Oxalate‐degrading bacteria, including Oxalobacter formigenes, colonise the gastrointestinal tract of healthy koalas (Phascolarctos cinereus) and those with oxalate nephrosis

Abstract

Background Koalas in the Mount Lofty Ranges, South Australia, have a high prevalence of oxalate nephrosis, or calcium oxalate kidney crystals. Gastrointestinal tract oxalate‐degrading bacteria, particularly Oxalobacter formigenes, have been identified in other animal species and humans, and their absence or low abundance is postulated to increase the risk of renal oxalate diseases. This study aimed to identify oxalate‐degrading bacteria in the gastrointestinal tract of koalas and determine their association with oxalate nephrosis. Methods Caecal and faecal samples were collected at necropsy from 22 Mount Lofty Ranges koalas that had been euthanased on welfare grounds, with 8 koalas found to have oxalate nephrosis by renal histopathology. Samples were analysed by PCR for the oxc gene, which encodes oxalyl‐CoA decarboxylase, and also by Illumina sequencing of the V3–V4 region of the bacterial 16S rRNA gene. Results The oxc gene was detected in 100% of koala samples, regardless of oxalate nephrosis status. Oxalobacter formigenes was detected in all but one faecal sample, with no difference in abundance between koalas affected and unaffected by oxalate nephrosis. Other species of known oxalate‐degrading bacteria were infrequently detected. Conclusion This is the first study to identify Oxalobacter and other oxalate‐degrading bacterial species in koalas, but an association with oxalate nephrosis and absence or low abundance of Oxalobacter was not found. This suggests other mechanisms underlie the risk of oxalate nephrosis in koalas.

Histological survey for oxalate nephrosis in Victorian koalas (Phascolarctos cinereus)

“…The histopathological features in Victorian koalas were as described previously in Mount Lofty Ranges koalas, 2 suggesting a common aetiology. Causes of oxalate nephrosis in other mammalian species include high dietary intake of oxalate or its precursors or absence of oxalate degrading gastrointestinal microorganisms; these have previously been investigated in Mount Lofty Ranges koalas 5,6 and not been considered to be primary causes. It is currently hypothesised that oxalate nephrosis in Mount Lofty Ranges koalas may in fact have a genetic basis, based on their bottlenecked history of translocation via Kangaroo Island from French Island, 10 which itself was founded with as few as two to three individuals from South Gippsland, Victoria in the 1880s.…”

“…2 Oxalate nephrosis is an uncommon finding in koalas elsewhere, with <2% prevalence of oxalate nephrosis found in necropsied New South Wales koalas. 4 The primary cause of oxalate nephrosis in Mount Lofty Ranges koalas remains unknown, but dietary 5 and gut microbial 6 causes have been investigated previously and are thought to play secondary, rather than primary, roles.…”

Porphyromonas spp., Fusobacterium spp., and Bacteroides spp. dominate microbiota in the course of macropod progressive periodontal disease

“…Adapter trimming, fixed length trimming, merging paired reads and filtering based on the number of reads (to remove the samples with low coverage) were performed to obtain high quality sequence reads with enough depth for microbiota profiling and comparison as previously described 37 . CLC Microbial Genomics Module (QIAGEN) Version 11 was used to assign taxonomy to the reads from different samples.…”

In this issue ‐ May 2019: West Nile virus in horses · Treating horses with dexamethasone via nebulisation · Animal hoarding in NSW · Dangers of powdered washing soda for emesis in dogs · Pneumocystis in a dog following toceranib phosphate · Oxalate nephrosis in koalas

“…7 The cause is unknown and does not appear to be related to oxalate levels in eucalyptus leaves. 7 The cause is unknown and does not appear to be related to oxalate levels in eucalyptus leaves.…”

“…Koalas in the Mount Lofty ranges in South Australia have a higher incidence of oxalate nephrosis that those in other areas. 7 The cause is unknown and does not appear to be related to oxalate levels in eucalyptus leaves. However other herbivores that eat high levels of oxalate (such as the cactus-eating woodrat) have been found to have oxalate-degrading bacteria in the gastrointestinal tract, in particular Oxalobacter formigenes, which is a specific degrader that uses oxalate as its only source of energy.…”