Transmission of oral bacterial species between spouses

The human oral phageome

Oral bacteriophages (or phages), especially periodontal ones, constitute a growing area of interest, but research on oral phages is still in its infancy. Phages are bacterial viruses that may persist as intracellular parasitic deoxyribonucleic acid (DNA) or use bacterial metabolism to replicate and cause bacterial lysis. The microbiomes of saliva, oral mucosa, and dental plaque contain active phage virions, bacterial lysogens (ie, carrying dormant prophages), and bacterial strains containing short fragments of phage DNA. In excess of 2000 oral phages have been confirmed or predicted to infect species of the phyla Actinobacteria (>300 phages), Bacteroidetes (>300 phages), Firmicutes (>1000 phages), Fusobacteria (>200 phages), and Proteobacteria (>700 phages) and three additional phyla (few phages only). This article assesses the current knowledge of the diversity of the oral phage population and the mechanisms by which phages may impact the ecology of oral biofilms. The potential use of phage-based therapy to control major periodontal pathogens is also discussed.

Porphyromonas spp. have an extensive host range in ill and healthy individuals and an unexpected environmental distribution: A systematic review and meta-analysis

Studies on the anaerobic bacteria Porphyromonas, mainly focused on P. gingivalis, have revealed new bacterial structures, metabolic pathways, and physiologic functionalities. Porphyromonas are mainly described as being associated with mammals and involved in chronic oral infections and secondary pathologies such as cancers or neurodegenerative diseases. In this review, we collected and analyzed information regarding Porphyromonas isolation sites and associated conditions and showed that Porphyromonas are detected in numerous pristine and anthropic environments and that their host range appears wider than previously believed, including aquatic animals, arthropods, and birds, even if their predominant hosts remain humans, pets, and farm animals. Our analyses also revealed their presence in multiple organs and in a substantial proportion of healthy contexts. Overall, the growing numbers of microbiota studies have allowed unprecedented advances in the understanding of Porphyromonas ecology but raise questions regarding their phylogenic assignment. In conclusion, this systematic and meta-analysis provides an overview of current knowledge regarding Porphyromonas ecological distribution and encourages additional research to fill the knowledge gaps to better understand their environmental distribution and inter- and intra-species transmission.

The Oral Microbiota

The oral microbiota represents an important part of the human microbiota, and includes several hundred to several thousand diverse species. It is a normal part of the oral cavity and has an important function to protect against colonization of extrinsic bacteria which could affect systemic health. On the other hand, the most common oral diseases caries, gingivitis and periodontitis are based on microorganisms. While (medical) research focused on the planktonic phase of bacteria over the last 100 years, it is nowadays generally known, that oral microorganisms are organised as biofilms. On any non-shedding surfaces of the oral cavity dental plaque starts to form, which meets all criteria for a microbial biofilm and is subject to the so-called succession. When the sensitive ecosystem turns out of balance - either by overload or weak immune system - it becomes a challenge for local or systemic health. Therefore, the most common strategy and the golden standard for the prevention of caries, gingivitis and periodontitis is the mechanical removal of this biofilms from teeth, restorations or dental prosthesis by regular toothbrushing.

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.

Pathogenicity of the highly leukotoxic JP2 clone of Aggregatibacter actinomycetemcomitans and its geographic dissemination and role in aggressive periodontitis

For decades, Aggregatibacter actinomycetemcomitans has been associated with aggressive forms of periodontitis in adolescents. In the middle of the 1990s, a specific JP2 clone of A. actinomycetemcomitans, belonging to the cluster of serotype b strains of A. actinomycetemcomitans and having a number of other characteristics, was found to be strongly associated with aggressive forms of periodontitis, particularly in North Africa. Although several longitudinal studies still point to the bacterial species, A. actinomycetemcomitans as a risk factor of aggressive periodontitis, it is now also widely accepted that the highly leukotoxic JP2 clone of A. actinomycetemcomitans is implicated in rapidly progressing forms of aggressive periodontitis. The JP2 clone strains are highly prevalent in human populations living in Northern and Western parts of Africa. These strains are also prevalent in geographically widespread populations that have originated from the Northwest Africa. Only sporadic signs of a dissemination of the JP2 clone strains to non-African populations have been found despite Africans living geographically widespread for hundreds of years. It remains an unanswered question if a particular host tropism exists as a possible explanation for the frequent colonization of the Northwest African population with the JP2 clone. Two exotoxins of A. actinomycetemcomitans are known, leukotoxin (LtxA) and cytolethal distending toxin (Cdt). LtxA is able to kill human immune cells, and Cdt can block cell cycle progression in eukaryotic cells and thus induce cell cycle arrest. Whereas the leukotoxin production is enhanced in JP2 clone strains thus increasing the virulence potential of A. actinomycetemcomitans, it has not been possible so far to demonstrate such a role for Cdt. Lines of evidence have led to the understanding of the highly leukotoxic JP2 clone of A. actinomycetemcomitans as an aetiological factor of aggressive periodontitis. Patients, who are colonized with the JP2 clone, are likely to share this clone with several family members because the clone is transmitted through close contacts. This is a challenge to the clinicians. The patients need intense monitoring of their periodontal status as the risk for developing severely progressing periodontal lesions are relatively high. Furthermore, timely periodontal treatment, in some cases including periodontal surgery supplemented by the use of antibiotics, is warranted. Preferably, periodontal attachment loss should be prevented by early detection of the JP2 clone of A. actinomycetemcomitans by microbial diagnostic testing and/or by preventive means.

