IADR Abstract Archives
Reduced Susceptibility to Chlorhexidine and Silver Diamine Fluoride in Cariogenic Microbiota
Objectives: The objective of the present study was to evaluate the susceptibility of bacteria isolated from dentin samples from patients undergoing 3 different cavity cleaning protocols: 2%CHX, 30% SDF and 38% SDF with potassium iodide (KI).
Methods: Forty children aged 7 to 10 years presenting carious lesions in primary molars were selected. Subjects were randomly divided into four groups: G1 (38% SDF + KI), G2 (30% SDF), G3 (2%CHX) and G4 (control group). Bacterial colonies grown in Mitis Salivarius Bacitracin (MSB) culture medium after interventions in groups G1 (n=3) and G3 (n=5) were cultured in Brain Heart Infusion (BHI) liquid culture medium. Minimum Inhibitory Concentrations (MICs) of antimicrobial agents for clinical isolates were determined in vitro and compared to the reference strains Streptococcus mutans (ATCC 25175) and Streptococcus sobrinus (ATCC 27607). 16S rDNA from clinical isolates were PCR amplified and sequenced for confirmation of S. mutans colonies.
Results: The 3 clinical isolates of G1 had lower sensitivity to SDF with MIC of 76 µg/mL compared to S. mutans with 4 times lower MIC (19 µg/mL) and S. sobrinus 2 times lower (38 µg/mL). These same G1 samples were also less sensitive to CHX with MIC 7.8 μg/mL 64 times higher than S. mutans (0.12 μg/mL) and 32 times to S. sobrinus (0.24 μg/mL). The five clinical isolates from G3 had the same reduced sensitivity to CHX with MIC 7.8 µg/mL, and were also less sensitive to SDF with MIC between 38 and 76 µg/mL. Interestingly, the association of KI with SDF had a negative effect on SDF antimicrobial activity, reducing its efficacy (MIC 76 µg/mL) in reference strains S. mutans and S. sobrinus and especially in bacteria isolated from patients with MICs between 76 and 608 ug/ml.
Conclusions: Finally, these in vitro data confirm in vivo results previously obtained by our group and raise questions about the association of KI with SDF for aesthetic purpose of reducing the enamel darkening with possible compromise of its antibacterial effect. It also emphasizes the caution with the use of antiseptics and the development of resistance by disease associated microorganisms in the oral microbiome.
Methods: Forty children aged 7 to 10 years presenting carious lesions in primary molars were selected. Subjects were randomly divided into four groups: G1 (38% SDF + KI), G2 (30% SDF), G3 (2%CHX) and G4 (control group). Bacterial colonies grown in Mitis Salivarius Bacitracin (MSB) culture medium after interventions in groups G1 (n=3) and G3 (n=5) were cultured in Brain Heart Infusion (BHI) liquid culture medium. Minimum Inhibitory Concentrations (MICs) of antimicrobial agents for clinical isolates were determined in vitro and compared to the reference strains Streptococcus mutans (ATCC 25175) and Streptococcus sobrinus (ATCC 27607). 16S rDNA from clinical isolates were PCR amplified and sequenced for confirmation of S. mutans colonies.
Results: The 3 clinical isolates of G1 had lower sensitivity to SDF with MIC of 76 µg/mL compared to S. mutans with 4 times lower MIC (19 µg/mL) and S. sobrinus 2 times lower (38 µg/mL). These same G1 samples were also less sensitive to CHX with MIC 7.8 μg/mL 64 times higher than S. mutans (0.12 μg/mL) and 32 times to S. sobrinus (0.24 μg/mL). The five clinical isolates from G3 had the same reduced sensitivity to CHX with MIC 7.8 µg/mL, and were also less sensitive to SDF with MIC between 38 and 76 µg/mL. Interestingly, the association of KI with SDF had a negative effect on SDF antimicrobial activity, reducing its efficacy (MIC 76 µg/mL) in reference strains S. mutans and S. sobrinus and especially in bacteria isolated from patients with MICs between 76 and 608 ug/ml.
Conclusions: Finally, these in vitro data confirm in vivo results previously obtained by our group and raise questions about the association of KI with SDF for aesthetic purpose of reducing the enamel darkening with possible compromise of its antibacterial effect. It also emphasizes the caution with the use of antiseptics and the development of resistance by disease associated microorganisms in the oral microbiome.
