Typing of mutans streptococci by arbitrarily primed polymerase chain reaction

Vertical and Horizontal Transmission of Streptococcus Mutans and Effective Factors: An In Vivo Study

Aim:

The degree of vertical (intrafamilial) and horizontal (extrafamilial) transfer of Streptococcus mutans ( S. mutans) to a child shows differences according to cultures. The wrong care habits may result in transfer of S. mutans. The aim of this study was to determine the vertical and horizontal transmission of S. mutans to a child and effective factors.

Materials and Methods:

Mothers and kindergarten staff of 37 children aged between 4 and 5 years who initially started in two kindergartens (Group 1, n = 19; Group 2, n = 18) were included in this in vivo study according to 95% reliability and 80% theoretical power. Intraoral examination of mothers and children made according to the World Health Organization criteria (dmf-t/DMF-T) was done, following which mothers were asked to fill questionnaire forms including knowledge and attitudes of them about oral/dental health care. 1 mL saliva samples received from children/mothers/staff were examined microbiologically in order to isolate and quantify S. mutans. Arbitrarily primed polymerase chain reaction analysis was done to determine the genetic characteristics of S. mutans. All examinations were repeated to evaluate the horizontal transmission in the fifth month. Parametric tests ( t-test and two-way analysis of variance) were employed for comparison of the variables that meet the normality assumption and nonparametric tests (Mann–Whitney) were also used.

Results:

It was observed that there is a statistically significant correlation between mother DMF-T values and mother–child S. mutans similarity level ( P < .05). There is a statistically positive correlation between the habits of using a common fork, spoon, glass, and mother–child similarity level.

Conclusion:

Vertical and horizontal transfers occurred in Turkish families in order to prevent the transfer of S. mutans; wrong baby care habits that may lead to the transfer of S. mutans, which is the main factor in case of tooth decay, should be avoided.

Genotypic diversity and acidogenicity of Streptococcus mutans in Down syndrome children

AIMS

To evaluate the genotypic diversity and acidogenicity of Streptococcus mutans (S. mutans) and the potential association of these factors with dental caries experience in children with DS compared to non-DS children (controls).

METHODS AND RESULTS

Seventeen children (age 6-12 years) with high salivary S. mutans counts (> 2.5 × 10⁵ CFU/mL) were selected and divided into two groups: DS and non-DS. Five children in each group were caries-free, while the remainder had elevated caries experience. S. mutans isolates were obtained from each participant. The genotypic profile of the isolates was analyzed with the AP-PCR methodology. The acidogenicity of a representative strain from each genotype of S. mutans was also evaluated. DS children had 16 different S. mutans genotypes, while the control group had 21. Twelve genotypes were present in both groups and one of them was associated with caries-free status (P < .05). Although the acidogenicity of the genotypes found in DS children was significantly lower (P < .05) compared to controls, this fact was not associated with caries experience in both groups.

CONCLUSIONS

DS children have a lower S. mutans genotypic diversity and genotypes with lower acidogenicity than those of non-DS children. However these findings were not associated with their caries experience.

Genotypic diversity of Streptococcus mutans isolated from preschoolers with and without early dental care

Abstract Introduction Streptococcus mutans (S. mutans) exhibits extensive genotypic diversity, but the role of this variation is poorly understood. Objective To evaluate the genotypic diversity of S. mutans in preschoolers with and without early dental care and to associate it with dental caries experience. Material and method Twenty children, aged five year old, with history of dental care since they were one year old (G1) and 20 children without history of dental care (G2) were included. Their oral health status was assessed by the dmft index. S. mutans samples were isolated from the saliva and analysed by polymerase chain reaction. A total of 339 S. mutans isolates (173 from G1 and 166 from G2) were genotyped by random amplified polymorphic DNA with arbitrary primers OPA-02 and OPA-13. Result The results revealed 75 distinct genotypes of S. mutans in G1 and 73 in G2. Furthermore, G1 and G2 subjects harboured one to eight and one to seven distinct genotypes of S. mutans, respectively. A statistically significant association (P=0.021) and a moderate correlation (r= 0.503) were observed between dental caries experience and genotypic diversity of S. mutans in G1. Conclusion From the limitations of the study design, we just can hypothesize that actions of early dental care carried out by an educative-preventive program can contribute to a distinct oral microbiota.

Contribution of Streptococcus Mutans Virulence Factors and Saliva Agglutinating Capacity to Caries Susceptibility in Children: A Preliminary Study

BACKGROUND

Many factors contribute to caries development in humans, such as diet, host factors - including different saliva components - and the presence of acidogenic bacteria in the dental biofilm, particularly Streptococcus mutans (S. mutans). Despite the influence of S. mutans in caries, this bacterium is also prevalent among healthy individuals, suggesting the contribution of genetic variation on the cariogenic potential. Based on this hypothesis, the present work investigated the influence of S. mutans virulence factors and saliva agglutinating capacity on caries susceptibility in children.

STUDY DESIGN

Saliva samples of 24 children from low income families (13 caries-free and 11 caries-active individuals) were collected and tested for their ability to agglutinate S. mutans. The bacteria were isolated from these samples and analyzed for the presence of the gene coding for mutacin IV (mut IV). Biofilm formation and acid tolerance were also investigated in both groups (caries-free and caries-active).