Comparison of mutans streptococcal strains of father, mother, and child in indian families using chromosomal DNA fingerprinting

INTRODUCTION

It is now understood and accepted that there is a direct transmission of mutans streptococci (MS) from the mother to the child. There is also a direct correlation between the levels of MS in the mother and the caries status of the child. Advanced technologies in molecular biology like chromosomal DNA fngerprinting have established beyond doubt that the mother and the child bear similar strains of MS.

AIM

A study was designed with the aim of comparing the MS strains between the father, mother and the child in Indian families.

MATERIALS AND METHODS

A group of 20 Indian families comprising of the father, mother and child were selected and divided into caries free and caries active groups. Mixed salivary samples were collected from the individuals and were cultured for the growth of Mutans streptococci. The colonies were counted on a colony counter and a comparison was made between the mutans streptococcal counts of the mother and the caries status of the child. Further, the genotypes of the father, mother and the child were isolated and compared using the technique of chromosomal DNA fngerprinting. Following electrophoresis, the band pattern obtained was compared for similarities or differences. The results of the same were tabulated and evaluated statistically.

RESULTS

When the colony counts of the mother (in CFU/ml) were compared with the 'dft' status of the child, a positive correlation was seen in group II. Intergroup comparison using the unpaired T test was statistically signifcant. Electrophoretic analysis of the chromosomal DNA on the agarose gels revealed identical band patterns in 13 mother-child pairs, which was statistically signifcant. Three of the father-child pairs showed identical band patterns, which was statistically signifcant. Intergroup comparison using Chi-square test was not statistically signifcant.

CONCLUSION

One may conclude that irrespective of the caries status of the child, majority of the mother child pairs share identical strains of MS and hence the mother is the primary source of infection. However, in children with a high dft, the father may also play an important role in the acquisition and transmission of MS.

Genomic Stability of Aggregatibacter actinomycetemcomitans during Persistent Oral Infection in Human

The genome of periodontal pathogen Aggregatibacter actinomycetemcomitans exhibits substantial variations in gene content among unrelated strains primarily due to the presence or absence of genomic islands. This study examined the genomic stability of A. actinomycetemcomitans during its persistent infection in the same host. Four pairs of A. actinomycetemcomitans strains, each pair isolated from an individual over time (0–10 years), were examined for their gains/losses of genes by whole genome sequencing, comparative genomic hybridization by microarray and PCR analysis. Possible effects due to genomic changes were further assessed by comparative transcriptome analysis using microarrays. The results showed that each pair of strains was clonally identical based on phylogenetic analysis of 150 core genes. A novel 24.1-Kb plasmid found in strain S23A was apparently lost in the sibling strain I23C. A 353-bp inversion affecting two essential genes of the serotype-specific gene cluster was found in the serotype antigen-nonexpressing strain I23C, while the same gene cluster was intact in the serotype-expressing sibling strain S23A. A 2,293-bp deletion affecting a gene encoding oxaloacetate decarboxylase and its neighbor region was found in strain SCC2302 but not in the sibling strain AAS4a. However, no evidence of gains or losses of genomic islands was found in the paired strains. Transcriptome profiles showed little or no difference in the paired strains. In conclusion, the genome of A. actinomycetemcomitans appears to be relatively stable during short-term infection. Several types of genomic changes were observed in the paired strains of A. actinomycetemcomitans recovered from the same subjects, including a mutation in serotype-specific gene cluster that may allow the bacteria to evade host immune response.

Horizontal transmission of Streptococcus mutans in schoolchildren

Objetive: The aim of this study was to analyze possible horizontal transmission patterns of S. mutans among 6-7-yr-old schoolchildren from the same class, identifying genotypes and their diversity and relationship with caries disease status. Study Design: Caries indexes and saliva mutans streptococci and lactobacilli counts were recorded in 42 schoolchildren. Mutans streptococci colonies were identified by means of biochemical tests and all S. mutans strains were genotyped by arbitrarily primed polymerase chain reaction. A child was considered free of S. mutans when it could not be isolated in 3 samples at 1-week intervals. Results: S. mutans was isolated in 30 schoolchildren: 20 having one genotype and 10 two genotypes. Higher mutans streptococci and caries index values were found in those with two genotypes. Five genotypes were isolated in more than 1 schoolchild and one of these was isolated in 3 schoolchildren. Our results suggest that horizontal transmission may take place. Conclusion: Schoolchildren aged 6-7 yrs may be the source of mutual transmission of S. mutans.

Key words:Streptococcus mutans, Horizontal transmission, AP-PCR, genotyping

Five questions about Streptococcus mutans: theoretical study of its transmission and colonisation

PURPOSE

This theoretical study aimed to identify the decisive (and controllable) factors involved in Streptococcus mutans (Sm) infection through addressing questions about (i) the time and prevalence pattern (including the raison d'etre of the discrete period for the infection or WI) of initial Sm colonisation and (ii) the infant's selection of bacterial types and their diversity, which are not yet definitely answered by empirical works.

