Cytological and microbiotic aspects of the diagnosis of otitis externa in dogs

Cover Page

Cite item


The purpose of the study was to compare cytological samples from two consecutive swabs obtained from ear canals of dogs with otitis externa and to determine the minimum number of samples required to obtain up-to-date information on the degree of microbiological contamination of the affected ear canals. Samples were obtained using sterile applicators with a cotton tip, which were sequentially inserted into ear canal until slight resistance (the junction between vertical and horizontal parts of ear canal), after making a circular motion, the applicator was removed and the material from the tip was applied to the glass slide with rolling movements so that on each slide there were four single parallel smears — two from each ear of the dog. The slides were air dried for one hour and stained using the standard Diff-­Quick method. The actual counting was carried out at 1000 × magnification (at a high magnification field). Bacteria were differentiated according to their shape into cocci and bacilli. The numbers of bacteria and fungi in the two samples were compared using the Wilcoxon matched pair test. Qualitative agreement between two consecutive swabs was determined using the k-test. Among the studied animals, a breed predisposition to otitis externa was revealed in Cocker Spaniels and French Bulldogs, and an anatomical predisposition in animals with drooping auricles. There was no significant difference in the number of microorganisms present in two ear cytology samples taken consecutively from the same ear at the same site in the external auditory canal, and there was significant agreement between the results of two consecutive smears for the presence of cocci and rods. For yeast, the agreement was only moderate. The data obtained indicate that in cases of otitis externa in dogs, reproducibility of cytological pattern with a single sample of material, as a rule, reflects current stage of pathogenesis of the disease and provides the best opportunity to detect local proliferative activity of opportunistic microbiota and corresponding inflammatory response of the macroorganism.

Full Text


Table 1. Number of microorganisms on two consecutive swabs obtained from ears of 41 dogs with otitis externa, descriptive statistics


Arithmetic mean


Standard deviation

Confidence interval


Sample 1





Sample 2






Sample 1





Sample 2






Sample 1





Sample 2






Table 2. Cytological data of microorganisms of two consecutive smears taken from 302 ears of dogs with external otitis


Positive results

Similar results

Different results

of different results

















Table 3. Number and percentage of different combinations of microorganisms found in ears of dogs with otitis externa

Associativity of microorganisms

Yeasts (%)

Number of cocci (%)

Bacilli (%)

Not in combination (single organism)

58 (19)

24 (8)


In combination with:





180 (60)

2 (0.7)


180 (60)

6 (2)


2 (0.7)

6 (2)



About the authors

Egor A. Pustovit

Moscow State Academy of Veterinary Medicine and Biotechnology named after K.I. Scriabin

SPIN-code: 6055-0918
PhD student, Department of Immunology and Biotechnology, Faculty of Biotechnology and Ecology 23/6 Akademika Scryabina st., Moscow, 109472, Russian Federation

Nikolai V. Pimenov

Moscow State Academy of Veterinary Medicine and Biotechnology named after K.I. Scriabin

Author for correspondence.
ORCID iD: 0000-0003-1658-1949
SPIN-code: 1911-3815

Doctor of Biology, Professor, Department of Immunology and Biotechnology, Faculty of Biotechnology and Ecology

23/6 Akademika Scryabina st., Moscow, 109472, Russian Federation


  1. Hader C. Canine otitis externa - microbial investigations including antibiotic susceptibility testing of ear swabs from the year 2016. Kleintierpraxis. 2020;65:312-324. doi: 10.2377/0023-2076-65-312
  2. Goodale EC, Outerbridge CA, White SD. Aspergillus otitis in small animals - a retrospective study of 17 cases. Vet. Dermatol. 2016;27(1):3-e2. doi: 10.1111/vde.12283
  3. Saridomichelakis MN, Farmaki R, Leontides LS, Koutinas AF. Aetiology of canine otitis externa: a retrospective study of 100 cases. Vet Dermatol. 2007;18(5):341-347. doi: 10.1111/j.1365-3164.2007.00619.x
  4. August JR. Otitis externa: a disease of multifactorial etiology. Vet Clin North Am Small Anim Pract. 1988;18(4):731-742. doi: 10.1016/S0195-5616(88)50076-1
  5. Perry LR, MacLennan B, Korven R, Rawlings TA. Epidemiological study of dogs with otitis externa in Cape Breton, Nova Scotia. Can Vet J. 2017;58(2):168-174.
  6. Kowalski JJ. The microbial environment of the ear canal in health and disease. Vet Clin North Am Small Anim Pract. 1988;18(4):743-754. doi: 10.1016/S0195-5616(88)50077-3
  7. Kroemer S, El Garch F, Galland D, Petit JL, Woehrle F, Boulouis HJ. Antibiotic susceptibility of bacteria isolated from infections in cats and dogs throughout Europe (2002-2009). Comp Immunol Microbiol Infect Dis. 2014;37(2):97-108. doi: 10.1016/j.cimid.2013.10.001
  8. Santos AJ, Vieira MCG, Lima PPA, de Oliveira LRC, Cardinot CB, Rocha TVP, Lanna LLE, Franciscato C. Prevalência de microrganismos e ácaros encontrados em amostras dermatológicas e otológicas de cães e gatos. Revista Brasileira de Higiene e Sanidade Animal. 2020; 14(3):1-11.
  9. Woelms C. Otitis externa - Bacterial distribution and resistance patterns of isolates from swab samples from the year 2011. Kleintierpraxis. 2014;59(6):297-312. doi: 10.2377/0023-2076-59-297
  10. Nakamura T, Kitana J, Fujiki J, Takase M, Iyori K, Simoike K, et al. Lytic activity of polyvalent staphylococcal bacteriophage PhiSA012 and its endolysin Lys-­PhiSA012 against antibiotic-­resistant staphylococcal clinical isolates from canine skin infection sites. Front Med. 2020;7:234. doi: 10.3389/fmed.2020.00234
  11. Li Y, Fernández R, Durán I, Molina-­López RA, Darwich L. Antimicrobial resistance in bacteria isolated from cats and dogs from the Iberian Peninsula. Front Microbiol. 2021;11:621597. doi: 10.3389/fmicb.2020.621597
  12. Henneveld K, Rosychuk RA, Olea-­Popelka FJ, Hyatt DR, Zabel S. Corynebacterium spp. in dogs and cats with otitis externa and/or media: a retrospective study. J Am Anim Hosp Assoc. 2012;48(5):320-326. doi: 10.5326/JAAHA-MS-5791
  13. King SB, Doucette KP, Seewald W, Forster SL. A randomized, controlled, single-­blinded, multicenter evaluation of the efficacy and safety of a once weekly two dose otic gel containing florfenicol, terbinafine and betamethasone administered for the treatment of canine otitis externa. BMC Vet Res. 2018;14(1):307. doi: 10.1186/s12917-018-1627-5
  14. O’Neill DG, Jackson C, Guy JH, Church DB, McGreevy PD, Thomson PC, et al. Epidemiological associations between brachycephaly and upper respiratory tract disorders in dogs attending veterinary practices in England. Canine Genet Epidemiol. 2015;2:10. doi: 10.1186/s40575-015-0023-8
  15. O’Neill DG, Volk AV, Soares T, Church DB, Brodbelt DC, Pegram C. Frequency and predisposing factors for canine otitis externa in the UK - a primary veterinary care epidemiological view. Canine Med Genet. 2021;8(1):7. doi: 10.1186/s40575-021-00106-1

Copyright (c) 2023 Pustovit E.A., Pimenov N.V.

Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

This website uses cookies

You consent to our cookies if you continue to use our website.

About Cookies