Comparative recovery of Streptococcus mutans on ten isolation media

The Associations between Snack Intake and Cariogenic Oral Microorganism Colonization in Young Children of a Low Socioeconomic Status

Cariogenic microorganisms are crucial pathogens contributing to the development of early childhood caries. Snacks provide fermentable carbohydrates, altering oral pH levels and potentially affecting microorganism colonization. However, the relationship between snack intake and cariogenic microorganisms like Candida and Streptococcus mutans in young children is still unclear. This study aimed to assess this association in a prospective underserved birth cohort. Data from children aged 12 to 24 months, including oral microbial assays and snack intake information, were analyzed. Sweet and non-sweet indices based on the cariogenic potential of 15 snacks/drinks were created. Mixed-effects models were used to assess the associations between sweet and non-sweet indices and S. mutans and Candida carriage. Random forest identified predictive factors of microorganism carriage. Higher non-sweet index scores were linked to increased S. mutans carriage in plaques (OR = 1.67, p = 0.01), potentially strengthening with age. Higher sweet index scores at 12 months were associated with increased Candida carriage, reversing at 24 months. Both indices were top predictors of S. mutans and Candida carriage. These findings underscore the associations between snack intake and cariogenic microorganism carriage and highlight the importance of dietary factors in oral health management for underserved young children with limited access to dental care and healthy foods.

Effects of Nystatin oral rinse on oral Candida species and Streptococcus mutans among healthy adults

OBJECTIVES

To examine the effect of Nystatin oral rinse on oral Candida species and Streptococcus mutans carriage.

MATERIALS AND METHODS

Twenty healthy adults with oral candidiasis participated in the single-arm clinical trial and received Nystatin oral rinse for 7 days, 4 applications/day, and 600,000 International Units/application. Demographic-socioeconomic-oral-medical conditions were obtained. Salivary and plaque Candida species and Streptococcus mutans were assessed at baseline and 1-week and 3-month follow-ups. Twenty-four salivary cytokines were assessed. Candida albicans isolates underwent Nystatin susceptibility test.

RESULTS

Half of participants (10/20) were free of salivary C. albicans after using Nystatin rinse. Salivary S. mutans was significantly reduced at 3-month follow-up (p < 0.05). Periodontal status reflected by bleeding-on-probing was significantly improved at 1-week and 3-month follow-ups (p < 0.05). Plaque accumulation was significantly reduced at 1-week follow-up (p < 0.05). Interestingly, the responses to Nystatin oral rinse were not associated with race, gender, age, oral hygiene practice, adherence to Nystatin rinse, or sweet consumption (p > 0.05). No C. albicans isolates were resistant to Nystatin. Furthermore, salivary cytokine eotaxin and fractalkine were significantly reduced at 3-month follow-up among participants who responded to Nystatin rinse (p < 0.05).

CONCLUSIONS

The study results indicate that oral antifungal treatment had an effect on S. mutans salivary carriage. Future clinical trials are warranted to comprehensively assess the impact of antifungal treatment on the oral flora other than S. mutans and Candida.

CLINICAL RELEVANCE

Due to the potential cariogenic role of oral Candida species, antifungal approaches shed new light on the prevention and management of dental caries from a fungal perspective.

Changes in Candida albicans, Streptococcus mutans and oral health conditions following Prenatal Total Oral Rehabilitation among underserved pregnant women

Objectives

To assess the oral health condition and oral microbial outcomes from receiving an innovative treatment regimen - Prenatal Total Oral Rehabilitation (PTOR).

Methods

This prospective cohort study included 15 pregnant women in the PTOR group who had a baseline visit before PTOR and three follow-up visits (immediate after, 2 weeks and 2 months) after receiving PTOR. A historical control group of additional 15 pregnant women was matched from a separate study based on a propensity score. Along with demographic and medical background, oral health conditions and perinatal oral health literacy were assessed. Oral samples (saliva and plaque) were analyzed to identify and quantify Streptococcus mutans and Candida species by culturing-dependent and -independent methods.

