Intro to Antibiotics / Chemotherapy

What is empirical treatment?

based on clinical educated guess of likely causative organism

Why do we perform Antibiotic susceptibility testing?

To make sure we are Tx w/ most effective drug and not perpetuating resistance

What method of antibiotic suseptability testing is the most sensitive and controlled?

Dilution based

Define MIC?

Minimum inhibitory concentration - bacteriostatic

Define MBC?

Minimum bacteriacidal concentration - No visible bacteria

Explain what a break point is?

The expected susceptibility of an organism to an antibiotic

If an organism is susceptible to an antibiotic what does this mean?

MIC is lower than the breakpoint - antibiotic will work well

If an organism is intermediate to an antibiotic what does this mean?

MIC is approaching or at the break point - close to resistance/ may not work

If an organism is resistant to an antibiotic what does this mean?

MIC is much higher than the break point and antibiotic will not achieve therapeutic success

When should a culture be taken?

always before giving the antibiotics

Bactericidal drugs will typically affect what?

Cell walls

Cell membranes

DNA formation

RNA formation

Bacteriostatic drugs will typically affect what?

Proteins

A bactericidal drug will have no remarkable difference between ___ and ___ concentrations?

Bacteriostatic and bactericidal concentrations - will be in safe and effective range

A bacteriostatic drug can be bactericidal but will be ___ very high concentrations

Toxic and not safe

A bacteriostatic drug can be ___ against certain organisms?

Bactericidal

Why are pharmacokinetics so important in antibiotic use?

Patient must maintain adequate blood levels in order to prevent development of resistance

Maintianence of plasma concentrations of antibiotics are more important in what kind of antibiotics?

Bacteriostatic

Aminoglycosides and quinolones will have ____ dependent killing?

Concentration dependent

B-lactams and vancomycin will have ____ dependent killing?

Time dependent

Typically ___ dependent killing antibiotics will have decreased AE?

Time

Which type of antibiotic would you try to avoid in an immunocompramized patient?

Bacteriostatic - immune system not strong enough to clear

What is the post antibiotic effect?

Suppression of bacterial growth for a time after limited antibiotic exposure

What antibiotics could give Postantibiotic effect?

Aminoglycosides and quinolones

What antibiotics are very effective in tx an abscess?

Rifampin

Florfenicol

Tetracyclines

What antibiotics are NOT effective in tx an abscess?

Aminoglycosides

B-lactams

Sulfonamides

What are 5 reasons we might combine antibiotics?

Drug synergy

Improved therapeutic effect

Reduce resistance

Spectrum of coverage

Reduce AE?

Explain how synergism of antibiotics works?

inhibitory/ killing effects are greater than expected when used together - ie opening up a cell wall so a protein inhibitor could get in and kill

Name a few ways that combining antibiotics could cause antagonism?

Inhibition of bactericidal agents by bacteriostatic agents

Induction of antibiotic destroying enzymes

Binding to same cellular target decreasing efficacy

When would we use antibiotics prophylactically?

If efficacy has been demonstrated and benefit outweighs the risk of resistance

What is metaphylaxis?

Admin to all/ susceptible after dx of dz in a member go the group has been established

What are common times we will use prophylactics or metaphylaxis?

Sx,

Immunosuppressed animals

BRD

What is the vet feed directive final rule?

Dictates that antibiotics can not be used for production - makes promoting animal growth extra label putting it in the hands of vets due to compounding

What are mechanisms of drug resistance?

Fails to absorb drug

Drug is inactivated

Efflux pumps

Target modified

Increased production of target

Altered metabolism pathways

How is drug resistance often transmitted between species?

Plasmid transfer

What is transduction performed by?

Bacteriophages

What is transformation?

Picking up of free DNA

What is conjugation?

Transfer of plasmids via sex pili

Can we use high AMR risk drugs?

NO human use only

How do you mitigate AE of antibiotics?

Lowest effective dose

Shortest duration

Synergistic combination

High risk situations

Responsible

When are superinfections most common?

After using broad spectrum ABX

What is an example of a superinfections?

Pseudomembranous colitis caused by clostridium difficile

When does misuse antibacterial drugs cause failure of therapy?

Improper: Dosage, Duration

Noninfectious dz

Incorrect ABX choies

Incomplete responses

Poor compliance

Immunosuppression

What drugs are prohibited in food animals?

Chloramphenicol

Nitroimidazoles

Nitrofurans

What antibiotics are only as labeled in cattle? (Extra-label prohibited)

Sulfonamides

Floroquinolones

Medicated feeds

Cephalospornins

What drug is voluntarily not used in food animal?

Aminoglycosides