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microbiology > antiBiotics > Flashcards

antiBiotics Flashcards

1
Q

what are the categories of antibiotics that target cell wall synthesis?

A

penicillins
cephalosporins
carbapenems
monobactams

(all B-lactams)

  • vancomycin
  • tercoplanin

(both glycopeptides)

bacitracin
(polypeptide)

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2
Q

name the different types of penicillin.

A

penicillin V
penicillin G
fluctoxacillin / methicillin
amoxicillin / ampicillin
piperacillin

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3
Q

outline the pharmacokinetics of b-lactams.

A
  • target penicillin-binding proteins (PBPs), enzymes involved in peptidoglycan synthesis.
  • peptoglycans maintain the strength and rigidity of the bacterial cell wall.
  • without this the cell wall is compromised and the cell dies via lysis
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4
Q

name some bacterium which penicillin can be used to treat and outline some cases when penicillins should be used.

A

S. pneumoniae
S. pyogenes
S. aureas
N. meningitidis
N. gonorrhoea
H. influenza
- effective for many gram-positive
- narrow mechanism of action meaning can disrupt certain species without effecting flora
- not effective against lactamase producing species.

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5
Q

name the bacterial species of cephalosporins.

A
  • cefa-lexin
  • cefu-roxime
  • cefo-taxime
  • cefria-xone
  • cefta-zimide
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6
Q

outline when you would prescribe cephalosporins and what species of bacteria they are effective against.

A
  • versatile and broad spectrum of activity
  • usually prescribed when penicillins are ineffective
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7
Q

outline the different species of the carbapenems.

A
  • metropenem
  • ertapenem
  • imipenem
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8
Q

outline when carbapenems are used.

A
  • broad spectrum
  • resistant to beta lactamases
  • reserved for treating serious infections caused by multi-drug resistance
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9
Q

outline when monobactams are used.

A
  • primarily effective against aerobic gram-negative bacteria
  • unique structure - only consist of a single beta lactam ring
  • resisstant to beta-lactamase producing organisms
  • used in severe gram negative infections
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10
Q

what drug is under the catagory monobactams?

A

aztreonam

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11
Q

name the 2 glycoproteins that target the cell wall and when you would use each one

A

vancomycin:
- serious infections caused by gram positive
- MRSA
- binds to petidoglycan precursors, inhibiting cell wall synthesis

teicoplanin:
- topical because very toxic effects
- prevents encorporation of new peptoglycan into cell wall
- gram positive
- superficial skin infections - minor cuts, burns, eye infections

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12
Q

outline why beta lactams work best with gram positive antibiotics.

A
  • to bind to PBPs, it must diffuse through the cell wall
  • gram-negative organisations have an additional lipopolysaccharide layer that decreases andibiotic penetration
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13
Q

why are penicillins ineffective at treating intracellular pathogens?

A

because they poorly penetrate mammalian cells

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14
Q

outline why the different B-lactams have different acitivity.

A

due to their relative affinity for different PBPs

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15
Q

name the antibiotics that work by targeting nucleic acid synthesis.

A

rifampicin
metronidazole
fluoroquinolones:
- ciprofloxacin
- levofloxa§cin
- moxifloxacin

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16
Q

how do floroquinolones work?

A

inhibit bacterial DNA gyrase and topoisomerase IV enzymes critical for DNA replication and repair
- cell death

17
Q

outline when the floroquinolones would be used?

A

Ciprofloxacin: Best for Gram-negative and Pseudomonas.

Levofloxacin: Respiratory infections with better Gram-positive coverage.

Moxifloxacin: Broader spectrum, including anaerobes.

18
Q

rifampicin

A
  • rifamycin class antibiotic
  • inhibits rna polymerase, preventing rna synthesis and bacterial replication leading to death
  • bacteriacidal
  • Broad-spectrum, effective against Mycobacterium tuberculosis, Gram-positive bacteria, and some Gram-negative bacteria.
19
Q

Metronidazole

A
  • a nitroimidazole class antibiotic
  • disrupts bacterial DNA in anaerobic organisms and protozoa
  • bacteriacidal
20
Q

name the classes on antibiotic that affect protein synthesis.

A

30s:
tetracyclines:
- doxycycline
aminoglycosides:
- gentamicin

50s
macrolides:
- erythromycin
- clarithromycin
- azithromycin
clindamycin
linezolid
chloramphenicol

21
Q

name the antibiotics which work by inhibiting folate synthesis.

A

sulphonamides:
- sulphamethoxazole
blocks conversion of PABA to DHFA

trimethopim
blocks conversion of DHFA to HFA

both bacteriastatic but co-trimoxazole is bacteriacidal

co-trimoxazole - combination of sulfamethaxazole and trimethropim

22
Q

outline the difference between bacteriostatic and bactericidal antibiotics.

A

bacteriostatic - inhibit protein synthesis, dna replication or metabolism (prevents bacteria multiplying)

bacteriacidal - inhibit cell wall synthesis (kills bacteria)

23
Q

what are the 2 major determinants of antibiotics to be effective?

A
  • concentration - must bind to an adequate number of binding sites
  • time that the antibiotic remains on the binding sites

but for this to happen the antibiotic must reach and stay at the site of bacterial infection - this depends on pharmacokinetics eg release, absorption, distribution, elimination
- therefore when choosing an antibiotic you must choose one which will be able to reach the site of infection, in a large enough concentration, in an amount of time suitable

24
Q

nitrofurantonin

A
  • used for UTIs
  • S. Saprophyticus
  • bacteriacidal
  • works by being low level in the blood but being excreted in the urine so high levels in there and working that way
  • targets dna, protein synthesis and other cell components
25
Q

Discuss the patient and pathogen factors considered for choosing antibiotics

A

patient:
- neonates and infants
- elderly
(weaker liver and renal for excretion and metabolism)
- penicillin alergy
- immunocomprimised
(broad spectrum antibiotics needed to treat opportunistic infections)

pathogen:
- likely organism causing the infection
- consider local resistance patterns eg MRSA
- sensitivity of the organism to the antibiotic

26
Q

bacitracin

A
  • inhibits cell wall synthesis
  • glycoprotein
  • topical
  • gram positive

microbiology (19 decks)

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