Antimicrobial treatment is commonly interpreted through two linked observations: a pathogen is categorized as susceptible and an antimicrobial is administered at an accepted dose. Neither observation establishes that microbiologically active exposure occurs at the infection site or that bacterial control will follow. Veterinary patients introduce additional variation through species-specific disposition, disease-altered pharmacokinetics, anatomically protected compartments, biofilm growth, bacterial burden, host immune competence, foreign material, devitalized tissue, and the feasibility of delivering the intended regimen. This original non-empirical article develops a physiology- and mechanism-guided treatment model in which success is treated as a time-dependent state emerging from concordance among pathogen identity and phenotype, free-drug exposure, pharmacodynamic target attainment, site penetration, bacterial organization, host contribution, and source control. The model distinguishes drug delivery from effective exposure, effective exposure from bacterial effect, and bacterial effect from clinical recovery. It also separates remediable exposure failure from conditions in which dose escalation cannot compensate for inaccessible infection, protected bacterial states, uncontrolled sources, or an incorrect diagnosis. Reassessment is therefore framed as causal adjudication rather than automatic antimicrobial broadening. The proposed model may support more disciplined escalation, de-escalation, sampling, monitoring, and source-control decisions while preserving stewardship. It is not a validated prediction rule, additive score, or substitute for culture interpretation, clinical examination, imaging, surgery, or longitudinal response assessment. Its components require prospective testing across animal species, infection syndromes, production settings, antimicrobial classes, and clinically meaningful outcomes.
