Antimicrobials

Question 1

What is selective toxicity?

Answer 1

It kills microbial cells but do not kills host cells., They have a microbial that is different or lacking in humans (peptidogylcan)

Question 2

Define and give an example of antibiotic:
Broad spectrum
Narrow spectrum

Answer 2

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)

Question 3

What is a disk diffusion assay used to determine?

Answer 3

used to determine effectiveness of chemical agents against a particular microbe

Question 4

A broth dilution test is used to determine what?

Answer 4

Minimal Inhibitory Concentration (MIC)
(lowest concentration of the drug that inhibits growth of the microbe)

Question 5

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

Answer 5

False, it does not determine MIC

Question 6

Do Kirby Bauer test and broth dilution test measure whether it static or Cidal? Why or why not?

Answer 6

No it does not, need to subculture

Question 7

(Define)
Static:
Cidal:

Answer 7

Static: stop growth, cold temperatures
Cidal: kills microbe, hot temperatures

Question 8

(Define)
Therapeutic dose:
Toxic dose:
Chemotherapeutic dose:

Answer 8

• 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

Question 9

Define synergism

Answer 9

• Synergism occurs when the effect of two drugs together is greater than the effect of either alone

Question 10

Define antagonism

Answer 10

Antagonism occurs when the effect of two drugs together is less than the effect of either alone

Question 11

Penicillin disrupts cell wall and leads to…
Why?

Answer 11

Osmotic lyses
It targets peptidoglycan

Question 12

What makes a bacteria resistant to penicillin? What does it do?
Give an example of a species that produces this

Answer 12

Penicillinase (b-lactamase)
Claves to B-lactam ring in penicillin, inactivates it
Staphylococcus

Question 13

How many ribosomes in bacteria and humans?

Answer 13

70S
80S

Question 14

What are natural penicillins effective against? Is it narrow or broad spectrum? What is it susceptible to?

Answer 14

Effective against gram (+), not gram (-)
Narrow spectrum
Susceptible to penicillinase

Question 15

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

Answer 15

Effective against gram (+) and (-)
Extended spectrum
Resistant to penicillinase
Include cephalosporins
Ampicillin (inhibits gram negative)

Question 16

Polymyxin is an antibiotic that targets the bacterial membrane. What species does it come from?
What does it do?
Why is it used topically?

Answer 16

bacillus polymyxa
Positively charged polypeptide that disrupts structure of phospholipid bilayer.
Used topically because it can also damage human cell membrane

Question 17

What is inhibit replication?

Answer 17

Inhibit replication: Bacterial replication uses enzymes that closely resemble human enzymes; not many unique targets

Question 18

What is Quinolones?

Answer 18

– 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

Question 19

Rifamycin binds to what? Inhibits what? Used to treat what?

Answer 19

Bind to bacterial RNA polymerase
Inhibits transcription
Used to treat tuberculosis

Question 20

Erythromycin inhibits translation.Why does erythromycin have a spectrum of activity limited mostly to gram-positive bacteria?

Answer 20

– Erythromycin is blocked by the Gram negative cell wall. Gram positive bacteria accumulate 100-fold more erythromycin than Gram negative bacteria.

Question 21

What on the 3 inhibitors of protein synthesis? What do they do?

Answer 21

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)

Question 22

What is an important target for selectively toxicity antifungals?

Answer 22

Ergosterol and B gluten are important selectively toxic target

Question 23

What are the 4 Main classes of Antifungal drugs licensed for use in humans?

Answer 23

Polyenes
Flucytosine
Echinocandins
Azoles

Question 24

Acyclovir is used to treat what? What does it inhibit?

Answer 24

Used to treat herpes simplex virus, Chicken pox, and singles
Inhibits DNA synthesis of host cells

Question 25

AZT (azidothymidine)
What type of drug?
What does it inhibits?

Answer 25

Antiviral drug
Inhibits human DNA polymerase (protease inhibitors and integrase)

Question 26

Zanamivir and oseltamvir (tamiflu) inhibits what? Prevents what ?

Answer 26

Inhibits neuraminidase
Prevents release of mature viruses

Question 27

What are the 4 steps of antibiotic resistance?

Answer 27

1. Modify target so that it no longer binds (the altered DNA gyrase no longer bind to quinolones)
2. Destroy the antibiotic before it gets into cells (penicillinase)
3. Add modifying groups that inactivate the antibiotic
4. Pump the antibiotic out of cells using specific or non specific transport proteins (efflux pump causes resistance)

Question 28

Resistance can arise spontaneously through ____ or ____ replication followed by random mutations that repurpose the duplication

Answer 28

Mutation or gene replication

Question 29

MDR efflux pumps evolved from genes encoding other transport mechanisms, this is an example of what?

Answer 29

Horizontal transfer

Question 30

What are the 3 parts of horizontal transfer?

Answer 30

Transformation, transduction and conjugation

Question 31

C. Difficile is an ____forming bacteria

Answer 31

Endospore forming

Question 32

Drug resistant Candida auris
Type?
What does it cause? How is it spread?
Clinical cases in 2018?

Answer 32

Fungus
Can cause severe infections and spread easily between hospitalized patients and nursing home residents
323 cases

Question 33

Clostridoides difficile
Type?
Also known as?
Causes what?
Found in who?
Deaths per year?

Answer 33

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

Question 34

Misuse of antibiotics create what?

Answer 34

Resistance

Question 35

Give some examples of misuse of antibiotics
Up to __% of antibiotics prescribed are not needed or not effective

Answer 35

• Not completing prescribed course
• using them for common cold and other inappropriate conditions
  -antibiotics in animal feed
  -50%

Question 36

___-___% of all antibiotics are used in the us are fed to healthy livestock
” Growth ProMotion “ protocols involve ______ concentrations of antibiotics

Answer 36

~70-80%
Subtherapertic

Question 37

FDA regulates use of some medically important antibiotics in live stock
What happened in April 2012?
What happened in January 2012?

Answer 37

• 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