microbio exam 2

what facility has a high prescription rate of inappropriate use of antibiotics

urgent care

alexander fleming

accidentally discovered penicillin. never mentioned would be good as clinical treatment, only good research tool for killing bacteria

first discovered penicillin but discovery lost to history. worked on animal models to cure the disease

ernest duchesne

fleming insight about his plate. perimeter around colony of fungi where nothing grew

some molecule was diffusing out of the penicillin that was kicking or blocking the growth of bacteria. concentration dependent (perimeter was inhibition/no growth zone)

reason antibiotics work. general characteristics of antimicrobial drugs

selective toxicity, therapeutic dose/effective dose, toxic dose, therapeutic index

selective toxicity

ability of drug to kill or inhibit pathogen while damaging host as little as possible

antibiotics, due to selective toxicity, is __ toxic at the same dose to a bacterium than they are to us

more

therapeutic/effective dose

drug level required for clinical treatment (how much you need to give a person to have a clinically beneficial effect)

toxic dose

drug level at which drug becomes too toxic for patient (produces side effects)

therapeutic index

ratio of toxic dose to therapeutic dose

how we evaluate medications when they first are in development

therapeutic index

_ therapeutic index is better, creating _ therapeutic window

higher, larger

side effects

undesirable effects of drugs on host

disruption of own metabolic processes and enzymes that has a negative effect on us

side effect

allergic reaction

immune response to the molecule itself

clinical considerations for antimicrobial use

side effects, allergic reactions, existing sensitivity/resistance profile, likelihood of developing resistance, narrow-spectrum or broad-spectrum, aerobic or anaerobic metabolism, bioavailability of agent to the sites of infection and the route of administration

cidal or static agent

no significant difference unless immune compromised or severe infection

static agent

blocks the growth of the organism

cidal agent

kills the bacteria

effectiveness of antibiotics expressed in two ways

MIC: minimal inhibitory concentration

MLC: minimal lethal concentration

MIC: minimal inhibitory concentration

lowest concentration of drug that inhibits growth of pathogen

MLC: minimal lethal concentration

lowest concentration of drug that kills pathogen

ways of determining susceptibility and resistance

dilution susceptibility tests for MIC

disk diffusion tests (Kirby Bauer)

E-test MIC and diffusion

dilution susceptibility test

inoculate media containing different concentrations of drug

expose a bacteria in liquid culture to increasing concentrations of the antibiotic to reach a threshold where it cannot grow

MIC (minimal inhibitory concentration)

take bacteria out of solution and add it to a fresh broth that doesnt have antibiotic in it and it reactivates and starts growing again

reached MIC but not MLC

if you stir it up into that median and never grows again

reached the MLC

broth or agar with lowest concentration showing no growth

MIC

if broth used, tubes showing no growth can be sub-cultured into

drug free medium

broth from which microbe cannot recover growth

MLC

diffusion disk test

disks impregnated with specific drugs are placed on agar plates inoculated with test microbe

in diffusion disk test, drug diffuses from disk into agar, establishing ___

concentration gradient

zone of inhibition in diffusion disk test

clear zones (no growth) around disks

diffusion works in disk test when the concentration is lowering as the radius __ until you get to the distance where you met the MLC

increases

clear/brown circles

antibiotic concentration is above their MIC

kirby bauer method

standardized method for disk diffusion test

sensitivity/resistance determined using tables relating zone diameter with microbial resistance

kirby bauer method

table values plotted, used to determine if effective concentration of drug in body can be reached. standard curve is created

kirby-bauer method

if a bacteria is sensitive to an antibiotic, it gets _ by an antibiotic

killed

sensitivity/resistance diameters are _ for each antibiotic disc