Page 4 - Clinical Connections - Summer 2022

RVC RESEARCH STUDY VETERINARY SERVICES RVC.AC.UK
Advancements
MALASSEZIA AND DOGS WITH CHRONIC
ENTEROPATHY

Ross Bond, Professor of Veterinary Dermatology, and Aarti Kathrani, Senior Lecturer in Small Animal
Internal Medicine
he veterinary profession is whereas fungi have received much chronic inflammatory enteropathy (n=38),
increasingly aware of the role less attention. More recently however, granulomatous colitis (n=2), gastric
T intestinal dysbiosis may play in a considerable scientific interest in enteric adenocarcinoma (n=2), duodenal small
range of disorders in body systems other Malassezia has developed following cell lymphoma (n=1) and idiopathic
than the gastrointestinal tract. Attention has recognition of significant fungal dysbiosis in severe gastrointestinal hemorrhage
tended to focus on bacterial dysbiosis of the humans with Crohn’s disease, a subtype of (n=2). Fungi were cultured from 14 dogs:
gut but the role of intestinal fungal dysbiosis human inflammatory bowel disease. M. pachydermatis was isolated from
in the overall process is something we are eight (chronic inflammatory enteropathy
exploring as well. [n=7] [along with Candida albicans
The RVC’s Dermatology Service has n=1]; granulomatous colitis [n=1]) and
been investigating colonisation and M. sympodialis from another (gastric
infection of canine and feline skin by adenocarcinoma). Five dogs with chronic
Malassezia yeasts since 1992, when inflammatory enteropathy yielded
Professor Bond undertook a PhD research other yeasts (C. albicans, C. glabrata,
programme funded by Clinical Studies Kazachstania slooffiae, K. telluris, Pichia
Trust Fund, the predecessor of BSAVA kudriavzevii [syn. C. krusei]).
Petsavers. During that time, Mrs Anne Cytological specimen from the duodenum of Yeast organisms were not observed
a dog with small cell duodenal lymphoma.
Lamport, the then dermatology research Whilst bacteria and fungi were rarely in any of the biopsy specimens by
technician, noted the occasional isolation observed in cytological specimens from the histopathological examination, despite
of M. pachydermatis from duodenal juice duodenum in this study, this dog had quite staining with Gomori’s methenamine
abundant cocci and rods.
samples obtained during endoscopy of silver (which stains fungal cell walls
dogs with enteropathy. Although this was Furthermore, Malassezia spp. dysbiosis black). In cytological samples stained
not followed up, there were no reports of has been implicated in tumorigenesis with Diff-Quik (n=45) and examined using
the isolation of this genus from the intestine of human and mouse pancreatic ductal light microscopy, yeasts / fungi were
of mammals at that time. The usual adenocarcinomata. In mouse models, never observed. However, in cytological
ecological niche for this genus of lipophilic fungal ablation was tumour-protective, specimens also stained with calcofluor
yeasts is the stratum corneum of a variety whereas Malassezia re-population white and examined using fluorescence
of mammals and birds. accelerated oncogenesis. These microscopy (n=19), fungi were observed
observations, and our own previous only in one case. In this case, a single
unreported observations from the 1990s, example of a yeast with a germ tube was
prompted Professor Bond and Dr Aarti noted (Kazachstania slooffiae isolated).
Kathrani to devise a study with the aim of Dogs with yeast growth had significantly
defining the duodenal mycobiota of dogs higher serum vitamin B12, canine chronic
undergoing endoscopy for the investigation enteropathy clinical activity index and
of chronic enteropathy. The study was done dermatological signs at the time of yeast
in collaboration with Bart Theelen of the isolation versus those with no growth
Westerdijk Fungal Biodiversity Institute, (p=0.003, p=0.034 and p=0.043)
Utrecht, and funded by BSAVA Petsavers. To our knowledge, this is the first report
The study was approved by the RVC’s of isolation of M. pachydermatis, and M.
Clinical Research Ethical Review Board sympodialis and Kazachstania spp. from
Primary isolation plates (Sabouraud’s and informed consent was obtained from the canine duodenum. Future studies
dextrose agar) showing growth of dog owners prior to sampling. Quantitative will help to determine the effect of yeast
Kazachstania telluris from the duodenum of a microbial culturing was performed on colonization on treatment response and
dog with chronic intestinal enteropathy. Note
the larger colonies on plates incubated at duodenal juice aspirated from dogs with prognosis – and thus whether any benefit
37oC (left plate) versus 32oC (right plate). suspected chronic enteropathy during could be gained from anti-fungal therapy
routine upper gastrointestinal endoscopy. in these dogs. We are most grateful to
The mammalian intestinal microbiota Samples were cultured on Sabouraud the owners of the dogs for agreeing to
represents a highly complex ecosystem dextrose agar and modified Dixon agar participate in the study, and to the members
of bacteria, fungi, viruses and protozoa for 14 days. Isolates were identified of the Internal Medicine and Endoscopy
that protects the host against potential phenotypically, and by matrix-assisted teams who facilitated the investigation.
enteric pathogens. Microbial dysbiosis is laser desorption / ionisation time-of-flight
often marked in various enteropathies; (MALDI-TOF) and internal transcribed For small animal referrals, please call:
investigations have primarily focused on spacer (ITS) sequencing. 01707 666399
modifications in bacterial populations, A total of 45 dogs were recruited with Email:
qmhreception@rvc.ac.uk

4 Summer 2022