RESULTS

Saliva samples from caries-free children showed an increased capacity to agglutinate S. mutans (p=0.006). Also, bacteria isolated from the caries-free group formed less biofilm when compared to the caries-active group (p=0.04). The presence of mut IV gene did not differ between bacteria isolated from caries-free and caries-active individuals, nor did the ability to tolerate an acidic environment, which was the same for the two groups.

CONCLUSIONS

Altogether, the results suggest that the adhesive properties of S. mutans and the agglutinating capacity of the saliva samples correlated with the presence of caries lesions in children.

Mother-to-child transmission of mutans streptococci

Mutans streptococci (MS) are the major group of pathogens implicated in dental caries. Like other infectious diseases, transmission of the causative microorganisms is the initial and essential step that should be understood relative to disease control and prevention. This review summarizes current knowledge regarding MS transmission, especially from mothers to their children. Included are methods used to study transmission, sources of MS, initial acquisition, factors concerning transmission and prevention of transmission. Information accumulated over many decades showed the involvement of MS transmission in the pathogenesis of caries, hence several preventive measurements have been proposed. Nevertheless, some essential aspects remain to be elucidated for more benefits of practical application.

Genotypic diversity and virulence traits of Streptococcus mutans isolated from carious dentin after partial caries removal and sealing

The aim of this study was to compare the genotypic diversity and virulence traits of Streptococcus mutans isolated from carious dentin before and after partial dentin caries removal (PDR) and sealing. Carious dentin samples were obtained three months before and after the PDR and cavity sealing. Up to seven isolates of each morphological type of S. mutans were selected and strain identity was confirmed using gtfB primer. Genotyping was performed by arbitrary primer-PCR (AP-PCR). Acidogenesis and acidurance of the genotypes were evaluated as virulence traits. A paired t-test and a Wilcoxon test were used to compare the virulence of genotypes. A total of 48 representative S. mutans isolates were genotyped (31 before and 17 after the sealing). At least one of the genotypes found before the sealing was also found on dentin after the sealing. The number of genotypes found before the sealing ranged from 2 to 3 and after the sealing from 1 to 2 genotypes. No difference was observed in the acidogenesis and acidurance between genotypes isolated before and after the sealing. In conclusion, genotypic diversity of S. mutans decreased after the PDR and sealing, but the virulence traits of S. mutans remained unchangeable.

Reverse transcription and polymerase chain reaction: principles and applications in dentistry

Various molecular biology techniques have become available in the last few years. One of the most revolutionary of these techniques regarding nucleic acid analysis is the polymerase chain reaction (PCR), which was first described in 1985. This method relies on the exponential amplification of specific DNA fragments, resulting in millions of copies that can serve as templates for different kinds of analyses. PCR can be preceded by a reverse transcription (RT) reaction in order to produce cDNA from RNA (RT-PCR). RT-PCR provides the possibility to assess gene transcription in cells or tissues. PCR and RT-PCR techniques have been instrumental in dental research, and show potential to be used for diagnosis as well as for treatment and prevention of many diseases (dental caries, periodontal disease, endodontic infections and oral cancer). Compared to other traditional methodologies, PCR and RT-PCR show many advantages including high specificity, sensitivity, and speed. Since PCR and RT-PCR are relatively new techniques and are not available to most students and professionals involved with dentistry, the aim of this work is to present the details of these techniques as well as dental literature reports in which they were used.

Genotypic diversity of Streptococcus mutans and Streptococcus sobrinus in 3-4-year-old children with severe caries or without caries

BACKGROUND.  The genotypic diversity of both Streptococcus mutans and Streptococcus sobrinus in children with different caries experience remains unclear. AIM.  To investigate the genotypic diversity of S. mutans and S. sobrinus in children with severe early childhood caries (SECC) and in caries-free (CF) children. METHODS.  Stimulated saliva of 87 SECC and 91 CF children aged 3-4 years was collected and submitted to cultivation, and MS colonies were enumerated. The genomic fingerprint analysis of S. mutans and S. sobrinus was carried out using AP-PCR. RESULTS.  One to five genotypes of S. mutans were colonized in an oral cavity of SECC and CF children; 85.5% SECC children and 57.9% CF children harboured more than one genotype of S. mutans. One to three genotypes of S. sobrinus were detected from each SECC child; 31.25% SECC children harboured more than one genotype of S. sobrinus. And one genotype was colonized in each CF child. S. mutans isolates from different individuals displayed distinctive DNA fingerprints. CONCLUSIONS.  DNA fingerprints of S. mutans and S. sobrinus isolates from 3- to 4-year-old children displayed genetic polymorphism, and S. mutans has greater genetic diversity than S. sobrinus. SECC children harboured more genotypes of S. mutans and S. sobrinus than CF children.

