Antibacterial Pharmacology

Question 1

Discovery of abx

Answer 1

Alexander Fleming 1928 Penicillium mold on Petri dish Later used as a “cure all” drug, resulting in resistance

Question 2

Cycle of ID

Answer 2

susceptible host -> causative agent -> reservoir -> Portal of Exit blood -> Mode of transmission -> portal of entry blood

Question 3

Properties of bacteria

Answer 3

• Prokaryotic cells - no membrane enclosed organelles - single cellular - reproduce through binary fission - plasmids and nucleoid DNA are easy to transport and communicate because they are free -> cause for resistance

Question 4

Gram Positive Bacteria

Answer 4

• thick peptidoglycan - relatively featureless - no outer membrane - susceptible to cell wall disruption

Question 5

Gram Negative Bacteria

Answer 5

• cytoplasmic and outer membranes - thin peptidoglycan - lots of lipids because of outer membrane - resistant to cell wall disruption

Question 6

Cell wall structure

Answer 6

Peptidoglycan Layer: rigid glycerin cross-linked by flexible peptide bridges Periplasmic spaces: Very small on gram (+), multiple on gram (-): generate B-lactamases which inhibit abx Wall tetracholic acid: accessory protein on g(+) Lipoprotein, Porin protein, LPS: on gram (-) Lipoprotein: protection layer Porin: if needed bacteria can down regulate LPS: for inflammatory response

Question 7

PBP

Answer 7

• Important for MoA for abx - enzymes that catalyze: transglycosylation, transpeptidation, carboxypeptidation, endopetidation - for: cell wall synthesis (peptidoglycan), cell wall remodeling, cell division, cell shape

Question 8

Bactericidal

Answer 8

direct action of bacteria - kill/lysis biochemical pathways in wall assembly compromised cell wall progressively weaker cells - daughter cells don’t have what is needed to keep cell wall up. eventually integrity of cell wall fails

Question 9

Bacteriostatic

Answer 9

does not directly kill may be reversible - or relapse target nucleic acid synthesis and protein synthesis slow bacteria growth allows immune system to act and destroy the cells

Question 10

Broad spectrum

Answer 10

Treat many kinds of infections - wide range of bacteria - targets common structures so can also go against commensal bacteria -> LEADS TO SUPERINFECTION - Once the agent is identified it should be discontinued

Question 11

Superinfection

Answer 11

Bacteria that aren’t supposed to grow well in a particular area but do because the niche (normally keeps it away) is dead.

Question 12

Narrow spectrum

Answer 12

Against a single or few bacteria (specific) - when agent is known - reduces chance of superinfection and abx resistance

Question 13

Classification of bacteria

Answer 13

With 16s ribosome which share amplified DNA from a single cell. Polymer chain reaction is used to compare (DNA template to RNA to ribosomal subunits)

Question 14

Where do abx come from?

Answer 14

Soil (but hard to isolate) Bottom feeders like roaches, catfish, alligators, bacteriophages (viruses that infect bacteria), cannabinoids. They are exposed to more bacteria than anyone else so they evolved to develop mechanisms to protect themselves.

Question 15

MoA of abx

Answer 15

• inhibition of bacterial cell wall synthesis - direct action on cell membrane - inhibition of protein synthesis - modification of protein synthesis (change how it works) - inhibition of nucleic acid synthesis - inhibition of biosynthetic pathways

Question 16

Inhibition of Cell wall synthesis

Answer 16

Attack cell wall synthesis - Beta Lactams (PBP in periplasmic space)

Penicillins, cephalosporins - inhibit transpeptidase from creating long chains of glycopeptide polymer chains (D-ala addition) carbapenems, monobactams

Inhibit pathways of peptidoglycan and sugars: Vancomycin (periplasmic space) & Bacitracin (cytoplasm)

Attack cell membrane Polymyxins

Question 17

3 places to attack

Answer 17

1. cell wall synthesis
2. Protein synthesis
3. Nucleic acid synthesis

Question 18

Nucleic acid synthesis

Answer 18

Attack DNA and/or biosynthetic pathways

Folate synthesis Sulfonmides, Trimethoprim

DNA Gyrase/ topoisomerase (mRNA translation- unwinding and unkinking DNA) Quinolones

RNA polymerase (reads sequencing) Rifampin

Question 19

Protein synthesis

Answer 19

Intracellular - interfere with translation Together 50s and 30s make 70s subunit. 50s subunit: Macrolides, clindamycin, linezolid, chloramphenicol, streptogramins 30s subunit: Tetracyclines, aminoglycosides

Question 20

Detergents

Answer 20

Cell wall is degraded because it suck out lipids.

Question 21

Daptomycin

Answer 21

Inhibits cell wall by squishing lipid tail into cell wall lipids -> forms complexes -> forms into channels (from the subunits coming together) -> disrupts the normal order of cell/ influx and eflux of materials

Question 22

Penicillins and other B-lactam MoA

Answer 22

5 AA peptide ends in D-ala D-ala. The PBP removes the end alanine to form a cross-link with a nearby peptide (gives cell wall rigidity). B-lactam abx are analogues of D-ala D-ala which covalently bonds to PBP - inhibiting transpeptidation reaction and stops peptidoglycan synthesis - cell dies.

