Cytology, culture and genomics to evaluate the microbiome in healthy rabbit external ear canals

Nikoleta Makri, Natalie Ring, Darren Shaw, Athinodoros Athinodorou, Victoria Robinson, Gavin Paterson, Jenna Richardson, Deborah Gow, Tim Nuttall

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Background: Lop-eared rabbits may be predisposed to otitis externa (OE) due to their ear conformation. Although otoscopy, otic cytology, and culture are valuable tools in dogs and cats, published data on rabbits is lacking.
Hypothesis/Objectives: This study aimed to assess the utility of otoscopy and cytology in evaluating healthy rabbit external ear canals (EECs) and to characterize ear cytological and microbiological findings through culture techniques and metagenomic sequencing.
Animals: Sixty-three otitis free client-owned rabbits.
Materials and methods: All rabbits underwent otoscopy and ear cytology. In a subset of 12 rabbits further bacterial and fungal culture, fungal DNA assessment, and metagenomic sequencing were performed.
Results: Otic cytology revealed yeast in 73%, cocci in 42.9%, and rods in 28.6% of healthy rabbit EECs. Compared to upright-eared rabbits, lop-eared rabbits had more discharge and more bacteria per oil immersion field (OIF). Culture isolated 8 different species but metagenomic sequencing identified 36, belonging to the Bacillota (Firmicutes), Pseudomonadota and Actinomycetota phyla. Staphylococcus were the most commonly observed species with both methods. Ten out of 12 rabbits were yeast-positive on cytology with only three yielding fungal growth identified as Yarrowia (Candida) lipolytica, Eurotium echinulatum, and Cystofilobasidium infirmominiatum.
Conclusions and clinical relevance: Healthy rabbit EECs lack inflammatory cells but can host yeast and bacteria, emphasizing the need to evaluate cytology alongside the clinical signs. Lop-ear anatomy may predispose to bacterial overgrowth and OE. Notably, yeasts may be present despite a negative culture.
Original languageEnglish
Pages (from-to)1-11
Number of pages11
JournalVeterinary Dermatology
Early online date14 May 2024
Publication statusE-pub ahead of print - 14 May 2024


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