Development of lyophilized faecal inoculation capsules for use in koala rehabilitation and conservation
Year: 2026
Type: preprint
Abstract: As a specialist herbivore, koalas rely on their gut microbiomes to help digest their toxic and fibrous diet of Eucalyptus leaves. Without these critical microbes, koalas may not be able to obtain the nutrients and energy they need to survive. As such, a large proportion of koalas that undergo rehabilitation for chlamydiosis develop gut dysbiosis from the antibiotic treatment and are either euthanized or die. Here we aimed to modify previously developed fresh faecal inoculation capsules for an extended shelf-life such that they could be applied in a clinical setting to prevent or treat gut dysbiosis. Using 16S rRNA gene amplicon sequencing we demonstrated that air-drying faecal material leads to an overgrowth of facultative anaerobes, whereas lyophilised material retains a similar microbial composition to fresh material. Initial survival of koala faecal microbes as assessed by live/dead staining combined with microscopy was high after lyophilisation regardless of which excipient was used, except for 20% glycerol that resulted in ∼15% lower survival than other treatments. Lyophilised fine particles extracted from koala faeces and packaged into acid-resistant capsules maintained their original microbial composition and had high microbial survival over a year, regardless of the excipient used. Dry-fill, single-layer capsules maintained integrity after 10 hrs in synthetic koala stomach acid. These capsules may be useful in adapting the gut microbiomes of koalas to novel diets e.g. during translocations. However, attempts to apply the capsules in the clinical setting were unsuccessful due to unanticipated difficulties in administrating the capsules to sick koalas. Importance In recent years wildlife conservation has begun to appreciate the importance of the gut microbiome to animal nutrition, health and fitness. This has led to the increasing use of probiotics and faecal transplants to change or support the gut microbiomes of animals during translocation, reintroduction and rehabilitation. Unfortunately, in many instances it is difficult to source appropriate inoculant for these interventions and what is available often has limited viability. In this study, we developed and tested acid-resistant faecal inoculation capsules for use in koalas and showed that they have a shelf-life of at least a year at room temperature. These capsules may be useful in adapting the gut microbiomes of koalas to novel diets during translocations and the lyophilisation approach will contribute to the ongoing development of strategies to prevent gut dysbiosis during antibiotic treatment. The design of the capsules could also be adapted for use in other wildlife species.
Institution: The University of Queensland
Language: English
Topic: Gut microbiota and health
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7214963253