Generation of diversity in Streptococcus mutans genes demonstrated by MLST

Streptococcus mutans, consisting of serotypes c, e, f and k, is an oral aciduric organism associated with the initiation and progression of dental caries. A total of 135 independent Streptococcus mutans strains from caries-free and caries-active subjects isolated from various geographical locations were examined in two versions of an MLST scheme consisting of either 6 housekeeping genes [accC (acetyl-CoA carboxylase biotin carboxylase subunit), gki (glucokinase), lepA (GTP-binding protein), recP (transketolase), sodA (superoxide dismutase), and tyrS (tyrosyl-tRNA synthetase)] or the housekeeping genes supplemented with 2 extracellular putative virulence genes [gtfB (glucosyltransferase B) and spaP (surface protein antigen I/II)] to increase sequence type diversity. The number of alleles found varied between 20 (lepA) and 37 (spaP). Overall, 121 sequence types (STs) were defined using the housekeeping genes alone and 122 with all genes. However pi, nucleotide diversity per site, was low for all loci being in the range 0.019-0.007. The virulence genes exhibited the greatest nucleotide diversity and the recombination/mutation ratio was 0.67 [95% confidence interval 0.3-1.15] compared to 8.3 [95% confidence interval 5.0-14.5] for the 6 concatenated housekeeping genes alone. The ML trees generated for individual MLST loci were significantly incongruent and not significantly different from random trees. Analysis using ClonalFrame indicated that the majority of isolates were singletons and no evidence for a clonal structure or evidence to support serotype c strains as the ancestral S. mutans strain was apparent. There was also no evidence of a geographical distribution of individual isolates or that particular isolate clusters were associated with caries. The overall low sequence diversity suggests that S. mutans is a newly emerged species which has not accumulated large numbers of mutations but those that have occurred have been shuffled as a consequence of intra-species recombination generating genotypes which can be readily distinguished by sequence analysis.

Horizontal transmission of mutans streptococci in children

It has not been established whether transmission of mutans streptococci occurs between unrelated children older than 4 years of age. The aim of the study was to investigate the possible transmission of mutans streptococci genotypes from child to child in kindergarten. We studied 96 children (ages 5-6 yrs) in three San Francisco Bay Area public schools. Mutans streptococci colonies from each child were isolated from selective culture on Mitis Salivarius Sucrose Bacitracin agar. We used arbitrary primed polymerase chain reactions to determine the mutans streptococci genotypes. Two children (not siblings) in each of the three schools (6%) shared an identical amplitype of S. mutans, unique to each pair. The 19 S. sobrinus amplitypes were found in 12 children, and all were unique to each child. The presence of matching genotypes of S. mutans demonstrates horizontal transmission of this species between unrelated children aged 5-6 years.

Genotypic Diversity of Streptococcus mutans in Caries-Free and Caries-Active Preschool Children

Aim. The aim of the present paper was to evaluate the genotypic diversity of S. mutans in caries-free and caries-active preschool children in Brazil. Design. Twenty-eight preschool children were examined regarding caries experience by the dmft index. DNA from 280 isolates of S. mutans was extracted. S. mutans evaluated using to the PCR method, with primers for the glucosyltransferase gene. The genetic diversity of S. mutans isolates was analyzed by arbitrary primed-PCR (AP-PCR) reactions. The differences between the diversity genotypic and dmft/caries experience were evaluated by χ2 test and Spearman's correlation. Results. The Spearman correlation test showed a strong association between genotypic diversity and caries experience (r = 0.72; P < .001). There were more S. mutans genotypes in the group of preschool children with dental caries, compared with the caries-free group. Among the children with more than 1 genotype, 13 had dental caries (2 to 5 genotypes) and 4 were caries-free (only 2 genotypes). Conclusion. Our results support the previous findings of genetic diversity of S. mutans in preschool children being associated with dental caries. The investigation of such populations may be important for directing the development of programs for caries prevention worldwide.

Molecular and clinical analyses of the gene encoding the collagen-binding adhesin of Streptococcus mutans

Streptococcus mutans is a known pathogen of dental caries and its major cell surface antigens have been widely investigated. Recently, an approximately 120 kDa Cnm protein with binding properties to type I collagen was identified, and its encoding gene (cnm) cloned and sequenced. In the present study, we sequenced cnm from 47 different clinical S. mutans strains and found that the nucleotide alignment of the collagen-binding domain was well conserved. We devised a PCR method for identifying the cnm gene, examined the prevalence of cnm-positive S. mutans strains in various mother-child groups, and assessed the significance of such strains for transmission and dental caries. The detection rate of cnm-positive strains was significantly lower in strains isolated from Japanese children in the 2000s (8.0 %) as compared to those isolated in the 1980s (15.8 %) (P<0.05). Furthermore, the presence of S. mutans possessing cnm in salivary specimens collected from 55 S. mutans-positive mother-child pairs was 40 and 32.7 % in the mothers and children, respectively. The frequency of cnm-positive children whose mothers were also positive was 72 %, which was significantly higher than that of cnm-positive children with negative mothers (P<0.0001, odds ratio 17.5). In addition, clinical parameters indicating dental caries were significantly increased in children with cnm-positive S. mutans in saliva (n=13), as compared to those with cnm-negative S. mutans (n=15) and S. mutans-negative children (n=20) (P<0.01). These results indicate that cnm-positive S. mutans strains are closely correlated with dental caries, while vertical transmission in cnm-positive mother-child pairs was also demonstrated.

Evaluation of genotypic diversity of Streptococcus mutans using distinct arbitrary primers

Streptococcus mutans has been considered one of the main etiological agents of dental caries and the genotypic diversity rather than its salivary counts may be considered as a virulence factor of this bacterium. For genotyping with polymerase chain reaction (PCR) with arbitrary primers, several primers have been used in order to improve complexity and specificity of amplicon patterns. Thus, the aim of this study was to evaluate the degree of agreement of genotypic identification among AP-PCR reactions performed with 5 distinct arbitrary primers of S. mutans isolated from saliva. Stimulated saliva was collected from 11 adult volunteers for isolation of S. mutans, and a total of 88 isolates were genotyped with arbitrary primers OPA 02, 03, 05, 13 and 18. Fourteen distinct genotypes were identified in the saliva samples. Most volunteers (9 out of 11) presented only one genotype. The results of the present study suggest that primers OPA 02, 03, 05 and 13 were suitable for genotypic identification of S. mutans isolates of saliva from adult volunteers.