Results

Significant reductions of salivary S. mutans were observed following PTOR, the effect remained until 2-month follow-up (p < 0.05). The carriage of salivary and plaque S. mutans at the 2-month visit of the PTOR group was significantly lower than that of the control group (p < 0.05). Oral health conditions reflected by BOP and PI were significantly improved upon receiving PTOR (p < 0.05). Receiving PTOR significantly improved the perinatal oral health literacy score, and the knowledge retained until 2-month follow-up (p < 0.05).

Conclusions

PTOR is associated with an improvement in oral health conditions and perinatal oral health literacy, and a reduction in S. mutans carriage, within a 2-month follow-up period. Future clinical trials are warranted to comprehensively assess the impact of PTOR on the maternal oral flora other than S. mutans and Candida, birth outcomes, and their offspring's oral health.

Identification of Non- Streptococcus mutans Bacteria from Predente Infant Saliva Grown on Mitis-Salivarius-Bacitracin Agar

Objective: Although mitis-salivarius-bacitracin (MSB) agar is a commonly used selective medium for detecting Streptococcus mutans in clinical studies, non-S. mutans microorganisms are cultivatable on MSB agar. Since few studies have identified non-S. mutans bacteria grown on MSB, this study aimed to identify and differentiate MSB-grown non-S. mutans bacteria from predente infants' oral cavity. Study design: The saliva from 51 predente infants were plated on MSB agars. Bacteria colonies were characterized based on their morphology under direct visualization and light microscopic observation. Colony PCR targeting S. mutans htrA locus and 16S rRNA DNA sequencing were used for further bacteria identification. Results: Overall, 80% of the predente infants had oral bacteria grown on the MSB agar. Nine bacteria were identified, including S. mutans, Staphylococcus epidermidis, Klebsiella quasi-pneumoniae, Klebsiella pneumoniae, Enterobacter kobei, Enterococcus faecalis, Staphylococcus hominis, Streptococcus anginosus and Phytobacter. The most frequently detected bacteria were S. epidermidis (41.5%), followed by E. kobei (24.4%), K. pneumoniae (17.1%) and S. mutans (9.8%.) Conclusions: Multiple non-S. mutans bacteria from infants' oral cavity could grow on MSB agar. Caution should be exercised in counting the colony forming units of S. mutans from oral samples on MSB agar to avoid overestimation by assuming that all colonies on the MSB agar are S. mutans. Using the colony morphological guide we summarized, these non-S. mutans bacteria could be distinguished from S. mutans. Our study provides a key reference to pediatric cariology clinical-epidemiological studies that commonly use MSB to identify/quantify S. mutans in infants and young children.

Oral health and Candida carriage in socioeconomically disadvantaged US pregnant women

Background

Despite the well-documented associations between poor maternal oral health and increased risk for adverse birth outcomes and dental caries in children after birth, prenatal oral health care is under-utilized, especially among the underserved population. In addition, oral Candida has recently been suggested as a potential culprit for children’s dental caries, with evident maternal contributions. Therefore, this study aimed to obtain epidemiological data on the oral health and oral Candida carriage in a cohort of underserved US pregnant women, and reveal factors associated with their oral Candida carriage.

Methods

Demographic-medical-oral hygiene practice data were collected. Comprehensive oral examination was conducted. Caries status and plaque index were recorded. Oral samples (saliva, plaque and swab) were processed to identify Candida species and Streptococcus mutans by culturing-dependent and -independent methods. Multiple logistic regression analyses were used to identify factors associated with oral Candida carriage and caries severity.

