 84% (231/276) of the time that the SPC did not, compared with 33% (4/12) of the time when qPCR failed to detect S. mutans and the SPC did. The qPCR technique was found to be more sensitive for detection of S. mutans from oral samples, a method that is not dependent on the viability of the sample taken and therefore is proposed as a more reliable and efficient means of quantification of S. mutans.

Evaluation of in-office dental unit waterline testing

In-office dental unit waterline (DUWL) testing systems are commercially available for monitoring DUWL bacteria. The current study compared Aquasafe, Petrifilm, and Heterotrophic Plate Count Sampler (HPCS) with R2A plating methodology, considered the gold standard for enumerating heterotrophic bacteria in potable water. Samples were collected from 20 dental units. Heterotrophic bacterial counts of ≤500 CFUs/mL were used as the cut-off for assessing in-office testing compared to R2A laboratory plating. Validity was assessed using sensitivity and specificity, along with positive and negative predictive values. Results were also compared using concordance and kappa statistics. All in-office tests demonstrated 100% specificity and positive predictive values, while sensitivity and negative predictive values were low (Petrifilm, 57%/50%; HPCS, 50%/46%; Aquasafe, 21%/35%). Concordance and kappa values for agreement with R2A plating were as follows: Petrifilm 70% (κ = 0.44), HPCS 65% (κ = 0.38), and Aquasafe 45% (κ = 0.14). In-office DUWL testing with Aquasafe, Petrifilm, and HPCS agreed poorly with R2A plating methodology and is not valid or reliable as a means of accurately monitoring bacterial density in DUWL. These in-office test systems should not be used for assessing compliance with the ADA and CDC standard for acceptable heterotrophic bacterial counts in DUWLs (≤500 CFUs/mL).

Genetic diversity of plaque mutans streptococci with rep-PCR

Mutans streptococci (MS) are key organisms associated with the etiology of dental caries. Using probabilities that were tested by oversampling, we designed this study to determine the minimal number of MS isolates from an individual required to evaluate diversity of genotypes. MS isolates were genotyped by repetitive extragenic palindromic-polymerase chain-reaction (rep-PCR). Analysis of 20 isolates from individuals resulted in a mean of 1.6 and 2.4 genotypes in children (N = 12) and adults (N = 10), respectively. In a follow-up study, reducing the number of isolates to 7-10 resulted in a theoretical probability of up to 78% for detecting up to 4 genotypes. A mean of 1.5 genotypes was found in 35 children and 10 adults. These findings provide evidence for the design of studies of MS genotyping that can serve as a model for the analysis of genotypes within individuals.

The Caries Phenomenon: A Timeline from Witchcraft and Superstition to Opinions of the 1500s to Today's Science

This historical treatise follows the documented timeline of tooth decay into today's understanding, treatment, and teaching of caries biology. Caries has been attributed to many different causes for several millennia, however, only since the late 1900s has research revealed its complex multifactorial nature. European writers of the 1600s to 1700s held views that general health, mechanical injuries, trauma, and sudden temperature changes all caused caries-holding a common belief that decay was due to chemical agents, faulty saliva, and food particles. Until the early 1800s most writers believed that caries was due to inflammation from surrounding diseased alveolar bone. Today's science has demonstrated that caries is caused by indigenous oral microorganisms becoming a dynamic biofilm, that in the presence of fermentable sugars produce organic acids capable of dissolving inorganic enamel and dentin followed by the proteolytic destruction of collagen leaving soft infected dentin. As bacteria enter the pulp, infection follows.

Maternal transmission of mutans Streptococci in severe-early childhood caries

PURPOSE

This study utilized multiple genetic analyses to detect evidence of maternal MS acquisition in children with S-ECC.

METHODS

Twenty-seven mother/child pairs were selected from children with 5-ECC preceding dental rehabilitation under general anesthesia. Plaque samples were collected from the mother, child, and the child's carious lesion. Arbitrarily primed-polymerase chain reaction (AP-PCR) genotyped 6-8 MS isolates from each plaque sample, and unique genotypes were identified. Representative MS isolates with unique genotypes were characterized by pulsed-field gel electrophoresis (PFGE). Cluster analysis using the Dice band-based similarity coefficient was used to generate dendrograms from gel bonding patterns. A Dice coefficient >70% indicated similarity or match among PFGE genotypes.

RESULTS

In 26% (7/27) of mother/child pairs, all of the child's isolates matched the mother. In 15% (4/27), some of the child's genotypes matched the mother, and in 59% (16/27), no isolates matched the mother. Maternal transmission was a mode of MS acquisition in 41% (11/27) of mother/child pairs, while acquisition from non-maternal sources occurred in 74% (20/27).

CONCLUSIONS

MS genotypes that did not match maternal strains were identified in the majority of children (74%) within this S-ECC population. Evidence of maternal transmission was detected in 41% of mother/child pairs.

