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MCD - Microbiology > Hospital acquired infection and antibiotic resistance > Flashcards

Hospital acquired infection and antibiotic resistance Flashcards

1
Q

Reasons for high rate of hospital-acquired infection

A
  • High numbers of ill people
  • Very crowded wards
  • High amounts of pathogen nearby
  • Broken skin from surgical wounds, IVs, catheters
  • Antibiotic therapy allows antibiotic-resistant pathogens to accumulate
  • Transmission by staff who don’t wash hands properly
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2
Q

Antimicrobial definition

A

A chemical that selectively kills or inhibits microbes

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3
Q

Bactericidal definition

A

Kills bacteria

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4
Q

Bacteriostatic definition

A

Stops bacteria growing

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5
Q

Antiseptic definition

A

A chemical that kills or inhibits microbes, usually used topical to prevent infection

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6
Q

Minimal inhibitory concentration definition

A

The lowest concentration of antibiotic required to inhibit growth

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7
Q

Tetracycline mechanism of action

A
  • Targets protein synthesis
  • Binds to 30s ribosomal subunit
  • Prevents peptide elongation
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8
Q

Chloramphenicol mechanism of action

A
  • Targets protein synthesis
  • Binds to 50s ribosomal subunit
  • Prevents peptidyl transfer step
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9
Q

Erythromycin mechanism of action

A
  • Targets protein synthesis
  • Gram positive bacteria affected
  • Truncation of polypeptides
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10
Q

Sulphonamides mechanism of action

A
  • Inhibition of essential metabolites

- Targets specific enzymes

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11
Q

List of important bacteriostatic antimicrobials

A
  • Tetracycline
  • Chloramphenicol
  • Erythromycin
  • Sulphonamides
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12
Q

List of important bactericidal antimicrobials

A
  • Beta-lactams (penicillin, methicillin)
  • Quinolones
  • Gentamicin
  • Streptomycin
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13
Q

Penicillin/methicillin (beta-lactams) mechanism of action

A
  • Targets cell wall synthesis
  • Bind to Penicillin Binding Protein (PBP) and inhibit function
  • No peptidoglycan synthesised
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14
Q

Quinolones mechanism of action

A
  • Inhibit nucleic acid replication and transcription
  • Target DNA gyrase in Gram negative
  • Target topoisomerase in Gram positive
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15
Q

Gentamicin/Streptomycin mechanism of action

A
  • Target protein synthesis

- Targets 30s ribosomal subunit

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16
Q

Reason for antimicrobials acting as selective pressure on microbes

A

Antimicrobial usage will kill all bacteria who do not possess resistance genes in a population. However, those that do will survive, and thus proliferate further until the new population is entirely resistant to that antimicrobial. Thus here the antimicrobial has acted as a selection pressure.

17
Q

Genetic mechanisms of resistance

A
  • Altering target site for antimicrobials, e.g. encoding an alternative PBP
  • Inactivation of antibiotic, e.g. enzyme degradation of antibiotic molecules, encode beta-lactamase which breaks down beta-lactams
  • Antibiotic efflux, e.g. encoding for efflux pumps which pump antibiotic molecules back out of cell
  • Altered metabolism, e.g. increasing production of substrate to out-compete antibiotic as inhibitor, can switch to other uninhibited metabolic pathways
  • Decreased drug accumulation, e.g. reduced penetration of antibiotic into bacteria
18
Q

Non-genetic mechanisms of antibiotic resistance

A
  • Forming a biofilm
  • Changing intracellular location of targeted sites
  • Slow growth
  • Spores
  • Persisters
19
Q

Penicillin resistance mechanisms

A
  • Penicillinases break down antibiotic, gained from plasmid transformation
  • Modification of PBP, gained from point mutation
20
Q

Tetracycline resistance mechanism

A

Efflux pump, gained by plasmid conjugation

21
Q

Quinolone resistance mechanism

A

Target site modification, gained by point mutation

22
Q

Cefotaxime resistance mechanisms

A

Target site modification, gained by point mutation

23
Q

Sources of antibiotic resistance genes

A
  • Plasmids
  • Transposons, integrate into chromosomal DNA, allows transfer of genes from plasmid to chromosome and vice versa
  • Naked DNA from dead bacteria in environment
24
Q

Mechanisms of antibiotic resistance gene spread

A
  • Transformation, uptake of extracellular DNA
  • Transduction, phage inserts resistance gene into cell
  • Conjugation, DNA transferred from cell to cell by a conjugation bridge
25
Q

Examples of important antibiotic-resistant bacteria

A
  • Methicillin-resistant staph.aureus (MRSA)
  • Vancomycin-insensitive S.aureus (VISA)
  • Clostridium difficile
  • Vancomycin-resistant enterococci (VRE)
  • E.coli
  • P.aeruginosa
26
Q

Reasons for longer hospital stays, more medical costs and increase in mortality and morbidity caused by antibiotic-resistant bacteria

A
  • New resistant strain must be treated
  • More specific/expensive treatment required to eliminate resistant strains
  • Mortality and morbidity increased because disease is more severe and some may have no treatment
27
Q

Strategies for decreasing antimicrobial resistance rate of increase

A
  • Tighter controls on prescribing strategies
  • Temporary withdrawal of certain antibiotic classes
  • Restriction of antibiotics for certain serious infections
  • Reducing use of broad-spectrum antibiotics
  • Quicker identification of infections caused by resistant strains
  • Combination therapy
  • Better knowledge of local strains/resistance patterns
28
Q

Strategies for overcoming resistance

A
  • Modification of existing medications, preventing cleavage of beta-lactams and enhancing efficacy of methicillin
  • Combinations of antibiotic and inhibitor of resistance mechanism e.g. beta-lactams with augmenting (inhibits beta-lactamases)

MCD - Microbiology (6 decks)

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