Results

Eighty-two socioeconomically disadvantaged women (48 pregnant and 34 non-pregnant) were enrolled. More pregnant women (79.1%) had > = 1 untreated decayed tooth when compared to their non-pregnant counterparts (47.1%) (p = 0.01). The average number of decayed teeth in pregnant and non-pregnant women was 3.9 and 3.1 (p > 0.05). Caries severity was positively associated with race (African American vs. white), plaque index and salivary Candida albicans level. C. albicans was the most predominant/abundant Candida strain, with cheek and tonsil as the most common colonized sites. The detection of C. albicans was 56%/56% in saliva and 40%/47% in plaque of the pregnant and non-pregnant groups, respectively. Study women’s oral Candida carriage is positively associated with hypertension [p = 0.03, odds ratio = 14.47(1.28, 163.51)], decayed teeth number [p = 0.04, odds ratio = 1.31 (1.01,1.69)] and salivary S. mutans level [p = 0.03, odds ratio = 4.80 (1.18–19.43)].

Conclusions

Socioeconomically disadvantaged US women are in need of improved prenatal oral health, a large proportion of them have untreated decayed teeth and high carriage of oral Candida. Due to the observed significant association between the decayed teeth number and oral Candida carriage, providing oral health care during pregnancy (including limiting decayed teeth) will not only improve women’s oral health, but also present as a promising approach to reduce oral Candida carriage in women.

Candida albicans Carriage in Children with Severe Early Childhood Caries (S-ECC) and Maternal Relatedness

Introduction

Candida albicans has been detected together with Streptococcus mutans in high numbers in plaque-biofilm from children with early childhood caries (ECC). The goal of this study was to examine the C. albicans carriage in children with severe early childhood caries (S-ECC) and the maternal relatedness.

Methods

Subjects in this pilot cross-sectional study were recruited based on a convenient sample. DMFT(S)/dmft(s) caries and plaque scores were assessed during a comprehensive oral exam. Social-demographic and related background information was collected through a questionnaire. Saliva and plaque sample from all children and mother subjects were collected. C. albicans were isolated by BBL^™ CHROMagar^™ and also identified using germ tube test. S. mutans was isolated using Mitis Salivarius with Bacitracin selective medium and identified by colony morphology. Genetic relatedness was examined using restriction endonuclease analysis of the C. albicans genome using BssHII (REAG-B). Multilocus sequence typing was used to examine the clustering information of isolated C. albicans. Spot assay was performed to examine the C. albicans Caspofungin susceptibility between S-ECC children and their mothers. All statistical analyses (power analysis for sample size, Spearman’s correlation coefficient and multiple regression analyses) were implemented with SAS 9.4

Results

A total of 18 S-ECC child-mother pairs and 17 caries free child-mother pairs were enrolled in the study. Results indicated high C. albicans carriage rate in the oral cavity (saliva and plaque) of both S-ECC children and their mothers (>80%). Spearman’s correlation coefficient also indicated a significant correlation between salivary and plaque C. albicans and S. mutans carriage (p<0.01) and caries severity (p<0.05). The levels of C. albicans in the prepared saliva and plaque sample (1ml resuspension) of S-ECC children were 1.3 ± 4.5 x10⁴ cfu/ml and 1.2 ± 3.5 x10⁴ cfu/ml (~3-log higher vs. caries-free children). Among 18 child-mother pairs, >60% of them demonstrated identical C. albicans REAG-B pattern. C. albicans isolated from >65% of child-mother pairs demonstrated similar susceptibility to caspofungin in spot assay, while no caspofungin resistant strains were seen when compared with C. albicans wild-type strain SC5314. Interestingly, the regression analysis showed that factors such as antibiotic usage, birth weight, inhaler use, brushing frequency, and daycare attendance had no significant effect on the oral carriage of C. albicans in the S-ECC children.

Conclusions

Our results reveal that both the child with S-ECC and the mother were highly infected with C. albicans, while most of the strains were genetically related, suggesting that the mother might be a source for C. albicans acquisition in the oral cavity of children affected by the disease.

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.

