S4) Antimicrobials and Resistance Flashcards Preview

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Flashcards in S4) Antimicrobials and Resistance Deck (30)
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1

Identify 4 different ways in which antibacterial agents can be classified

- Bactericidal / bacteriostatic (kill/disable)

- Broad / narrow (spectrum)

- Mechanism of action (target site)

- Antibacterial class (chemical structure)

2

What are the 6 ideal features for antimicrobial agents?

- Selectively toxic

- Few adverse effects

- Reach site of infection

- Oral/IV formulation

- Long half-life (infrequent dosing)

- No interference with other drugs

3

Identify the different classes of antimicrobials based on their different mechanisms of action

4

Identify and describe the different types of resistance

- Intrinsic: no target or access for the drug (usually permanent)

- Acquired: acquires new genetic material or mutates (usually permanent)

- Adaptive: organism responds to a stress (usually reversible)

5

Identify the different mechanisms of resistance and provide examples

- Drug-inactivating enzymes e.g. b-lactamases, aminoglycoside enzymes

- Altered target (lowered affinity for antibacterial) e.g. resistance to macrolides & trimethoprim

- Altered uptake

I. ↓permeability e.g. b-lactams

II. ↑efflux e.g. tetracyclines

6

Identify the four Beta-lactam subgroups

- Penicllins

- Cephalosporins

- Carbapenems

- Monobactams

7

Provide some examples of penicillins in the Beta-lactam sub-group and describe their use

- Penicillin – active against strep

- Amoxicillin – active against staph & strep (+ ↑Gneg)

- Flucloxacillin – active against staph & strep

- Β-lactamase inhibitor combinations e.g. co-amoxiclav  – acitive against staph & strep and anaerobes (↑Gneg)

8

Describe the use of cephalosporins in the Beta-lactam sub-group and provide some examples

↑Gneg and ↓Gpos activity

- ↑broad-spectrum (no anaerobes)

E.g. ceftriaxone has good activity in the CSF IV but associated with C. difficile

9

Describe the use of carbapenems in the Beta-lactam subgroup and provide some examples

- Broad spectrum (+ anaerobes)

- Active against most Gnegs

- Safe in penicillin allergy

E.g. meropenem and imipenem

10

Provide two examples of glycopeptides

- Vancomycin

- Teicoplanin

11

Describe the use of vancomycin in the Glycopeptide subgroup

- Active against most Gpos

- Rare resistance in staphs

- Oral for C. difficile only (otherwise IV)


 

12

Describe the use of teicoplanin in the Glycopeptide subgroup

- Similar activity to vancomycin

- Easier to administer

13

Provide two examples of tetracyclines

- Tetracycline

- Doxycycline

14

Describe the use of doxycyline & tetracycline in the tetracyline subgroup 

- Oral administration

- Broad-spectrum

- Gpos (use in pencillin allergy)

- Active in atypical pathogens in pneumonia & against chlamydia

- Shouldn’t be given to children < 12 years

15

Provide an example of an aminoglycoside

Gentamicin

16

Describe the use of gentamicin in the aminoglycoside subgroup

- Activity against Gnegs

- Good activity in the blood/urine

- Generally reserved for severe Gram neg sepsis

17

Provide two examples of macrolides

- Erythromycin

- Clarithromycin

18

Describe the use of erythromycin and clarithromycin in the macrolide subgroup

- Used for mild Gpos infections (alternative to penicillin)

- Active against atypical respiratory pathogens

19

Provide an example of a quinolone

Ciprofloxacin

20

Describe the use of quinolones

- Inhibit DNA gyrase

- Very active against Gnegs

- Active against atypical pathogens

- Increasing resistance

- Risk of C. difficile

21

Describe the use of trimethoprim

- Inhibits folic acid synthesis

- Used alone in the UK for UTI

 

22

Identify two subgroups of antifungal agents

- Azoles

- Polyenes

23

Describe the use of azoles and provide some examples

Inhibit cell membrane synthesis:

- Flucanazole used to treat candida

- Posaconazole also active against aspergillus 

24

Describe the use of polyenes and provide some examples

Inhibit cell membrane function:

- Nystatin for topical treatment of candida

Amphotericin for IV treatment of systemic fungal infections

25

Provide some examples of antiviral agents

- Aciclovir

- Oseltamivir

- Specialist agents for HIV, HBV, HCV, CMV

26

Describe the use of aciclovir

- Inhibits viral DNA polymerase (when phosphorylated)

- Used to treat HSV and varicella zoster virus

27

Describe the use of oseltamivir

- Inhibits viral neuraminidase

- Used to treat influenza A & B

28

Describe the use of metronidazole (antibacterial and antiprotozoal agent)

- Active against anaerobic bacteria

- Also active against protozoa e.g. amoebae, giardia (diarrhoea), trichomonas (vaginitis)

29

What are the consequences of antibacterial resistance?

- Treatment failure

- Prophylaxis failure

- Economic costs

30

Identify and describe the different definitions of antimicrobial resistance

- MDR (multi-drug resistant): non-susceptibility to at least one agent in three or more antimicrobial categories

- XDR (extensively drug resistant): non-susceptibility to at least one agent in all but two or fewer antimicrobial categories

- PDR (pan-drug resistant): non-susceptibility to all agents in all antimicrobial categories