Antibiotics and Antimicrobial Resistance Flashcards by lauren telford

What is antimicrobial stewardship

Coordinated interventions designed to improve and measure the appropriate use of antimicrobials by promoting the selection of the optimal antimicrobial drug regimen, dose, duration of therapy, and route of administration.

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What questions should you ask when deciding to use antimicrobials

Is there good evidence of a bacterial infection?
What diagnostics will you employ that help decision-making?
When are cultures (and sensitivity used) used?
If you make the choice to use what drives your final choice of antibiotic?

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What is critically important antibiotic (CIA)

Last line resorts for human medicines - very bad if any resistance builds up

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What are the different ‘lines’ of antibiotics

Primary (1st line)
Secondary (2nd line)
Tertiary (3rd line)
Restricted

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Which line of antibiotics should you reach for first, and how to approach using the other lines

Primary
To use secondary - justify why didn’t use primary
To use tertiary - need C&S and justification

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Why are some antibiotics restricted in animals

Critical in human medicine

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Give some examples of primary (1st line) antibiotics (x6)

Penicillins
1st generation cephalosporins
Amoxy/clav
Tetracyclines
TMPS (Trimethoprim/sulfonamide)
Lincosamides

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Give some examples of broad (x1) and narrow (x2) spectrum secondary (2nd line) antibiotics

Broad
- Chloramphenicol
Narrow
- Aminoglycosides
- Metronidazole
- Macrolides

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Name 2 secondary (2nd line) antibiotics which are critically important

Fluoroquinolones
Cefovecin

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Name some tertiary (3rd line) antibiotics

3rd and 4th gen cephalosporins
Rifampicin
Fosfomycin

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Name the steps in the 7-point plan for the responsible use of antimicrobials

Work with clients to avoid the need for antimicrobials
Avoid inappropriate use
Choose the right drug for the right bug
Monitor antimicrobial sensitivity - C&S
Minimise use
Record and justify deviations from protocols
Report suspected treatment failure to the VMD

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Name 4 ways to work with clients to avoid the need for antimicrobials (step 1 in the 7-point plan)

Regular health checks
Use symptomatic relief or topical treatment where appropriate
Isolate infected animals where possible
Keep animals healthy - vaccinations, good diet, good practices

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Name 4 ways to avoid inappropriate use of antibiotics (step 2 in the 7-point plan)

Avoid using them when not needed - viral infections
Restrict use to animals who are unwell or at risk
Advise clients on correct use
Avoid underdosing

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Name 3 ways to choose the right drug for the right bug (step 3 in the 7-point plan)

Identify target organisms
Use narrow-spectrum where possible
Understand how antimicrobials work and their pharmacodynamic properties

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Name 2 ways to monitor antimicrobial sensitivity (step 4 in the 7-point plan)

Culture and sensitivity where you can
If C&S is not possible - empirical antibiotic therapy

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Name 3 ways to minimise use of antimicrobials (step 5 in the 7-point plan)

Use only when necessary
Assess use and develop protocols
Use alongside aseptic techniques and guidelines

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Name 2 ways to record and justify deviations from protocols (step 6 in the 7-point plan)

Justify choice - especially when using secondary or tertiary line antimicrobials
Keep accurate records

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Why do we report suspected treatment failure to the VMD (step 7 in the 7-point plan)

It may be the first indicator of resistance

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What does PROTECT ME stand for

Prescribe only when necessary
Reduce prophylaxis
Offer other options
Treat effectively
Employ narrow spectrum
Culture appropriately
Taylor practice policy
Monitor
Educate others

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What 6 factors can influence choice of antimicrobials

Principals of treatment
Cost/client
Food producing animals
Empirical selection
Pharmacodynamic considerations
Other factors - risk of drug class

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Name the 2 spectrums of antibiotics

Narrow spectrum - targets a narrow group of bacteria (gram +ve or -ve)
Broad spectrum - targets gram +ve and -ve bacteria, will have more impact on other bacteria in the host so more likely to cause a bad reaction

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What is the difference between bacteriocidal and bacteriostatic antibiotics and give examples

Bacteriocidal - Kills the organism e.g. penicillin, cephalosporins
Bacteriostatic - temporarily inhibit the growth of an organism (reversible if removed) e.g. tetracyclines, chloramphenicol

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If a patient is immunocompromised, should you use bacteriocidal or bacteriostatic antibiotics

Bacteriocidal
Bacteriostatic require the hosts immune system to remove the bacteria, so if immunocompromised this is not ideal

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What does MIC stand for and what is its definition

MIC = minimum inhibitory concentration
The concentration required at the site of infection to achieve bacterial inhibition

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What does MBC stand for and what is its definition

MBC = minimum bactericidal concentration The concentration required at the site of infection to kill the bacteria

Name the 7 main targets of action for antibiotics

Cell wall targeting Inhibition of cell wall synthesis Inhibition of protein synthesis Inhibition of cell membrane function Disruption of DNA structure Inhibition of DNA dependent RNA polymerase Interfering with other pathways

Why is peptidoglycan a good target for antimicrobials

It is unique to bacterial cell walls

Name the 4 groups of antibiotics which target the cell wall

Beta lactams Peptide antibiotics Bacitracin Teixobactin

How do beta lactams target the cell wall and give some examples

Inhibit the transpeptidase penicillin-binding protein (PBP) which stops peptide links from forming in the cell wall Examples: - Penicillins - Cephalosporins

How do peptide antibiotics target the cell wall and give some examples

Directly interact with the cell wall D-Ala-D-Ala section which prevents the synthesis of the NAG/MAM polymers Examples: - Vancomycin - CIA protected