Principles and applications of polymerase chain reaction in medical diagnostic fields: a review

Recent developments in molecular methods have revolutionized the detection and characterization of microorganisms in a broad range of medical diagnostic fields, including virology, mycology, parasitology, microbiology and dentistry. Among these methods, Polymerase Chain Reaction (PCR) has generated great benefits and allowed scientific advancements. PCR is an excellent technique for the rapid detection of pathogens, including those difficult to culture. Along with conventional PCR techniques, Real-Time PCR has emerged as a technological innovation and is playing an ever-increasing role in clinical diagnostics and research laboratories. Due to its capacity to generate both qualitative and quantitative results, Real-Time PCR is considered a fast and accurate platform. The aim of the present literature review is to explore the clinical usefulness and potential of both conventional PCR and Real-Time PCR assays in diverse medical fields, addressing its main uses and advances.

Distribution and activity of IS elements in Streptococcus mutans

Insertion sequence (IS) elements are widely distributed selfmobilizing genetic elements that can affect genetic changes by integrating into the chromosome, mediating genetic rearrangements and facilitating horizontal gene transfer. Three members of the IS3 family have been identified in Streptococcus mutans: IS199 was discovered by its transposition while ISSmu1 and ISSmu2 were predicted from the genome sequence of S. mutans UA159. Sixty-eight strains of S. mutans were screened by PCR for carriage of the IS elements IS199, ISSmu1 and ISSmu2. Twenty-seven (30%) of the strains were positive for IS199, 33 (49%) were positive for ISSmu1 and 51 (75%) carried ISSmu2. All three IS were found in 11 strains, two were found in various combinations in 31, one was found in 16, while only 10 strains had none of the three IS for which we screened. ISSmu1 was demonstrated to be capable of transposition at a low frequency but no transposition of ISSmu2 was observed.

Evaluation of (GTG)5-PCR for rapid identification of Streptococcus mutans

Repetitive sequence-based polymerase chain reaction (PCR) fingerprinting using the (GTG)(5) primer was applied for fast screening of bacterial strains isolated from dental plaque of early childhood caries (ECC)-affected children. A group of 29 Gram-positive bacteria was separated into a homogeneous cluster together with Streptococcus mutans reference strains and constituted an aberrant branch after the numerical analysis of (GTG)(5)-PCR fingerprints. Automated ribotyping with EcoRI restriction enzyme (RiboPrinter microbial characterization system) revealed high genetic heterogeneity among the tested group and proved to be a good tool for strain-typing purposes. Further characterization of the studied strains was achieved by extensive phenotyping and whole-cell protein fingerprinting and confirmed all the strains as S. mutans representatives. Obtained results showed rep-PCR fingerprinting with the (GTG)(5) primer to be a fast and reliable method for identification of S. mutans.

Genotypic diversity of Streptococcus mutans in 3- to 4-year-old Chinese nursery children suggests horizontal transmission

OBJECTIVE

The aims of this study were to investigate the colonisation of Streptococcus mutans and to determine the possibility of horizontal transmission in Chinese nursery children.

DESIGN

Fifty-six children aged between 3 and 4 years old from a nursery were included in this study. Twenty-four children were from the day and night nursery class, the others were from the day nursery class. Dental plaque samples were collected with sterile toothpicks and cultured on S. mutans-selective tryptone-yeast-cystine agar supplemented with 0.2U/ml bacitracin and 15% sucrose. The typical isolates of S. mutans were identified by classical microbiological methods and genotyped by arbitrarily primed PCR (AP-PCR) and restriction fragment length polymorphism analysis.

RESULTS

S. mutans was isolated from 41 of the 56 children. The prevalence of S. mutans was higher in the children from day nursery class, compared with the children from day and night nursery class (P<0.05). A total of 140 S. mutans isolates from 41 children were analysed by AP-PCR, and 88 different amplitypes were identified. Of 41 children with S. mutans isolates, 82.9% carried two or more genotypes. Two genotypes of S. mutans were repeatedly isolated among 13 children in the day and night nursery class, and one genotype was isolated from two children in the day nursery class.

CONCLUSION

The presence of matching genotypes of S. mutans among children attending the same nursery suggests the possibility of horizontal transmission.

Identification of genetic differences between two clinical isolates of Streptococcus mutans by suppression subtractive hybridization

Streptococcus mutans is generally considered to be the principal aetiological agent for dental caries. Phenotypic variation in strains is often associated with differences in gene content, so the isolation of DNA fragments from these genes or associated regions is illuminating. The S. mutans strains 9-1 and 9-2, which both colonized the same oral cavity, were selected after screening for the possession of suspected virulence traits. Genomic DNA of strain 9-1 was used as the tester, and that of 9-2 was used as the driver. Suppression subtractive hybridization (SSH) was applied between the tester and the driver DNAs. The subtractive products were cloned into a pCR2.1 vector. Clone libraries representing sequence differences were obtained. The subtractive fragments that were found specifically in strain 9-1 but not in strain 9-2 were identified by dot blotting and then sequenced. BLASTn and BLASTx sequence homology analyses were subsequently performed. Twenty-seven sequences were found in the genome of strain 9-1 that were not in 9-2. Among them, three revealed no homology to published nucleotide sequences while the remaining sequences showed 81-100% homology to known genes of S. mutans strain UA159. These sequences are involved in competence development, signal transduction and transcriptional regulation, repairing stress damage, transport, carbohydrate catabolism, biochemical synthesis, or unknown functions. Differences exist in the genomes of different S. mutans isolates. SSH is effective in screening for S. mutans strain specific DNA sequences.

