Isolation of Cryptococcus humicolus from an immunocompromised HIV-negative patient

Abstract number: 1734_178

Baka S., Antonopoulou S., Salomidou P., Meretaki S., Kaparos G., Demeridou S., Velegraki A., Kouskouni E.

Objectives: Cryptococcosis is a disease caused usually by Cryptococcus neoformans, an encapsulated yeast-like organism. The number of species included in the genus Cryptococcus has increased over the last years. Cryptococcus humicolus is a rare opportunistic yeast which starts to be implicated more often in diseases of severely debilitated hosts. Prevalence data are not available since the reports in the literature are scarce. We report a case of cryptococcaemia by C. humicolus in an immunocompromised HIV-negative surgical patient.

Methods: A 39-year old man was referred to our hospital with a history of sigmoidectomy and colostomy 2 months ago because of permeative peritonitis on the ground of acute diverticulitis. Two explorative laparotomies and drainage of the intraabdominal collection were also performed. He presented in a septic condition and 2 sets of blood cultures were sent to the laboratory on admission in the ICU. Identification of the pathogen was performed using the API System (boiMérieux, France) and susceptibility testing was carried out with 2 different methods (NCCLS and E-Test).

Results: Blood cultures became positive after two days of incubation and C. humicolus was identified by means of colonies' characteristics, Gram stain morphology and ID 32 API (boiMérieux, France). The isolated strain was sensitive to the antifungal agents studied: NCCLS (amphotericin B, fluconazole, voriconazole) and E-Test (amphotericin B, 5-fluorocytocine, ketoconazole, fluconazole, itraconazole). Two new antifungal agents, caspofungin and posaconazole, were tested and the MIC for caspofungin was 4 in both methods while for posaconazole 0.125 and 0.064, respectively. The patient was immediately put on liposomal amphotericin B, voriconazole and fluconazole. Clinical improvement was seen after 3 weeks of treatment and the patient was discharged from the ICU.

Conclusions: It seems that C. humicolus emerges as an important pathogen in HIV-negative patients. Diagnosis must rely on positive cultures followed by identification of the pathogen. Early recognition and proper therapy after appropriate susceptibility testing may improve clinical outcomes.