In vivo emergence of high-level resistance during treatment reveals the first identified mechanism of amphotericin B resistance in Candida auris

OBJECTIVE

Candida auris has emerged as a healthcare-associated and multidrug-resistant fungal pathogen of great clinical concern. While as many as 50% of C. auris clinical isolates are reported to be resistant to amphotericin B, to date, no mechanisms contributing to this resistance have been identified. Here we describe the clinical case in which high-level amphotericin B resistance was acquired in vivo during therapy and undertake molecular and genetic studies to identify and characterize the genetic determinant of resistance.

METHODS

Whole genome sequencing was performed on four C. auris isolates obtained from a single patient case. Cas9-mediated genetic manipulations were then used to generate mutant strains harboring mutations of interest, and these strains were subsequently subjected to amphotericin B susceptibility testing, and comprehensive sterol profiling.

RESULTS

A novel mutation in C. auris sterol-methyltransferase gene, ERG6, was found to be associated with amphotericin B resistance, and this mutation alone conferred a >32-fold increase in amphotericin B resistance. Comprehensive sterol profiling revealed an abrogation of ergosterol biosynthesis and a corresponding accumulation of cholesta-type sterols in isolates and strains harboring the clinically-derived ERG6 mutation.

CONCLUSIONS

Together these findings definitively demonstrate mutations in C. auris ERG6 as the first identified mechanism of clinical amphotericin B resistance in C. auris and represent a significant step forward in the understanding of antifungal resistance in this emerging public health threat.

The role of fluorine-18 fluorodeoxyglucose positron emission tomography in patients with mycosis fungoides

Purpose:

The aim of the present study is to evaluate the possible role of fluorine-18 fluorodeoxyglucose positron emission tomography-computed tomography (¹⁸F-FDG PET-CT) in the management of mycosis fungoides (MF).

Materials and Methods:

Nineteen patients (mean age, 40.6 years; median age 41 years; 16 males and 3 females) with risk of secondary lymph node (LN) involvement (those with large cell transformation, tumors, erythroderma, or enlarged LNs on physical examination) were included in the study. All patients underwent PET-CT scan by injecting 0.06 mCi/kg of F18 FDG. The maximum standard uptake value (SUVmax) was recorded for each patient.

Results:

The ¹⁸F-FDG PET-CT was positive in 15 patients. PET-CT detected local cutaneous disease in 13 cases. The range of SUVmax is 2.8–14.1. Out of 19 patients, hypermetabolic adenopathy is found in 9 patients and visceral involvement in one.

Conclusions:

Although the study population is small our findings suggests that ¹⁸F-FDG PET-CT can detect cutaneous and extracutaneous lesions in MF and may guide biopsies especially in patients with risk of secondary LN involvement.