Effect of glucose on Treponema denticola cell behavior

INTRODUCTION

Treponema denticola inhabits the oral subgingival environment and is part of a proteolytic benzoyl-dl-arginine-naphthylamide-positive 'red complex' associated with active periodontal disease. Spirochetes have a unique form of chemotactic motility that may contribute to their virulence. Chemotaxis is essential for efficient nutrient-directed translocation.

METHODS

We examined the effect of glucose on T. denticola cell velocity, expression of periplasmic flagella proteins, and chemotaxis, e.g. translocation into capillary tubes.

RESULTS

The presence of glucose did not significantly effect T. denticola cell velocity in high viscosity conditions nor did it alter periplasmic flagella protein expression. The addition of glucose to capillary tubes resulted in greater numbers of T. denticola cells in tubes containing glucose. A non-motile mutant did not migrate into capillary tubes containing glucose.

CONCLUSION

These results are consistent with a chemotactic response to glucose that is motility dependent.

SalivaryActinomyces naeslundiiGenospecies 2 andLactobacillus caseiLevels Predict Pregnancy Outcomes

BACKGROUND

Gravida's poor periodontal health is emerging as a modifiable independent risk factor for preterm delivery and low birth weight.

METHODS

To test the hypothesis that oral bacteria other than periodontal pathogens are also associated with pregnancy outcomes, specific oral bacterial levels measured during pregnancy were evaluated in relation to gestational age and birth weight while controlling for demographic, medical, and dental variables. The study population consisted of 297 predominantly African- American women who were pregnant for the first time. The salivary bacterial levels evaluated were Streptococcus mutans, Streptococcus sobrinus, Streptococcus sanguinus, Lactobacillus acidophilus, Lactobacillus casei, Actinomyces naeslundii genospecies (gsp) 1 and 2, total streptococci, and total cultivable organisms.

RESULTS

For 1 unit increase in log(10) A. naeslundii gsp 2 levels, there was a 60 gm decrease in birth weight (beta = -59.7 g; SE = 29.1; P = 0.04), and a 0.17 week decrease in gestational age (beta = -0.17 wk; SE = 0.09; P = 0.05). In contrast, per 1 unit increase in log(10) L. casei levels, there was a 42 gm increase in birth weight (beta = 42.2 g; SE = 19.3; P = 0.03), and a 0.13 week increase in gestational age (beta = 0.13 week; SE = 0.06; P = 0.04).

CONCLUSIONS

We conclude that other oral bacterial species can also be related to pregnancy outcomes in addition to previously reported periodontal pathogens. These organism levels may not only predict poor pregnancy outcomes, but also be used as modifiable risk factors in reducing prematurity and low birth weight.

Genetic diversity of Actinomyces naeslundii genospecies 2 in mother–child pairs

Actinomyces naeslundii genospecies 2 (gsp-2) are members of the autochthonous oral flora. Chromosomal DNA fingerprinting (CDF) with SmaI revealed extensive genetic diversity among A. naeslundii gsp-2 strains within individual mothers and children. There was a low prevalence of genotype match among A. naeslundii gsp-2 strains between all mother and child pairs.

Genetic characterization of the oral Actinomyces

Actinomyces are difficult to identify using serological and biochemical methods but genotyping is an efficient and reliable means of bacterial characterization and can be used to determine clonal identity. The purpose here was to genotype 13 American type culture collection (ATCC) reference strains representing six different oral Actinomyces spp. by using chromosomal DNA fingerprinting (CDF), arbitrarily primed-polymerase chain reaction (AP-PCR) and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). In CDF analysis, BamHI, BstEII and SmaI yielded digestion patterns revealing characteristic differences among the known Actinomyces spp., with SmaI demonstrating optimal resolution. Amplicons generated by AP-PCR with primer OPB-07 displayed banding patterns that permitted discrimination of all Actinomyces strains tested. PCR-RFLP with MnlI digests generated fragment patterns that also characterized the reference strains. Collectively, genotypic profiles generated by CDF, AP-PCR and PCR-RFLP permitted differentiation of all 13 ATCC Actinomyces strains. SmaI CDF analysis of 18 clinical isolates of catalase-positive A. naeslundii genospecies 2 revealed extensive genetic diversity among these strains. These molecular approaches may be useful in determining genetic diversity within oral Actinomyces populations and fidelity of Actinomyces transmission between mother and child.

Effect of temperature and viscosity on the motility of the spirochete Treponema denticola

Treponema denticola is an oral spirochete associated with periodontal diseases. Because bacterial motility is likely to be a potential virulence factor, we investigated the effect of viscosity and temperature on cell speed. In agreement with the work of others, translational motility was a function of the macroscopic viscosity of the medium. In addition, we found that although the speed of spirochetes was slow at 25 degrees C (4 microns s-1), it increased quite markedly at 35 degrees C (19 microns s-1). The results indicate that both viscosity and temperature are critical factors in T. denticola translational motility.

