Inhibitory effect of polyunsaturated fatty acids alone or in combination with fluconazole on Candida krusei biofilms in vitro and in Caenorhabditis elegans

Abstract

The incidence of infections by non-albicans Candida species, including Candida krusei, is increasing. Candida krusei exhibits intrinsic resistance to fluconazole and rapidly develops acquired resistance to other antifungals. Moreover, this yeast can form biofilm with increased resistance. Hence, there is a need to develop novel therapeutic strategies to combat infections caused by this pathogen. One such approach is through combination therapy with natural compounds, such as polyunsaturated fatty acids (PUFAs). This study aims to investigate the effect of PUFAs on fluconazole susceptibility of C. krusei biofilms, as well as the conserved nature of these effects in the Caenorhabditis elegans infection model. C. krusei biofilms were exposed to various fatty acids as well as combinations of fluconazole and linoleic acid (LA) or gamma-linolenic acid (GLA). The effect of these treatments on biofilm formation, cell ultrastructure, membrane integrity, oxidative stress and efflux pump activity was evaluated. In addition, the ability of the PUFAs to prolong survival and reduce the fungal burden of infected C. elegans, in the absence and presence of fluconazole, was assessed. Two P|UFAs, LA and GLA had he displayed significant inhibition of C. krusei biofilms and both of them increased the susceptibility of C. krusei biofilm to fluconazole in vitro via induction of oxidative stress, cell membrane damage, and disruption of efflux pump activity. These PUFAs also extended the lifespan of infected nematodes and displayed a potentiating effect with fluconazole in this model. This may pave the way for future studies into novel antifungal drug targets and treatment options. Lay Abstract The pathogenic yeast, Candida krusei, is naturally resistant to the antifungal drug, fluconazole. This study finds that polyunsaturated fatty acids, linoleic and gamma-linolenic acid, can inhibit C. krusei and overcome this resistance of in vitro biofilms, as well as in a nematode infection model.

Antibiofilm Activity of Essential Fatty Acids Against Candida albicans from Vulvovaginal Candidiasis and Bloodstream Infections

“…The biofilm inhibition rates (%) ranged from 20.52% to 80.99% (LOA < ALA < AA <EPA < DHA < GLA) ( Table S1 ). A recent study by Jamiu et al 20 also demonstrated LOA and GLA displayed significant inhibition of C. krusei biofilms. Both increased the susceptibility of C. krusei biofilm to fluconazole via induction of oxidative stress, cell membrane damage, and disruption of efflux pump activity.…”

“…and have recently been considered potential alternative antifungal agents. [17][18][19][20][21][22] Nevertheless, few published studies have investigated the activities of essential fatty acids (EFAs) on biofilms in the formation and mature stages of clinical C. albicans isolates. EFAs, which are types of polyunsaturated fatty acids (PUFAs), cannot be synthesized by the human body and must be obtained in the diet.…”

Talus osteomyelitis by Candida krusei with multiple huge cystic lesions: a case report and review of literatures

“…Among the Candida species, Candida albicans is the most common pathogen, however, recently non- albicans Candida infections are increasing [ 3 ]. Especially, C. krusei has intrinsic resistance against fluconazole and low susceptibility to amphotericin B and flucytosine, at the same time, it develops acquired resistance to other antifungals enhanced by its ability to form biofilm [ 3 , 12 , 13 ]. Moreover, the yeast has lowest 90-day survival rate when compared to other systemic Candida species infections [ 14 ].…”

“…In contrast, osteomyelitis of foot bones is limited to only 3% of all Candida osteomyelitis cases, as reported by Slenker et al [ 2 ]. The organism spreads by predominantly hematogenous route, direct inoculation and, rarely, by contiguous manner, and Candida albicans was identified in 65% of cases, although non- albicans Candidal infection is increasingly reported [ 3 ]. Albeit intact neutrophil function is critical to defense against Candida infection, surprisingly, less than 20% of all cases were associated with significant immunosuppression such as neutropenia, organ/bone marrow transplantation, underlying hematologic malignancy and others.…”

Emerging Antifungal Targets and Strategies

“…Another flavonoid, kaempferol, could downregulate CDR1 and CDR2 genes in fluconazole-resistant C. albicans [ 99 ]. Berberine hydrochloride, traditional Chinese medicine with antimicrobial effects, reduces intracellular efflux of fluconazole by downregulating CDR1 [ 100 ], while polyunsaturated fatty acids could reduce efflux from C. krusei cells [ 101 ]. Benzoxazole derivatives could interfere with both cell efflux and ergosterol synthesis in C. albicans [ 62 ].…”