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Principles Of Medicine > Antimicrobial resistance > Flashcards

Antimicrobial resistance Flashcards

1
Q

What is prontosil?

A

First example of a sulphonamide antibiotic.

It is synthetic and bacteriostatic.

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2
Q

What is protonsil used for?

A

Use to treat UTIs (urinary tract infection), RTIs (respiratory tract infection), bacteraemia (bacteria in blood stream) and prophylaxis (antibiotics given to present disease beforehand) in HIV sufferers.

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3
Q

What is the function of beta lactams?

A

They interfere with the synthesis of the peptidoglycan component of the bacterial cell wall. They bind to penicillin-binding proteins. These proteins usually catalyse a number of steps in the synthesis of peptidoglycan.

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4
Q

What are 2 examples of beta lactams?

A

Penicillin and methicillin

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5
Q

What is an antimicrobial?

A

Chemical that selectively kills or inhibits microbes

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6
Q

What is the dIfference between bactericidal, bacteriostatic and antiseptic.

A

Bactericidal - kills bacteria

Bacteriostatic - stops bacteria growing

Antiseptic - chemical kills or inhibits microbes that is used topically (are applied directly to skin or mucous membranes)

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7
Q

What is the minimal inhibitory concentration?

A

The lowest concentration of antibiotic required to inhibit growth. As bacteria become more resistant the MIC increases.

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8
Q

How does antibiotic resistance occur?

A
  1. A population of bacterial cells contain a few cells with antibiotic resistance due to random mutations in DNA.
  2. In the absence of selection pressure the resistant strains have no advantage or have a disadvantage and therefore there is a low prevalence of resistant strains in patient population.
  3. However in the presence of a selection pressure, for example antibiotics, the antibiotic resistant bacteria out-compete the wild type bacteria leading to high prevalence of antibiotic resistant strains in patient population.
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9
Q

What are 5 consequences of antibiotic resistance?

A
  1. Effective therapy takes longer
  2. Additional approaches e.g. surgery required
  3. More expensive
  4. More toxic drugs required e.g. vancomycin
  5. Use of less effective antibiotics
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10
Q

GIve 5 examples of gram negative antibiotic resistant bacteria

A
  1. Pseudomonas aeruginosa - cystic fibrosis
  2. E-coli - neonatal meningitis, septicaemia, UTI/GI infection
  3. Salmonella - GI infection, typhoid fever
  4. Acinetobacter baumannii (MDRAB) - UTI, pneumonia
  5. Neisseria gonorrhoeae - gonorrhoea
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11
Q

Give 5 examples of gram positive antibiotic resistant bacteria

A
  1. Staphylococcus aureus (MRSA, VISA) - pneumonia, septicaemia, infective endocarditis
  2. Streptococcus pneumoniae - pneumonia, septicaemia
  3. Clostridium difficile - Antibiotic associated diarrhoea
  4. Enterococcus - UTI, bacteraemia, infective endocarditis
  5. Mycobacterium tuberculosis - tuberculosis
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12
Q

What are aminoglycosides?

A

Bactericidal antibiotics that target protein synthesis, RNA proofreading and cause damage to cell membrane.

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13
Q

2 examples of aminoglycosides

A

Gentamicin and streptomycin

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14
Q

What is rifampicin?

A

Bactericidal antibiotic that targets the RNA polymerase beta subunit and causes secretions to go orange/red.

Spontaneous resistance is frequent.

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15
Q

Vancomycin

A

A bactericidal antibiotic that targets the lipid component of cell wall biosynthesis as well as crosslinking D-alanine residues.

Has limited use due to its toxicity however is become more common due to bacteria being resistant to most other types of antibiotics.

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16
Q

Linezolid

A

A bacteriostatic antibiotic which inhibits the intiation of protein synthesis by binding to the 50S rRNA subunit.

17
Q

Daptomycin

A

A bactericidal antibiotic that targets the bacterial cell membrane.