Enumeration of Salivary Streptococci and Lactobacilli in Children with Differing Caries Experiences in a Rural Indian Population

Objectives. Compare the total salivary Streptococci and Lactobacilli counts in cleft and noncleft children with differing caries experiences, correlate the bacterial counts with dmft/DMFT status and identify the different biotypes of Mutans Streptococci (MS). Patients. Group I included thirty subjects with dental caries (DC) and cleft lip and palate (CL/P); Group II had thirty subjects with DC but without CL/P. Group III comprised a control of thirty subjects with neither DC nor CL/P. Methodology. Enumeration of total salivary Streptococci and Lactobacilli was done by the plate count method and correlation of counts with dmft/ DMFT status examined. Differences in biochemical reactions were used to identify the biotypes. Results. Streptococci colonies in CL/P children with caries (64.30 ± 24.52) was significantly higher than in children with no CL/P or caries (45.57 ± 16.73). No significant differences in the Lactobacilli count were observed. dmft/DMFT status and Streptococci counts showed a strong positive correlation whereas Lactobacilli counts showed a moderate correlation. S. mutans was the predominant biotype. Conclusions. Higher total salivary Streptococci and Lactobacilli counts exist in cleft subjects with caries than in the non-cleft subjects. Positive correlation between dmft/DMFT scores and salivary Streptococci reinforces its role in DC. S. mutans and S. sobrinus are the biotypes more frequently associated with dental caries in children.

Recovery of mutans streptococci on MSB, SB-20 and SB-20M agar media

OBJECTIVE

The recovery of mutans streptococci in saliva and dental biofilm samples depends, in part, on the culture medium used. In this study, we compared (i) the culture media Sucrose-Bacitracin agar (SB-20), Modified SB-20 (SB-20M) and Mitis Salivarius Bacitracin agar (MSB) in the count of colony forming units (cfu) of mutans streptococci and (ii) in the morphological and biochemical differentiation between Streptococcus mutans and Streptococcus sobrinus.

DESIGN

Samples of non-stimulated saliva from 20 children were plated on SB-20, SB-20M and MSB, and incubated in microaerophilia at 37°C for 72h. Identification of microorganisms was based on analysis of colony morphology under stereomicroscopy. The biochemical identification of colonies was done by biochemical tests using sugar fermentation, resistance to bacitracin and hydrogen peroxide production.

RESULTS

There was no significant difference (p>0.05) in the number of cfu of mutans streptococci recovered on SB-20 and SB-20M agar. Comparing the media, SB-20 and SB-20M yielded a larger number of mutans streptococci colonies (p<0.05) and were more effective than MSB in the identification of S. sobrinus (p<0.05), but not of S. mutans (p>0.05).

CONCLUSION

There was no significant difference between SB-20 and SB-20M culture media in the count of mutans streptococci, demonstrating that the replacement of sucrose by coarse granular cane sugar did not alter the efficacy of the medium. Compared with MSB, SB-20 and SB-20M allowed counting a larger number of mutans streptococci colonies and a more effective morphological identification of S. sobrinus.

Morphological differentiation between S. mutans and S. sobrinus on modified SB-20 culture medium

Due to the major role of Streptococcus mutans and Streptococcus sobrinus in the etiology of dental caries, it is important to use culture media that allow for differentiating these bacterial species. The aim of this study was to evaluate the suitability of a modified SB-20 culture medium (SB-20M) for the isolation and morphological differentiation of S. mutans and S. sobrinus, compared to biochemical identification (biotyping). Saliva samples were collected using the spatula method from 145 children, seeded on plates containing the SB-20M, in which sucrose was replaced by coarse granular cane sugar, and incubated in microaerophilia at 37°C during 72 h. Identification of the microorganisms was performed under stereomicroscopy based on colony morphology of 4904 colonies. The morphological identification was examined by biochemical tests of 94 randomly selected colonies with the macroscopic characteristic of S. mutans and S. sobrinus using sugar fermentation, resistance to bacitracin and production of hydrogen peroxide. There was no statistically significant difference (p>0.05) between morphological identification in the SB-20M medium and biochemical identification (biotyping). Biotyping confirmed that S. mutans and S. sobrinus colonies were correctly characterized in the SB-20M in 95.8% and 95.5% of the cases, respectively. Of the mutans streptococci detected in the children 98% were S. mutans and 2% S. sobrinus. The SB-20M medium is reliable for detection and direct morphological identification of S. mutans and S. sobrinus.

