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Microbiology & Immunology > 12 - antibiotics > Flashcards

12 - antibiotics Flashcards

1
Q

what are antibiotics?

A

natural or synthetic compounds that prevent microorganism growth or cause lysis

anti life - stops life

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2
Q

whats the difference between viable and total population?

A

viable = able to reproduce

total = actual population

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3
Q

what are the 3 different kinds of antibiotics?

A

bacteriostatic
bacteriocidal
bacteriolytic

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4
Q

what is bacteriostatic?

A

stationary (no increase)

total and viable cell count remain constant

prevents replication, used to stabilise the population and control the infection

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5
Q

what is bacteriocidal?

A

to die

total cell count stays same but viable cell count decreases

used for invasive and aggressive infections

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6
Q

what is bacteriolytic?

A

to lyse/burst

both total and viable cell count decrease

interferes with structural integrity

very strong antibiotics but hugely affect the microbiota

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7
Q

what is MIC?

A

minimum inhibitory concentration

the minimum antibiotic to inhibit growth

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8
Q

MIC susceptibility testing

A

sensitive
intermediate
breakpoint
resistant

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9
Q

MIC susceptibility testing - SENSITIVE

A

appropriate dosage of standard agent

S = routine prescription

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10
Q

MIC susceptibility testing - INTERMEDIATE

A

MIC higher than sensitive

equals the concentration the drug reaches in patient

I = in-vivo and in-vivo concentration

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11
Q

MIC susceptibility testing - BREAKPOINT

A

concentration of drug attainable in serum

B = limit of therapeutic success

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12
Q

MIC susceptibility testing - RESISTANT

A

isolate unaffected by safe concentration of drug

drug would harm patient at a higher dose

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13
Q

MIC variables

A
  • media
  • pH
  • temperature
  • oxygen level
  • population density
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14
Q

what are breakpoints?

A

discriminatory antimicrobial concentrations used in the interpretation of results of susceptibility testing to define isolates as susceptible, intermediate or resistant

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15
Q

targets in the bacterial cell

A
  • inhibition of cell wall synthesis
  • inhibition of replication, transcription and translation
  • inhibition of synthesis of essential metabolites
  • membrane integrity lesions
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16
Q

major classes of protein synthesis-inhibiting antibacterials

A

chloramphenicol, macrocodes and lincosamides

aminoglycosides

tetracyclines

17
Q

what do chloramphenicol, macrocodes and lincosamides do?

A
  • bind to the 50S ribosomal subunit
  • prevent peptide bond formation
  • stop protein synthesis
18
Q

what do aminoglycosides do?

A
  • bind to the 30S ribosomal subunit

* impair proofreading, resulting in production of faulty proteins

19
Q

what do tetracyclines do?

A
  • bind to the 30S ribosomal subunit

* block the binding of tRNAs inhibiting protein synthesis

20
Q

how do antibiotics affect microbial metabolism?

A

target essential biochemical pathway anti-metabolites

stop the pathway or generate a toxic intermediate

21
Q

how do antibiotics target DNA?

A

target replication or DNA packing

prevent chromosomal replication (e.g.. DNA gyrase inhibition)

examples:
• quinolones - broad range as Gyrase found in all bacteria
• ciprofloxacin - used in UTI treatment but also bacteremia

22
Q

how do antibiotics break the cell wall?

A

target cell wall synthesis or integrity

causes the cells to lyse

examples:
• penicillins - beta-lactam antibiotics, bind to PG synthesis machinery, useful for both gram +ive and -ive infections
• vancomycin - binds to PG precursors

23
Q

mechanisms of resistance to antibiotics in bacteria

A
  • reduced permeability
  • inactivation of antibiotic
  • alteration of target
  • development of resistant biochemical pathway
  • efflux - pumping out
24
Q

last resort antibiotics

A

antimicrobial resistance and healthcare associated infections (AMRHAI) is part of Public Health England’s
bacteria reference department (BRD)

AMRHAI = 7 sections:
• staphylococcus reference
• opportunist pathogens
• antibiotic susceptibility testing
• resistance mechanisms section
• infection prevention and control
• bacterial identification services (BIDS)
• antimicrobial resistance in STIs

Microbiology & Immunology (30 decks)

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