METHOD

A model of Sm infection (within-host type) was developed. For questions (i): using the basic model, stochastic simulation was performed to reproduce longitudinal observations of the initial colonisation time. A symmetrical or right-skewed gamma distribution was assumed for the maximum colonisable area (K(max)) and transmission rate (mx). Additionally, 3 or 4 developmental modes of colonisable area [K(t)] were assigned based on the K(max) value. For (ii): by extending the basic model to the two-bacterial type model, intraspecific competition analysis focusing on the differences in mx (received by the infancy) and colonisation ability (θD) was performed.

RESULTS

The basic model simulation showed that mx and K(t) played a pivotal role in determining the individual time of initial colonisation and their variations among infants in forming its prevalence patterns (with or without WI). The competition model simulation showed that higher mx could be more advantageous in competitive colonisation than higher θD under repeated invasions. Accordingly, it played a decisive role in infant's selection of initially, persistently and transiently colonising bacterial types, and thus in their diversity.

CONCLUSIONS

(i) The mx is the primary and controllable (risk) factor that extensively affects various aspects of the Sm infection process. (ii) Also, the growing carrying capacity, i.e., K(t) is another important factor when considering how to effectively delay the onset of the colonisation. (iii) Thus, currently, the most feasible and effective control measure for the infection should be microbiological interventions in the primary host with concurrent oral hygiene and dietary control in the exposed child.

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.

Prospective study of potential sources of Streptococcus mutans transmission in nursery school children

Transmission of Streptococcus mutans, a major dental caries pathogen, occurs mainly during the first 2.5 years of age. Children appear to acquire S. mutans mostly from their mothers, but few studies have investigated non-familial sources of S. mutans transmission. This study prospectively analysed initial S. mutans oral colonization in 119 children from nursery schools during a 1.5-year period and tracked the transmission from child to child, day-care caregiver to child and mother to child. Children were examined at baseline, when they were 5-13 months of age, and at 6-month intervals for determination of oral levels of S. mutans and development of caries lesions. Levels of S. mutans were also determined in caregivers and mothers. A total of 1392 S. mutans isolates (obtained from children, caregivers and mothers) were genotyped by arbitrarily primed PCR and chromosomal RFLP. Overall, 40.3 % of children were detectably colonized during the study, and levels of S. mutans were significantly associated with the development of caries lesions. Identical S. mutans genotypes were found in four nursery cohorts. No familial relationship existed in three of these cohorts, indicating horizontal transmission. Despite high oral levels of S. mutans identified in most of the caregivers, none of their genotypes matched those identified in the respective children. Only 50 % of children with high levels of S. mutans carried genotypes identified in their mothers. The results support previous evidence indicating that non-familial sources of S. mutans transmission exist, and indicate that this bacterium may be transmitted horizontally between children during the initial phases of S. mutans colonization in nursery environments.

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.

Genotypic characterization of Porphyromonas gingivalis isolated from subgingival plaque and blood sample in positive bacteremia subjects with periodontitis

AIM

The objective of this study was to investigate clonal relationship among Porphyromonas gingivalis isolated from subgingival plaque and blood samples in positive transient bacteremia subjects with periodontitis.

MATERIAL AND METHODS

Unrelated patients with general chronic periodontitis or general aggressive periodontitis requiring scaling and root planing (SRP) were included in the study. Genotyping of each isolate was performed using pulsed field gel electrophoresis technique. Genetic relatedness of strains isolated within an individual or between different patients was determined by dendogram analysis.

RESULTS

Following SRP, from 16 patients, seven patients showed positive P. gingivalis bacteremia and nine were negative. Thirty-two strains were isolated from subgingival plaque and blood samples before and during induced transient bacteremia. The majority of the patients harboured one clonal type. Two patients showed different clones in plaque and blood samples suggesting that more than one clone can be found in subgingival plaque. P. gingivalis isolates from periodontitis patients after transient bacteremia following SRP, revealed a high heterogeneity among isolates.

CONCLUSION

In 6/16 subjects the same P. gingivalis isolate was found in the blood and in oral cavity. P. gingivalis heterogeneity suggests no association of a unique clonal type with transient bacteremia.

Java project on periodontal diseases: a study on transmission of Porphyromonas gingivalis in a remote Indonesian population

AIM

To study transmission of Porphyromonas gingivalis in a population living in a remote area in Southern Java, Indonesia.

MATERIAL AND METHODS

Subgingival plaque samples from 167 subjects with varying degrees of periodontal breakdown were obtained and cultured for the presence of P. gingivalis. After extraction and purification of bacterial DNA, amplified fragment length polymorphism technique was applied to genotype the bacterial isolates. Computer-assisted analysis of the bacterial DNA profiles was used to study distribution of P. gingivalis genotypes within family units.

RESULTS

One hundred and five of the 167 (63%) subjects were culture positive for P. gingivalis. In total, 371 P. gingivalis isolates were obtained from the 105 subjects. Of the 105 subjects, 30 were siblings representing 13 families. In six of the 13 families (46%), identical P. gingivalis genotypes were found among siblings. In the study group of 105 subjects, 13 married couples were identified of which both spouses were culture positive for P. gingivalis. None of the 13 couples shared an identical P. gingivalis genotype. Twenty P. gingivalis-positive subjects had spouses that were culture negative for P. gingivalis.

CONCLUSIONS

In this study population, vertical transmission of P. gingivalis has occurred within family units, most likely from parents to children. Transmission of P. gingivalis between spouses could not be established.

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.

