Faculty Bibliography

The heterogeneous group of oral bacteria within the sanguinis (sanguis) streptococci comprise members of the indigenous biota of the human oral cavity. While the association of Streptococcus sanguinis with bacterial endocarditis is well described in the literature, S. sanguinis is thought to play a benign, if not a beneficial, role in the oral cavity. Little is known, however, about the natural history of S. sanguinis and its specific relationship with other oral bacteria. As part of a longitudinal study concerning the transmission and acquisition of oral bacteria within mother-infant pairs, we examined the initial acquisition of S. sanguinis and described its colonization relative to tooth emergence and its proportions in plaque and saliva as a function of other biological events, including subsequent colonization with mutans streptococci. A second cohort of infants was recruited to define the taxonomic affiliation of S. sanguinis. We found that the colonization of the S. sanguinis occurs during a discrete "window of infectivity" at a median age of 9 months in the infants. Its colonization is tooth dependent and correlated to the time of tooth emergence; its proportions in saliva increase as new teeth emerge. In addition, early colonization of S. sanguinis and its elevated levels in the oral cavity were correlated to a significant delay in the colonization of mutans streptococci. Underpinning this apparent antagonism between S. sanguinis and mutans streptococci is the observation that after mutans streptococci colonize the infant, the levels of S. sanguinis decrease. Children who do not harbor detectable levels of mutans streptococci have significantly higher levels of S. sanguinis in their saliva than do children colonized with mutans streptococci. Collectively, these findings suggest that the colonization of S. sanguinis may influence the subsequent colonization of mutans streptococci, and this in turn may suggest several ecological approaches toward controlling dental caries.

The aim of this investigation was to evaluate the relationship between MHC alleles at the HLA-DRB1, DQB1 and TNFa microsatellite loci and levels of oral bacteria that play a role in the etiology of dental caries, and the DMFS index in 186 AA primparous women. The average age of the cohort was 20.8+/-3.7 years. The median DMFS index was 9 (range 0-68). High levels of S. mutans were positively associated with DRB1*3 and DRB1*4 presence (p < or = 0.005). DRB1*8 was positively associated with higher levels of S. mutans as a percentage of total Streptococci (p = 0.04). DRB1*1 was positively associated with high levels L. casei (p = 0.04). DQB1 alleles were not observed associated with oral bacterial levels. TNFa allele 103 was negatively associated (p = 0.04), and TNFa 117 was positively associated (p = 0.007), with high levels of L. acidophilus. No significant associations were observed between any DRB1, DQB1 or TNFa allele and the DMFS index. These results support an hypothesis of an association between host HLA class II and TNFa genetic profile and colonization of S. mutans, L. casei, and L. acidophilus thought to be pathogens involved in the etiology of dental caries.

Determining whether two strains of bacteria are unique, identical or clonally related depends upon comparisons of phenotypic and/or genotypic traits. Individual isolates can then be grouped according to differences or similarities among those traits. One method of genotyping strains of bacteria is commonly referred to as chromosomal DNA fingerprinting. Previously, we generated chromosomal DNA fingerprints of mutans streptococci to study the transmission of this organism within families. Here, we developed and evaluated an arbitrarily primed polymerase chain reaction (AP-PCR) method for the genotypic characterization of mutans streptococci. Results were compared to those derived from the more conventional chromosomal DNA fingerprinting method. First, we showed that randomly selected clinical isolates displayed a unique banding profile by both methods; the mean similarity indices between DNA fragment patterns were 0.69 for chromosomal DNA fingerprinting and 0.74 for AP-PCR. This indicated that AP-PCR demonstrated less diversity than chromosomal DNA fingerprinting. Subsequently, we tested the agreement between chromosomal DNA fingerprinting and AP-PCR in determining genotypic similarities among 21 mutans streptococci strains obtained from 10 mother-child pairs, and 5 mutans streptococci strains from 5 fathers. The Kappa value for agreement was 0.88. We conclude that AP-PCR, which generates patterns of 8 to 12 amplicons, is capable of distinguishing strains of mutans streptococci among non-related individuals. Moreover, AP-PCR can discern both homogeneity and heterogeneity of mutans streptococci genotypes among mother and child pairs. Overall, we found that AP-PCR gave results comparable to those of chromosomal DNA fingerprinting.

The purpose of this study was to investigate whether there was an intrafamilial similarity of mutans streptococcal strains in some Swedish families using chromosomal DNA fingerprinting. Plaque samples were obtained from buccal and occlusal surfaces of 25 three-year-old children, their mothers and 18 fathers. The colonization levels of mutants streptococci were estimated with the 'Strip mutans' test, and caries experience was scored by decayed, missing and filled teeth or decayed, extracted and filled teeth. Interviews about medical history, diet regimes, breastfeeding and care of the child were performed. In 11 families isolates of mutans streptococci were detected in all three individuals. These isolates were serotyped by immunofluorescent technique and genotyped using the restriction endonuclease Hae III. The results showed that 5 children harbored mutans streptococci genotypes different from their parents. Six children showed genotypes identical to their mothers. None of the children harbored genotypes similar to their fathers, even though two thirds of the fathers had high or very high mutans streptococci levels. No matching of genotypes was observed within the 11 parental pairs. Mothers as primary caregivers with high 'Strip mutans' scores were more often observed in the group with identical genotypes within the mother-child pairs, the 'matching group', than in the 'no-matching group'. These data indicate that the fathers and the children had not acquired each others' strains of mutans streptococci nor had the spouses. The results suggest that the children acquired mutans streptococci both from outside and inside the family