Conclusion: BDG is a useful biomarker in the diagnosis of IFI and for antifungal stewardship, best utilised as an adjunct to clinical assessment. A KILLER DARLING – A CASE PRESENTATION OF HISTOPLASMA CAPSULATUM Bryant Koh, Rebecca Davis Department of Infectious Diseases and Microbiology, Royal Prince Alfred Hospital, Camperdown, NSW, Australia Darling’s disease has diverse presentations and raises several laboratory diagnostic and safety issues. This case report discusses the laboratory work-up of a renal transplant patient from New Caledonia, transferred with prolonged respiratory illness progressing to respiratory failure, and subsequent multi-organ failure. Disseminated histoplasmosis was diagnosed, with Histo- plasma capsulatum isolated from bronchoalveolar lavage and evidence of fungaemia in blood film examination. H. capsulatum is a dimorphic fungus with a wide spectrum of clinical disease manifestations. Strict adherence to laboratory protocols and risk assessment minimises risk of laboratory-related exposure and acquisition of disease. DIAGNOSTIC CHALLENGES IN HISTOPLASMOSIS: A RECENT CASE SERIES FROM ST VINCENT’S HOSPITAL, MELBOURNE Stephen Muhi, Penny McKelvie, Harsha Sheory St Vincent’s Pathology, St Vincent’s Hospital (Melbourne), Vic, Australia Histoplasma capsulatum is a zoonotic endemic mycosis with a widespread geographical distribution. The key challenges for clinicians include the non-specific presentation of acute cases and the indolent and undifferentiated nature of chronic and disseminated cases. The relative rarity of the organism, the lack of knowledge of autochthonous endemnicity and the limited availability of diagnostic tools are all limitations to timely diagnosis of this significant pathogen. Infection control issues are also an important consideration for diagnostic laboratories. These challenges are highlighted by a number of recent cases that have presented to St Vincent’s Hospital, Melbourne. PAEDIATRIC CANDIDAEMIA AND OTHER CHALLENGING FUNGAL INFECTIONS Tom M. Chiller Mycotic Diseases Branch, Centers for Disease Control and Prevention, Atlanta, Georgia, USA Paediatric fungal infections continue to remain both a diagnostic and treatment challenge. Infections are commonly seen in pa- tients with immunocompromising conditions and those on immunosuppressing medicines, but they can also be seen in pa- tients without obvious risk factors. Candidaemia in the paediatric population varies greatly by age where the highest incidence occurs in neonates. There has been a changing epidemiology in the type of species causing infection and the development of more highly resistant candida. Other fungal infections like aspergillosis and mucormycosis continue to cause high mortality in high risk patients. Overall, fungal infections remain under- diagnosed and therefore the true burden of diseases is unknown. Early and better diagnostics are needed. THE CONCEPT OF CLINICAL EQUIPOISE AND ITS RELEVANCE TO INFECTIOUS DISEASE CLINICAL TRIALS Matthias Maiwald 1,2,3 1 Department of Pathology and Laboratory Medicine, KK Women’s and Children’s Hospital, Singapore; 2 Department of Microbiology and Immunology, National University of Singapore, Singapore; and 3 Duke-National University of Singapore Graduate Medical School, Singapore Evidence-based medicine places big emphasis on randomised clinical trials and systematic reviews as the best evidence sour- ces. However, this may happen at the expense of other evidence sources, such as laboratory research. The relevant concept is the ‘evidence pyramid’, whereby evidence sources are ranked ac- cording to quality. However, ‘lower-level’ evidence often provides valuable information, and any drug development pro- gresses through stages, such as compound discovery, laboratory testing, preclinical testing, and clinical trials. The concept of clinical equipoise is a principle in research ethics that stipulates that there should be genuine uncertainty over which treatment is more effective, before starting a trial. If one treatment is already known to be superior, a trial may not be ethically justified. In the absence of prior trials, an important source to know about such imbalance is ‘lower-level’ evidence. I will provide examples from infectious disease research where clinical equipoise likely did not exist because other evidence sources indicated superi- ority of one treatment. I will discuss examples from antiseptic trials, antimicrobial treatment trials, and emerging infectious diseases trials. I will discuss ethical and research rigour implications, highlight potential approaches to address the problem, and call for a more holistic approach to evidence as- sessment. UPDATE ON TICK-BORNE INFECTIONS IN AUSTRALIA Stephen R. Graves 1,2 , John Stenos 1 1 Australian Rickettsial Reference Laboratory, University Hospital Geelong, Geelong, Vic, Australia; and 2 Department of Microbiology, Nepean Hospital, NSW Health Pathology, Penrith, NSW, Australia Bacterial infections due to Rickettsia spp. (spotted fever group rickettsiae) and Coxiella burnetii (Q fever) are the currently- known human pathogens transmitted by the bite of Australian ticks. There are likely to be others, not yet discovered, although it appears unlikely that Borrelia burgdorferi (Lyme disease) is endemic in Australia. Queensland tick typhus (Rickettsia australis), Flinders Island spotted fever (Rickettsia honei) and Australian spotted fever (R. australis subsp. marmionii) are the known tick-transmitted infections. There are no known viral human pathogens that are tick-trans- mitted in Australia, but this is likely due to ignorance rather than S58 PATHOLOGY 2019 ABSTRACT SUPPLEMENT Pathology (2019), 51(S1)