Comparative in vitro fungicidal activity of echinocandins against Candida albicans in peritoneal dialysis fluids

Autophagy in peritoneal fibrosis

Peritoneal dialysis (PD) is a widely accepted renal replacement therapy for patients with end-stage renal disease (ESRD). Morphological and functional changes occur in the peritoneal membranes (PMs) of patients undergoing long-term PD. Peritoneal fibrosis (PF) is a common PD-related complication that ultimately leads to PM injury and peritoneal ultrafiltration failure. Autophagy is a cellular process of "self-eating" wherein damaged organelles, protein aggregates, and pathogenic microbes are degraded to maintain intracellular environment homeostasis and cell survival. Growing evidence shows that autophagy is involved in fibrosis progression, including renal fibrosis and hepatic fibrosis, in various organs. Multiple risk factors, including high-glucose peritoneal dialysis solution (HGPDS), stimulate the activation of autophagy, which participates in PF progression, in human peritoneal mesothelial cells (HPMCs). Nevertheless, the underlying roles and mechanisms of autophagy in PF progression remain unclear. In this review, we discuss the key roles and potential mechanisms of autophagy in PF to offer novel perspectives on future therapy strategies for PF and their limitations.

Card9 protects fungal peritonitis through regulating Malt1-mediated activation of autophagy in macrophage

Fungal peritonitis is an inflammatory condition of the peritoneum which occurs secondary to peritoneal dialysis. Most cases of peritonitis are caused by microbial invasion into the peritoneal cavity, resulting in high morbidity and mortality. Unlike bacterial peritonitis, little is known on fungal peritonitis. Card9, an adapter protein, plays a critical role in anti-fungal immunity. In this study, by using zymosan-induced peritonitis and C. albicans-induced peritonitis mouse model, we demonstrated that fungal peritonitis was exacerbated in Card9^-/- mice, compared with WT mice. Next, we found the autophagy activation of peritonealmacrophages was impaired in Card9^-/- peritonitis mice. The autophagy agonist, MG132, ameliorated peritonitis in Card9^-/- mice. The result of microarray analysis indicates Malt1 was significantly decreased in Card9^-/- peritonitis mice. Furthermore, we demonstrated that Malt1 interacts with P62 and mediates the function of P62 to clear ubiquitinated proteins. After overexpression of Malt1, impaired autophagy activation caused by Card9 deficient was significantly rescued. Together, our results indicate that Card9 protects fungal peritonitis by regulating Malt1-mediated autophagy in macrophages. Our research provides a new idea for the pathogenesis of fungal peritonitis, which is of great significance for the clinical treatment of fungal peritonitis.

Antifungal Activity of Crude Extract from the Rhizome and Root of Smilacina japonica A. Gray

This study aimed to investigate the antifungal activity of hydroalcoholic extract from Smilacina japonica A. Gray (SJA) against different fungi. The minimum inhibitory concentration (MIC) for SJA was determined by the broth microdilution method. The antifungal effects of SJA against Candida albicans were further confirmed by cell growth test and time-kill curve test. The effects of SJA on the fungal morphology and ultrastructure were also evaluated. SJA has a broad-spectrum antifungal activity. The MICs of SJA against different fungi, including fluconazole-sensitive and -resistant Candida albicans, other Candida species, and Cryptococcus neoformans, ranged from 208 μg/ml to 1665 μg/ml. Furthermore, SJA displayed fungicidal activity against varied fungi and obviously inhibited the hyphal growth of fungi. The mechanism study revealed that the antifungal activity of SJA might be associated with its effect on the cell morphology and ultrastructure.

Fungal peritonitis in peritoneal dialysis: 5-year review from a North China center

PURPOSE

Fungal peritonitis (FP) is a rare but devastating complication in peritoneal dialysis (PD), accounting for high rates of technique failure, morbidity and mortality. This study was conducted to investigate FPs with regard to peritonitis rate, microbiology testing, patient characteristics, clinical features, antifungal treatments, and clinical outcomes in patients on PD.

METHODS

This single-center study retrospectively reviewed all FP episodes diagnosed from June 1, 2012 to June, 2017. All FPs were matched in a 1:5 ratio with PD patients diagnosed with bacterial peritonitis. Clinical, biochemical characteristics and detailed data on peritonitis episodes were recorded.

RESULTS

Eleven fungal peritonitis episodes (rate of 0.0067 episodes per patient-year on dialysis) were identified. All FPs were caused by Candida species (identification and antifungal susceptibility testing were performed with VITEK 2^® compact system), including C. albicans (6/11), C. parapsilosis (4/11) and C. krusei (1/11). Except C. krusei, no Candida resistance to fluconazole was detected. Compared to bacterial peritonitis (matched cases, n = 55), FP group showed higher rate of previous antibiotic use (p = 0.002), higher total effluent cell count (p = 0.007), and lower serum albumin (p = 0.01), higher rate of infection-related surgery (p < 0.001), HD transfer (p = 0.001), and all-cause death (p = 0.006). High prevalence (≥ 50%) of female gender, anuria, CCI ≥ 4, hypoalbuminemia, anemia, and hypokalemia were also observed in FP patients. More than half of the FP patients presented gastrointestinal symptoms (7/11) and extraperitoneal infection (6/11). Eight (72.7%) patients had catheter surgically removed with a median 5.5 lag days, four (36.4%) patients died within 3 months and six (54.5%) cases led to technique failure.