Question 23

Half life of penicillins & clinical

Answer 23

penicillins = 30 mins / 10 hours for renal failure. 1-2 hours before or after meals. without regard with amoxicillin amplicillins = 1 hour these are cleared with kidney so adjust when needed nafcillin - biliary excretion oxacilin, dicloxacillin - biliary and kidney -> no dose adjustment

Question 24

Tetracyclines MoA

Answer 24

Binds to 30s active site. can’t make proteins to let the chain grow

Question 25

Macrolides MoA

Answer 25

binds to 50s - interferes with peptide conjugation

Question 26

Aminoglycoside MoA

Answer 26

blocks initiation complex of 50s binding to 30s -\> causes miscoding of proteins which won't fold and bind to active site -\> can't move out of ribosome (translocation step)

Question 27

Folate synthesis Inhibition

Answer 27

PABA**-\>**Dihydrofolic acid**-\>**tetrahydrofolic acid -\>purines -\>DNA Sulfonamides competes with PABA at dihydropteroate synthase Trimethoprim inhibits dihydrofolate reductase

Question 28

Bacterial Resistance

Answer 28

1. lots of bacteria - few are resistant 2. use of abx - kills bad bacteria and good bacteria 3. still some resistant that are left and grow (no good bacteria to protect) 4. sharing of information to other bacteria -\> more reisistance

Question 29

Topoisomerase 4

Answer 29

Divides/ seperates part of DNA so daughter cells can get equal amounts Used in inhibition of nucleic acid synthesis think DNA gyrase - unwinding DNA inhibited by fluroquinolones

Question 30

Origin of drug resistance

Answer 30

- bacteria in inactive site (non dividing) - Genetics (horizontal gene transfer - ex) PBP dont bind to B-lactams on MRSA) - Spontaneious mutation: misreading, mutation - plasmid-encoded resistant gene products - cross resistance of one type: same MoA drug doesnt reach the target drug activity is decreased/ destroyed drug target is altered

Question 31

How do bacteria exchange genetic information?

Answer 31

Transduction - bacterial virus - transfer its genes into bacteria -\>resistance from virus Transformation - naked DNA transfer Ex) shock E. Coli then transfer DNA -\> gets sucked up by another Conjugation - transfer by direct cell-cell contact - through pilli of fusion of membrane Transposition - transposon medicated exchange : small segments jump out of DNA and go elsewhere to disrupt chromosomes

Question 32

Production of enzymes that destroy or inactivate the drug

Answer 32

B-lactamases inactivate B-lactam Abx B-lactamases are normally in bacteria and activate Antibodies -\> too much B-lactamases = resistance Aminoglycosides altered by acetylation, phosphorylation. or adenylation just enough change to not work with antibodies Ex) kinases (protein that phosphorylates) can mutate so that it disrupts normal order Chloramphenicol acetyltransferases in inactive chloramphenicol

Question 33

Decrease entry or increased efflus

Answer 33

Decreased active transport across membrane in anaerobic conditions - effect on channels -\> can't get in, can't get out Down regulation of porin expression -\> throws everything out of the cell Mutation in efflux transporter

Question 34

Altered structural target for the drug

Answer 34

Altered: binding sites on ribosonal subunits (decreased affinity for macrolides - protein syn inhibitors) binding proteins (B-lactams no longer able to bind to PBP) mutation in DNA genes (decreased affinity for abx-fluroquinolones)

Question 35

Alterante metabolic pathway

Answer 35

Resistant strains produce D-ala D-lactate instead of D-ala D-ala (affinity for Vancomycin reduced) Resistant strains overproduce PABA which antagonizes sulfonamide abx.

Question 36

MIC

Answer 36

* Minimum inhibitory concentration * lowest concentration of abx required to inhibit bacterial growth * defines susceptibility of drug * DOES NOT indicate bactericidal activity

Question 37

MBC

Answer 37

* Minimum Bacerial Concentration * concentration of abx required to inhibit bacterial growth by 99.9% * more quantitative than MIC

Question 38

PAE

Answer 38

* Post abx effect * period of bacterial growth supression after brief exposure to drug * abx with PAE requires LESS frequent administration [abx] \< MIC time afterward is still slowing growth

Question 39

PALE

Answer 39

* Post-antibiotic Leukocyte effect * period during which bacteria are more susceptible to leukocyte action * After drug has cleared, stimulation of phagocytosis mechanism still at work * also explains drug efficacy below MIC

Question 40

Broth/Agar dilution Test

Answer 40

Same number of bacteria in each tube but at different concentrations of the drug. The minimum inhibitory concentration of drug = not cloudy

Question 41

Disk diffusion test

Answer 41

Filter paper disks concentrated with abx. Check for zone of inhibition. No zone = resistant Little zone = intermediate Large zone = sensitive

Question 42

Gradient Diffusion Test

Answer 42

* gradient of abx * higher concentration of abx as go up on strip * Find MIC/ decreasing growth as you go down (lower concentration of abx)