Comparative analysis of a monoclonal antibody-based Streptococcus mutans detection method with selective culture assays using polymerase chain reaction as a gold standard

The aim of this study was to compare a recently developed monoclonal antibody (MAb)-based salivary Streptococcus mutans detection method with various selective media using polymerase chain reaction (PCR) as the gold standard. Salivary S. mutans cells were enumerated with a MAb-based method, along with three commonly used selective media, mitis-salivarius-bacitracin agar (MSB), trypticase yeast-extract cystine sucrose bacitracin agar (TYCSB), and glucose-sucrose-potassium tellurite-bacitracin (GSTB) agar. Statistical analysis showed no significant correlations between each method. With PCR as the standard, a MAb-based detection method was found to provide the highest sensitivity (91%) and specificity (96%) among these four methods. This study demonstrates that the MAb-based detection method may provide more accurate enumeration of salivary S. mutans than selective media.

Comparison of culture media and chairside assays for enumerating mutans streptococci

AIM

This study compared several traditional culture-based media and chairside cultural assays for ability to recover mutans streptococci (MS) from pure cultures and from saliva samples.

METHODS AND RESULTS

When pure cultures were used with traditional culture-based media, mitis-salivarius bacitracin (MSB) agar demonstrated less support for bacterial recovery than trypticase-yeast extract-cysteine sucrose-bacitracin (TYCSB) agar and the modified medium of Ritz (HLR-S). One species of MS, Streptococcus ferus (c), was not recovered on MSB medium. Chairside cultural tests displayed considerable disparity between tests in recovering bacteria from pure cultures. On the glass adherence assay (Mucount), S. ferus was not detected and Streptococcus criceti was not detected on the dipslide assay (Cariescreen SM) or on the plastic adherence assay (Dentocult SM Strip mutans). The frequency of isolation of pure strains of bacteria other than MS was common. From saliva samples, the frequency of isolation of MS on HLR-S and TYCSB media and the glass adherence assay was 91-97%. The frequency of isolation on MSB medium and on the dip-slide and plastic adherence assays was significantly decreased (37, 47 and 69%, respectively). Recovery scores varied considerably among the culture methods studied and tended to be highest on the HLR-S medium and on the glass adherence assay.

CONCLUSIONS

Growth and recovery profiles of pure bacterial cultures and of saliva samples for the MS varied according to different media.

SIGNIFICANCE AND IMPACT OF THE STUDY

Caution should be exercised in comparing results between studies that employ different cultural methods for MS enumeration.

Influences of orthodontic appliances on oral populations of mutans streptococci

A study was conducted to assess the influence of fixed appliances on the mutans streptococcal in a group of patients receiving orthodontic treatment. Mutans streptococcal counts in stimulated saliva of 27 patients were obtained at baseline, and at 1-month intervals for 4 months. The difference in mutans streptococcal counts at baseline and at the 4-month sampling was less than an order of magnitude in 18 of the patients, between 1 and 2 orders of magnitude in eight of the patients, and 3 orders of magnitude in one patient. Restriction endonuclease digests of genomic DNA from representative mutans streptococci isolates taken from baseline and 4-month saliva samples, as well as from 4-month tooth and appliance surfaces, were examined by pulsed field gel electrophoresis, after restriction endonuclease digestion. Results of the DNA banding patterns associated with isolates from 19 patients showed that, for 12 patients, all isolates examined represented the same clone of Streptococcus mutans, whereas for six patients two different S. mutans clones were detected. One patient yielded three different clones of S. mutans. A much larger number of baseline, as well as post-appliance, isolates will have to be examined from each patient in future studies, in order to determine if the number of different S. mutans clones harbored by individual patients is related to orthodontic treatment.

