Ear cytology in dogs: cocci, yeasts and what to do next
2-year-old French Bulldog with a first episode of right otitis externa: erythema, brown wax and pruritus. Tympanic membrane visible and intact. Cytology of the wax stained with a Diff-Quik-type rapid stain:
| Parameter | Result | Reference |
|---|---|---|
| Yeasts (Malassezia) | 15–20 per field (×400) | < 5 per field |
| Cocci | 40–50 per field (×400) | < 25 per field |
| Rods | None seen | Absent |
| Neutrophils | None seen | Absent |
What is the most appropriate course of action?
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A. Culture and susceptibility testing before starting any treatment
It is not indicated in a first episode with cocci and yeasts: the pattern is predictable (Staphylococcus pseudintermedius and Malassezia) and responds to topical therapy. Culture is reserved for rods, recurrent non-responsive otitis or otitis media.
B. No treatment: those counts are within normal limits for a healthy canal
A healthy ear can have the odd yeast or coccus, but counts at this level, with clinical signs, indicate overgrowth. As a guide, in dogs ≥5 yeasts and ≥25 bacteria per ×400 field are considered abnormal.
C. Ear cleaning and topical treatment with antibiotic, antifungal and glucocorticoid; follow-up cytology
Correct. This is a mixed overgrowth of cocci and Malassezia. With an intact eardrum, a combined ear product and appropriate cleaning are the mainstay. Repeat cytology at the recheck (around 2 weeks): cure is confirmed by cytology, not by appearance alone.
D. Systemic antibiotic and antifungal (amoxicillin-clavulanate and ketoconazole)
Systemic treatment achieves low concentrations in the wax and canal epithelium, and exposes the animal to adverse effects and selection of resistance. Otitis externa is treated topically.
lightbulb Key takeaway
Perform cytology in every otitis case, before treatment and at every recheck. Cocci and yeasts: empirical topical therapy. Rods or many neutrophils: think of Pseudomonas or other Gram-negative bacteria and consider culture. Numerical thresholds are a guide; the clinical context prevails.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.