Relationship of Treponema denticola periplasmic flagella to irregular cell morphology

Treponema denticola is an anaerobic, motile, oral spirochete associated with periodontal disease. We found that the periplasmic flagella (PFs), which are located between the outer membrane sheath and cell cylinder, influence its morphology in a unique manner. In addition, the protein composition of the PFs was found to be quite complex and similar to those of other spirochetes. Dark-field microscopy revealed that most wild-type cells had an irregular twisted morphology, with both planar and helical regions, and a minority of cells had a regular right-handed helical shape. High-voltage electron microscopy indicated that the PFs, especially in those regions of the cell which were planar, wrapped around the cell body axis in a right-handed sense. In those regions of the cell which were helical or irregular, the PFs tended to lie along the cell axis. The PFs caused the cell to form the irregular shape, as two nonmotile, PF-deficient mutants (JR1 and HL51) were no longer irregular but were right-handed helices. JR1 was isolated as a spontaneously occurring nonmotile mutant, and HL51 was isolated as a site-directed mutant in the flagellar hook gene flgE. Consistent with these results is the finding that wild-type cells with their outer membrane sheath removed were also right-handed helices similar in shape to JR1 and HL51. Purified PFs were analyzed by two-dimensional gel electrophoresis, and several protein species were identified. Western blot analysis using antisera to Treponema pallidum PF proteins along with N-terminal amino acid sequence analysis indicated T. denticola PFs are composed of one class A sheath protein of 38 kDa (FlaA) and three class B proteins of 35 kDa (FlaB1 and FlaB2) and one of 34 kDa (FlaB3). The N-terminal amino acid sequences of the FlaA and FlaB proteins of T. denticola were most similar to those of T. pallidum and Treponema phagedenis. Because these proteins were present in markedly reduced amounts or were absent in HL51, PF synthesis is likely to be regulated in a hierarchy similar to that found for flagellar. synthesis in other bacteria.

Morphology and dynamics of protruding spirochete periplasmic flagella

We recently characterized the three-dimensional shape of Treponema phagedenis periplasmic flagella (PFs). In the course of these studies, we observed protrusions on swimming cells that resembled PFs. Here we present a detailed characterization of the shape, structure, and motion of these protrusions. Although protrusion formation occurred primarily in wild-type cells during the stationary phase, a large fraction of exponential-phase cells of cell cylinder helicity mutants (greater than 90% of mutant T-52) had protrusions. These results suggest that cells bearing protrusions can still participate in cell division. T. phagedenis protrusions had the identical helix handedness, pitch, and diameter to those of purified PFs. Protrusions were not present on mutants unable to synthesize PFs, but were present in all motile revertants which regained PFs. These results, taken together with electron microscope observations, suggest that protrusions consist of PFs surrounded by an outer membrane sheath. To analyze protrusion movements, we held cells against a coverglass surface with optical tweezers and observed the motion of protrusions by video-enhanced differential interference contrast light microscopy. Protrusions were found to gyrate in both clockwise and counterclockwise directions, and direct evidence was obtained that protrusions rotate. Protrusions were also observed on Treponema denticola and Borrelia burgdorferi. These were also left-handed and had the same helix handedness, pitch, and diameter as purified PFs from their respective species. The PFs from T. denticola had a helix diameter of 0.26 microns and a helix pitch of 0.78 micron; PFs from B. burgdorferi had a helix diameter of 0.28 micron and a helix pitch of 1.48 microns. Protrusions from these spirochete species had similar structures and motion to those of T. phagedenis. Our results present direct evidence that PFs rotate and support previously proposed models of spirochete motility.

Extracellular iodophilic polysaccharide synthesized by Neisseria in human dental plaque

Dental plaque collected from the label aspect of the anterior dentition of children harbored Neisseria that synthesized an extracellular iodophilic polysaccharide (EIP) from sucrose. Gas chromatograms of fully-acetylated EIP derivatives indicated that glucose (97%) and galactose (3%) were the only monosaccharide constituents present. The characterization of the partially-methylated alditol acetate (PMAA) derivatives of EIP indicated that it was primarily a linear 1,4 glucan (75.5%), with some 1,6 glucan (8.4%). The relative linearity of EIP (96.6%) as compared to that of amylose and glycogen was confirmed by spectrophotometric absorption studies.

Streptococcus mutans, an assessment of its physiological potential in relation to dental caries

Streptococcus mutans converts low levels of sucrose to lactic acid, but at high levels favours synthesis of glucans for plaque accumulation. Thus, the continued exposure to sucrose fluxes would select microorganisms in the oral cavity (S. mutans being a prototype) with highly specialized adaptation and potential dental caries activity. The bacteria that have evolved physiological systems to function efficiently under these conditions are the lactic acid bacteria. These organisms survive in environments where carbohydrate availability is constantly changing. High tolerances to acidic environments may be an important determinant in establishing the ecology of the carious lesion. Also, the intercellular polysaccharide storgae (glycogenamylopectin) and extracellular polymer reserves (levan and soluble glucan) are important during carbohydrate depletion. Further, the formation of insoluble glucans is a prerequisite for the caries process on smooth surfaces of teeth through plaque development. These conditions could result in an increase in S. mutans and cariogenic microorganisms. As a result, this process may be best understood as a manifestation of an amphibiotic shift.