General Antimicrobial Pharmacology

Question 1

Define antimicrobials

Answer 1

chemicals that kill microorganisms

Question 2

Define antiseptics

Answer 2

Chemicals the reduce the microbial population on a living surface

Question 3

List 2 examples of antiseptics

Answer 3

povidone iodine

chlorhexidine gluconate

Question 4

What is the mechanism of action of povidone iodine

Answer 4

the free iodine dissociates and interacts with bacterial protein/nucleotides and fatty acids

Question 5

What is the mechanism of action of chlorhexidine gluconate? How does it compare to povidone iodine?

Answer 5

It disrupts cell membranes

It is better than povidone iodine as a pre-surgical use (except on face) and there is no documented resistance yet

Question 6

Define disinfectant

Answer 6

A biocide that reduces microorganisms on a non-living surface

Question 7

Define antibacterials

Answer 7

chemicals that kill or inhibit bacteria

Question 8

How are antibacterials classified? What are the 6 classifications?

Answer 8

by the site of action in the microbe

• folate synthesis inhibitor
• call wall synthesis inhibitor
• RNA pol inhibitor
• DNA gyrase inhibitor
• cell membrane inhibitor
• protein synthesis inhibitor

Question 9

Define minimum inhibitory concentration

Answer 9

The lowest concentration needed to completely inhibit bacterial growth

Question 10

Define minimum bactericidal concentration

Answer 10

The lowest concentration needed to kill 99.9% of bacterial isolates in vitro

Question 11

Compare bacteriocidal and bacteriostatic

Answer 11

bacteriocides: interfere with the vital processes of the bacteria to kill
- the MIC = MBC

bacteriostatic: prevent bacterial growth but don’t kill
- the MIC is very different from the MBC

Question 12

What are narrow spectrum antibacterials

Answer 12

they have efficacy against a single or small population of pathogens

associated with low adverse effects and a reduce AMR risk

Question 13

What are broad spectrum antibacterials

Answer 13

They have efficacy against a wide range of pathogens

Question 14

What are extended spectrum antibacterials

Answer 14

they have efficacy against an intermediate number of pathogens (not narrow but not broad spectrum)

Question 15

Give 3 examples of concentration dependent antibacterials

Answer 15

aminoglycosides

fluoroquinolones

metranidazole

Question 16

Explain what concentration dependent antibacterials are

Answer 16

Their efficacy depends on how high above the MIC they are
- more effective if they are at higher concentrations

Question 17

What is the post antimicrobial effect

Answer 17

bacterial inhibition after treatment with antibacterials has stopped

removal of the bacteria by the host immune system maintains low levels for a while

Question 18

Explain what time dependent antibacterials are

Answer 18

Efficacy depends how long that drug is at the site of infection above the MIC

the dosing will maximize the time the concentration is maintained above the MIC
- concentration has no effect on efficacy (as long as it is above the MIC)

Question 19

Give 7 examples of time dependent antibacterials

Answer 19

penicillin

cephalosporin

macrolide

lincosamide

sulfonamide

phenicol

tetracycline

Question 20

How to plan dosing intervals of antibacterials

Answer 20

give the next dose during the post antimicrobial effect period
- before the bacterial concentrations begin to increase again

Question 21

What are 3 methods for testing antibacterial susceptibility

Answer 21

broth dilution test

disc diffusion test

e-test method

Question 22

How does the broth dilution susceptibility test work

Answer 22

add abx + growth media + bacteria

see what concentration of abx is needed to prevent bacterial growth

Question 23

How does the disc diffusion susceptibility test work

Answer 23

put abx discs on an agar plate innoculated with bacteria

measure zone of inhibition

Question 24

How does the e-test susceptibility test work

Answer 24

it is a plastic strip with a gradient of abx

Question 25

How are bacteria deemed susceptible or resistant? What are the 3 categories of susceptibility?

Answer 25

based on the MIC breakpoints - MIC values are specific to different bacteria susceptible - MIC < susceptible breakpoint intermediate - MIC is between the susceptible and resistant breakpoint resistant - the MIC is above the resistant breakpoint

Question 26

What is 'de-escalating' and antibacterial treatment plan?

Answer 26

When you switch antibacterials during a treatment to a less important or more specific type

Question 27

What is empirical treatment

Answer 27

treating based on your knowledge and experience of what is most likely the cause of the problem

Question 28

What should you consider when thinking about your rationale for using antibacterial

Answer 28

are they needed is the causative agent susceptible will they recover without abx will abx improve the outcome or significantly reduce the risk to other individuals

Question 29

Provide examples of topical abx

Answer 29

triple abx ointment silver sulfadiazine cream betadine ointment chlorhex gel honey

Question 30

What are the 2 types of ways antibacterial can be used

Answer 30

prophylactic/metaphylactic - preventative use therapeutic - to treat infection

Question 31

What are the 3 types of situations for therapeutic abx treatment? How do they change the type of abx you use?

Answer 31

non life threatening and not serious - narrow spectrum - don't usually need C/S on first treatment serious but not life threatening - consider C/S if they need long term abx - avoid big guns - target common pathogens life threatening - target full range of pathogens - use a combo treatment or big gun abx

Question 32

What other considerations should you have before using antibacterial

Answer 32

site of infection - is it immune-privileged or intracellular treat underlying causes - lance abcess/remove FB/debride history - signalment - concurrent disease - hygeine/housing - diet - immunosuppressive drugs

Question 33

Define obligate anaerobe

Answer 33

can only live with oxygen

Question 33

What is the 4 quadrant approach

Answer 33

categorize bacterial types to choose most effective treatment if you don't have a C/S gram (+) aerobe - include facultative anaerobe + aerotolerant anaerobe gram (-) aerobe - include facultative anaerobe + aerotolerant anaerobe gram (+) anaerobe - obligate anaerobes only gram (-) anaerobe - obligate anaerobes only

Question 34

Define facultative anaerobe

Answer 34

can use aerobic or anaerobic respiration

Question 35

Define aerotolerant anaerobe

Answer 35

is anaerobic but can live in the presence of oxygen

Question 36

Define obligate anaerobe

Answer 36

can only live without oxygen

Question 37

What enzymes facilitate oxygen metabolism in bacteria

Answer 37

superoxide dismutase catalse peroxidase

Question 38

List 9 categories of antibacterials (not the same as classification)

Answer 38

macrolides folate synthesis inhibitors - sulfonamides - diaminopyrimidines fluoroquinolones animoglycosides lincosamides -phenicols nitroimidazoles beta lactams (cell wall disruption) tetracycline

Question 39

List 7 examples of gram (+) aerobes

Answer 39

staphylococcus streptococcus enterococcus truperella listeria bacillus nocardia

Question 40

Give examples of gram (-) aerobes that affect the GI, resp and opportunistic

Answer 40

enteric: - e. coli - kleibsiella - proteus - campylobacter resp: - manheimmia - pasturella - histophilus - bordatella opportunistic - pseudomonas

Question 41

Give 3 examples of gram (+) anaerobes

Answer 41

clostridium actinomyces peptostroptococcus

Question 42

Give 2 examples of gram (-) anaerobes

Answer 42

fusobacterium bacteroides

Question 43

What are the 2 main antibacterial classes that are used to treat Pseudomonas infection in companion animals and horses?

Answer 43

fluoroquinolones and aminoglycosides