Central-Line–Associated Bloodstream Infection Caused by Sporobolomyces salmonicolor

To the Editor—Sporobolomyces salmonicolor is one of the Basidiomycetous yeasts, which include Cryptococcus spp., Malassezia spp., Rhodotorula glutinis, and Trichosporon asahii. ¹ It has long been isolated from environmental sources, such as freshwater, marine water, air, tree leaves, and orange peels. ² However, Sporobolomyces species causing human infections have rarely been reported, ^{2 – 7} and most of the reported cases developed in AIDS patients. ^{5 , 6} To best of our knowledge, central-line–associated bloodstream infection caused by S. salmonicolor has not been previously reported.

A 65-year-old woman with poorly controlled diabetes mellitus was admitted for evaluation of a breast mass of approximately 9×9 cm. After serial examinations, local advanced breast cancer was diagnosed. Ten days later, she received central-line insertion due to poor venous access. However, she developed a fever after 3 weeks of hospitalization. Physical examinations were unremarkable except for the breast mass. Laboratory examination results were as follows: white blood cell count (WBC), 29,400/mm³ (94.1% neutrophils) and C-reactive protein, 297.2 mg/L (normal reference, <3 mg/L). Neither pyuria, bacteria, nor funguria was detected by urinalysis. Chest radiography did not show any active lung lesions. An empirical antibiotic with ciprofloxacin (400 mg every 8 hours) was prescribed, but in vain. Three days later, blood cultures from the central venous catheter (CVC) and peripheral blood yielded a yeast-like organism. Therefore, intravenous micafungin was added to the regimen to cover fungemia. However, no other specimens, including sputum, or urine grew any yeast. Finally, the pathogen was further identified as S. salmonicolor. The antifungal treatment was shifted to voriconazole, and the CVC was removed. Thereafter, her fever abated and repeated blood culture did not yield fungus.

S. salmonicolor rarely infects humans, and the infections reported include endophalmitis, meninigitis, lymphadenitis, and dermitis. ^{2 , 3 , 6 , 7} Herein, we present the first reported case of a central-line–associated bloodstream infection caused by S. salmonicolor. Our finding indicates that S. salmonicolor can cause catheter-associated infection and further expands the clinical spectrum of S. salmonicolor infections.

Most reported cases have shown that Sporobolomyces spp. develops in immunocompromised patients, especially patients with AIDS. ^{5 , 6} Although the patient in the present case did not have AIDS, the possible risk factor may be the underlying breast cancer and poorly controlled diabetes mellitus. In contrast, Sporobolomyces spp. infection is known to develop among immunocompetent patients, as in 1 reported case with endogenous endophalmitis ² and another case with possible meningitis. ⁴ All of these findings suggest that clinicians should consider Sporobolomyces spp. as a possible pathogen for immunocompromised patients, such as HIV-infected patients, cancer and diabetic patients, and even rarely for immunocompetent patients.

The clinical outcomes of patients with S. salmonicolor fungemia have not been well defined because of the limited number of cases. In the present report, the patient had favorable outcomes after antifungal treatment and removal of catheters. However, further large-scale studies are needed to better understand the clinical manifestations and prognosis of S. salmonicolor fungemia.

Because the studies and the reported case regarding S. salmonicolor infections are limited, the drug of choice remains unclear. A previous in vitro study ¹ showed that the minimum inhibitory concentration needed to kill 90% of the organisms (MIC₉₀) of the tested azoles, including albaconzaole, voriconazole, itraconazole, ravuconazole, ranged only from 0.06 to 0.12 µg/mL. In contrast, the MIC range and MIC₉₀ of the micafungin were as high as 128 and 128 µg/mL, respectively. Based on the aforementioned in vitro studies, azoles may be considered the drugs of choice to treat S. salmonicolor infection.

In conclusion, S. salmonicolor is an emerging pathogen that can cause invasive infections, and it may play an important role in the clinical setting of central-line–associated bloodstream infections. Healthcare-associated catheter-associated bloodstream infections due to that pathogen may respond well to an appropriate antifungal agent plus catheter removal.