Acidogenicity of dual-species biofilms of bifidobacteria and Streptococcus mutans.

OBJECTIVE: The aim of this study was to evaluate the acidogenicity of dual-species biofilms of bifidobacteria and Streptococcus mutans. MATERIALS AND METHODS: The following strains were tested: Bifidobacterium dentium DSM20436, Parascardovia denticolens DSM10105, and Scardovia inopinata DSM10107. Streptococcus mutans UA159 and Lactobacillus acidophilus ATCC4356 were used as control. Bifidobacteria were studied planktonically as they were not able to form monospecies biofilm, they were grown in biofilms associated with S. mutans. Endogenous polysaccharide reserves of cultures at log phase were depleted. Standardized suspensions of the microorganisms were incubated in growth media supplemented with 10 mM glucose, lactose, raffinose, glucose, or xylitol. S. mutans biofilms were grown on glass cover slips for 24 h to which bifidobacteria were added. After 24 h, the dual-species biofilms were exposed to the same carbon sources, and after 3 h, the pH of spent culture media and concentrations of organic acids were measured. Statistical analyses were carried out using ANOVA and Tukey's test (α = 0.05). RESULTS: A higher pH drop was observed when S. mutans was associated with P. denticolens or S. inopinata, in either planktonic or biofilm cultures, than with S. mutans alone. Bifidobacteria showed a higher pH drop in the presence of raffinose than S. mutans or L. acidophilus. CONCLUSIONS: Dual-species biofilms of bifidobacteria and S. mutans produced more acid and greater pH drops than biofilms of S. mutans alone. CLINICAL RELEVANCE: New insights on the complex process of caries pathogenicity contribute to the establishment of preventive and therapeutic measures, in particular in specific cases, such as in early childhood caries.

Oral microbial colonization in children with sickle cell anaemia under long-term prophylaxis with penicillin.

BACKGROUND AND OBJECTIVE: Sickle cell anaemia (SCA) is the most frequent haematological hereditary disease. Children with SCA are submitted to long-term prophylactic therapy with penicillin, but little is known about its impact on oral microflora. The aim of this study was to evaluate the oral microbial colonization of paediatric patients with SCA. DESIGN: Forty children (4-11yrs old) with SCA (genotype SS) under long-term prophylactic treatment with penicillin were included in the study. Age/gender-matched control group of healthy children was also included. Scores of dmft/DMFT (number of decayed (D), missing (M), or filled (F) teeth; dmft, for primary dentition; DMFT, for permanent dentition) were obtained and stimulated saliva was sampled. Salivary flow rate and buffering capacity were evaluated. Counts of microorganisms (mutans streptococci, lactobacilli and yeasts) were determined by plating method. Yeasts were identified by API 20C AUX and PCR. RESULTS: Mean dmft/DMFT values were similar in the studied groups (SCA 2.13/1.60 and control 2.38/1.3). Although no significant differences between cariogenic microorganism counts were observed, significantly higher yeasts oral levels were observed in SCA group. Controls showed lower salivary buffering capacity. Candida albicans was the most frequently isolated species in both groups. Candida famata, Candida parapsilosis and Candida tropicalis were also isolated from controls. Candida dubliniensis, Candida rugosa and Candida sphaerica were found only in SCA group. CONCLUSIONS: Based on the results, it could be concluded that paediatric patients with SCA showed significantly higher oral level of yeasts. Uncommon fungal species were found in SCA group. Similar caries prevalence and counts of lactobacilli and streptococci in relation to controls were observed.