Page 4 - Clinical Connections - Summer 2022

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Page 4 - Clinical Connections - Summer 2022
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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
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