Ch. 15 Flashcards
What is half-life and what role does it play in the dosing of medications?
- amount of time it takes for 1/2 of the amt of drug to be eliminated from the body
- how often your patient takes the drug
- Ex: PenV = every 4 hrs bc it elimanates from body in 30 min –> short half-life
- Long half-life = taken less frequently
antimicrobial drug: bacteriostatic
- prevent bacteria from growing
- target protein synthesis and diff metabolic pathways
antimicrobial drug: bactericidal
- kill bacteria –> more effective but can also kill off our normal microbiota
- target CW, plasma membrane, DNA, RNA
superinfections
- when superbugs become the primary bacteria in an infxn
superinfections development
- in any microbial pop., some cells may be resistant to the administered antimicrobial drug
- susceptible cells, which include pathogens as well as members of the normal microbiota, are eliminated
- resistant microbes thrive in the absence of competition and lead to a superinfxn
- resistant microbes may share resistance tools through horizontal gene transfer
What are some examples of things healthcare providers can do to help reduce the acceleration of antimicrobial resistance?
limiting unnecessary prescriptions, use narrow spectrum drugs when possible, educate pts about importance of following drug dose regimens and finish, educate on when antimicrobials are appropriate and when they are not (viral vs bact)
What does it mean for a drug to have a narrow therapeutic index?
- Drugs with a narrow TI (NTIDs) have a narrow window between their effective doses and those at which they produce adverse toxic effects
- less safe
How do we define therapeutic index?
maximum effective/safe dose over a minimum effective/therapeutic dose
intrinsic resistance
- built in qualities that they already had that lets them be resistant to antimicrobial drugs
- makes certain pathogens harder to eliminate; tends to limit what drugs can be used to combat those pathogens
acquired resistance
resistance is from GENETIC MUTATION or by acquisition of RESISTANCE GENES *can be from horizontal gene transfer
Why did Alexander Fleming suspect that the mold on his plates might be producing an antimicrobial?
- little dots didn’t go near this blob. blob turned out to be mold and it was inhibiting S. aureus growth
- this turned out to be penicillin
- mold was exuding penicillin
What drugs target ribosomes? Do they target human ribosomes?
- macrolides: effective against various Gram-negative cocci as well as aerobic and anaerobic Gram-positive rods and cocci
- lincosamides: work against a wide collection of aerobic and anaerobic Gram-positive as well as anaerobic Gram-negative bacteria and even some protozoans
- chloramphenicol: effective against Gram-positive and Gram-negative cocci and bacilli
- tetracyclines: bacteriostatic drugs mainly used in clinical settings
- aminoglycosides: use this when all drugs have failed
- we have different subunits so it doesn’t target human ribosomes
sulfa drugs
- bacteriostatic, broad spectrum, don’t affect mammalian cells; can administer many routes; often used in conjunction with trimethoprim bc it also targets folic acid cycle so the effects are stronger when used tgthr
- don’t produce folic acid so can’t attack our cells
kirby-bauer test
used to determine a bacterium’s susceptibility to antimicrobial drugs; the diameter of the zone of inhibition that may develop around a drug infused disk is measured and compared to a standard table to ascertain if the bacterium is susceptible, resistant, or intermediate in its response to the tested drug.
E-test
An agar diffusion test for bacterial susceptibility (with modified protocols for testing fungi) that is conceptually similar to the Kirby-Bauer test, but instead of applying round disks infused with a set amount of an antimicrobial drug to the agar plate, strips infused with a variable gradient of drug are placed on the agar surface; it can reveal the minimal inhibitory concentration (MIC) of the drug.
broad spectrum drugs
effective against WIDE VARIETY of gpos or gneg bact; often prescribed 1st bc we don’t know the causative agent
narrow spectrum drugs
SPECIFIC usually for either 1 or 2 species but don’t have broad effects, so this is preferred bc more specific to pathogen of interest and so cause less disruption of nL microbiota; drawback: u have two know what pt’s infected with
what drugs are examples of beta-lactam drugs?
penicillins, cephalosporins, carbapenems, and monobactams
what is the definition of combination therapy?
use two or more drugs together that will prevent drug resistance, and make sure that the drug therapy is a success
why is it difficult to make drugs that target viruses and eukaryotes like fungi?
- viruses need to live in host cells to replicate and fxn, so they are difficult to treat w/o also targeting host cells
- fungi are eukaryotic cells like us, so they share similar features to our host cells
- drugs for fungi target CW and membrane structures
What microbes are listed as urgent by the CDC?
- Clostridium difficile (C. diff)
- carbapenem-resistant Enterobacteriaceae (CRE)
- Drug-resistant Neisseria gonorrhoeae
polymyxin drugs (Polymyxin B and colistin (polymyxin E))
A bactericidal narrow-spectrum polypeptide drug that targets the outer membrane of facultative anaerobes and aerobic Gram-negative cells.
dr. jane hinton
associate with kirby-bauer test
dr. selman and elizabeth bugie
associate with streptomycin
