Microbiology Basics: Antimicrobial Drugs, and How Resistance Happens (2026)

Use this episode as a focused review of the antimicrobial drugs chapter of your microbiology text, with the antimicrobial chapter of your nursing pharmacology text and the public health guidance on resistance beside it. The episode opens on the idea that holds the subject together — selective toxicity, the reason a drug has to aim at something the microbe has and the patient's own cells do not — and then sorts the drugs by the target each one aims at: the cell wall, protein synthesis, nucleic acid synthesis, the folate pathway, and the cell membrane, with the drug classes that sit at each one 1. From there it covers narrow against broad spectrum and what a broad-spectrum drug costs through the normal microbiota; why selective toxicity is hardest for fungi and viruses; and the pair the exam asks you to tell apart at the bedside, a drug that stops growth and a drug that kills. It closes on the bench, where the culture is collected before the first dose and where a disk diffusion plate and a minimum inhibitory concentration each answer a different question 2 3.

The second half is about escape. It walks through the five ways bacteria resist a drug and shows why one of them — a changed target — sits behind methicillin-resistant Staphylococcus aureus 4, then follows a resistance gene as it moves sideways between bacteria and as our own prescribing selects for it, with the World Health Organization's global figures 5 and the Public Health Agency of Canada's Canadian ones 6 on what resistance already costs, and what the federal action plan says is at stake 7. It ends on the line that belongs to whoever is holding the prescription bottle: antibiotics do not work on viruses 8. A retrieval round finishes the episode, covering the five targets, the five resistance mechanisms, and when the sample has to be taken.