CONCLUSIONS

FP results in high rates of catheter loss and all-cause mortality in 3 months of follow-up, candida species were the commonest pathogens in our center. Variations of clinical features and susceptibility patterns were observed. Gastrointestinal disorders maybe a potential risk factor for FP.

Effect of peritoneal dialysis fluids on activity of echinocandins against Candida spp. biofilm

Peritoneal dialysis fluids (PDFs) impair microorganisms' growth, which may compromise effectivity of some antimicrobials. The purpose of this study was to investigate the effect of three different PDFs (lactate/bicarbonate-buffered Physioneal 40® with 2.2% glucose, lactate-buffered Nutrineal PD4® with 1.1% amino acid, and lactate-buffered Extraneal® with 7.5% icodextrin) on biofilm formation of four different Candida spp and antibiofilm effectiveness of anidulafungin, caspofungin and micafungin against Candida spp. biofilm in PDFs. All tested PDFs attained inhibitory effect on the biofilm formation but also reduced biofilm effectiveness of echinocandins against biofilm in PDFs was detected.

Antifungal Effects of Saponin Extract from Rhizomes of Dioscorea panthaica Prain et Burk against Candida albicans

Candida albicans is the most common fungal pathogen causing serious diseases, while there are only a paucity of antifungal drugs. Therefore, the present study was performed to investigate the antifungal effects of saponin extract from rhizomes of Dioscorea panthaica Prain et Burk (Huangshanyao Saponin extract, HSE) against C. albicans. HSE inhibits the planktonic growth and biofilm formation and development of C. albicans. 16–64 μg/mL of HSE could inhibit adhesion to polystyrene surfaces, transition from yeast to filamentous growth, and production of secreted phospholipase and could also induce endogenous reactive oxygen species (ROS) production and disrupt cell membrane in planktonic cells. Inhibitory activities against extracellular exopolysaccharide (EPS) production and ROS production in preformed biofilms could be inhibited by 64–256 μg/mL of HSE. Cytotoxicity against human Chang's liver cells is low, with a half maximal inhibitory concentration (IC₅₀) of about 256 μg/mL. In sum, our study suggested that HSE might be used as a potential antifungal therapeutic against C. albicans.

Peritonitis in a neonate due to Cyberlindnera fabianii, an ascomycetic yeast

The ascomycetous yeast Cyberlindera fabianii is not only present in the environment, but is also occasionally pathogenic. Especially, neonates seem to be prone to infection. Here, we describe a case of peritoneal infection of a neonate after congenital heart surgery. The correct identification of this peculiar species is made by MALDI-TOF and especially by molecular biology methods, whereas the standard biochemical identification methods fail.The neonate with a hypoplastic left heart syndrome had a Norwood palliation followed by transient ECMO therapy for 3 days. The patient developed a renal insufficiency, so that peritoneal dialysis was initiated. After a few days, a peritoneal infection due to C. fabianii emerged. The proper source of this rare and particular yeast remains obscure. In spite of a reasonable antimycotic therapy, the patient developed a capillary leak syndrome and died finally in septic shock with multiorgan failure. One reason is probably that the yeast population, which was highly susceptible to all common antimycotic drugs at the beginning of therapy with fluconazole (and for a short period with caspofungin and liposomal amphotericin B), became rapidly resistant.

Effects of magnolol and honokiol on adhesion, yeast-hyphal transition, and formation of biofilm by Candida albicans

Background

The first step in infection by Candida albicans is adhesion to host cells or implanted medical devices and this followed by hyphal growth and biofilm formation. Yeast-to-hyphal transition has long been identified as a key factor in fungal virulence. Following biofilm formation, C. albicans is usually less sensitive or insensitive to antifungals. Therefore, development of new antifungals with inhibitory action on adhesion, yeast-hyphal transition and biofilm formation by C. albicans is very necessary.

Methods

The effects of magnolol and honokiol on hypha growth were investigated using different induction media. Their inhibitory effects were determined using the 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5- carboxanilide assay, and biofilm thickness and viability were observed by a confocal scanning laser microscope. Mammalian cells were used in adhesion assays. Genes related to hyphae development and cell adhesions were analyzed by real-time reverse transcription-polymerase chain reaction. The exogenous cyclic adenosine monophosphate was used to determine the mechanisms of action of magnolol and honokiol. Caenorhabditis elegans was used as an in vivo model to estimate the antifungal activities of magnolol and honokiol.

Results and conclusions

Magnolol and honokiol inhibited adhesion, the transition from yeast to hypha, and biofilm formation by C. albicans through the Ras1-cAMP-Efg1 pathway. Moreover, magnolol and honokiol prolonged the survival of nematodes infected by C. albicans. Magnolol and honokiol have potential inhibitory effects against biofilm formation by C. albicans.

General Significance

This study provides useful information towards the development of new strategies to reduce the incidence of C. albicans biofilm-associated infection.