Koalas in the Mount Lofty Ranges have been shown to have a high prevalence of renal dysfunction due to the formation of calcium oxalate crystals within the kidneys, oxalate nephrosis, however the cause is currently unknown. In humans, presence of Oxalobacter formigenes, a specialist oxalate-degrading bacteria found in the gastrointestinal tract, has been found to reduce the risk of calcium oxalate kidney stone formation in those who are genetically predisposed. This study aims to determine the presence of O. formigenes in koalas and its association with oxalate nephrosis. Caecal and faecal samples from 22 Mount Lofty Ranges (MLR) koalas that had been euthanased on welfare grounds were collected at necropsy (n=42 samples), with 9/22 koalas found to have oxalate nephrosis by kidney histopathology. Faecal samples were also collected from 20 wild-caught MLR koalas and 20 hospitalised Queensland (Qld) koalas, all of unknown oxalate nephrosis status. Total bacterial DNA was extracted using PowerFecal™ DNA Isolation kit (MO BIO Laboratories, Carlsbad, CA, USA). A standard DNA concentration of 5ng/μL was obtained before amplification in T100 Thermal Cycler (Biorad) for 16S metagenomics library preparation according to the manufacturer’s protocol. PCR was performed using O. formigenes specific primers OXFf and OXFr to detect the oxc gene, which codes for the enzyme Oxalyl-CoA decarboxylase. The oxc gene was seen in 100% of necropsied MLR koala caecal and faecal samples (42/42), regardless of oxalate nephrosis status. However Oxc was detected in only 45% of faecal samples from wild MLR koalas (9/20) and 55% of wild Qld koala faecal samples (11/20). Illumina MiSeq platform results for Oxalobacter spp detection in the faecal microbiome, targeting the V3-V4 region of the 16S rRNA gene, are pending. This is the first study to focus on detection of Oxalobacter spp. in koalas and its possible association with oxalate nephrosis, however a causative link has not been identified.
* Corresponding author: darren.trott@adelaide.edu.au