Presence of L701 M mutation in the FKS1 gene of echinocandin-susceptible Candida krusei isolates

Rifaximin use favoured micafungin-resistant Candida spp. infections in recipients of allogeneic hematopoietic cell transplantation

Damage to gut mucosa following conditioning regimens may favour bacterial infections that can trigger graft versus host disease (GvHD) in patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT). Rifaximin, an oral and non-absorbable antibiotic, has been recently proposed as effective prophylaxis to reduce bacterial infections in the gut and consequently acute GvHD in this setting. The present study evaluated safety and outcomes of HSCT patients that were treated with rifaximin prophylaxis at Perugia University Hospital. Rifaximin prophylaxis was introduced as standard of care in HSCT patients in May 2018. We retrieved data from 118 consecutive transplants, and we compared the outcomes of rifaximin-treated patients with historical controls that did not receive antibiotic prophylaxis. While incidences of neutropenic fever, documented bacterial infections, and aGvHD were similar in the two groups, we found an increased frequency of invasive candidiasis and clinically relevant Candida spp. infections in rifaximin-treated patients (5 patients vs 1 patient, 25% [± 0.99%] vs 1% [± 0.01%], p < .0001). Three rifaximin-treated patients experienced life-threating candidemia (2 C. krusei, 1 C. orthopsilosis). Rifaximin was the only factor that increased the risk of Candida spp. infections. Rifaximin could have contributed to microbiome disruption which favoured an outbreak of life-threatening Candida infections. This important complication forced us to halt its use. Larger, prospective studies are needed to assess the impact of rifaximin prophylaxis on incidence of bacterial infections, aGvHD, and survival of HSCT patients.

Antifungal Activity and Mode of Action of Miltefosine Against Clinical Isolates of Candida krusei

Candida krusei attracts attention from medical professionals mainly for its intrinsic resistance to fluconazole and the limited number of drugs available to treat C. krusei vulvovaginal candidiasis. Miltefosine was demonstrated to have good antifungal activity both in vitro and in vivo. Here, we determined the susceptibility profiles of 57 clinical C. krusei isolates from vulvovaginal candidiasis patients and assessed the antifungal activity of miltefosine against C. krusei. All isolates were susceptible to voriconazole and itraconazole, whereas 1.8% of the isolates were of non-wild-type phenotype to amphotericin B. In contrast, miltefosine showed low MICs against all C. krusei isolates with fungicidal activity. The checkerboard assay showed that the synergistic effect of miltefosine in combination with amphotericin B was observed in 25% of the tested planktonic C. krusei isolates and 18.8% of the tested preformed biofilms, whereas miltefosine in combination with fluconazole showed indifferent interaction for all tested planktonic isolates. The presence of sorbitol in the broth microdilution assay did not influence the MIC values of miltefosine against C. krusei, but the presence of ergosterol increased the MIC values. Visible changes in cell content in cells treated with miltefosine were observed. We found that cells treated with miltefosine showed decreased cell viability and chromatin condensation under PI staining, which indicates that miltefosine may induce apoptosis-like cell death in C. krusei. In conclusion, we found miltefosine has a good activity against C. krusei isolates and exerts its fungicidal effect by binding to ergosterol in the cell membrane and inducing apoptosis.