DNA fingerprinting of isolates of Streptococcus mutans by pulsed-field gel electrophoresis

Forty isolates and five standard laboratory strains, representing serotypes c, e and f of Streptococcus mutans were analyzed by pulsed-field gel electrophoresis (PFGE) after digestion of the genomic DNA with BssH II. The digestion patterns of standard laboratory strains were characteristic of serotypes c, e and f. Serotypes c and f generated diagnostic DNA fragments of approximately 145 kbp and of approximately 130-175 kbp in length, respectively. Serotype e generated a ladder of at least 14 fragments of 15-155 kbp in length. The digestion patterns of isolates were essentially similar to those of the standard laboratory strains. The patterns of almost all isolates obtained from a single individual were identical, but patterns of a few different types were also observed among isolates obtained from two individuals. Digestion with BssH II revealed differences among isolates obtained from different individuals. We used differences in banding patterns among isolates to construct a dendrogram. The dendrogram included two major clusters, one that consisted of isolates of serotypes c and f, and an other that consisted of isolates of serotype e. Our results indicate that BssH II is a useful enzyme for distinguishing among isolates of S. mutans and that digestion patterns obtained by PFGE can be used for chromosomal DNA fingerprinting.

Colonization and vertical transmission of Streptococcus mutans in Turkish children

The aim of the study was to establish the colonization of Streptococcus mutans and to determine the possibility of intra-familial transmission in a group of Turkish children and their parents. A total of 56 children participated in the study together with their parents (20 fathers and 49 mothers). Saliva samples were collected from the individuals and cultivated on S. mutans selective TYCSB agar. The typical isolates of S. mutans were identified by using classical microbiological methods, as well as molecular typing of S. mutans clones which was performed by using AP PCR with OPA5 primer for the detection of transmission. The vertical transmission of salivary S. mutans was detected among 14 mother-father-child, 35 mother-child (one twins) and 6 father-child combinations. The homologies of strain types were recorded as 24% and 16.6% for mother-child and father-child combinations, respectively. A significant positive correlation (p<0.001) was found between the infected children and their parents with high S. mutans counts.

Differentiation of mutans streptococci by intact cell matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

It is difficult to distinguish mutans streptococci on the species level, and even more so on the subspecies level. Intact cell matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) (ICM) was applied to reference strains of five of the species of the mutans group (Streptococcus criceti, Streptococcus downei, Streptococcus mutans, Streptococcus ratti, Streptococcus sobrinus), nonmutans streptococci (Streptococcus oralis, Streptococcus mitis, Streptococcus salivarius, and Streptococcus sanguinis), and 177 mutans streptococci isolated from saliva of 10 children. From the analysis of the reference strains, readily distinguishable ICM mass spectra were obtained for the different species. Based on multivariate statistical analysis, a correct and unambiguous assignment was made of the spectra of 159 isolated mutans streptococci to S. mutans and 16 isolates to S. sobrinus. Two isolates were sorted out and were identified by sequencing of their 16S rRNA genes as Streptococcus anginosus. In addition, ICM indicated a misclassification for some reference strains (AHT, V 100 and E 49) and re-classified AHT and E 49 as S. ratti and V 100 as S. sobrinus. This was confirmed by 16S rDNA sequencing. Based on a statistical similarity analysis of the spectra of reference strains and a quantitative assessment of the reproducibility of ICM, the isolates identified as either S. mutans or S. sobrinus were phenotyped on the subspecies level. In the population of the clinical isolates, 14 unambiguously different S. mutans and three different S. sobrinus phenotypes were detected. ICM proved to be a powerful tool for a differentiation of mutans streptococci down to the subspecies level.

Genotyping of Streptococcus mutans by using arbitrarily primed polymerase chain reaction in children with Down Syndrome

OBJECTIVE

The aim of this study was to compare the caries prevalence between Down Syndrome (DS) and non-DS children and to investigate the difference between the genotypes of Streptococcus mutans (S. mutans) colonized in both DS and non-DS groups.

DESIGN

Sixty children with DS and 64 non-DS children aged between 7 and 12 years old were included to this study. All erupted teeth were evaluated according to the criteria recommended by the World Health Organization. Unstimulated saliva samples were carried out from the children and cultivated on S. mutans selective Tryptone-yeast-cystine (TYC) agar with 0.2 U/ml bacitracin and 15% sucrose. Molecular typing of S. mutans strains was performed by using arbitrarily primed polymerase chain reaction (AP-PCR) with OPA-05 primer. All data were analysed by using SPSS (SPSS Inc., Chicago, IL, USA) 11.0 software program for windows.

RESULTS

The caries index scores were found significantly lower in DS individuals than the non-DS group (p < 0.05). The salivary S. mutans levels between DS and non-DS groups did not show significant difference (p > 0.05). The difference between dental caries and salivary S. mutans levels also was not statistically significant (p > 0.05). According to the results of the AP-PCR typing, all profiles of S. mutans which colonized in DS group were different from the control group. The relationship between these different profiles and dental caries prevalence was statistically significant (p < 0.05).

CONCLUSION

The profiles of S. mutans colonized in DS group might be a reason of low caries prevalence.

