Oral Lactobacilli Related to Caries Status of Children with Primary Dentition.

Oral lactobacilli are members of a group of bacteria implicated in caries progression, although information regarding their transmission, colonization, and caries-associated species is not well established. This study isolated oral lactobacilli from a group of children with primary dentition for determination of Lactobacillus prevalence, detection of Streptococcus mutans, a major pathogen of caries initiation, and dental caries status of the children. Species of Lactobacillus isolates were determined from examination of 16S rDNA sequences. Subsequently, the most prevalent species was evaluated for involvement in caries status, and binding ability to type I collagen of all Lactobacillus isolates was determined in association with caries status. Multilocus sequence typing (MLST) of eleven loci was carried out to study strains of the predominant Lactobacillus sp. The detection of oral lactobacilli together with S. mutans was significantly associated with the highest dental caries indices, but there was no involvement of collagen-binding properties of Lactobacillus isolates in caries status. Lactobacillus fermentum was the most prevalent, and its presence was related to high scores of caries indices. MLST analysis of L. fermentum population could not specify a particular clone associated with caries status, but revealed sharing of identical L. fermentum strains among children in the same classrooms. Taken together, the data contributed useful information on the role of oral lactobacilli, in particular L. fermentum in dental caries.

Genotyping of Candida albicans and Candida dubliniensis by 25S rDNA analysis shows association with virulence attributes in oral candidiasis.

OBJECTIVES: This study genotyped oral isolates of Candida albicans and C. dubliniensis by analyzing 25S rDNA transposable intron and evaluated their virulence attributes in oral candidiasis. DESIGN: C. albicans and C. dubliniensis were isolated from oral cavity of normal carriers (n = 100) and oral candidiasis patients (n = 100), genotyped by PCR, and virulence properties, namely, secreted phospholipase and proteinase activities (using an agar plate method) and binding to buccal epithelial cells, were determined. In addition, antifungal sensitivity was assayed for all Candida isolates. RESULTS: C. albicans genotypes A, B, C and D (C. dubliniensis) were identified. Genotype B was the most prevalent in both healthy and candidiasis groups and had highest buccal epithelial cell binding ability but lowest secreted phospholipase activity. Genotype C was the third most prevalent, with higher frequency in patients than normal carriers. Genotype A, the second most prevalent, was equally found in both groups. There were no significant differences in secreted proteinase activity among the three C. albicans genotypes. C. dubliniensis, the least prevalent, was more frequent in healthy carriers and demonstrated minimal levels of the virulence properties. When all Candida isolates were compared based on groups of subjects, only secreted phospholipase activity was significantly higher in isolates from candidiasis patients. All Candida isolates were susceptible to clotrimazole, fluconazole, miconazole and nystatin. CONCLUSIONS: Genotyping based on the 25S rDNA transposable intron region provided a simple method allowing studies of the pathogenicity of each genotype.

Cariogenic properties of Streptococcus mutans clinical isolates with sortase defects.

OBJECTIVE: In Streptococcus mutans, a Gram-positive pathogen of dental caries, several surface proteins are anchored by the activity of sortase enzyme. Although various reports have shown that constructed S. mutans mutants deficient of sortase as well as laboratory reference strains with a sortase gene mutation have low cariogenic potential, no known studies have investigated clinical isolates with sortase defects. Here, we examined the cariogenic properties of S. mutans clinical isolates with sortase defects as well as caries status in humans harboring such defective isolates. DESIGN: Sortase-defective clinical isolates were evaluated for biofilm formation, sucrose-dependent adhesion, stress-induced dextran-dependent aggregation, acid production, and acid tolerance. Additionally, caries indices of subjects possessing such defective isolates were determined. RESULTS: Our in vitro results indicated that biofilm with a lower quantity was formed by sortase-defective as compared to non-defective isolates. Moreover, impairments of sucrose-dependent adhesion and stress-induced dextran-dependent aggregation were found among the isolates with defects, whereas no alterations were seen in regard to acid production or tolerance. Furthermore, glucan-binding protein C, a surface protein anchored by sortase activity, was predominantly detected in culture supernatants of all sortase-defective S. mutans isolates. Although the sortase-defective isolates showed lower cariogenic potential because of a reduction in some cariogenic properties, deft/DMFT indices revealed that all subjects harboring those isolates had caries experience. CONCLUSIONS: Our findings suggest the impairment of cariogenic properties in S. mutans clinical isolates with sortase defects, though the detection of these defective isolates seemed not to imply low caries risk in the subjects harboring them.