Choosing an Antibiotic in Dogs: A Practical Framework

Choosing an antibiotic is one of the most frequently repeated decisions in daily practice. Precisely because it is so frequent, it is also the decision most likely to become automatic. Yet the choice shapes not only how quickly this patient recovers, but the resistance picture you will face in your own clinic years from now.

This article is not a dose list. It is about the order in which you ask the questions that lead to the right drug.

First: is there an infection at all?

This is the step most often skipped. Fever, leucocytosis or purulent discharge are not, on their own, proof of bacterial infection. Inflammation is not infection.

Before starting an antibiotic, be explicit with yourself: do I have a clinical picture, cytology or culture that points to a bacterial infection, or only a "maybe"? In allergic skin disease, sterile nodular panniculitis or viral upper respiratory infection, an antibiotic offers the patient nothing; it only disturbs the microbiota and the resistance profile.

Cytology is the cheapest and fastest tool at this point. A skin scraping, an ear swab, a fine needle aspirate — within minutes it tells you whether bacteria and neutrophils are present.

When is empirical treatment reasonable?

Waiting for culture in every patient is not realistic. Empirical treatment is reasonable when:

• The expected flora of the site is predictable (staphylococci in superficial pyoderma, for example)
• The patient is stable and you can reassess within a few days
• The presentation is a first episode and uncomplicated

Empirical is not the same as guessing: it is a decision made knowing the most likely organism at that site and the known susceptibility trend of that organism.

When does culture become non-negotiable?

In these situations, continuing without culture costs both the patient and you time:

• Failure to respond — no improvement despite adequate dose and duration
• Recurrent infection — particularly repeated episodes at the same site