Susceptibility of candida albicans to methylene blue dye compared to fluconazole

Dear editor, The increasing resistance of many fungal pathogens requires urgent new or repurposing therapeutic strategies. Methylene blue (MB) was previously used for treating cyanide poisoning and urinary tract infections. Few studies have been conducted on MB’s antifungal activity. Methylthioninium chloride, which is MB, is a salt utilized as a dye and therapeutic agent. As a pharmaceutical agent, it primarily addresses methemoglobinemia by converting or chemically reducing ferric iron in hemoglobin to ferrous iron [1] Candida albicans is a prevalent commensal fungus that inhabits the pharyngeal cavity, gastrointestinal system, vaginal canal, and the skin of healthy persons. C. albicans constitute a component of the normal microbiota in 50% of the population. The clinical symptoms of Candida species vary from localized, superficial mucocutaneous conditions to invasive infections affecting several organ systems and posing a life-threatening risk [2]. This study included 30C. albicans samples isolated from skin, oral, and vagina examined by their Gram stain, morphology, culture, and biochemical tests. MB was used as an antimicrobial by the good diffusion method, while fluconazole was investigated by the disc diffusion method. For statistical analysis, SPSS software 26 was used to present data as interquartile range. MB activity on candida isolates was strong in 100% of isolates. The activity of fluconazole on candida isolates was strong at 80%, moderate activity at 10%, and weak activity at 10%. This means that candida is more sensitive to MB than fluconazole (Fig. 1).Figure 1: Percentage of antifungal agents’ activity against Candida albicans.Table 1 compares the median among different antimicrobials for C. albicans. The sensitivity of C. albicans to fluconazole was 20.5 mm (19.75–22 mm) and to MB was 26 (26–28) with a significant difference (P<0.0001). Table 1 - Candida albicans sensitivity to agents Variables Groups IQR (mm) P value* Candida albicans Methylene blue 26 (26–28) <0.0001 Fluconazole 20.5(19.75–22) IQR, interquartile range; *Mann–Whitney U test. There was no correlation between fluconazole and MB (r=−0.02, P=0.88) (Table 2). Table 2 - Correlation between methylene blue and fluconazole Variables Methylene blue Fluconazole Correlation(r) −0.02 Sig. (2-tailed) 0.88 Antimicrobial resistance to pathogens is a worldwide challenge associated with high morbidity and mortality [3]. Antifungals are essential in modern medicine and treat various infectious diseases caused by candida. However, the emergence of antifungal-resistant candida has become a global public health threat, leading to increased morbidity, mortality, and healthcare costs. Therefore, it is crucial to seek alternative strategies to manage this antifungal resistance [4]. Sobel et al.[5] monitored 38 patients with candidiasis for an extended period with repeated resistance and discovered that 13 individuals (13/38, 34.2%) continued to be sensitive to fluconazole, 19 patients (19/38, 50%) exhibited persistent resistance to fluconazole, four patients (4/38, 10.5%) transitioned from susceptible to resistant, and two (2/38, 5.2%) transitioned from resistant to susceptible over time [5]. To conclude, MB has antimicrobial activity against C. albicans, so that it may be used in medical practices, especially for the treatment of C. albicans in the skin, oral, and vagina. Financial support and sponsorship Nil. Conflicts of interest There is no conflict of interest.