S4 Intro to Antibiotics and Resistance

Question 1

What are the 4 classes of antimicrobials?

Answer 1

• antibacterial
• antifungal
• antiviral
• antiprotozoal

Question 2

What ways can antibacterials agents be classified?

Answer 2

• bactericidal or bacteriostatic
• broad or narrow
• what is the target site? (Mechanism of action)
• what is the chemical structure? (Antibacterial class)

Question 3

How can you measure antibiotic activity/sensitivity?

Answer 3

• disc testing (disc diffusion testing)

* minimum inhibitory concentration (MIC) - broth microdilution or E test

Question 4

What are the 4 mechanisms of actions by antibacterials?

Answer 4

• cell wall synthesis
• protein synthesis
• cell membrane function
• nucleic acid synthesis

Question 5

What antibacterials affect bacteria cell wall synthesis?

Answer 5

• beta-lactams: penicillins, cephalosporins

* glycopeptides

Question 6

What antibacterials affect bacteria cell membrane function?

Answer 6

• polymixins e.g. colistin

Question 7

What antibacterials affect bacteria protein synthesis?

Answer 7

• tetracyclines
• aminoglycosides
• macrolides

Question 8

What antibacterials affect bacteria nucleic acid synthesis?

Answer 8

• quinolones
• trimethoprim
• rifampicin

Question 9

What are the 3 types of resistance?

Answer 9

1. Intrinsic
2. Acquired
3. Adaptive

Question 10

Describe intrinsic resistance.

Answer 10

• has no target to access for the drug

* usually permanent

Question 11

Describe acquired resistance.

Answer 11

• acquires new genetic material or mutates

* usually permanent

Question 12

Describe adaptive resistance.

Answer 12

• organism responses to a stress e.g. sub-inhibitory levels of antibiotic

Question 13

What are the 3 mechanisms of resistance?

Answer 13

1. Enzymatic modification/destruction of antibiotics
2. Enzymatic alteration of antibiotic targets
3. Mutations of bacterial target sites

Question 14

How can gene for resistance get to other bacteria cells?

Answer 14

• chromosomal gene mutation then bacterial replication
• horizontal gene transfer - two bacterial cells can conjugate and transfer plasmids from one to another (pilus conjugates cells, cells “fuse” partially, DNA polymerase replicates plasmid, pilus separate)

Question 15

What classes of antibiotics are beta-lactams?

Answer 15

• penicillins e.g. amoxicillin, flucloaxcillin, penicillin, etc
• cephalosporins e.g. cefalexin, ceftriaxone, cefepime, etc
• carbapenems e.g. meropenem, imipenem
• monobactams e.g. aztreonam

Question 16

What is penicillin active against?

Answer 16

Streptococci

Question 17

What is amoxicillin active against?

Answer 17

Streptococci and some activity against gram-negatives

Question 18

What is flucloaxcillin active against?

Answer 18

Staphylococci and streptococci

Question 19

What is Co-amoxiclav active against? What is it’s advantage?

Answer 19

Streptococci, staphylococci, gram negatives, anaerobes

It is a beta-lactamase inhibitor combination (between amoxicillin and clavulanate

Question 20

What is piperacillin/tazobactam active against? What is it’s advantage?

Answer 20

Streptococci, staphylococci, gram negatives (incl. pseudomonas), anaerobes

Question 21

What are cephalosporins? What is an example of one, where does it have good activity?

Answer 21

Broad spectrum antibacterials with no anaerobes activity

Cetriaxone, good activity in the CSF

Question 22

What are 3 carbapenems? Are they broad or narrow spectrum? What are they active against?

Answer 22

• meropenem, ertapenem, imipenem
• broad
• most gram negatives

Question 23

What are two types of glycopeptides?

Answer 23

• vancomycin (active against most gram positives)

* teicoplanin (easier to administer)

Question 24

Are tetracycline and doxycycline broad or narrow spectrum? What are they active against? Who shouldn’t they be given to?

Answer 24

• broad spectrum
• chlamydia and some protozoa
• children under 12 years, pregnant and breastfeeding women

Question 25

What is the most common aminoglycoside? What do they work against? Where do they have good activity?

Answer 25

* gentamicin * gram negatives * blood/urine

Question 26

What is an example of a macrolide? What do they act against?

Answer 26

* erythromycin | * alternative to penicillin for mild gram positive infections, also works against atypical respiratory pathogens

Question 27

What is the most common quinolone? What do they inhibit? What are they active against? What if becoming increasingly resistant to them?

Answer 27

* Ciprofloxacin * DNA gyrase * gram negatives and atypical pathogens * C.difficile

Question 28

What do trimethoprim and sulphonamides inhibit? What does trimethoprim treat on its own?

Answer 28

* folic acid synthesis | * UTI

Question 29

What are the two types of antifungals? What do they inhibit?

Answer 29

* azoles - inhibit cell membrane synthesis | * polyenes - inhibit cell membrane function

Question 30

What is an example of an azole? What does it work against?

Answer 30

Fluconazole - against candida

Question 31

What is an example of a polyene? What it is used against?

Answer 31

Nystatin - topical treatment for candida

Question 32

What does the antiviral, aciclovir do?

Answer 32

When phosphorylated, it inhibits viral DNA polymerase (works against herpes simplex and varicella zoster)

Question 33

What does the antiviral, oseltamivir do?

Answer 33

Inhibits viral nueraminidase (works against influenza A and B)

Question 34

What is metronidazole? What is it active against?

Answer 34

An antibacterial and an antiprotozoal agent anaerobic bacteria and protozoa - amoebae, giardia and trichomonas