Development of High-Level Echinocandin Resistance in a Patient With Recurrent Candida auris Candidemia

Open Forum Infect Dis. 2019 Jun 1;6(7):ofz262

Contributed by Dr Tanu Singhal

This is a case report of a 54-year old Africo-American man with multiple comorbidities (quadriplegia, multiple chronic wounds, osteomyelitis of the right hip with abscess formation, and active deep venous thrombosis in the right upper extremity), on a long term urinary catheter who had been admitted multiple times over 5 months. During this period, the patient had 11 urine cultures positive for candida (9 unidentified and 2 C. lusitaniae), 2 blood cultures which initially grew echinocandin susceptible C. auris (which had been misidentified as C. haemolunii by MALDI-TOF MS initially) and 1 blood culture which turned out to be an echinocandin resistant C.auris which could not be identified by Vitek MS. The patient had received multiple antibiotics and a long duration of echinocandins. Through this case, the authors wanted to highlight 4 key areas of concern with respect to C.auris: misidentification, persistence, recurrence, and the development of resistance.

In this patient, of the 14 positive cultures of candida isolates (11 Urine and 3 blood), candida species could not be identified in 11 samples (9 urine and 2 blood), 2 were identified as C.lusitaniae and 2 were identified as C. haemolunii by MALDI-TOF MS, both of which are closely related phylogenetically with C. auris. The latter 2 cultures were properly identified as C. auris by the Mycology Reference lab. The authors believe that the isolates identified as C. lusitaniae represent un/misidentified C. auris. Misidentification of C. auris may delay the implementation of infection control and prevention practices which predisposes to patient to patient transmission causing outbreaks. The authors recommend that apart from the CDC recommendations of further testing isolates of C. haemolunii and those species which are unidentified, institutions that utilize MALDI-TOF MS technology also should perform further identification testing on isolates of C. lusitaniae.

C. auris has the striking ability to cause persistent colonization or infection. Important risk factors associated with C. auris include the use of broad spectrum antibiotics and antifungals, urinary and central venous catheters, chronic wounds, immunosuppression, and mechanical ventilation. Authors opine that persistent colonization may lead to recurrent episodes of candidemia and suggest removal of urinary catheters as soon as feasibly possible. It is challenging to treat C.auris candiduria due to almost universal resistance to fluconazole, and poor urinary penetration of other azoles and echinocandins. Although the clinical experience with flucytosine to treat C. auris urinary tract infections is limited, this drug warrants consideration given the lack of primary resistance, excellent urinary penetration and clinical utility in symptomatic fluconazole-resistant C. glabrata. Amphotericin bladder wash may need to be considered too in case of lower urinary tract infections with susceptible C. auris strains due to limited treated options. Echinocandin resistance in C.auris, as described in this case and in a few others is caused by a point mutation in the FKS1 region, owing to previous exposure to echinocandins. The authors thus recommend that although there are no approved susceptibility breakpoints for C. auris, susceptibility testing must be performed for patients with persistent or recurrent infections who have previously received an echinocandin.