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MLSCI 242 > LECTURE - Antimicrobials > Flashcards

LECTURE - Antimicrobials Flashcards

1
Q

bactericidal

A

compound that kills the organism

> important for immunocompromised

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2
Q

bacteriostatic

A

compound inhibits growth of organism ; useful when immune system is intact

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3
Q

lines between bactericidal and bacteriostatic properties blur when…

A

organisms grow more slowly = biofilm

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4
Q

Pharmacokinetics

A

describes the action of body on the administered drug that includes absorption, distribution, metabolism, and excretion to define systemic exposure

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5
Q

pharmacodynamics

A

describes the biochemical and physiologic response of the drug and its mechanism of action

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6
Q

selective toxicity

A

kill bug not patient

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7
Q

side effects of antimicrobials can occur when

A
  • selectivity is not optimal or

- antimicrobial has unexpected interactions w host (penicillin combining w serum proteins = allergic rxns)

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8
Q

disinfectant

A

compound used to kill or inhibit organisms on surfaces r inanimate objects
> too toxic for body use (ex: phenolics)
> not selective

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9
Q

compound used to kill or inhibit organisms on skin but not internally

A 
antiseptic
 > sodium hypochlorite (bleach)
 > povidone iodine solutions (Betadyne)
 > 70% ethanol
 > 3.0% hydrogen peroxide
 > benzalkonium chloride
 >hexachlorophene
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10
Q

innate resistance to disinfectants and antiseptics

A

hyrophilic polysaccharide chains in LPS of gram negs can keep quaternary ammonium compounds (QACs) like cetramide and benzalkonium chloride at a distance from outer membrane

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11
Q

acquired resistance to disinfectants and antiseptics

A

plasmid-encoded efflux pumps for QACs in S. aureus

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12
Q

general characteristics of antibiotics

A
  • originate from microbes (actinomycetes; fungi)
  • have selective toxicity
  • possess a spectrum of action (broad vs narrow)
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13
Q

inhibitors of cell wall synthesis

A 
- peptidoglycan pathway was first to be capitalized on with penicillin
 > Fosomycin 
 > Bacitracin
 > Tunicamycin
 > Glycopeptides (vancomycin)
 > beta-lactam antibiotics
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14
Q

most important inhibitors of cell wall synthesis

A

beta-lactam

  • penicillins
  • cephalosporins
  • carbapenems
  • monobactams
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15
Q

bacitracin

A
  • interferes w recycling bactoprenol

- systemic toxicity limits its use to topical ointment

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16
Q

tunicamycin

A
  • powerful action against gram pos
  • has strong antiviral activity to envelope viruses growing in cultured cells as it arrests N-glycosylation of proteins destined for viral envelope = loss of infectivity of viruses released from host cells
  • no therapeutic use however as it is too toxic to animals = inhibits N-glycosylation of essential glycoproteins
17
Q

inhibitors of cell membrane function

A

polymyxins and colistins

  • bind to lipid A
  • act like detergents to disrupt membrane integrity
  • systemic toxicity has limited their main use to topical ointments however … will bind to lipids in our kidneys (nephrotoxicity) so dont ingest

polysporin = polymyxins

18
Q

assembled ribosomes in prokaryotes vs eukaryotes

A 
pro = 70S
eukaryo = 80S
19
Q

inhibitors of protein synthesis in bacteria

A

inhibitors of 30S

  • aminoglycosides (gentamicin, kanamycin)
  • tetracyclines (tetracycline, doxycyline)

inhibitors of 50S

  • macrolides
  • lincomides
  • streptogramins
  • oxazolidinones
20
Q

aminoglycosides

A
  • gentamicin, kanamycin
  • prevents complex of 50S and 30S
  • bactericidal
  • renal failure (reversible)
  • side effect of ototoxicity (hearing loss)
  • have no effect on anaerobes
21
Q

tetracyclines

A
  • distorts the A site in ribosome, inhibiting tRNA binding to colon
  • one of the least toxic antibiotics
  • over-used, so resistance is common
  • used to treat intracellular bacteria
22
Q

macrolides

A
  • inhibitors of the 50S ribosomal subunit
  • inhibit translocation near 23S rRNA
  • can be bacteriostaticc or bactericidal
  • works intracellularly
  • little toxicity
  • ketolides have similar mechanism of action
23
Q

lincosamides

A
  • clindamycin
  • inhibitors of 50S
  • same mechanism as macrolides
  • used for anaerobic infections and streptococcal infections
  • kills normal anaerobic flora, too, and can lead to overgrowth of nasty organisms
  • implicated in C. diff
24
Q

streptogramins

A
  • also inhibit translocation in prokaryotic ribosome
  • individually they are bacteriostatic, but together = bactericidal
  • used to treat MRSA and vancomycin-resistant enterococci
  • past use in animals as led to selection of resistant organisms
25
Q

oxazolidinones

A
  • Zyvox
  • newer class of antibiotic that acts at the initiation step of protein synthesis
  • can interfere with binding of other 50S-active antibiotics
26
Q

inhibitrs of DNa replication

A
  • quinolones (nalidixic acid)
  • fluoroquinolones (ciprofloxacin, norfloxacin and others)
  • metronidazole
27
Q

inhibitors of RNA replication

A

rifampin

28
Q

quinolones and fluoroquinolones

A
  • bind to two enzymes, DNA gyrase and topoisomerase IV interrupting DNA supercoiling after replication and leading to breaks in DNA
  • bactericidal, but no effect on anaerobes (not a lot of effect in GI)
  • works intracellularly within phagocytes
  • resistance arises easily; their see in chickens hasn’t helped situation!
29
Q

metronidazole

A

works on anaerobes and parasites (both use pathways that use a small protein called flavodoxin; reduces nitro group)

30
Q

rifampin

A
  • inhibits RNA polymerase
  • effective as prophylactic treatment of gram neg meningitis
  • used to treat TB; especially isoniazid-resistant strains
31
Q

inhibitors of folic acid pathway

A

sulfonamides and trimethoprim

tri = used in combo with sulfonamide, sulfamethoxazole as ‘cotrimoxazole’ aka Bactrim
to treat UTIs
- concentrated right where u need them in urine for urinary tract infections

32
Q

5 main microbial targets and mechanisms of action

A
  • cell wall (peptidoglycan synthesis)
  • cell membrane integrity
  • protein synthesis
  • NA synthesis
  • competitors of metabolic pathways (eg, folic acid pathway)
33
Q

glycopeptides

A
  • vancomycin, teichoplanin
  • bind to D-Ala-D-Ala portion of the UDP-muramyl pentapeptide after it is transferred out of the cytoplasm of the bacterial cell
  • inhibits both final steps of peptidoglycan synthesis, glycosyltransferase (GT) and transpeptidation (TP)
  • critical use in MRSA (beneficial narrow spectrum)

** too big to go through OM; so for gram pos **

34
Q

Fosfomycin

A
  • inhibits conversion of UDP-NAG to UDP-NAM early in synthesis of peptidoglycan
  • used for treatment of uncomplicated UTI with E. coli and Enterococcus faecalis
35
Q

this catalyzes the polymerization step of cell wall biosynthesis and are highly conserved across all bacteria

A

peptidoglycan glycosyltransferase (GTs)

MLSCI 242 (39 decks)

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