18
Q

Give 3 examples of antibiotics that inhibit cell wall synthesis

A

Penicillin, Cephalosporins and vancomycin

19
Q

Give 3 examples of antibiotics that inhibit protein synthesis

A

Streptomycin, Erythromycin and tetracyclines

20
Q

Give 2 examples of antibiotics that inhibit nucleic acid replication and transcription

A

Quinolones, rifampin

21
Q

Give 1 example of an antibiotic that injures the plasma membrane

A

Polymyxin B

22
Q

Give 2 examples of antibiotics that inhibit the synthesis of essential metabolites

A

Sulfanimide, trimethoprim

23
Q

What are the 4 mechanisms of antibiotic resistance?

A
  1. Altered target site
  2. Inactivation of antibiotic
  3. Altered metabolism
  4. Decreased drug accumulation
24
Q

2 examples of bacteria that alter target sites

A

Staphylococcus aureus (MRSA) - encodes an alternative penicillin binding protein with a low affinity for beta lactams

  1. Streptococcus pneumoniae - acquires the erm gene which encodes an enzyme that methylates the antibiotic target site of erythromycin.
25
Q

Give 2 examples of enzymes that can inactivate antibiotics

A
  1. beta-lactamase

2. chloramphenicol acetyl-transferase

26
Q

How might altered metabolism lead to antibiotic resistance?

A

Increased production of an enzyme substrate that out competes the antibiotic inhibitor. For example the production of PABA confers resistance to sulfonamides.

27
Q

How might decreased drug accumulation lead to antibiotic resistance?

A

Reduced penetration of antibiotic into bacterial cell or increased efflux of antibiotic out of cell prevents antibiotic from reaching threshold concentration required for the drug to be effective.

28
Q

2 examples of macrolides and mechanism

A

Erythromycin and azithromycin

Targets 50S ribsomal subunit preventing amino-acyl transfer and thus truncation of polypeptides.

29
Q

What are quinolones?

A

Synthetic broad spectrum bactericidal antibiotic that inhibits DNA replication.

30
Q

3 sources of antibiotic resistant genes

A
  1. Plasmids
  2. Transposons - these intergrate into plasmid and chromosomal DNA and allow the transfer of genes between both.
  3. Naked DNA - DNA from dead bacteria can be released into the environment.
31
Q

3 ways genes responsible for antibiotic resistance can be shared between bacteria

A
  1. Transformation - uptake of extracellular DNA
  2. Conjugation - formation of a pilus between bacteria that transfers DNA.
  3. Transduction - DNA transfer between bacteria facilitated by virus
32
Q

What could be other reasons for antibiotic treatment failure?

A
  1. Inappropriate choice of antibiotic for organism
  2. Poor penetration of antibiotic into target site
  3. Inappropriate dose
  4. Inappropriate administration (oral vs IV)
33
Q

Give 5 examples of hospital acquired infections

A
  1. MRSA
  2. VISA
  3. Clostridium difficile
  4. Vancomycin-resistant enterococci
  5. E-coli
34
Q

Give 7 risk factors for hospital acquired infections

A
  1. High number of ill people
  2. Crowded wards
  3. Presence of pathogens
  4. . Broken skin
  5. Indwelling devices
  6. Antibiotics may suppress normal flora
  7. Transmission by staff in contact with multiple patients
35
Q

What is the role of commensal flora?

A

Commensal organisms can out-compete pathogens in our body with respect to adhesion, metabolism and growth. Therefore pathogens cannot colonise sufficiently for infection.

36
Q

5 methods of addressing antibiotic resistance

A
  1. Prescribing strategies - tighter controls, temporary withdrawals of certain classes etc..
  2. Reduce use of broad-spectrum antibiotics
  3. Quicker identification of infections caused by resistant strains
  4. Combination therapy
  5. Knowledge of local strains/ resistance patterns
37
Q

What are 2 reactive approaches to antibiotic resistance?

A

Modification of existing medications to enhance efficacy

  1. Use combinations of antibiotic and inhibitor

Principles Of Medicine (34 decks)

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