Frequency of four different mutacin genes in Streptococcus mutans genotypes isolated from caries-free and caries-active individuals

The ability of Streptococcus mutans to produce mutacins, combined with the production of other virulence factors such as lactic acid, may contribute to the pathogenesis of this bacterium. In the present study, the detection of genes encoding mutacin types I/III, II and IV was performed by PCR with specific primers to each type in a total of 63 S. mutans genotypes isolated from caries-active and caries-free individuals. In the caries-free group, PCR screening for mutacin IV revealed that 31.8% of strains were positive for this mutacin. PCR for the other three mutacins tested (I/III and II) did not yield amplicons in any S. mutans strains in this group. The PCR with primers of mutacin IV showed 68.3% positive genotypes in the caries-active group, on the other hand, the amplicons of mutacins I/III revealed 41.5% positive strains that carried these genes. The chi square test showed significant differences in the number of positive strains to mutacin IV when comparing the caries-free and caries-active genotypes of S. mutans (P = 0.01). All tested S. mutans strains were negative by PCR for mutacin II. The low frequencies of detection of some mutacin genes suggest the existence of high diversity and polymorphism in the production of genetic determinants of mutacin-like substances. In addition, the production of a wide spectrum of mutacins can play an important biological role in colonization by S. mutans strains, mainly in the niche of high-complexity microbial communities.

Longitudinal study of dental caries incidence associated with Streptococcus mutans and Streptococcus sobrinus in pre-school children

Streptococcus mutans and Streptococcus sobrinus are known to be associated with the development of dental caries. In this study these bacteria were detected in pre-school children (each with primary dentition, age range 3-5 years, n = 60) using a PCR method, and then their presence was compared with the incidence of dental caries over a 1-year period. Plaque samples were collected from all erupted tooth sites using a sterile toothbrush. Dental examinations at the beginning of the study (baseline) and after 1 year were also performed to determine decayed, missing, filled teeth (dmft) scores using WHO caries diagnostic criteria. The prevalences of S. mutans and S. sobrinus across all the subjects were 61.7% and 56.6%, respectively; 13 subjects (21.7%) were positive for S. mutans alone, 10 (16.6%) were positive for S. sobrinus alone and 24 (40.0%) were positive for both S. mutans and S. sobrinus, whereas 13 (21.7%) were negative for both S. mutans and S. sobrinus. dmft scores of subjects positive for both S. mutans and S. sobrinus at baseline and after 1 year were significantly higher than of those positive for S. mutans alone at the same stages (P < 0.01 and P < 0.001, respectively). The caries incremental increase was also significantly greater in those with both bacteria detected (P < 0.05). Our results indicate that pre-school children harbouring both S. mutans and S. sobrinus have a significantly higher incidence of dental caries than those with S. mutans alone.

Mutacin production in Streptococcus mutans genotypes isolated from caries-affected and caries-free individuals

Relationships between genetic diversity and mutacin production in Streptococcus mutans were evaluated in 319 clinical isolates from eight caries-affected and eight caries-free individuals. The isolates were submitted to mutacin typing and AP-PCR (arbitrarily primed polymerase chain reaction) assay. The mutacin production was detected for 12 Streptococcus sp. indicator strains. Results showed significant variations in the mutacin production profiles and the inhibitory spectra of both groups. A possible association was seen between mutacin activity and the distinct patterns of Streptococcus sp. colonization in the two groups. Genotyping by AP-PCR using the primers OPA-02 and OPA-13 revealed 101 distinct genotypes against 48 phenotypes identified by mutacin typing. No correlation was observed between the inhibitory spectra of mutacin and genotypic similarities based on AP-PCR analyses. According to our results, strains of the same S. mutans genotype showed different mutacin profiles, suggesting a high degree of interstrain diversity. In conclusion, mutacin production seems to be of clinical importance in the colonization of S. mutans and is highly diversified in the S. mutans species.

Typing of Mutans Streptococci by Arbitrarily Primed PCR in Patients Undergoing Orthodontic Treatment

The aim of this study was to clarify the genotypic stability of mutans streptococci (MS) longitudinally during orthodontic treatment. Plaque samples were obtained from the supragingival smooth surface of the upper right teeth at four stages: prior to and after 1, 3 and 6 months of orthodontic treatment. Levels of total viable count, total streptococci and MS in dental plaque of 17 patients were recorded. Streptococci isolated from dental plaque samples were identified as MS on the basis of their morphological and biochemical properties. DNA was prepared from 713 strains of MS and the strains were then identified with polymerase chain reaction (PCR) again. Arbitrarily primed PCR (AP-PCR) fingerprinting was applied in determining the genotypes of MS. The results indicated that levels of total viable count, total streptococci and MS increased significantly after the fixed appliances were bonded. A maximum of 3 different genotypes were found in an individual. All the genotypes were found again after the application of the fixed appliances in 17 patients. A new AP-PCR typing pattern was found after the application of fixed appliances for 1 month in patient 1. That strain was not detected either prior to or after 3, or 6 months of treatment. The result indicated that the MS clones were very stable during orthodontic treatment.

