Antimicrobial Therapies

Question 1

What is an antibiotic

Answer 1

Antimicrobial agent produced by a microorganism that kills or inhibits other microorganisms

Question 2

What does bacteriocidal bacteria do

Answer 2

Kills bacteria

Question 3

What does bacteriostatic bacteria do

Answer 3

Stops bacteria from growing

Question 4

Why is antibiotic resistance bad

Answer 4

Requirement for additional surgeries
More expensive therapy
More toxic drugs
Less effective second choice drug
Increased time to effective therapy

Question 5

What type of antibiotic is aminoglycosides

Answer 5

Bactericidal

Question 6

What do aminoglycosides target

Answer 6

Protein synthesis (30s ribosomaml subunit), RNA proofreading and causes damage to cell membrane
Toxicity is high - hearing loss

Question 7

What type of antibiotic is rifampicin

Answer 7

Bactericidal

Question 8

What does rifampicin target

Answer 8

RpoB subunit of RNA polymerase
Secretions go orange/red
Spontaneous resistance is frequent

Question 9

What type of antibiotic is vancomycin

Answer 9

Bactericidal

Question 10

What does vancomycin target

Answer 10

Lipid II component of cell wall biosynthesis as well as wall crosslinking via D-ala residues
Used against MRSA

Question 11

What type of antibiotic is linezolid

Answer 11

Bacteriostatic

Question 12

What does linezolid do

Answer 12

Inhibits the initiation of protein synthesis by binding to 50s rRNA subunit
Does not affect gram negative bacteria due to LPS in the membrane

Question 13

What type of antibiotic is daptomycin

Answer 13

Bactericidal

Question 14

What does daptomycin target

Answer 14

Bacterial cell membrane
Cannot target LPS in gram negative
Toxicity limits dose - only inpatient settings

Question 15

What type of antibiotic is beta-lactams

Answer 15

Bacteriostatic

Question 16

What do beta-lactams target

Answer 16

Interfere with synthesis of peptidoglycan compoment of the bacterial cell wall

Question 17

What is selective toxicity

Answer 17

Target things in bacteria which aren’t present in humans

e.g. LPS layer and peptidoglycan layer

Question 18

What do macrolides target

Answer 18

Gram positive but sometimes gram negative

Targets 50s ribosomal subunit preventing amino-acyl transfer and truncation of polypetides

Question 19

What do quinolones target

Answer 19

DNA gyrase in gram neg
Topoisomerase 4 in gram pos
DNA damage and death of organism

Question 20

What type of antibiotic is quinolones

Answer 20

Bactericidal

Question 21

What is the breakpoint of antibiotics

Answer 21

Clinically-achieveable concentration of given antibiotic in host tissues

Question 22

What is the minimal inhibitory concentration

Answer 22

Lowest concentration of drug to inhibit growth

Question 23

What are the 4 mechanisms of antibiotic resistance

Answer 23

Altered target site
Inactivation of antibiotic
Altered metabolism
Decreased drug accumulation

Question 24

What is the action of altered target sites

Answer 24

Mutation in gene encoding target site
MRSA - alternative penicillin binding protein with low affinity to beta-lactams
Streptococcus pneumoniae - acquires genes which encodes enzyme that methylates target site

Question 25

What is the action of inactivation of antibiotic

Answer 25

Beta-lactamase enzyme which inhibits the beta lactame ring Enzymatic degradation of alteration of antibiotic ESBL and NDM-1 - broad-spectrum beta-lactamase

Question 26

What is the action of altered metabolism

Answer 26

Enzymes substrates are produced that outcompete target site | Bacteria switch to other metabolic pathways

Question 27

What is the action of decreased drug accumulation

Answer 27

Decrease penetration of antibiotic | Increase efflux of AB out of the cell

Question 28

What are some exogenous causes of antibiotic resistance

Answer 28

Plasmids - extra-chromosomal circular DNA Transposons - DNA that jumps, integrate into chromosomal DNA Naked DNA - DNA from dead bacteria

Question 29

How to bacteria take up DNA

Answer 29

Transformation - take up DNA from environment Transduction - Virus infect bacteria, take up DNA and then infect other bacteria Conjugation - bacterial sex to share plasmids

Question 30

Non-genetic mechanisms for treatment failure

Answer 30

``` Matrix incased communities of bacteria Intracellular location Slow growth - doesn't replicate fast Spores - antibiotic, antiseptic, heat resistant Persisters - dormant organisms ```

Question 31

Other reasons for treatment failure

Answer 31

Inappropriate choice of organisms Poor penetration of target site Inappropriate dose Inappropriate administration

Question 32

What are some hospital acquired infections

Answer 32

``` Methicillin-resistant S. aureus Vancomycin-insensitive S aurues Clostridium difficle Vancomycin-resistant enterococci E coli P aeruginosa Acineterbacter baumannii Stenotrophomonas maltophilia ```

Question 33

Risk factors for HAI

Answer 33

``` High number of ill people Crowded wards Presence of pathogens Broken skin Indwelling devices Transmission by staff ```

Question 34

How do we address resistance

Answer 34

``` Tighter control Temporary withdrawal of antibiotics Restriction for serious infections Reduce use of broad-spectrum antibiotics Quicker identification of infections Combination therapy ```

Question 35

How can beta lactams be modified to be more effective

Answer 35

Methicillin - prevent cleavage of beta-lactams | Augmentin - beta-lactamase inhibitor

Question 36

How can we prevent the gut flora biome from being destroyed

Answer 36

Use of non-pathogenic competitor strains