Necrotizing fasciitis (NF) is a severe, rapidly spreading soft-tissue infection with high morbidity and mortality. Bacteriology in NF may be varied, and the etiology is often polymicrobial. It is important to consider the potential for fungal involvement despite its rarity. Cryptococcal NF has been reported in immunocompromised patients, with Cryptococcus neoformans being the most common offending organism.1-4
C neoformans is a basidiomycotic yeast that was previously considered a homogenous species.5,6 From the antigenic properties of its polysaccharide capsule, 3 main variants were described: C neoformans var. grubii, C neoformans var. neoformans, and C neoformans var. gattii. Subsequently, C neoformans var. gattii was found to be genetically and biochemically different from C neoformans. This discovery led to the distinction of C neoformans var. gattii as a separate species and it being renamed C gattii.6
C gattii was first recognized on Vancouver Island in 2001.7 Although C gattii is predominantly restricted to tropical and subtropical climates, its true epidemiology has been limited by diagnostic methods. C gattii can be diagnosed with laboratory culture media such as birdseed agars and L-canavanine-glycine-bromothymol (CGB) agar.6 However, most reports of Cryptococcus NF do not specify the culture media used to isolate Cryptococcus. In addition to culture media, molecular genotyping studies also allow for confirmation of the diagnosis of C gattii and have the added benefit of enabling identification of the molecular genotype. Nonetheless, in many clinical microbiology laboratories, Cryptococcus is not identified to the species level, much less to the molecular genotype.7 Given these diagnostic limitations and the fact that C gattii was only recently identified as a separate species, it is possible that any pre-2006 cases of NF attributed to C neoformans could in fact have been caused by C gattii.
In this article, we review the literature and report a case of NF of the hand that was caused by C gattii in a patient with diabetes. To our knowledge, this is the first reported case of NF caused by C gattii. The patient provided written informed consent for print and electronic publication of this case report.
A 73-year-old man was admitted with a 1-week history of swelling and pain in the dorsum of the left hand. He had been sitting in an outdoor eatery in Singapore when an insect bit the hand over the dorsum. Two days later, he consulted his family physician, who began treatment with oral amoxicillin/clavulanic acid. After 4 days of treatment, there was clinical progression of increased swelling and pain in the hand. Six days after initial injury, the patient presented to the department of orthopedic surgery.
Physical examination revealed diffuse, brawny, nonfluctuant swelling over the entire dorsum of the left hand (Figure 1). There was a 1×1-cm ruptured blister with some nonpurulent discharge just distal to the wrist joint. Neurovascular status and the extensor mechanism of the fingers were intact. The wrist joint had full range of motion. There was no fever.
Laboratory testing revealed an elevated white blood cell count (16.6×109/L), a C-reactive protein (CRP) level of 237 nmol/L, a random blood glucose level of 12.6 mmol/L, and a LRINEC (Laboratory Risk Indicator for Necrotizing Fasciitis) score of 7.8
Given the severe swelling, intravenous amoxicillin/clavulanic acid was started. The patient received a total of 3 doses before operative débridement of the left hand. Operative findings were NF of the hand, grayish necrotic fascia, and foul-smelling “dishwater” fluid. A single specimen of fascia from the surgical site was sent for examination. Histopathologic examination of formalin-fixed, paraffin-embedded tissue revealed necrotizing suppurative inflammation with fungal organisms present (Figures 2, 3).
Tissue cultures were obtained during surgery. The organism grew as scanty, small, wet-looking colonies on sheep blood agar after 48 hours of incubation. Microscopy revealed an oval yeast. The organism was identified and reported as C gattii by matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS; Biotyper 2.0.1 software; Bruker Daltonics), with a score of 1.914.9 All other intraoperative cultures for aerobic and anaerobic bacteria were negative. Molecular genotyping was performed with polymerase chain reaction assay to identify the molecular subtype.10C gattii genotype VGII was isolated. A cryptococcal serum antigen assay was positive at 1:256.
A series of tests was performed to screen for disseminated disease. Blood cultures were negative for fungus. Chest radiography and computed tomography of the brain did not show any pulmonary or cerebral involvement. Cerebrospinal fluid was not available for examination, as the patient declined lumbar puncture. Blood tests included a negative result for human immunodeficiency virus (HIV). The patient was found to have previously undiagnosed diabetes mellitus (hemoglobin A1c, 7.9%). T-cell counts and ratios were normal.