Vetnuus | August 2025 43 Look for phagocytosed bacteria within neutrophils. This is the gold standard for confirming true infection. Cytology also differentiates cocci from rods to guide empiric antibiotic choice. Empiric Antibiotic Therapy: Use Wisely, Based on Cytology Culture and sensitivity testing are always recommended in deep pyoderma cases. Treatment courses are long and costly. Therefore, it is essential to choose the correct antibiotic from the start. When culture is not feasible, cytology can still guide empiric choice: Cocci (most likely Staphylococcus pseudintermedius): • Clindamycin 5.5 mg/kg q12h: penetrates abscesses and anaerobic pockets well, generally well tolerated, but potential adverse reactions must be discussed in advance. • Cephalexin 20–30 mg/kg q8-12h: first line for uncomplicated cases • Amoxicillin-clavulanate 20 mg/kg q12h: use with caution due to rising resistance • Trimethoprim-sulphonamide 15-30 mg/kg q12h: good tissue penetration, be careful of drug interactions and adverse reactions. Rods: • Culture and sensitivity strongly recommended! • Fluoroquinolones (enrofloxacin 5–10 mg/kg q24h, marbofloxacin 2–4 mg/kg q24h) may be used empirically if culture is not feasible, but are reserved for confirmed resistant or rod infections due to resistance risks. Treatment Duration: Patience is Essential Continue antibiotics for at least 2 weeks beyond full clinical resolution to ensure clearance of deep-seated bacteria and resolution of inflammation. Most cases require 6 to 12 weeks of therapy. Premature cessation risks relapse and worsened resistance. The Critical Role of Two-Week Rechecks Regular rechecks with repeat cytology every two weeks allow: • Monitoring of infection status and inflammatory cell burden • Adjustment of antibiotics based on clinical and cytological response • Early detection of new lesions or adverse drug reactions • Prevention of premature treatment discontinuation Consistency of the examining clinician is important: monitoring response is largely subjective and comparative. These cases should ideally be followed up by the same clinician. If cytology hasn’t improved after two weeks, or looks worse, it’s a red flag for resistance, and culture is the only way forward. Practical Takeaways for Clinicians • Deep pyoderma is an interplay of inflammation and infection: treat both. • Cytology on day one and at every recheck is essential – ensure the same clinician follows up their cases. • Use topical antiseptics and consider systemic antiinflammatories alongside antibiotics. • Recommend culture & sensitivity for every case. • Tailor empiric antibiotic choice to cytology; culture rods if possible. • Treat for at least 2 weeks beyond complete clinical resolution. • Two-weekly rechecks with cytology guide therapy to prevent relapse. Message to Clients to aid Compliance: “Treating deep pyoderma is like pulling weeds by the root. If you only trim the leaves, they’ll grow back. We need to destroy the root and keep checking to be sure the weeds don’t return.” References 1. Hillier, A., et al. (2014). Guidelines for the diagnosis and antimicrobial therapy of canine superficial bacterial folliculitis. Veterinary Dermatology, 25(3), 163–e43. 2. Medleau, L., & Hnilica, K.A. (2006). Small Animal Dermatology: A Color Atlas and Therapeutic Guide (2nd ed.). Saunders. 3. Beco, L., et al. (2013). Antibiotic use in dogs and cats: principles, prescribing guidelines, and use of bacterial culture and sensitivity testing. Veterinary Record, 173(11), 267–268. 4. Bensignor, E., et al. (2002). Canine deep pyoderma: a review of clinical, diagnostic and therapeutic features. Veterinary Dermatology, 13(4), 193–202. 5. Mueller, R.S. (2003). Treatment protocols for deep pyoderma: an evidence-based review. Veterinary Dermatology, 14(3), 157–167. 6. Fig 1: https://www2.zoetis.ca/content/_assets/images/Conditions/ cki_dp_img06_s.jpg 7. Fig 2: https://o.quizlet.com/IORfcsDPrggJg7Xfm4iA7g.png 8. Fig 3: © Ana Oliveira 9. Fig 4: https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQw pt8m2BxmjHOFubRfF6khjJ4zrvQ4Uxk0vA&s Royal Canin I Column Figures 2 & 3: both showing phagocytosed (intracellular) cocci in neutrophils. Figure 4: phagocytosed (intracellular) rod bacteria in a neutrophil.
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