Cryptococcus neoformans zyxw in tropical northern Australia: predominantly variant zyx gattii with good outcomes zy D. Fisher D. Lo Physician, Royal Darwin Hospital, Casuarina, NT. Physician, Royal Darwin Hospital, Casuarina, NT. J. Burrow B. Currie Physician, Royal Darwin Hospital, Casuarina, NT. Head ofclinical Unit, Menzies School of Health Research, Darwin; Physician, Royal Darwin Hospital, Casuarina, NT. Abstract Background: Infection with Cryptococcus neoformans is common in the Northern Territory of Australia. Disease is life threatening and treatment is prolonged and often complicated by the need for surgery and difficulties with medical therapy. zyxwvu Aims: TO document incidence, demography, risk factors, clinical features and outcomes of infec- tion and to determine differences between gattii and neoformans varieties. Methods: Case records of all patients (n zyxwvuts = 35) diagnosed with cryptococcal infection at the Royal Darwin Hospital between 1976 and 1992 were reviewed retrospectively. Current status of patients was ascertained. Variety identification of isolates was determined by growth in canavanine-glycine- bromthymol blue agar. Results: Of the 35 patients, 23 had meningitis, ten had pneumonia, one had a dermal infection and one had fingaemia with no obvious focus. Twelve (52%) meningitis cases and two (20%) pneu- monia cases had no predisposing disease. Thirteen zyxwv (57%) meningitis cases had concomitant pulmonary cryptococcosis. Twenty-nine patients were Aboriginal and zyxw six were Caucasian, with a relative risk for Aboriginals compared with non-Aboriginalsof 20.6 (95% CI 8.6-49.5). Arnhem- land was the commonest location of infection, with an annual incidence in Aboriginals of 0.14/1000. Fourteen (78%) of 18 isolates tested were C. neoformans var. gattii. Management was characterised by the frequent need for adjunctive surgery and prolonged or repeat courses of systemic antifimgal therapy. Despite this, long-term outcomes are encouraging with a mortality of 14% overall and 9% in meningitis patients. The river red gum (Eucalyptus camaldulensis) has a limited distribu- tion in Arnhemland and ongoing studies are seeking alternative environmental sources of C. neoformans var. gattii. (Aust NZ J Med 1993; 23: 678-682.) Key words: Cryprococcus neoformans, Cyptococcus neoformans var. guttii, meningitis, Aboriginal health. INTRODUCTION Cryptococcus neoformans is an encapsulated yeast-like fungus. Infection is considered to occur usually via inhalation of the organism from environmental sources. Two varieties, C. neofomans var. neofomans and C. neo- formans var. gattii were first distinguished in 1970 on morphological grounds.' Genetic, biochemical, serologic- al, ecological, epidemiological and possible virulence differences have since been To date, two environ- mental hosts of C. neofomans var. gattii have been iden- tified. They are the river red gum (Eucalyptus camaldu- lensisy and the forest red gum (Eucalyptusteretkornis). lo A host plant for C. neoformans var. neoformans has not been identified, but bird droppings (especially pigeon) may play a role in spread of the organism although zoonotic transmission remains to be documented.6 The Royal Darwin Hospital (RDH) serves an area of 670,000 km2and a population of 120,000, around one Correspondence ro: Dr Bart Currie, Menzies School of Health Researc :h, PO zyxwvu Box 41096, Casuarina, N T 0811, Australia. 678 Aust NZ J Med 1993; 23 FISHER ET AL.