Clonal diversity and turnover of Streptococcus mitis bv. 1 on shedding and nonshedding oral surfaces of human infants during the first year of life

Streptococcus mitis bv. 1 is a pioneer colonizer of the human oral cavity. Studies of its population dynamics within parents and their infants and within neonates have shown extensive diversity within and between subjects. We examined the genetic diversity and clonal turnover of S. mitis bv. 1 isolated from the cheeks, tongue, and primary incisors of four infants from birth to 1 year of age. In addition, we compared the clonotypes of S. mitis bv. 1 isolated from their mothers' saliva collected in parallel to determine whether the mother was the origin of the clones colonizing her infant. Of 859 isolates obtained from the infants, 568 were unique clones. Each of the surfaces examined, whether shedding or nonshedding, displayed the same degree of diversity. Among the four infants it was rare to detect the same clone colonizing more than one surface at a given visit. There was little evidence for persistence of clones, but when clones were isolated on multiple visits they were not always found on the same surface. A similar degree of clonal diversity of S. mitis bv. 1 was observed in the mothers' saliva as in their infants' mouths. Clones common to both infant and mothers' saliva were found infrequently suggesting that this is not the origin of the infants' clones. It is unclear whether mucosal immunity exerts the environmental pressure driving the genetic diversity and clonal turnover of S. mitis bv. 1, which may be mechanisms employed by this bacterium to evade immune elimination.

Transmission of periodontal bacteria and models of infection

BACKGROUND

Bacteria play an essential role in the aetiology of periodontitis. Most bacterial species isolated from subgingival plaque are indigenous to the oral cavity. Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis are detected infrequently in periodontal health, which makes these species prime candidates to study person-to-person transmission. The aim of the present study was to review the literature on transmission of these periodontal bacterial species.

METHOD

We review the literature on bacterial typing techniques and summarize the information on clonal distribution of A. actinomycetemcomitans and P. gingivalis in family units based on different typing techniques in order to establish the likelihood for person-to-person transmission of these periodontal pathogens.

RESULTS

Vertical transmission of A. actinomycetemcomitans is estimated to be between 30% and 60%, whereas vertical transmission of P. gingivalis has rarely been observed. Horizontal transmission between spouses ranges between 14% and 60% for A. actinomycetemcomitans and between 30% and 75% for P. gingivalis. There is some evidence to show that cohabitation with a periodontitis patient influences the periodontal status of the spouse; however, substantially more information is needed to prove this hypothesis.

CONCLUSIONS

Transmission of putative periodontal pathogens between family members has been shown. The clinical consequences of these events have been poorly documented. Based on the current knowledge, screening for and prevention of transmission of specific virulent clones of A. actinomycetemcomitans may be feasible and effective in preventing some forms of periodontal disease. P. gingivalis is usually recovered from diseased adult subjects, and transmission of this pathogens seems largely restricted to adult individuals. Horizontal transmission of P. gingivalis may therefore be controlled by periodontal treatment involving elimination or significant suppression of the pathogen in diseased individuals and by a high standard of oral hygiene.

Transmission of Streptococcus mutans in a group of Turkish families

BACKGROUND/AIMS

To investigate the transmission of Streptococcus mutans in a group of Turkish families using AP-polymerase chain reaction (PCR) detection.

METHODS

Eight mothers who had high S. mutans levels in unstimulated saliva and 8 children aged between 2 and 3 years participated in the study. Plaque samples from each child were collected with the tips of sterile toothpicks for S. mutans counts. Although not part of the original study design, S. mutans samples were also obtained from the unstimulated saliva of the three fathers who shared the same households. Three typical isolates of S. mutans were isolated from TYCSB agar of each subject and identified by sugar fermentation tests. S. mutans ATCC 10449 was used as the reference strain. AP-PCR was conducted with OPA-05 primer.

RESULTS

All of the mothers and fathers shared the similar genotypes within their children. The fathers also harbored similar genotypes to their spouses.

CONCLUSION

The mothers or the fathers could be the source for the transmission of S. mutans to their children.

Longitudinal study of intrafamilial mutans streptococci ribotypes

To explore the intrafamilial homology and longitudinal stability of colonization by early acquired mutans streptococci, genomic fingerprinting was performed on 254 strains (192 Streptococcus mutans and 62 Streptococcus sobrinus strains) collected from 16 families (16 mother-child pairs, seven fathers and four siblings). Genomic DNA was digested by the restriction endonuclease HindIII, followed by gel electrophoresis, Southern blotting, and hybridization with a digoxigenin-labeled 16S rDNA probe, and hybrid detection by enhanced chemiluminescence. One to five ribotypes were identified per person, and between two and nine (median five) within each family. Fourteen of the 16 mother-child pairs showed homology for at least one ribotype (range 1-4). Six of the seven father-child pairs had one ribotype in common. Ten of the 13 longitudinally examined children showed persistence of at least one ribotype over a period of up to 16 yr. The results support the notion of intrafamilial transfer of mutans streptococci, and suggest that colonization of early acquired strains persists into young adulthood.

Relationship Between Transmission ofPorphyromonas gingivalisandfimAType in Spouses

BACKGROUND

Porphyromonas gingivalis is one of the major microbial pathogens associated with chronic periodontitis. To eradicate such pathogens by periodontal therapy, it is essential to clarify the source of infection. Recent findings suggest that the genotype of the fimbriae is one of the important factors in infection by P. gingivalis. The objectives of the present study were to investigate the transmission of P. gingivalis between spouses and to determine the relationship between P. gingivalis fimA type and colonization.

