Session 4 Lecture 1

Question 1

What is an antimicrobial?

Answer 1

Agent that is active against a microbe

Question 2

What is an antibiotic?

Answer 2

Agent derived from a living organism that acts against a microbe.

Question 3

What are the different types of antimicrobials?

Answer 3

Antibacterial, antifungal, antiviral and antiprotozoal agents.

Question 4

How are antibacterial agents classified?

Answer 4

• Bactericidal or bacteriostatic
• Spectrum - broad v narrow
• Target site
• Chemical structure

Question 5

Define bacteriostatic effect

Answer 5

an antibiotic can have this effect if it stops the bacteria from reproducing while not necessarily killing the bacteria otherwise

Question 6

Define bactericidal effect?

Answer 6

An antibiotic can have this effect by which they inhibit the growth of the bacteria

Question 7

What are the ideal features of antimicrobial agents?

Answer 7

Selectively toxic, few adverse effects, reach site of infection, oral/IV formulation, long half life and no interference with other drugs

Question 8

What are the four fundamental mechanisms of action that antibacterials have?

Answer 8

Cell wall synthesis, cell membrane function, protein synthesis and nucleic acid synthesis

Question 9

What type of antibiotic is penicillin?

Answer 9

Beta lactate antibiotic

Question 10

What does penicillin do?

Answer 10

Inhibits the formation of peptidoglycan cross links in the bacterial cell wall.

Question 11

How does penicillin work?

Answer 11

Penicillin binds to enzyme DD-transpeptidase hence it can;t catalyse formation of cross links. Weakens the cell wall hence causes cell death.

Question 12

Why is vancomycin medially important?

Answer 12

Because of its effectiveness against multi drug resistance organisms such as MRSA.

Question 13

What does vancomycin do?

Answer 13

Inhibits the synthesis of bacterial cell wall phospholipids as well as peptidoglycan polymerisation at a site earlier than that inhibited by penicillin.

Question 14

What sort of bacteria does vancomycin work against?

Answer 14

gram positive bacteria

Question 15

What is the difference between penicillin and vancomycin?

Answer 15

For penicillin, the peptidoglycan is formed but not cross linked. For vancomycin you don’t form peptidoglycan.

Question 16

What is a quinolone?

Answer 16

Family of synthetic broad-spectrum antibiotic drugs

Question 17

What are fluoroquinolones?

Answer 17

These are the majority of quinolone that are used clinically. They have a fluorine atom attached to the central ring system.

Question 18

What suffix do most fluoroquinolone have?

Answer 18

• oxacin

Question 19

What do fluoroquinolones do?

Answer 19

Inhibit the replication of bacterial DNA

Question 20

What are the different types of resistance?

Answer 20

Intrinsic, acquired and adaptive

Question 21

Describe intrinsic resistance

Answer 21

No target or access for the drug. Usually permanent

Question 22

Describe acquired resistance

Answer 22

Acquires new genetic material or mutates. Usually permanent

Question 23

Describe adaptive resistance

Answer 23

The organism response to a stress (eg sub-inhibitory level of antibiotic). Usually reversible

Question 24

What are the different mechanisms of resistance?

Answer 24

• Drug inactivating enzyme
• Altered target
• Altered uptake

Question 25

What are the genetic basis of antibiotic resistance?

Answer 25

- Chromosomal gene mutation | - Horizontal gene transfer

Question 26

What are the different types of susceptibility testing?

Answer 26

- Disk sensitivity testing | - Minimal inhibitory concentration

Question 27

What is Dias sensitivity testing?

Answer 27

Place exact amounts of antimicrobial agents on culture dishes and inoculate with the microorganism.

Question 28

What does the organisms growth on a disk sensitivity test show?

Answer 28

Its resistance to the drug

Question 29

What type of method is the disk sensitive method?

Answer 29

Qualititative

Question 30

What type of method is minimal inhibitory concentration method?

Answer 30

Quantitative method

Question 31

What is the minimal inhibitory concentration?

Answer 31

The minimum concentration of the antibiotic necessary to prevent bacterial growth.

Question 32

What is the minimal inhibitory concentration method?

Answer 32

Dilution technique where tubes containing serial dilutions of an antibiotic are inoculated with the organism.

Question 33

What are the different types of beta lactams?

Answer 33

Penicillin, cephalosporins, carbapenems and monobactams.

Question 34

Give some examples of penicillins

Answer 34

Penicillin, amoxicillin, flucloxacillin

Question 35

Describe some features of cephalosporins

Answer 35

- High broad spectrum - Effective against gram neg and gram pos - No anaerobic activity

Question 36

Give an example of a cephalosporin

Answer 36

Cetriaxone - good activity in the CSF

Question 37

Describe some features of carbapenems

Answer 37

- Very broad spectrum (inc anaerobes) - Active against most (not all) gram negs - Generally safe in penicillin allergy

Question 38

Give some example of carbapenems

Answer 38

Meropenem

Question 39

Give some examples of glycopeptide antibiotics

Answer 39

Vancomycin, teicoplanin

Question 40

Describe some features of teicoplanin

Answer 40

Similar activity to vancomycin but easier to administer

Question 41

Describe some features of vancomycin

Answer 41

``` Active against most gram pos Not absorbed (oral for C.diff only) ```

Question 42

Describe some features of tetracyclines

Answer 42

- Similar spectrum, oral only | - Broad spectrum but specific use in penicillin allergy, usually for gram pos

Question 43

Give some examples of tetracyclines

Answer 43

Tetracycline and doxycycline

Question 44

Give some examples of aminoglycoside

Answer 44

Most common agent is gentamicin

Question 45

Describe some features of aminoglycosides

Answer 45

- Profound activity against gram neg - Good activity in blood and urine - Generally reserved for severe gram neg sepsis

Question 46

Give some examples of macrolides

Answer 46

Erythromycin and clarithromycin

Question 47

Describe some features of macrolides

Answer 47

- Well distributed including intracellular penetration | - Alternative to penicillin for mild gram pos infections

Question 48

Give an example of a quinolone

Answer 48

Cciprofloxacin

Question 49

Describe some features of quinolone

Answer 49

Inhibit DNA gyrase Very active against gram neg Increasing resistance and risk of c diff

Question 50

What is trimethoprim used for

Answer 50

UTI

Question 51

What is the action of trimethoprim and sulphonamides?

Answer 51

Inhibited of folic acid synthesis

Question 52

When trimethoprim and sulphonamides are combined with sulphamethoxazole what are the features?

Answer 52

Used to treat PCP and has activity against MRSA

Question 53

Give examples of antifungal drugs

Answer 53

Azoles | Polyenes

Question 54

What do azoles do?

Answer 54

Inhibit cell membrane synthesis

Question 55

What is fluconazole used to treat?

Answer 55

Candida

Question 56

What do polyenes do?

Answer 56

INhibit cell membrane function

Question 57

Give some examples of antivirals

Answer 57

Aciclovoir | Oseltamivir

Question 58

What does aciclovir do?

Answer 58

When phosphorylates inhibits viral DNA polymerase