Antimicrobials Flashcards
What is selective toxicity?
It kills microbial cells but do not kills host cells., They have a microbial that is different or lacking in humans (peptidogylcan)
Define and give an example of antibiotic:
Broad spectrum
Narrow spectrum
Broad spectrum – effective against wide range of species, including both Gram negative and Gram positive species; e.g. tetracycline
• Narrow spectrum – only active against select species; e.g. penicillin G
(Information- Outer membrane of Gram negative species inhibits passage of many antibiotics)
What is a disk diffusion assay used to determine?
used to determine effectiveness of chemical agents against a particular microbe
A broth dilution test is used to determine what?
Minimal Inhibitory Concentration (MIC)
(lowest concentration of the drug that inhibits growth of the microbe)
True or false: disk diffusion method will let you know if the drug inhibits growth in killer species and does give you a measurement of MIC
False, it does not determine MIC
Do Kirby Bauer test and broth dilution test measure whether it static or Cidal? Why or why not?
No it does not, need to subculture
(Define)
Static:
Cidal:
Static: stop growth, cold temperatures
Cidal: kills microbe, hot temperatures
(Define)
Therapeutic dose:
Toxic dose:
Chemotherapeutic dose:
• therapeutic dose:minimum dose per kg of body weight that inhibits growth of the pathogen
•toxic dose: maximum dose tolerated by thepatient
• chemotherapeutic index: ratio of the toxic dose to therapeutic dose
Define synergism
• Synergism occurs when the effect of two drugs together is greater than the effect of either alone
Define antagonism
Antagonism occurs when the effect of two drugs together is less than the effect of either alone
Penicillin disrupts cell wall and leads to…
Why?
Osmotic lyses
It targets peptidoglycan
What makes a bacteria resistant to penicillin? What does it do?
Give an example of a species that produces this
Penicillinase (b-lactamase)
Claves to B-lactam ring in penicillin, inactivates it
Staphylococcus
How many ribosomes in bacteria and humans?
70S
80S
What are natural penicillins effective against? Is it narrow or broad spectrum? What is it susceptible to?
Effective against gram (+), not gram (-)
Narrow spectrum
Susceptible to penicillinase
What are semi synthetic penicillin effective against?
Is it narrow or Broad spectrum?
Is it resistant to penicillinase?
It also includes what?
Give an example of a semi synthetic penicillin
Effective against gram (+) and (-)
Extended spectrum
Resistant to penicillinase
Include cephalosporins
Ampicillin (inhibits gram negative)
Polymyxin is an antibiotic that targets the bacterial membrane. What species does it come from?
What does it do?
Why is it used topically?
bacillus polymyxa
Positively charged polypeptide that disrupts structure of phospholipid bilayer.
Used topically because it can also damage human cell membrane
What is inhibit replication?
Inhibit replication: Bacterial replication uses enzymes that closely resemble human enzymes; not many unique targets
What is Quinolones?
– Quinolones: drugs that target topoisomerases, like DNA gyrase, which introduces negative supercoils in DNA ahead of replication forks
• Inhibition of gyrase blocks DNA replication
• Bacterial DNA gyrase is structurally distinct from mammalian DNA
gyrase
SELECTIVELY TOXIC
Rifamycin binds to what? Inhibits what? Used to treat what?
Bind to bacterial RNA polymerase
Inhibits transcription
Used to treat tuberculosis
Erythromycin inhibits translation.Why does erythromycin have a spectrum of activity limited mostly to gram-positive bacteria?
– Erythromycin is blocked by the Gram negative cell wall. Gram positive bacteria accumulate 100-fold more erythromycin than Gram negative bacteria.
What on the 3 inhibitors of protein synthesis? What do they do?
Chloramphenicol (binds to 50S portion and inhibits formation of peptide bond)
Streptomycin (chances shape of 30S Portion causing code on mRNA to be read incorrectly)
Tetracyclines (interfere with attachment of tRNA to mRNA -ribosome complex)
What is an important target for selectively toxicity antifungals?
Ergosterol and B gluten are important selectively toxic target
What are the 4 Main classes of Antifungal drugs licensed for use in humans?
Polyenes
Flucytosine
Echinocandins
Azoles
Acyclovir is used to treat what? What does it inhibit?
Used to treat herpes simplex virus, Chicken pox, and singles
Inhibits DNA synthesis of host cells
AZT (azidothymidine)
What type of drug?
What does it inhibits?
Antiviral drug
Inhibits human DNA polymerase (protease inhibitors and integrase)
Zanamivir and oseltamvir (tamiflu) inhibits what? Prevents what ?
Inhibits neuraminidase
Prevents release of mature viruses
What are the 4 steps of antibiotic resistance?
- Modify target so that it no longer binds (the altered DNA gyrase no longer bind to quinolones)
- Destroy the antibiotic before it gets into cells (penicillinase)
- Add modifying groups that inactivate the antibiotic
- Pump the antibiotic out of cells using specific or non specific transport proteins (efflux pump causes resistance)
Resistance can arise spontaneously through ____ or ____ replication followed by random mutations that repurpose the duplication
Mutation or gene replication
MDR efflux pumps evolved from genes encoding other transport mechanisms, this is an example of what?
Horizontal transfer
What are the 3 parts of horizontal transfer?
Transformation, transduction and conjugation
C. Difficile is an ____forming bacteria
Endospore forming
Drug resistant Candida auris
Type?
What does it cause? How is it spread?
Clinical cases in 2018?
Fungus
Can cause severe infections and spread easily between hospitalized patients and nursing home residents
323 cases
Clostridoides difficile
Type?
Also known as?
Causes what?
Found in who?
Deaths per year?
Bacteria (spore forming)
C.diff
Causes life threatening diarrhea and colitis (inflammation of the colon)
Found in people who have had both recent medical care and antibiotics
12,800 deaths
Misuse of antibiotics create what?
Resistance
Give some examples of misuse of antibiotics
Up to __% of antibiotics prescribed are not needed or not effective
- Not completing prescribed course
- using them for common cold and other inappropriate conditions
-antibiotics in animal feed
-50%
___-___% of all antibiotics are used in the us are fed to healthy livestock
” Growth ProMotion “ protocols involve ______ concentrations of antibiotics
~70-80%
Subtherapertic
FDA regulates use of some medically important antibiotics in live stock
What happened in April 2012?
What happened in January 2012?
• April2012–certain uses of cephalosporin class of antibiotics prohibited in cattle, swine, chickens, and turkeys
– Cephalosporins are β-lactam antibiotics
• January2017–veterinaryfeeddirective
– VFD (prescription) from a licensed veterinarian required for use of medically important antibiotics in feed or water for food animal species