METHODS

A total of 14 couples were selected to investigate the transmission of P. gingivalis and its association with the fimA types. To examine the distribution of fimA type in the general population, 32 subgingival plaque samples from 47 patients with periodontitis were also tested. The transmission of P. gingivalis strains was determined by using pulsed field gel electrophoresis (PFGE). P. gingivalis strains isolated from the couples and subgingival dental plaque samples were studied for fimA classification.

RESULTS

The PFGE patterns of P. gingivalis strains from matched husbands and wives were identical for six of the 14 couples. In five of these six couples (83.3%), P. gingivalis strains harboring the type II fimA gene were present. The proportion of type II fimA in the strains isolated from couples with probable intrafamilial transmission was significantly higher than that in patients with periodontitis or in the group of samples isolated from one member of a couple.

CONCLUSION

This study suggests that fimA type II, even though widely distributed in patients with periodontitis, may be an important factor in the transmission of P. gingivalis between spouses.

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.

Microbiological composition of whole saliva and caries experience in minority populations

Microbiological factors in whole saliva, previously implicated in dental caries formation, were studied in four caries-positive adult ethnic groups: Asians, blacks, whites, and Hispanics. Whole saliva was collected from each patient and used for the enumeration of total cultivable microflora (T), streptococci, mutans streptococci (MS), and lactobacilli. In the female subgroup, statistically significant differences were found among the ethnic groups with regard to T in saliva. In the male subgroup, statistically significant differences were found among the ethnic groups with regard to MS in saliva. Statistically significant differences were also found among the ethnic groups in relation to caries score (DMFS), with the Hispanic group having the highest mean DMFS score; and among socioeconomic groups with regard to MS in saliva. Moreover, microbial composition (T and MS) of whole saliva and DMFS scores differed significantly (P < 0.05) among the ethnic groups studied.

Periodontopathogens in the saliva and subgingival dental plaque of a group of mothers

The aim of this study was to assess the periodontal condition and the presence of putative periodontal pathogens in 30 Brazilian mothers, aging 21-40 years (28.4 4.49 years), and in their children, aging 5-6 years, since mothers can be a source of pathogens and, thus, influence their children's bacteriological and clinical condition. Besides assessing the plaque index (PI), gingival index (GI) and pocket probing depth (PD), the survey analyzed four subgingival dental plaque samples from mothers and children, as well as a sample of stimulated saliva from mothers. Those samples were analyzed by means of the slot immunoblot (SIB) technique, in order to determine the presence of Actinobacillus actinomycetemcomitans (Aa), Prevotella nigrescens (Pn), Porphyromonas gingivalis (Pg) and Treponema denticola (Td). The mean values and standard deviations of the evaluated clinical variables for mothers and children were, respectively: 1.86 0.67 and 1.64 0.68 for PI, and 1.24 0.67 and 0.82 0.37, for GI. Only for mothers, the total PD was 1.81 0.69 mm, and the PD of four sites was 4.03 1.40 mm. The Wilcoxon test revealed significant difference (p < 0.05) between mothers and their children only as to GI. The most prevalent bacteria in mothers were, in decreasing order: Aa, Pn, Pg and Td. The children presented patterns of oral hygiene and bacterial profiles similar to those of their mothers, in spite of the fact that most of them did not present enough subgingival plaque for testing. The comparison between mothers' subgingival dental plaque and saliva samples revealed statistically significant differences (p < 0.05) for all bacteria, with greater positivity and scores in the saliva, which demonstrates that it is an indicator of oral colonization and can work as a vehicle for the transmission of periodontopathogens from mothers to their children.

Actinobacillus actinomycetemcomitans in a rural adult population in southern Thailand

The prevalence of Actinobacillus actinomycetemcomitans isolates was examined in a rural population of southern Thailand. Sixty individuals aged 30-39 and 50-59 years were randomly selected from a group of 363 persons, living in four villages, who had been clinically examined previously. A subgingival plaque sample was taken with a curette from the mesial aspect of the two upper and lower first molars. Each sample was dispersed in 3.3 ml of VMGA III transport medium and spread onto Trypticase Soy Broth with Bacitracin and Vancomycin (TSBV)-agar plates on the same day. After incubation in 10% CO2 for 5 days the plates were examined for typical A. actinomycetemcomitans colonies which were tested for catalase activity. Each strain was further tested for biochemical characteristics, serotyped against serotype-specific antisera a-e and ribotyped after DNA digestion using the restriction endonucleases HindIII and EcoRI. For 53 (88%) of the 60 individuals, A. actinomycetemcomitans was present in at least one subgingival sample, which is considerably higher than the prevalence in Western European adults. In 11 individuals, two or three different strains were found. Serotypes a and c were the most prevalent, and serotype b was found only once among 46 tested isolates. Eleven ribotypes were found among the 46 strains. While the same ribotype could be found among individuals of the same village, no ribotype of A. actinomycetemcomitans was unique for individuals of any one village. The study demonstrated a high prevalence of A. actinomycetemcomitans among adults of the rural population of southern Thailand and indicates that this species is present as part of the resident oral flora in this population.

The effects of toothpastes on the residual microbial contamination of toothbrushes

BACKGROUND

Contaminated toothbrushes have been shown to harbor and transmit viruses and bacteria. The authors conducted a study to evaluate the effect of a triclosan-containing toothpaste on the residual anaerobic microbial contamination of toothbrushes.

