CaIPF19998 reduces drug susceptibility by enhancing the ability of biofilm formation and regulating redox homeostasis in Candida albicans

In Vitro Anti-Biofilm Activities of Citral and Thymol Against Candida Tropicalis

Candida tropicalis is an emerging non-albicans Candida species which is pathogenic to the immune-compromised humans, especially in tropical countries, including India. The acquired resistance of Candida species towards antifungal therapies is of major concern. Moreover, limited efficacy and dosage constraint of synthetic drugs have indicated the prerequisite of finding new and natural drugs for treatment. In the present study, we have compared the influence of citral and thymol on C. tropicalis and its biofilm along with expression levels of certain antifungal tolerance genes. The antifungal and anti-biofilm activities of the both were studied using 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide sodium salt (XTT) reduction assay, field emission scanning electron microscope (FE-SEM) and confocal laser scanning microscope (CLSM) and real-time reverse transcription polymerase chain reaction (RT-PCR) analysis. Citral and thymol have damaged the cells with distorted surface and less viability. Quantitative real-time PCR analysis showed augmented expression of the cell membrane biosynthesis genes including ERG11/CYT450 against citral and the cell wall related tolerance genes involving CNB1 against thymol thus, depicting their differential mode of actions.

Comparative Ploidy Proteomics of Candida albicans Biofilms Unraveled the Role of the AHP1 Gene in the Biofilm Persistence Against Amphotericin B

Candida albicans is a major fungal pathogen causing lethal infections in immunocompromised patients. C. albicans forms antifungal tolerant biofilms contributing significantly to therapeutic failure. The recently established haploid C. albicans biofilm model provides a new toolbox to uncover the mechanism governing the higher antifungal tolerance of biofilms. Here, we comprehensively examined the proteomics and antifungal susceptibility of standard diploid (SC5314 and BWP17) and stable haploid (GZY792 and GZY803) strains of C. albicans biofilms. Subsequent downstream analyses identified alkyl hydroperoxide reductase 1 (AHP1) as a critical determinant of C. albicans biofilm's tolerance of amphotericin B. At 32 μg/ml of amphotericin B, GZY803 haploid biofilms showed 0.1% of persister population as compared with 1% of the diploid biofilms. AHP1 expression was found to be lower in GZY803 biofilms, and AHP1 overexpression in GZY803 restored the percentage of persister population. Consistently, deleting AHP1 in the diploid strain BWP17 caused a similar increase in amphotericin B susceptibility. AHP1 expression was also positively correlated with the antioxidant potential. Furthermore, C. albicans ira2Δ/Δ biofilms were susceptible to amphotericin B and had a diminished antioxidant capacity. Interestingly, AHP1 overexpression in the ira2Δ/Δ strain restored the antioxidant potential and enhanced the persister population against amphotericin B, and shutting down the AHP1 expression in ira2Δ/Δ biofilms reversed the effect. In conclusion, we provide evidence that the AHP1 gene critically determines the amphotericin B tolerance of C. albicans biofilms possibly by maintaining the persisters' antioxidant capacity. This finding will open up new avenues for developing therapies targeting the persister population of C. albicans biofilms. The mass spectrometry proteomics data are available via ProteomeXchange with identifier PXD004274.

Candida albicans Biofilms and Human Disease

In humans, microbial cells (including bacteria, archaea, and fungi) greatly outnumber host cells. Candida albicans is the most prevalent fungal species of the human microbiota; this species asymptomatically colonizes many areas of the body, particularly the gastrointestinal and genitourinary tracts of healthy individuals. Alterations in host immunity, stress, resident microbiota, and other factors can lead to C. albicans overgrowth, causing a wide range of infections, from superficial mucosal to hematogenously disseminated candidiasis. To date, most studies of C. albicans have been carried out in suspension cultures; however, the medical impact of C. albicans (like that of many other microorganisms) depends on its ability to thrive as a biofilm, a closely packed community of cells. Biofilms are notorious for forming on implanted medical devices, including catheters, pacemakers, dentures, and prosthetic joints, which provide a surface and sanctuary for biofilm growth. C. albicans biofilms are intrinsically resistant to conventional antifungal therapeutics, the host immune system, and other environmental perturbations, making biofilm-based infections a significant clinical challenge. Here, we review our current knowledge of biofilms formed by C. albicans and closely related fungal species.

Extracellular enzymes and susceptibility to fluconazole in Candida strains isolated from patients with vaginitis and healthy individuals

BACKGROUND

Extracellular phospholipase, proteinase, and coagulase are accounted as the major virulence factors in Candida albicans. Several reports showed that the incidence of resistance to fluconazole has risen during last two decades.

OBJECTIVES

The present study has investigated the extracellular enzymes of C. albicans and non-albicans species isolated from both patients with vaginitis and healthy women. In addition, susceptibility of the isolates was evaluated against fluconazole.

PATIENTS AND METHODS

Vaginal samples were collected using sterile cotton swabs and inoculated on CHROMagar Candida. Routine morphological tests and ID 32C and API 20C AUX Kits were used to identify species. Phospholipase, proteinase, and coagulase activity were determined by standard methods. Susceptibility to fluconazole was also evaluated using ATB Fungus 3 Kits.

RESULTS

The phospholipase activity was detected in 66.7% of the tested isolates recovered from patients with vaginitis. In the present study, phospholipase activity with higher Pz values (< 0.70) was more common in patients with vaginitis (28 of 66 isolates) whereas this rate in the normal individual was 13 of 42. Proteinase activity was detected in 74.2% and 61.9% of tested isolates recovered from patients and normal individuals, respectively. All tested isolates were negative for coagulase activity. In the present study, resistance to fluconazole was found in 34.8% of isolates. C. dubliniensis was the most common isolate (6 out of 11 isolates) that showed resistance to fluconazole.

CONCLUSIONS

Our results showed that C. albicans was the most frequently isolated from both patients with vaginitis and normal individual. In the present study, we could not find any correlation between extracellular activities and sources of isolates (patients and normal flora) and sensitivity or resistance to fluconazole.