Candida colitis is a very rare condition that affects mainly immunocompromised patients [1],[2],[3]. While there are nearly 150 species in the genus Candida, C. albicans, glabrata, and tropicalis comprise greater than 80% of all clinically isolated Candida cases [3]. Most of the reported cases of Candida colitis are of C. albicans infections with only one reported case of C. glabrata [4] and C. tropicalis [5]. Our patient, to the best of our knowledge, is the first reported case in the literature of C. krusei-induced colitis.

A 68-year-old male with stage IIA kappa light chain multiple myeloma and a history of two previous complicated autologous peripheral blood stem cell transplants was admitted to the bone marrow transplant unit. After undergoing BEAM conditioning (carmustine, etoposide, cytarabine, and melphalan), the patient received a stem cell transplant from his human leukocyte antigen (HLA)-identical brother. Fifteen days post-transplant, the patient showed no signs of engraftment yet was pancytopenic and displayed altered mental status. He experienced nausea, vomiting, and fifteen to twenty large watery bowel movements per day without improvement with anti-diarrheal medications or octreotide. The patient experienced weight loss and developed acute kidney injury secondary to dehydration. Computerized axial tomography (CT) scan of the abdomen showed subtle bowel wall thickening in the ascending colon and cecum. Esophagogastroduodenoscopy and colonoscopy (Figure 1) were performed and demonstrated white plaques within the esophagus and mucosal ulceration within the colon. Histologic examination of biopsy specimens showed yeast forms within the ascending colon and esophagus (Figure 2 and Figure 3). Yeast forms were identified within mucosa, lamina propria, and within vascular spaces. Concomitant blood cultures were positive for C. krusei. Sensitivities showed the organism to be resistant to fluconazole, but susceptible to micafungin. The patient was initiated on Micafungin 150 mg intravenously (IV) daily and follow-up blood cultures demonstrated no growth. Ophthalmology evaluation showed no endophthalmitis or eye involvement. Transthoracic echocardiogram was negative for presence of vegetation.

C. krusei was first discovered in 1839 [6]. It is considered a commensal organism in humans with very low pathogenicity [3]. It has been isolated from mucosal membranes of healthy individuals and has been found in soil and various foods. C. krusei is biotechnologically employed in the fermentation of cocoa to chocolate and the fermentation of milk and juices [6]. Interestingly, recent genome sequencing showed that C. krusei and Pichia kudriavzevii are the same species with P. kudriavzevii being the sexual teleomorph form, thus it is possible in the near future that one of these classifications is removed from the taxonomy [6]. Rarely, C. krusei is implicated as an opportunistic infection causing candidemia, candiduria, disseminated infection, including soft tissue infection, or endophthalmitis [7],[8],[9]. Fortunately, krusei is the least common of the non-albican Candida species to cause disseminated infection because it has the lowest 90-day survival rates (53.6%) among the common Candida spp. [10]. Severe immunodeficiency is a high-risk factor for the development of a C. krusei infection, such as azole prophylaxis, hematologic malignancies, stem cell recipients, and corticosteroid therapy [3],[11]. C. krusei is intrinsically resistant to fluconazole [12] due to decreased sensitivity of cytochrome p450 isoenzyme [13]. Therefore, the use of alternative azoles, including posaconazole or voriconazole, echinocandins or amphotericin B, is required for treatment [14].

The presenting patient had several risk factors including hematologic malignancy, neutropenia, and immunosuppression after three peripheral blood stem cell transplants, and previous azole anti-fungal therapy. He developed candidemia and Candida colitis with diarrhea without any abdominal pain or fever. On the contrary, the patient who had developed C. tropicalis colitis had developed large voluminous mucous diarrhea and high-grade fever of 39 °C. In addition, stool examination revealed a few white red blood cells [5]. In contrast, the C. glabrata colitis patient presented with bloody diarrhea associated with sepsis and multi-organ failure [4].

Candida colitis is rarely reported in literature and to the best of our knowledge our patient is the first reported case of C. krusei colitis. For patients who are considered to be at high risk for opportunistic infections, Candida species should be considered as a possible cause for colonic and other gastrointestinal symptoms, such as diarrhea, melena, and nausea. Fungal cultures are vital to identify the specific fungal organism to determine the appropriate antifungal therapy taking into consideration drug sensitivity and intrinsic resistance, especially in cases of C. krusei.