METHODS

Twenty patients who had Type III or Type IV periodontitis participated in this study. One side of each of their mouths served as a control (no toothpaste). The teeth on the other side were brushed with a regular toothpaste or a triclosan-containing toothpaste. After the toothbrushes were allowed to dry in air for four hours, the authors placed the toothbrush heads in solution, dislodged the microbes from the brushes by vortexing and plated them in culture dishes. The authors anerobically incubated the culture dishes and determined the presence or absence of Prevotella species or Ps; Porphyromonas gingivalis, or Pg; and Actinobacillus actinomycetemcomitans, or Aa.

RESULTS

The authors detected Aa and Pg on the control toothbrushes more frequently than they did Ps. This variation in isolation frequency was statistically significant by chi 2 analysis (P < .001). The authors compared the isolation frequency of the three test organisms between the control and regular-toothpaste groups, between the control and triclosan-containing--toothpaste groups, and between the triclosan-containing--toothpaste and regular-toothpaste groups. They found no significant intergroup differences in the isolation frequencies after using chi 2 analysis.

CONCLUSIONS

Toothpaste use reduced the residual microbial contamination for two of three test organisms, but the lower isolation frequencies were not statistically significant. Further study in this area is indicated.

CLINICAL IMPLICATIONS

Dental professionals should advise patients who have systemic, localized or oral inflammatory diseases to disinfect or frequently replace their toothbrushes.

Genotypic diversity of mutans streptococci in Brazilian nursery children suggests horizontal transmission

Streptococcus mutans strains were isolated from cohorts of Brazilian nursery school children and genotyped by arbitrarily primed PCR and restriction fragment length polymorphism analysis. Of 24 children with two to five S. mutans isolates, 29% carried two or more genotypes. The presence of matching genotypes of S. mutans among children attending one nursery suggests horizontal transmission.

Evidence for the role of highly leukotoxic Actinobacillus actinomycetemcomitans in the pathogenesis of localized juvenile and other forms of early-onset periodontitis

BACKGROUND

Actinobacillus actinomycetemcomitans leukotoxin is thought to be an important virulence factor in the pathogenesis of localized juvenile and other forms of early-onset periodontitis. Some highly leukotoxic A. actinomycetemcomitans strains produce 10 to 20 times more leukotoxin than other minimally leukotoxic strains. The distribution, clonality, and intrafamilial transmission of highly leukotoxic A. actinomycetemcomitans were examined in order to determine the importance of leukotoxin in the pathogenesis of periodontitis.

METHODS

The polymerase chain reaction (PCR) was used to differentiate highly leukotoxic from minimally leukotoxic strains in examining 1,023 fresh A. actinomycetemcomitans isolates and strains from our culture collection. These were obtained from 146 subjects including 71 with localized juvenile periodontitis (LJP), 4 with early-onset periodontitis, 11 with post-localized juvenile periodontitis, 41 with adult periodontitis, and 19 periodontally normal subjects. The arbitrarily primed polymerase chain reaction (AP-PCR) analysis of 30 oral isolates from each of 25 subjects was used to determine the intraoral distribution of A. actinomycetemcomitans clones. AP-PCR was also used to examine the transmission of A. actinomycetemcomitans in 30 members of 6 families. The clonality of 41 highly leukotoxic A. actinomycetemcomitans strains was evaluated by both AP-PCR and ribotyping.

RESULTS

Highly leukotoxic A. actinomycetemcomitans was found only in subjects with localized juvenile and early-onset periodontitis. Fifty-five percent of the LJP subjects harbored highly leukotoxic A. actinomycetemcomitans isolates. Seventy-three percent of the A. actinomycetemcomitans isolates in these subjects were highly leukotoxic. Highly leukotoxic A. actinomycetemcomitans infected younger subjects (mean age 13.95 years, range 5 to 28 years) than minimally leukotoxic (mean age 35.47 years, range 6 to 65 years). Most subjects were infected with only one A. actinomycetemcomitans genotype. However, PCR of whole dental plaques and subsequent analysis of up to 130 individual oral isolates suggested a possible shift in A. actinomycetemcomitans over time in that a few subjects harbored both highly leukotoxic and minimally leukotoxic strains. AP-PCR analysis was consistent with intrafamilial A. actinomycetemcomitans transmission. Ribotyping and AP-PCR analysis confirmed a previous report that highly leukotoxic A. actinomycetemcomitans consists of a single clonal type.

CONCLUSIONS

This study suggests that localized juvenile and other forms of Actinobacillus-associated periodontitis are primarily associated with the highly leukotoxic clone of A. actinomycetemcomitans.

Viridans-group streptococcal infections in immunocompromised hosts

Viridans streptococci, a diverse group of streptococcal species, are important causes of sepsis and pneumonia in the neutropenic host and sepsis and meningitis in the neonate. The oral mucosa is the most common portal of entry. Among the factors that predispose to development of viridans streptococcal sepsis are: profound neutropenia; mucositis, especially oral mucositis; cytarabine (Ara-C) therapy, which seems to have an effect beyond its association with mucositis; young age; and trimethoprim-sulphamethoxazole or quinolone administration. Fever is usually more than 39 degrees C and prolonged for several days even though blood cultures are typically negative after 24 h of therapy. The majority of patients recover uneventfully if appropriate therapy is initiated early. However, fulminant septic shock may occasional occur at onset. Delayed shock 2 or 3 days after presentation may also occur despite administration of microbiologically effective antibiotics. In severe cases, adult respiratory distress syndrome may be manifested two or three days after the initial bacteremia. There is considerable variability among institutions, but the median death rate associated with viridans streptococcal sepsis is about 10%. Local susceptibility patterns should be used to guide initial therapy for suspected viridans streptococcal infections. Some isolates of viridans streptococci are resistant to penicillins and cephalosporins, in which case vancomycin is preferred. Recurrence during subsequent neutropenic episodes is not unusual.