Comparison of five selective media for the growth and enumeration of Streptococcus mutans

BACKGROUND

Although a few growth media are available for selective isolation of the cariogenic bacteria, Streptococcus mutans (S. mutans), it is still unclear as to which is the most efficacious. This study compared the selectivity and sensitivity of five different media for growing a laboratory strain of S. mutans (NCTC 10449), and for enumerating S. mutans from teeth of a group of young children, aged 2-10 years.

METHODS

The media tested in this study were mitis salivarius with bacitracin (MSB), mitis salivariuskanamycin-bacitracin (MSKB), glucose-sucrose-tellurite-bacitracin (GSTB), trypticase soy-sucrose-bacitracin (TYS20B) and tryptone-yeast-cysteine-sucrose-bacitracin (TYCSB) agars. These were prepared according to the respective manufacturer's instructions.

RESULTS

The results showed that at concentrations of bacteria 1 x 10(3) to 1 x 10(10)/mL, the recovery of the laboratory S. mutans strain was highest in TYCSB agar, followed by in descending order by TYS20B, MSB, GSTB, and MSKB (p<0.01). Similar results were obtained using dental plaque samples collected from swabs of the teeth of a group of children. In the clinical samples, TYCSB again showed the highest recovery rates of S. mutans compared to the other four media. Results were reproduced at dilutions of the samples at 1:20 x 10(6) to 1:2 x 10(6), and S. mutans concentrations of 1.6 to 7.7 Log 10 CFU/mL. In addition, there were highest ratios of mutans to non-mutans bacteria in TYCSB compared to the other media, suggesting high selectivity of this media for mutans species.

CONCLUSION

The results of our study suggest that TYCSB is the most sensitive and selective media for culture of S. mutans for laboratory and clinical studies.

Identification of Streptococcus sobrinus with monoclonal antibodies

Identification of Streptococcus sobrinus is often difficult to perform because of the great resemblance of the organism to other oral streptococcal species. Therefore, monoclonal antibodies were prepared which were shown to be highly specific for S. sobrinus. Cross-reactivity with other oral microorganisms has not been observed in an enzyme-linked immunosorbent assay and an immunofluorescence assay. These monoclonal antibodies belonged to the subclass immunoglobulin G2b. To be certain that the strains used in cross-reactivity tests were S. sobrinus, their DNA base composition was measured as a golden standard. Additional tests like colony morphology and sugar fermentation with the API 20 Strep system (Analytab Products, Montalieu-Vercieu, France) were performed. These additional tests turned out to be necessary because 100% correct identification could not be obtained by separate tests. Immunological characterization with the clones OMVU10 and OMVU11 proved to be discriminative between S. sobrinus and other streptococcal species.

Comparative recovery of Streptococcus mutans on five isolation media, including a new simple selective medium

For the isolation of Streptococcus mutans, several selective media have been developed, of which Mitis-Salivarius Sucrose Bacitracin agar (MSB) is the most widely used (Gold et al., 1973). Recently, the Trypticase Yeast-Extract Cystine agar medium (TYC, de Stoppelaar et al., 1967) was modified into a selective medium for S. mutans, called Trypticase Yeast-Extract Cystine Sucrose Bacitracin (TYCSB, van Palenstein Helderman et al., 1983). The aim of this study was to compare the recovery of S. mutans from clinical samples on Mitis-Salivarius agar (MS), MSB, TYC, and TYCSB. Further, a new simple selective medium for S. mutans was introduced. This medium, called TSY20B, was supposed to have the same qualities as TYCSB, but its preparation is less laborious. One hundred eighty-five plaque and saliva samples from 37 subjects were plated on MS, MSB, TYC, and TYCSB, and 285 samples from 23 subjects were plated on TYCSB and TSY20B. All plates were incubated at 37 degrees C in a 91% N2, 5% CO2, 4% H2 atmosphere for five days. The S. mutans counts on TYC and TYCSB were significantly higher than on MS or MSB by almost a factor of 10. Seventy-seven percent of the samples gave higher S. mutans counts on TYCSB than on MSB. Especially, samples with high S. mutans d/g numbers gave lower S. mutans counts on MSB. These data clearly indicate that MSB agar is inhibitory for S. mutans and should not be used. An additional advantage of TYCSB over MSB agar is the possibility of distinguishing S. mutans serotypes d/g from other serotypes.(ABSTRACT TRUNCATED AT 250 WORDS)

