Catheter-Associated Rhodotorula mucilaginosa Fungemia in an Immunocompetent Host
A 77-year-old man with a history of diabetes, hypertension, and Parkinson's disease developed new-onset fever 10 days after admission at the intensive care unit of our hospital. He was initially diagnosed with community-acquired pneumonia at right lower lung, and received ceftriaxone and azithromycin as empirical intravenous antibiotics. Because he was in a hypoxic state, he was transferred to the intensive care unit and started on mechanical ventilation. We inserted a central venous catheter for monitoring the central venous pressure and total parenteral nutrition. Six days after admission, a chest radiograph showed diffuse, peripherally located reticulonodular infiltrates in both lung fields. Pseudomonas aeruginosa was isolated in the sputum. We diagnosed the patient with ventilator-associated pneumonia and switched the antibiotic regimen to piperacillin-tazobactam. Following the modified treatment, the patient's fever decreased and other laboratory parameters stabilized. Ten days after admission, new-onset fever developed. The patient's vital signs were as follows: temperature was 38.4℃, pulse rate was 90 beats/min, respiratory rate was 24 breaths/min, and blood pressure was 130/80 mmHg. Further laboratory evaluation demonstrated the following results: white blood cell count 6,090/mm3 (neutrophils 86.4%), hemoglobin was 8.6 g/dL, platelet count was 119,000/mm3, blood urea nitrogen was 30 mg/dL, creatinine was 1.8 mg/dL, aspartate aminotransferase was 18I U/L and alanine aminotransferase was 81 IU/L. Two sets of blood culture were drawn, from peripheral venipuncture and the central venous catheter. After 72 hours, both blood culture sets had confirmed fungal growth with a yeast form. Blood cultures drawn from the central venous catheter demonstrated positive results 3 hours earlier than the peripheral cultures. We diagnosed the patient with central venous catheter-associated blood-stream infection and started intravenous fluconazole (400 mg/day) and removed the catheter. The yeast was subsequently subcultured on Sabouraud dextrose agar, producing multiple colonies. They were moist, glistering, smooth to mucoid and salmon pink to coral red color. Gram staining revealed budding yeast cells, which were short, ovoid, 2-6 µm in diameter and arranged in short chains and clusters. The organism was urease-positive and did not ferment conventional sugars. The isolate was identified as R. mucilaginosa on the basis of these characteristics and by an API 20C AUX system. (bioMerieux, Marcy l'Etoile, France). In addition, we identified the isolate using sequences of the D1/D2 domain of the large subunit (LSU) rRNA. Portions of the LSU rRNA gene were amplified using the primer sets LSU-F (5'-GCA TAT CAA TAA GCG GAG GAA AAG-3') and LSU-R (5'-GGT CCG TGT TTC AAG ACG-3') []. Unambiguously determined sequences (559 bp) were compared with the GenBank public database, using the BLASTn program (). The LSU rRNA gene sequence of the isolate showed 100% similarity with R. mucilaginosa ATCC32736T followed by 96.7% with Rhodosporidium sphaerocarpum SJ105 (AY953966). Thus, we could confirm that the isolate was R. mucilaginosa.\nAfter 5 days, we changed fluconazole to amphotericin B deoxycholate. New sets of blood culture drawn 48 hours later were also positive for yeast, confirmed as R. mucilaginosa. After 3 days of amphotericin B treatment, we switched the patient to liposomal amphotericin B because he developed azotemia. The patients responded to this treatment; fever resolved and blood culture result converted to negative. Liposomal amphotericin was continued for 10 days and followed by fluconazole for an additional 14 days. After 34 days of additional hospitalization, he was discharged to a long-term care facility.