Microbiology, Pathology and Pharmacology
Microbiology, Pathology and Pharmacology is a combined science domain: how organisms cause disease, how tissues respond, and how drugs act and are handled. Questions tend to be factual with one applied calculation.
Microbiology essentials
Bacteria are classified by Gram stain and shape; mycobacteria are acid-fast; viruses need living cells. The infection chain is organism, reservoir, portal of exit, mode of transmission, portal of entry and susceptible host; hand hygiene breaks the transmission link. Autoclaving at 121 °C and 15 psi for 15–20 minutes sterilises; alcohol disinfects but does not reliably kill spores.
Pathology essentials
Inflammation is redness, heat, swelling and pain from vasodilatation and increased permeability. Healing may be by regeneration or fibrosis. Benign tumours are encapsulated and do not metastasise; malignant tumours invade and spread. Cell injury may be reversible or lead to necrosis or apoptosis.
Pharmacology essentials
Pharmacokinetics is absorption, distribution, metabolism and excretion; the liver metabolises most drugs and the kidney excretes them. Half-life is the time for plasma concentration to halve. Agonists activate receptors, antagonists block them. Narrow-therapeutic-index drugs such as digoxin, lithium, warfarin and phenytoin need monitoring.
Worked example
A drug has a half-life of 6 hours. After 24 hours, four half-lives have passed, so the fraction remaining is (1/2)^4 = 1/16, or 6.25%. If the initial concentration was 80 mg/L, it is now 5 mg/L. Steady state is usually reached after about four to five half-lives.
Traps
Sterilisation kills spores; disinfection may not. Bactericidal kills, bacteriostatic inhibits. Do not confuse an adverse effect with a side-effect. Enzyme inducers lower drug levels; inhibitors raise them.