Glucose-sucrose-potassium tellurite-bacitracin agar, an alternative to mitis salivarius-bacitracin agar for enumeration of Streptococcus mutans

An agar medium for selective recovery and enumeration of Streptococcus mutans was developed as an alternative to mitis salivarius-bacitracin (MSB) agar. Combinations of dyes, antibiotics, and tellurite were added to a nonselective medium which, because of its sucrose content, allowed easy recognition of S. mutans colonies. Candle jar incubation for 2 days, by comparison with anaerobic incubation, reduced background flora but did not diminish S. mutans recoveries from clinical samples. Quantitative comparisons were made of the simultaneous recoveries of a number of authentic S. mutans serotype representatives and fresh clinical isolates, using various glucose-sucrose-potassium tellurite-bacitracin (GSTB) formulations and mitis salivarius, MSB, and blood agars. Mitis salivarius counts were not detectably different from blood counts, but counts on MSB were distinctly lower. A formulation of the new medium containing 5% glucose 5% sucrose, 0.001% potassium tellurite, 0.3 U of bacitracin per ml (hence GSTB), and 2% agar gave recoveries nearly equal to those on mitis salivarius agar and much greater than those on MSB. The medium yielded readily recognized S. mutans colonies and facilitated detection of intracellular polysaccharide formers upon flooding with I2 reagent. Freshly isolated serotype c, E, and f colonies could often be distinguished from serotype d and g colonies, a distinction made reliable by testing for intracellular polysaccharide. A study of 300 salivary samples revealed GSTB to give significantly higher recoveries than MSB. About 72% of all samples were substantially underestimated for S. mutans with MSB, and 6.7% of samples were falsely negative for S. mutans with MSB. Recovery of background flora on GSTB was as low or lower than on MSB, and both types of agar could be stored for at least 9 weeks without notable change of selectivity. Thus, GSTB agar appears to be simple and reliable to use and requires no anaerobic incubation. Caution is voiced about interpretation of data previously reported which evaluated S. mutans on MSB agar.

Slide-scoring method for estimation of Streptococcus mutans levels in saliva

A method was developed to facilitate the estimation of S. mutans levels in saliva. Paraffin-stimulated saliva was poured on a special slide coated with mitis-salivarius-sucrose agar. Two discs containing bacitracin (5 micrograms) were placed on the inoculated slide and the growth density of S. mutans around the bacitracin discs was scored after incubation in candle jars at 37 degrees C for 48 h. The obtained score values correlated well with the numbers of CFU of S. mutans per 1 ml of saliva estimated by a conventional method using mitis-salivarius-bacitracin agar. The experimental method was further tested by incubating the slides in an atmosphere created by CO2-generating tables that were placed into the cover tubes of the slides. These score values were similar to those after conventional incubation. The method is suggested for epidemiologic studies and in selecting persons at high risk for caries and in controlling the effectiveness of prophylactic measures of these patients.

