Several studies have highlighted SB’s potential antimicrobial properties. In vitro antifungal activity of SB was studied using 70 fungal strains derived from human skin and nail samples. The strains of fungi responsible for human skin and nail infections, 40 dermatophytes (23 T. rubrum, 17 T. interdigitale), 12 molds (3 S. brevicaulis, 3 Fusarium spp., 3 Acremonium spp., 3 A. versicolor) and 18 yeasts (6 C. albicans, 6 C. parapsilosis, 2 C. guilliermondii, 1 C. zeylanoides, 3 Trichosporon spp.) were included. Findings demonstrated that a 10 g/L solution of SB inhibited growth of nearly 80% of the isolated fungi cultivated in Sabouraud dextrose agar (SDA).4 It was further found that the “minimal inhibitory concentration 90” (MIC90) of SB measured on SDA, Sabouraud dextrose broth and potato dextrose broth was 20 g/L for the dermatophytes, 5 g/L for the yeasts, and 40 g/L for the molds.4
The next phase of the experiment was a prospective study focusing on ex vivo antifungal activity of SB on 24 fungal strains: 15 dermatophytes (5 T. interdigitale and 10 T. rubrum), 7 yeasts (2 C. parapsilosis, 1 C. albicans, 1 C. lusitaniae, 1 C. guilliermondii and 2 Trichosporon spp.) and 2 molds (2 A. versicolor) isolated from 15 human foot nail and 9-foot skin scrapings.4 Supplementing Sabouraud dextrose-chloramphenicol agar (SDCA) with 10 g/L of SB solution reduced 4 out of 24 specimens (17%) and fully inhibited fungal growth of 19 specimens (79%) after a 7-day incubation period compared to SDCA alone.4 These findings highlight SB concentrations effective against different strains of fungi responsible for human skin and nail infections. However, it was noted that the mechanism of action of SB remains unexplored.
A study examining the potential mechanism of SB’s in vitro inhibition of a plant fungal pathogen, Botrytis cinerea, discovered that SB exhibits anti-fungal properties by impeding yeast-to-hyphae transition, also known as hyphae switching in this fungal species.5 Similarly, opportunistic pathogenic yeasts such as C. albicans have the ability to hyphae switch which can cause superficial skin infections as well as potentially life-threatening systemic infections.6 The proposed mechanism of hyphae switching involves the expression of agglutinin-like sequence (Als) molecules, particularly Als3, which act as invasins inducing host cell endocytosis by binding to host cell E-cadherin and N-cadherin.5-7 The effect of several salts such as: ammonium, potassium, and sodium bicarbonates on B. cinerea colony growth in vitro revealed inhibition of colony growth even at low concentrations such as 20 mM, with bicarbonate anions playing a primary role in this effect.5 Comparisons with other salts suggested that those with high pKa values or acting as reducing agents were effective inhibitors of growth. The pH was found to influence colony growth, with bicarbonates and phosphates exhibiting greater inhibition as pH increased, indicating the involvement of pH and buffering capacity in growth inhibition.5 Furthermore, SB was found to control B. cinerea growth in vitro independently of pH, suggesting its potential as an effective control agent against this pathogen. With the addition of SB, the extracellular environment becomes more alkaline, causing the fungal cells to expel more acid to counteract this alkaline effect. This process demands additional energy expenditure from the fungal cell, diverting resources that would typically be allocated to hyphae switching towards maintaining pH balance, ultimately compromising the cell’s function, growth, and survival.5 Further investigation is warranted to delineate the specific mechanism underlying SB’s anti-hyphae activity in C. albicans.
In the dental setting, SB exhibits antifungal properties against C. albicans and antibacterial properties against Streptococcus mutans, the culprit of dental caries and tooth decay. In a study to assess the impact of 5% SB on the adherence of C. albicans to denture-based materials, fifty specimens of acrylic resin were prepared and inoculated with C. albicans then treated with different disinfectants. The results showed that both 5% sodium bicarbonate and 0.12% digluconate chlorhexidine significantly reduced the number of colony-forming units (cfu/mL) compared to the control group. However, when comparing the effectiveness of disinfecting solutions, only 0.12% digluconate chlorhexidine showed a statistically significant difference in reducing cfu/mL. Nonetheless, the study concludes that 5% sodium bicarbonate also presents itself as a viable alternative for reducing C. albicans adherence to thermally activated acrylic resin.6
Another in vitro experiment investigated the impact of sodium bicarbonate and hydrogen peroxide on the cariogenic bacteria S. mutans by analyzing their effects through spectrophotometric analysis. Seven different environments were created for testing, incubated in multi-well plates and monitored over 42 hours. Results indicated that both sodium bicarbonate and hydrogen peroxide, individually or in combination, effectively prevented bacterial growth of S. mutans. Despite hydrogen peroxide being bactericidal and sodium bicarbonate being bacteriostatic, no significant differences were observed among the treatments in terms of optical density readings. These findings suggest that products containing sodium bicarbonate and/or hydrogen peroxide could potentially be beneficial for caries-prone patients, although further studies on patients are necessary to validate these results.8 Some studies have shown that SB’s effectiveness against fungi and bacteria can be time dependent. For example, killing S. mutans, may require exposure to SB for 30 minutes or longer.8 While dermatology and dentistry are distinct specialties, they often intersect in the diagnosis and management of conditions affecting the skin and oral mucosa.
The potential synergistic effect of ascorbic acid, dexamethasone and SB as an in vivo triple therapy to reduce virulence factors in staphylococcus aureus—a gram-positive cocci, highly virulent and persistent bacterial pathogen responsible for various skin infections such as impetigo, folliculitis, furuncles, abscesses, and mastitis was also explored. SB demonstrated a significant reduction of expression in several virulence factors as follows: biofilm formation, S. aureus proteases, hemolysin, staphyloxanthin, and lower S. aureus resistance to oxidative burst orchestrated by neutrophils.9 Furthermore, findings from quantitative reverse transcription polymerase chain reaction (qRT-PCR) show reduced expression of several virulence-specific genes in S. aureus (crtM, sigB, sarA, agrA, hla, fnbA, and icaA).9
The concentrations mentioned above were utilized in in vitro and ex vivo studies, and therefore may not be readily translated to clinically applicable quantities for use by clinicians. While these antimicrobial properties have been demonstrated experimentally, the paucity of clinical data precludes making conclusions on its utility in patient care at this time.
