Candida albicans is a polymorphic, opportunistic fungal species that naturally resides as a commensal organism in the human microbiota. However, under certain circumstances, such as immunosuppression or antibiotic treatment, C. albicans can transition from a harmless commensal to a life-threatening agent. It is the main causative agent of candidiasis and the primary fungal infection in adults and pediatric patients, leading to superficial and systemic infections, including candidemia, which has a mortality rate of up to 40% [1]. Current antifungal treatments are limited by toxicity, poor selectivity, rising resistance, and disruption of the natural microbiome. These limitations highlight an urgent need for novel, targeted antifungal therapies.
The inspiration for our project stems from a personal experience with onychomycosis, a persistent nail fungal infection. During treatment, we encountered the firsthand limitations of current antifungal therapies. The standard medication, itraconazole, required high-dose pulse therapy that posed a risk of irreversible hepatotoxicity [2] and demanded a prolonged treatment schedule (one week of administration followed by a three-week interval, last up to 24 weeks), which results in poor patient adherence. Incomplete treatment often leads to frequent recurrences, which in turn increases the risk of antifungal resistance, creating a frustrating and dangerous cycle for patients.
Although Candida albicans is not the main cause of onychomycosis, our experience with the challenges of long-term antifungal treatment reveals a broader problem: the lack of targeted and sustainable therapies for fungal infections. This prompted us to look deeper into C. albicans, a more clinically significant and often life-threatening opportunistic fungal pathogen, especially in immunocompromised patients. Its increasing resistance to conventional antifungal medicines and high mortality rate in systemic infections make it a critical target for innovation. These challenges motivated us to explore an alternative, biologically-based antifungal strategy. We chose Bacillus subtilis as our chassis organism because it is GRAS (Generally Recognized As Safe) and naturally produces Iturin A, a potent lipopeptide with antifungal activity. However, effective antifungal effect requires sufficient local concentration of Iturin A at the infection site, something systemic exposure often fails to achieve without high doses and side effects. To address this, our goal is to engineer B. subtilis as a living therapeutic that can selectively colonize infection sites and locally produce Iturin A. By concentrating the antifungal substance directly where it is needed, our approach minimizes systemic exposure, reduces potential toxicity, and may even prevent resistance development. Moreover, since B. subtilis can survive and proliferate on the skin, this strategy holds promise for sustained, long-term protection against sustained, long-term release of antifungal substances and prevent recurrent infections.Engineer Bacillus subtilis to selectively detect and attach to C. albicans. Achieve local colonization and production of antifungal substance Iturin A at infection sites.
Explain the entire experimental design in detail here or in the wetlab part?