Intrafamilial Transmission of Black-pigmented, Putative Periodontal Pathogens

Porphyromonas gingivalis and Prevotella intermedia are black-pigmented, putative periodontopathogenic bacteria considered to cause some forms of periodontal disease. Porphyromonas gingivalis and P. intermedia can be transmitted between humans and produce periodontal disease in susceptible hosts. In this article, studies using molecular typing methods for determining the transmission of black-pigmented, putative periodontopathogens between family members are reviewed. As individuals living close to each other are more prone to transmit bacteria, the studies on transmission of periodontopathogens have been performed on family members. It has been shown that black-pigmented bacteria are not only transferred between spouses but also between parents and child. Since only a limited number of studies have been done, longitudinal and controlled studies should be carried out to elucidate further the transmittance potential of these bacteria.

Assessment of familial patterns of microbial infection in periodontitis

The purpose of this article is to review approaches to the assessment of familial patterns of microbial infection and disease in periodontitis, and to identify statistical methods appropriate to such considerations of family data. Previous studies have provided evidence for the presence of familial aggregation of periodontal pathogens and periodontitis and have alluded to possible transmissibility of these organisms within families. Modern statistical techniques permit the appropriate analysis of the correlated data inherent in families, properly allowing for these statistical dependencies while including the possibility of adjustment for risk factors which may also aggregate in families. Such approaches as multiple linear regression, multivariate logistic regression, and regressive modeling provide the necessary tools to assess the familial aggregation of risk factors and disease in periodontitis. In particular, regressive models permit the analysis of familiality (membership to family) as a risk factor without reference to a specific underlying biologic mechanism, and also permit the possibility of adjustment for covariates, such as age and access to dental care. They also allow consideration of specific mechanisms, e.g., susceptibility genes of major effect. Using such techniques, it is possible to more completely explore and describe familial patterns of periodontal infection and other aspects of periodontal disease.

Milestones in periodontal research and the remaining critical issues

A significant recent development in periodontal research has been the convergence of basic and clinical research resulting in a logarithmic increase in the rate of progress. Scientific consensus has been reached in many areas. In most populations, moderate to severe periodontitis affects a relatively small segment of adults who are at high risk. The microbial etiology is accepted and the identity of the major pathogenic bacterial species is known. The mechanisms through which resistant individuals successfully fend off the microbial challenge are known, and the immuno-inflammatory pathways activated by bacteria that underlie destruction of the alveolar bone and the connective tissues of the periodontium are reasonably well understood. The evidence shows that these pathways are held in common by all forms of periodontitis. Therapeutic modulation of these pathways is now possible, and new treatments based on such modulation are now becoming available. Although bacteria are essential for disease to occur, they are insufficient; a susceptible host is also necessary. Host susceptibility, disease progression and response to treatment are determined predominantly by heredity and environmental and acquired risk factors. Some of these can be changed while others are immutable. Concepts and procedures for treatment are generally scientifically based and appropriately applied. Preventive measures are largely successful and widely practiced in industrialized countries. Clearly, control of these ancient chronic diseases is now within our reach. In spite of the tremendous progress, many unresolved issues remain. The purpose of this paper is to summarize some of the major accomplishments of periodontal research, and identify and discuss some of the more important critical issues that still need to be addressed.

Oral ecology and person-to-person transmission of Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis

The ecological characteristics of the oral cavity are dissimilar for A. actinomycetemcomitans and for P. gingivalis, as judged by differences in their colonization preferences and patterns, associations with periodontal disease parameters, relationships with the subgingival microbiota and the type of periodontitis and their clonal persistence in the oral cavity. These features also suggest that as a periodontal pathogen, A. actinomycetemcomitans is different from P. gingivalis. Probably in most infected individuals, low levels of A. actinomycetemcomitans can persist for years in equilibrium with the host and the resident oral microbiota. However, it is well established that A. actinomycetemcomitans can cause disease in some individuals or in some circumstances when the regulatory mechanisms are unable to maintain homeostasis in the ecosystem. Elevated A. actinomycetemcomitans proportions of the biota can be regarded as a sign of ecological imbalance, leading to increased risk of periodontal destruction. There is also evidence showing elevated pathogenic potential of certain A. actinomycetemcomitans clones. Although A. actinomycetemcomitans seems to be relatively rarely transmitted between cohabiting adults, transmission can occur to periodontally healthy children of A. actinomycetemcomitans-positive parents. Parents and children may share factors that promote successful oral colonization of A. actinomycetemcomitans, or the window of opportunity is in childhood. Therefore, to prevent parent-child transmission of A. actinomycetemcomitans, bacterium-positive parents of young children are optimal targets for enhanced information and treatment. In selected populations, screening for specific clones of A. actinomycetemcomitans has been employed in prevention of peridontitis. Future research aiming at finding the reasons which cause the changes in the oral homeostasis to allow the growth of A. actinomycetemcomitans may give insight into novel prevention strategies for A. actinomycetemcomitans-associated periodontitis. Compared with A. actinomycetemcomitans, P. gingivalis shows a different pattern of coexistence with the host. In periodontal health or in children, P. gingivalis is absent or only rarely detected. When present, P. gingivalis is commonly recovered in high numbers from dentitions exhibiting inflamed periodontitis and poor oral hygiene. Contrary to A. actinomycetemcomitans, the data on the vertical transmission of P. gingivalis are limited. The major infection route of P. gingivalis seems to be between adults, indicating that P. gingivalis commonly colonizes in an established oral microbiota. These characteristics suggest that the degree of tolerance between P. gingivalis and the host is inferior to that between A. actinomycetemcomitans and the host. It appears that the association of P. gingivalis with disease is a rule rather than an accidental incident. On these grounds, it seems that the host-P. gingivalis relationship approaches antibiosis. Since P. gingivalis infection is related to a typical periodontal eco-pathology, the susceptibility to person-to-person transmission of this pathogen may be controlled by periodontal treatment and emphasizing the significance of high standard oral hygiene.