Prevalence, distribution of serotypes, and cariogenic potential in hamsters of mutans streptococci from elderly individuals

The prevalence of mutans streptococci (Streptococcus mutans, Streptococcus cricetus, Streptococcus sobrinus, and Streptococcus rattus) was determined in the salivas of 169 elderly individuals ranging in age from 60 to 87 years. Approximately 40% of these individuals were edentulous and wore full upper and lower dentures. With the exception of a higher proportion of saliva counts below 1,000 CFU/ml in the full-denture wearers, the prevalence and the serotype and species distributions of the mutans streptococci were similar in the denture wearers and individuals with natural teeth only. The species and serotype distributions of mutans streptococci in this elderly population were also consistent with reported observations of other workers on younger, more caries-prone populations. A total of 87 representative isolates of the mutans streptococci were tested for cariogenic potential in a hamster model system. A considerable degree of variation in virulence between different strains was observed. However, these differences were not relatable to individual species or serotypes or to whether the organisms were isolated from denture wearers or naturally dentate subjects. The results of our studies indicate that elderly individuals with either natural or artificial dentitions may be a hitherto unrecognized reservoir of mutans streptococci having varying degrees of potential cariogenicity. Hence, in close family situations they could serve, along with parents and siblings, as vectors in the initial transmission of cariogenic microorganisms to young children.

A selective medium for the two major subgroups of the bacterium Streptococcus mutans isolated from human dental plaque and saliva

A selective medium was developed on which both major subgroups of Strep. mutans (c/e/f and d/g) can be cultured and recognized on the basis of colonial morphology, Trypticase, yeast, cystine (TYC) agar was modified by adding separately autoclaved sucrose to a final concentration of 20 per cent and 0.1 unit/ml bacitracin (TYCSB). This medium yielded significantly higher counts of Strep. mutans than the widely used mitis-salivarius bacitracin (MSB) medium.

Biology, immunology, and cariogenicity of Streptococcus mutans

Images

Microflora and chemical composition of dental plaque from subjects with hereditary fructose intolerance

We compared the microbiological and chemical composition of dental plaque from subjects with hereditary fructose intolerance who restrict their dietary sugar intake with that of control subjects who do not. The two groups showed no significant differences in chemical composition of plaque: the mean protein, carbohydrate, calcium, magnesium, and phosphate contents were similar. Dental plaque from both groups contained similar numbers of total colony-forming units per microgram of plaque protein, and Streptococcus sanguis, an indigenous nonpathogen, was isolated with equal frequency from plaque samples of both groups. However, potentially odontopathic Streptococcus mutans and Lactobacillus were isolated three to four times more frequently from plaque samples of control subjects than from plaque samples of subjects with hereditary fructose intolerance. Clearly, diet (sucrose in particular) influences the colonization and multiplication of specific cariogenic organisms in dental plaque.

Comparison of selective broth and plating methods for isolation of Streptococcus mutans from root surface dental plaques

Approximately 150 sound root surfaces in 44 subjects prone to root surface caries were sampled longitudinally to determine the microbial flora associated with root caries initiation. During the first 16 months of the study, a comparison of Streptococcus mutans recovery was made by using three bacteriological media: mitis-salivarius agar (MSA), mitis-salivarius-bacitracin-sucrose agar (MSB), and a partially selective mannitol-containing broth. Total streptococcal and S. mutans populations were found to be much lower than in previous reports. MSB was more selective; S. mutans was detected in many samples when its numbers were too low for isolation on MSA. However, recovery of S. mutans was greater on MSA than on MSB for most samples yielding colonies on both media. Mannitol-containing broth used as an enrichment medium yielded the highest frequency of S. mutans isolation among the three media.

Antibiotic susceptibility of Streptococcus mutans: comparison of serotype profiles

A total of 82 strains of Streptococcus mutans representing serotypes a through g were tested for susceptibility to erythromycin, penicillin, methicillin, lincomycin, tetracycline, vancomycin, gentamicin, streptomycin, neomycin, kanamycin, bacitracin, and polymyxin B. Strains included stock cultures and isolates from human and animal dental plaque. Minimal inhibitory concentrations were determined by a broth-microdilution procedure. The major differences in antibiotic susceptibility observed among the serotypes resulted with antibiotics which act on the cell surface. Bacitracin was most active against serotype a strains and polymyxin B against serotype b strains. Serotypes a, d, and g were less susceptible than the other serotypes to methicillin.