Antibiotics

Question 1

What are the types of prescribing used in antibiotics?

Answer 1

Guided, Empirical, Prophylactic

Question 2

What is guided antibiotic prescribing?

Answer 2

Testing to determine the infectious agent, then treating with the most appropriate antibiotic

Question 3

What is empirical antibiotic prescribing?

Answer 3

Treating with antibiotics regardless of knowing the type of infection.
Used when leaving the patient would cause more harm than using the wrong antibiotic, i.e. in sepsis or meningitis.

Question 4

What is prophylactic antibiotic prescribing?

Answer 4

Prescribing antibiotics to prevent infection.

Used in severely immunocompromised (HIM, Splenectomy, transplantation), post-surgery, animal bites, exposure, insult

Question 5

What are the ideal characteristics of antibiotics?

Answer 5

Target Effects- toxic to bacterium, penetrate body area infected, limit bacterial-toxin release, easily administered
Co-lateral Damage- Non-toxic to patient, limits effect on colonizing bacteria (mucosal candida, clostridium difficile, selection of resistant bacteria), low ability of bacteria to escape treatment by developing resistance.

Question 6

What is the name of the antibiotics which treat specific infections?

Answer 6

Narrow spectrum agent, used typically for guided therapy

Question 7

What is the name of the antibiotics which treat a variety infections?

Answer 7

Broad spectrum, typically used in empirical treatment therapy

Question 8

What is an example of guided antibiotic therapy with positive, mid-stream urine test for E. coli?

Answer 8

Nitrofurantoin

• narrow spectrum
• penetrates only into urine, minimizing systemic exposure
• high cure rate

Question 9

What is an example of empirical antibiotic treatment with a positive pneumonia test?

Answer 9

Need to treat most common causes of pneumonia (strep. pneumoniae, staph. aureus, legionella pneumophilia, mycoplasma pneumoniae, haemophilus influenza).
Broad spectrum antibiotics, with combination therapy, to cover for different possibilities.
-Co-amoxiclav
- Clarithromycin
After testing, switch to best most narrow treatment

Question 10

What are the types of antibiotic actions?

Answer 10

Bactericidal and bacteriostatic

Question 11

What do bactericidal antibiotics do?

Answer 11

Stops bacterial growth and also kills the bacteria, achieving sterilization

• can lead to release of toxins and cause inflammation (typically given anti-inflammatorys alongside)
  i. e. penicillin

Question 12

What do bacteriostatic antibiotics do?

Answer 12

Inhibit bacterial growth but don’t kill and sterilize the bacterium.
-require secondary means to clear bacteria

Question 13

What is are important targets in antibiotics?

Answer 13

Cell wall, particularly peptidoglycan
Anti-metabolites
Ribosome
DNA / transcription process

Question 14

What do the beta-lactam antibiotics have in common?

Answer 14

Presence of beta-lactam ring within its molecule

Question 15

What are important features of penicillin?

Answer 15

Rapid bacterial killing with low toxicity,

bactericidal

Question 16

What is the mechanism of action of penicillin?

Answer 16

Penicillin is an analogue of the D-ala-D-ala of the cell wall, and can mimic and place self into the wall to prevent the polymerization, and cause lysis
Broad Spectrum

Question 17

What is a major problem with penicillin?

Answer 17

Type 1 hypersensitivity mediated by IgE binding to the surface of mast cells, resulting in degranulation and inflammation. More common is sub-acute Type 2 hypersensitivity with IgG inducing complement (hours-days)
1% of patients have immune mediated reaction.
10% claim to have an allergy.

Question 18

What is the mechanism of action for Vancomycin?

Answer 18

Similar to penicillin, acts against peptidoglycan cell wall, however very large and therefore cant insert into gram-negative bacteria.

Question 19

What is the most commonly prescribed antibiotic?

Answer 19

beta-lactam antibiotics

Question 20

What is the mechanism of action for Clarithromycin and Doxycycline?

Answer 20

Target ribosome, switching off protein production
Bacteriostatic
Broad spectrum, act on both gram +/-
Resistance is a problem

Question 21

What is the mechanism of action for Ciprofloxacin?

Answer 21

Fluoroquinolones
Targets DNA replication leading to cell death
Broad spectrum
Can target most bacteria effectively
Resistance increasing and becoming big problem

Question 22

What is the mechanism of action for Trimethoprim?

Answer 22

Anti-metabolite that inhibits folate metabolism, making bacteria unable to produce basic units needed for DNA
Bacteriostatic
Typically used in UTI

Question 23

How is antibiotic resistance tested?

Answer 23

Disc diffusion sensitivity testing
You get zone of clearance in lawn of bacteria if the bacteria is sensitive, they will grow close if resistance is present

Question 24

How does antibiotic resistance occur?

Answer 24

Mutation/modification of target site
Inactivating enzymes produced by bacterium that lyse or alter the antibiotics so it isn’t effective
Limit access by reduced permeability so antibiotic cant get inside, or pump it out so the concentration inside is never high enough to work

Question 25

How is resistance carried and passed in bacteria?

Answer 25

Passed on plasmids of bacteria

Can be passed vertically between bacteria

Question 26

What is the New Delhi metallo-beta-lactamase 1?

Answer 26

Contains plasmids which are able to induce resistance to antibiotics, particularly the beta-lactam group of antibiotics.
Has other plasmids with resistance to quinolone, tetracycline, and many more antibiotics.
Contains beta-lactamase which cannot be inhibited in any way.

Question 27

What do beta-lactamases do?

Answer 27

Cut a whole which removes the beta-lactam ring of penicillin, once the ring is cut the penicillin becomes inactive

Question 28

How can we address beta-lactamase and prevent its resistance?

Answer 28

Can create antibiotic penicillin’s (flucloxacillin) which can resist the action of the beta-lactamase activity.
Can inhibit the the beta-lactamases using other beta-lactamase stable drugs (clavulanic acid), in conjunction with a beta-lactam antibiotic, therefore protecting the antibiotic

Question 29

What type of bacteria is typically more resisitant?

Answer 29

Pan-resistant gram negative strains

Question 30

What is the mechanism of action for Ampicillin?

Answer 30

Irreversibly inhibits transpeptidase enzyme which helps build bacterial cell wall.
Bactericidal