Identical clonal types of Porphyromonas gingivalis or Prevotella nigrescens recovered from infected root canals and subgingival plaque

Clinical samples from 10 infected root canals and from subgingival plaque in 10 patients were screened by anaerobic culture for black-pigmented anaerobes. A total of 17 Porphyromonas gingivalis and 9 Prevotella nigrescens were obtained from four patients and were identified by species-specific polymerase chain reaction (PCR) amplification. The arbitrarily primed PCR reaction used to examine the genetic diversity of the isolates revealed that the P. gingivalis or P. nigrescens simultaneously present in the root canal system and in subgingival plaque of all four patients were genotypically indistinguishable. These data indicate that the endodontium and the periodontium can be colonized by the same clonal types of black-pigmented anaerobes.

Intrafamilial distribution of mutans streptococci in Japanese families and possibility of father-to-child transmission

The purpose of this study was to investigate the intrafamilial distribution of mutans streptococci in Japanese families using chromosomal DNA fingerprinting with three endonucleases; EcoRI, HindIII and HaeIII. The analysis of 1,908 isolates cultured from the dental plaque of 76 subjects from 20 families (20 married couples and 36 of their children) resulted in the identification of 144 genotypes containing 114 strains of Streptococcus mutans (serotype c, 66.7%; e, 12.5%) and 30 strains of S. sobrinus (d, 13.2%; g, 7.6%). A mean of 1.89 genotypes (from one to four) was harbored in individual subjects, and a mean of 4.10 genotypes from two to seven was harbored in individual families. Among the 70 genotypes found in the children, 36 (51.4%) were in agreement with their mothers and 22 (31.4%) were in agreement with their fathers. The other genotypes (18.6%) did not correspond with the parents. Homologous strains between parents were found in only two couples. This result showed that fathers or others as well as mothers can be sources of transmission. Further, the serotype d, e and g strains showed significantly higher probabilities of transmission than serotype c.

Persistence of oral colonization by the same Actinobacillus actinomycetemcomitans strain(s)

BACKGROUND

The Gram-negative facultatively anaerobic coccobacillus Actinobacillus actinomycetemcomitans is the major pathogen in localized juvenile periodontitis (LJP) and some forms of adult periodontitis (AP). A. actinomycetemcomitans can be grouped into 5 serotypes (a through e) based on differences in the carbohydrate moiety of cell surface lipopolysaccharide. The A. actinomycetemcomitans population is genetically heterogeneous. Since the studies on A. actinomycetemcomitans colonization have mostly applied only culture techniques, the clonality of the follow-up isolates has not been established. Thus, it is possible that, although A. actinomycetemcomitans could be repeatedly isolated from an individual, the initial colonizing strain was replaced by another strain. The aim of the study was to determine whether oral A. actinomycetemcomitans strains change spontaneously over time or after periodontal treatment.

METHODS

A total of 922 A. actinomycetemcomitans isolates were recovered from 115 subjects. From each subject A. actinomycetemcomitans isolates were obtained from 2 to 9 follow-up samples 0.5 to 11.5 years apart. After the first sampling occasion, 99 subjects were treated for either LJP or AP, whereas the 16 non-periodontitis subjects received no treatment. All A. actinomycetemcomitans isolates were serotyped and 235 isolates from 52 subjects genotyped with AP-PCR and/or with ribotyping.

RESULTS

Isolates of only one serotype, or non-serotypeable isolates alone, were repeatedly found in 104 subjects; serotype a occurred in 25%, b in 33%, c in 23%, d in 5%, e in 7%, and non-serotypeable isolates in 8% of these subjects. Two serotypes (or serotypeable isolates together with non-serotypeable isolates) occurred simultaneously in 9 subjects and in each of these subjects at least one of the serotypes was detected at each sampling occasion. In one subject the initial serotype reappeared although a different serotype was once seen alone, whereas in another subject the initial serotype could not be recovered later. Identical genotypes of A. actinomycetemcomitans were repeatedly detected in each of 52 subjects with follow-up isolates of the same serotype.

CONCLUSIONS

The results showed that spontaneous or treatment-induced change in the oral A. actinomycetemcomitans strain(s) is extremely rare and that colonization with the same strain(s) seems to be remarkably persistent.