Give some examples of antibiotics which work by inhibiting protein synthesis

Aminoglycosides Tetracyclines Clindamycin

How do antibiotics commonly inhibit protein synthesis

Target ribosomes and bind specific proteins meaning proteins cannot be synthesised

Give an example of an antibiotic which targets RNA synthesis

Rifampicin

How do Sulphonamides/Trimethoprim (TMPS) affect the DNA

Competitive inhibitors of the enzyme dihydropteroate synthetase Inhibits the synthesis of dihydrofolate which is required for DNA synthesis

How do Quinolones and Novobiocin affect the DNA

Bind to and stop DNA gyros Inhibits supercoiling of the chromosome Disrupts DNA-associated processes

How do nitroimidazoles affect the DNA

The reduction products of this group are reactive with DNA which damaged the DNA Causes DNA strands to break

What conditions do aminoglycosides not work well in and why

Anaerobic conditions They require aerobic respiration to enter the cell

What conditions do nitroimidazoles require

Anaerobic conditions They need to be reduced by anaerobic bacteria to be metabolised into their active form

Give 2 examples of aminoglycosides

Streptomycin Neomycin

Give 2 examples of tetracyclines

Oxytetracycline Doxycycline

Name 3 reasons you may use a combination of antibiotics

1. Treating mixed bacterial infections 2. Achieving synergistic antimicrobial activity against resistant strains 3. To reduce risk or overcome bacterial resistance

Why might you use a combination of penicillins and aminoglycosides

Penicillins have good anaerobic coverage Aminoglycosides have a good effect on gram negatives

What action do B-lactams have which is useful when using other antibiotics

Facilitate movement of other drugs through the damages cell wall => the microbe

What action does Clavulanic acid have which aids penicillin

Prevents B-lactamase destruction of penicillin

Name 5 reasons that antibiotic treatment can fail

1. Unjustified therapy - a viral infection 2. Poor selection 3. Wrong dose/ regimen 4. Suppressed host response 5. Resistance

Name 3 ways resistance to antimicrobials can be assessed

1. Liquid culture MIC minimum inhibitory concentration) determination 2. Disk diffusion (Kirby-Bauer) - diameter of zone inhibition for a genus os matched to a breakpoint for MIC 3. Detection of known resistance genes or mutations

By which value is resistance defined

Clinical breakpoint values

How are clinical breakpoints related to MIC

If MIC is less than X, then it is scored as sensitive If MIC is more than X, the scored as resistant

Why are you at risk of bacterial resistance if you are below the MIC

The susceptible bacteria may survive but grow slower / less well compared to the resistant. So the resistant bacteria slowly take over.

What is the MSC and what does it mean

MSC= minimum selective concentration It is the concentration at which there is no therapeutic effect but there is still a selective advantage to being resistant or susceptible.

Why is a long MSC window bad

Can lead to increased resistance

Define intrinsic resistance

An innate ability to resist the activity of a particular antimicrobial agent through inherent structural or functional characteristics which allow a tolerance of the drug

Define acquired resistance

When a microorganism obtains the ability to resist the activity of a drug. Can be a mutation or new gene acquisition.

Give 3 examples of intrinsic resistance

1. Poor permeability due to the outer membrane 2. Target different to the other genera 3. Lack the target e.g. mycoplasma have no cell wall so any drugs targeting cell wall will not affect them

Give 3 ways in which a bacteria can have acquired resistance

1. Gene mutation 2. Gene acquisition 3. Co-resistance

Give an example of a compound which leads to "degradation" of an antibiotic

B-lactamases

Which bacteria type are B-lactamases found commonly in

Staphylococci

Name an antibiotic which is resistance to B-lactamase

Methicillin

How does "efflux" work as an acquired mechanism

Efflux systems pump solutes out of a cell Allow bacteria to regulate their internal environment by removing toxic substances (including antibiotics)

Which group of bacteria have the drug efflux mechanism

Gram negative

Name the 3 major mechanisms of resistance that work against B-lactams

Cleavage of B-lactams by B-lactamases Extended Spectrum Beta-Lactamase (ESBL's) Altered penicillin-binding proteins (PBP)

Name the 3 major mechanisms of resistance that work against aminoglycosides

Efflux Enzymatic modification Ribosomal mutations

Name the 3 major mechanisms of resistance that work against quinolones

Target mutations Efflux Modification

Name the 2 major mechanisms of resistance that work against glycopeptides

Altered cell wall peptides Efflux

Name the major mechanism of resistance that work against tetracyclines

Efflux

Name the major mechanism of resistance that work against rifamycins

Altered mutated RNA polymerase

Name the major mechanism of resistance that work against pleuromutilins

Mutations in the 23S rRNA genes ribosomal proteins preventing binding to target

Name 3 factors which increase the risk of resistance selection

Underdosing Length of selective level Presence of resistant bacteria to select

What does MDR, XDR and PDR stand for

MDR = multiple drug resistance XDR = extensive drug resistance PDR = Pan drug resistance (no usable options)

What is the mode of action of B-lactam antibiotics

Inhibition of cell-wall synthesis

What is the mode of action of Aminoglycoside antibiotics

Inhibition of protein synthesis

What is the mode of action of quinolones antibiotics

Inhibition of DNA gyros and supercoiling

What is the mode of action of glycopeptide antibiotics

Inhibition of cell wall synthesis

What is the mode of action of tetracycline antibiotics

Inhibition of translation

What is the mode of action of rifamycin antibiotics

inhibition of transcription

What is the mode of action of oxazolidinone antibiotics

Inhibition of formation of 70S ribosomal complex

What is the mode of action of pleuromutilin antibiotics

Inhibition of the of formation of 50S ribosomal complex

Antibiotics and Antimicrobial Resistance Flashcards

(77 cards)