The aim of this study is to select the optimal conditions for quantification in the oral cavity of Lactobacillus brevis CD2, a probiotic strain contained in a commercially available dietary supplement and to assess its persistency after oral administration. Different sets of primers for L. brevis detection will be tested in real-time PCR reactions to find optimal amplification efficiency and target specificity. Primers ability in the identification of L. brevis DNA will be assessed in a pilot study conducted on 12 healthy volunteers clinically free of oral pathologies. The subjects will take 3 tablets/day for 3 days and one tablet on the 4th day. Clinical samples (dorsal surface of tongue, first molar, vestibular fornix and saliva) will be collected at baseline (before beginning the trial), at T0 (in the morning before the assumption of the last tablet) and 3, 6, and 9 hours after taking the last tablet. The quantities of L. brevis DNA will be compared to the total number of bacteria present in the samples. The activity of the enzyme arginine deiminase, responsible for oral pH homeostasis (particularly abundant in the CD2 strain) will be also assessed in the saliva samples before and after treatment, by HPLC measurements.

Inclusion Criteria:

• Age > 18 years
• Healthy subjects with no oral cavity pathologies
• Written informed consent

Exclusion Criteria:

• Patients with oral diseases
• Patients with systemic diseases
• Celiac patients or subjects affected by allergic reactions to soy proteins
• Use of antibiotics or other probiotics