Longitudinal study of transmission, diversity, and stability of Streptococcus mutans and Streptococcus sobrinus genotypes in Brazilian nursery children

The aim of this study was to perform a follow-up evaluation of the Streptococcus mutans and Streptococcus sobrinus colonization profile of children's oral cavities, which included the pattern of vertical transmission from mother to child, genotypic diversity, and stability of the strains. The subjects were 16 mother-child pairs, who were monitored for 20 months. Samples of saliva, tongue dorsum, alveolar ridge mucosa, and dental plaque from the children were collected bimonthly. Saliva samples from the mothers were also collected. After isolation and identification, the arbitrarily primed PCR method was performed for the genotypic characterization of S. mutans (968 isolates) and S. sobrinus (111 isolates). At the time the strains were acquired, the children harbored one to four distinct genotypes of S. mutans and only one genotype of S. sobrinus. Although S. mutans prevalence and genotypic diversity were greater than those of S. sobrinus, the presence of matching genotypes of S. mutans and S. sobrinus was similar (in 81.25 and 83.33% of mother-child pairs, respectively), suggesting vertical transmission for both species. This longitudinal study showed an increase in genotypic diversity of S. mutans in the oral cavity during the follow-up period: most of the initially acquired genotypes persisted, normally those genotypes transmitted by the mother, and some were lost during follow-up; new strains were also acquired. In conclusion, S. mutans and S. sobrinus genotypes acquired from maternal or alternative sources may show effective persistence in the oral cavity and/or transitory detection in the children's mouths, reflecting the continuous development of oral microbiota in children.

Genotypic diversity and virulence traits of Streptococcus mutans in caries-free and caries-active individuals

The present study evaluated the relationship between clonal diversity and some virulence traits of Streptococcus mutans isolated from eight caries-free and eight caries-active subjects. A total of 155 S. mutans isolates from caries-free subjects and 144 isolates from caries-active subjects were obtained from samples of saliva, dental plaque and tongue surface and identified by PCR. The isolates were submitted to arbitrarily primed (AP)-PCR (OPA-2 and OPA-13) and multilocus enzyme electrophoresis (MLEE) to establish the genotypic diversity. Production of water-insoluble glucan (WIG) (monitored by SDS-PAGE), final pH of cultures and the ability of bacterial cells to adhere to smooth glass in the presence of sucrose were measured. High and comparable abilities of MLEE and AP-PCR were found to distinguish S. mutans genotypes, using Simpson's index of discrimination (0.971 and 0.968, respectively). The results showed a significant difference (P < 0.01) in the number of genotypes when caries-free and caries-active groups were compared by both fingerprinting methods used. Final pH (P = 0.32) and the percentage of adherence to a glass surface (P = 0.62) did not show differences between the two groups; however, the intensities of WIG bands from the caries-active group were greater than those from the caries-free group (P < 0.01). In addition, WIG was positively correlated with the ability of S. mutans to adhere to a glass surface (r = 0.34, P = 0.02) from caries-active subjects. These data showed that AP-PCR analysis and MLEE are both effective methods for assessing the genetic relatedness of S. mutans. Using these techniques, it was found that there is a larger number of genotypes of S. mutans with increased ability to synthesize WIG in caries-active individuals.

Effect of the environment on genotypic diversity of Actinomyces naeslundii and Streptococcus oralis in the oral biofilm

The genotypic diversity of Actinomyces naeslundii genospecies 2 (424 isolates) and Streptococcus oralis (446 isolates) strains isolated from two sound approximal sites in all subjects who were either caries active (seven subjects) or caries free (seven subjects) was investigated by using the repetitive extragenic palindromic PCR. The plaque from the caries-active subjects harbored significantly greater proportions of mutans streptococci and lactobacilli and a smaller proportion of A. naeslundii organisms than the plaque sampled from the caries-free subjects. These data confirmed that the sites of the two groups of subjects were subjected to different environmental stresses, probably determined by the prevailing or fluctuating acidic pH values. We tested the hypothesis that the microfloras of the sites subjected to greater stresses (the plaque samples from the caries-active subjects) would exhibit reduced genotypic diversity since the sites would be less favorable. We found that the diversity of A. naeslundii strains did not change (chi2 = 0.68; P = 0.41) although the proportional representation of A. naeslundii was significantly reduced (P < 0.05). Conversely, the diversity of the S. oralis strains increased (chi2 = 11.71; P = 0.0006) and the proportional representation of S. oralis did not change. We propose that under these environmental conditions the diversity and number of niches within the oral biofilm that could be exploited by S. oralis increased, resulting in the increased genotypic diversity of this species. Apparently, A. naeslundii was not able to exploit the new niches since the prevailing conditions within the niches may have been deleterious and not supportive of its proliferation. These results suggest that environmental stress may modify a biofilm such that the diversity of the niches is increased and that these niches may be successfully exploited by some, but not necessarily all, members of the microbial community.

Determination of mutacin activity and detection of mutA genes in Streptococcus mutans genotypes from caries-free and caries-active children

Relationships between genetic diversity, mutacin production and sensitivity to mutacins in Streptococcus mutans were evaluated in 19 clinical isolates from caries-free and caries-active children. Mutacin production was tested against 30 indicator strains; results showed significant variations in the inhibitory spectra of the clinical isolates. There was no association between the inhibitory spectrum of the infecting strain and the caries experience or the level of mutans streptococci infection of the host. Homology to the mutA gene coding for mutacin II was detected in one clinical isolate; none of the clinical isolates showed homology to the mutA genes coding for mutacins I or III. Genotyping by random amplified polymorphic DNA (RAPD) reactions grouped the isolates into three clusters, but no correlation was found between any of the clusters and mutacin activity, caries experience or level of mutans streptococci in the host.

