CRyptOcoccosis in Newcastle and the hUnTer (CRONUT) - An epidemiological study

Cryptococcus neoformans and Cryptococcus gattii are yeasts responsible for invasive infection, primarily pulmonary and neurological. Their clinical epidemiology has been previously described in an Australian national study, but this included no data from the Hunter region, where we anecdotally noted a high incidence of infection. We aimed to describe the epidemiology, management and outcomes of cryptococcal disease in the Hunter region and to compare this with previous Australian data.

We searched our laboratory database for positive cryptococcal antigen and culture results from January 2003-December 2016. We extracted demographic factors, risk factors, clinical presentation, treatment and outcomes from medical records. We used the 2010 census-derived estimated resident population to calculate population-based incidences.

Over a 13-year period, 107 patients had either a positive culture or a positive cryptococcal antigen with a compatible clinical syndrome. Of these, 46 (42.2%) were C. neoformans, 28 (25.7%) C. gattii, and 33 (30.3%) antigen only. The crude incidence (per million with 95% CI) for all disease was 9.5, and for culture proven disease was 2.5 for C. gattii and 4.1 for C. neoformans. Geospatial mapping by species revealed no evident cluster. Of the 63 patients where detailed information was available, around half were immunocompromised (3 [15%] for C. gattii and 25 [81%] for C. neoformans, p < 0.001). Complications were common, including visual loss (11 cases, 17.7%) and hearing loss (5 cases, 8%). Adverse outcomes at one year (death or neurological sequelae) occurred in 42%, and was significantly more likely (OR = 5.2, 95% CI 1.4-18.8) in those with raised intracranial pressure at baseline. Adverse outcomes were no more common in those treated with lower doses of liposomal amphotericin (≤150 mg/day, 5/10) than those treated with the recommended dose of 3-5 mg/kg (≥150 mg; 13/27).

Although a rare disease, cryptococcosis is more common in the Hunter region than in other parts of Australia, and long-term sequelae are serious and common.