Tracing genotypes of mutans streptococci on tooth sites by random amplified polymorphic DNA (RAPD) analysis

The aim of this study was to clarify the distribution and persistence of mutans streptococci on different tooth sites in the same oral cavity. Thirteen subjects, aged 20-40 years, were examined. Salivary levels of mutans streptococci, caries prevalence, oral hygiene habits and status of tooth surfaces sampled were recorded. Plaque samples were obtained from four sites, the mesial and buccal surfaces of the first permanent molar on the right side of the lower jaw (46m and 46b), the distal surface of the first permanent premolar (24d) and the mesial surface of the second permanent premolar (25m) on the left side of the upper jaw, using sterile toothpicks on two occasions at 4-7-month intervals. The samples were cultivated on site-specific Strip mutans. Up to 10 colonies/site were isolated when present and genotyped by random amplified polymorphic DNA (RAPD) analysis, after species identification with PCR. Genotyping was also performed by restriction endonuclease analysis (REA) on 148 isolates, and results were consistent with the RAPD results. Most mutans streptococcus-positive samples were obtained from 46m. Within each individual, the same genotype occurred on at least two sites on all but one sampling occasion. A maximum of seven different genotypes were found in an individual. For a particular tooth site, four genotypes occurred simultaneously and taking both sampling occasions together the maximum was six different types. The same genotypes/types were found again after 4-7 months on 25 sites in 12 subjects. Fifteen sites were mutans streptococcus-positive on only one sampling occasion. The results indicate that several different genotypes of mutans streptococci colonize a tooth site, and that the same genotype colonizes several sites in the same oral cavity. Persistence of genotypes on a site for several months and interindividual differences in the occurrence of genotypes were also found.

PCR-Based methods for genotyping viridans group streptococci

Standard repetitive extragenic palindromic (REP)-PCR, enterobacterial repetitive intergenic consensus-PCR, and Salmonella enteritidis repetitive element-PCR methods for bacterial strain typing were performed with DNA extracted by boiling members of each of the currently recognized species of human viridans group streptococci. Each of the methods was reproducible. The unique isolates (n = 72) from 15 species of viridans group streptococci were readily distinguishable, with no two isolates showing greater than 90% per cent similarity. The majority of strains exhibited much less than 90% similarity. Isolates identical by REP-PCR were also identical by the other two methods. These PCR-based typing methods, although they do not permit determination of the species of the isolates, are simple to perform and are suitable for clinical and ecological investigations of viridans group streptococci.

Inducible beta-lactam resistance in Aeromonas hydrophila: therapeutic challenge for antimicrobial therapy

Despite the abundant amount of knowledge about inducible chromosomally mediated beta-lactamases among Aeromonas species, extended-spectrum beta-lactam-resistant A. hydrophila strains selected in clinical practice were rarely reported. In the present study, two strains of A. hydrophila, A136 and A139, with markedly different susceptibilities to extended-spectrum cephalosporins were isolated from blood and the tip segment of an arterial catheter of a burn patient. Another strain (A136m) was selected in vitro by culturing A136 in a subinhibitory concentration of cefotaxime, the beta-lactam agent administered for the treatment of Aeromonas bacteremia in this patient. Typing studies by arbitrarily primed PCR and pulsed-field gel electrophoresis indicated a clonal relationship among strains A136, A136m, and A139. These strains were identified to be of DNA hybridization group 1. Wild-type strain A136 was resistant only to ampicillin and cephamycins, but A136m and A139 were highly resistant to the expanded- and broad-spectrum cephalosporins. The presence of increased beta-lactamase activity in A139 suggests that A139 is a derepressed mutant which overexpresses beta-lactamases. These results call attention to the use of beta-lactam agents for the treatment of invasive Aeromonas infections.

Colonization with mutans streptococci and lactobacilli and the caries experience of children after the age of five

Some authors suggest that there is a "window of infectivity" for mutans streptococci (MS) at an early age, after which colonization is not likely to occur. Moreover, children with low or non-detectable levels of MS at an early age are at lower risk for caries. It was our aim to study caries experience and colonization with MS and lactobacilli in a group of children at 11 years of age who had been documented to have been MS-free until 5 years of age. For this group, the mfs and MFS values at 11 years of age were found to be 1.12+/-2.81 and 0.44+/-0.88, respectively. These values are much lower than those of a control group of 11-year-old children who had always been MS-positive since the age of 2, being 3.10+/-3.43 and 1.20+/-1.91, respectively. Of the 30 children without detectable MS up to the age of 5, 22 had acquired MS at 11 years of age, but their MS counts were significantly lower than those of the control group. No correlation was observed between the levels of MS of the children and the mothers. In children at 11 years of age, no differences were found in the numbers of lactobacilli and sugar intakes per week between the children MS-free and the children MS-colonized at 5 years of age. The present study indicates that the acquisition of MS is still possible after the so-called "window of infectivity" and that a delayed acquisition of MS may reduce the caries experience in the primary and permanent dentition at a later age.

Current classification of the oral streptococci

The classification of the oral streptococci has long remained a difficult area of streptococcal taxonomy. This article reviews the current classification of these bacteria into four species groups, and each group is described in detail. The often confusing changes that have taken place in the classification, identification and nomenclature of the member species are reviewed against a historical background of gradually improving techniques and approaches, leading towards a natural classification based primarily on genotypic evidence. Identification schemes currently in use employing biochemical tests are also reviewed, together with alternative molecular approaches.