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Medical and general microbiology > antibiotics > Flashcards

antibiotics Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

three modes of action of antibiotics

A

bacteriostatic, bactericidal, bacteriolytic

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2
Q

bacteriostatic

A

agents that stops bacteria from reproducing, while not necessarily killing them otherwise

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3
Q

bacteriocidal

A

bacteria killed directly

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4
Q

bacteriolytic

A

dissolution or destruction of bacteria

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5
Q

antibiotics which effect cell wall synthesis

A

cycloserine, vancomycin, bacitracin, penicillins, cephalosporins, monobactams, carbapenems

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6
Q

DNA gyrate ( decoils DNA)

A

Nalidixic acid, ciprofloxacom.. novobiocin

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7
Q

RNA eleongation

A

actinomycin

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8
Q

DNA directed RNA polymerase

A

Rifampin, Streptovaricins

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9
Q

Protein synthesis (50s inhibitor)

A

Erythromycin (macrocodes)
Chloramphenicol
Clindamycin
Lincomycin

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10
Q

Proteinsynthesis (30s)

A

tetracyclines, spectinomycin, streptomycin, gentamicin, kanamycin, amikacin, nitrofurans

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11
Q

protein synthesis (tRNA)

A

Mupirocin, puromycin

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12
Q

Lipid biosynthesis

A

platensimycin

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13
Q

Cytoplasmic membrane structure and function

A

Polymyxins, daptomycin

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14
Q

folic acid production

A

trimethoprim, sulfonamides

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15
Q

Macrolides

A

12-16 member macrolactone rings decorated with amino-sugars. Binding site is the large ribosomal subunit in the upper part of the nascent peptide exit tunnel

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16
Q

nascent peptide exit tunnel of macrolides

A

allows easy passage of the newly made protein through the tunnel- crucial for protein synthesis

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17
Q

How do macrocodes inhibit translation

A

binding of the macrolide in the tunnel impedes profession of the nascent peptide and results in a general inhibition of translation

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18
Q

target of fluorquinolones

A

target DNA gyrate (topoisomerase II and IV)

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19
Q

how to fluorquinolones enter bacteria

A

passive diffusion into gram +ve and via outer membrane prions in gram -ves

20
Q

newer fluoroquinonlines have a

A

broader spectrum and work best against gram +ve

21
Q

how common are fluoroquinolone

A

2nd most used

22
Q

how do fluoroquinolone work

A

topoisomerase IV carries out decatenation and relaxation of DNA, and assists the segregation of replicating chromosomes or plasmid in bacteria. Inhibition disrupts this process, contributing to bactericidal activity of fluoroquinolobnes.

23
Q

which bacteria have high levels of resistance to fluorquinolones

A

S pneumonia and staphylococcus aureus - have demonstrated that for ciprofloxacin-selected mutatantsm the first step involves a motion in parC- suggesting topoisomerase IV is the primary target in these bacteria.

24
Q

are fluorquinolones synthetic

A

yes

25
Q

name a broad spectrum, semi synthetic beta- lactic antibiotic

A

cephalosporins

26
Q

cephalosporins are derived from the

A

mould, cephalosporium

27
Q

cephalosporins are chemically related to

A

penicillins, same mechanism of action

28
Q

how do cephalosporins and penicillins cause cell damage

A

by interfering with bacterial cell wall synthesis

29
Q

new antibiotics are being discovered

A

semi- regularly, although not as frequently as in the past

30
Q

alternative phage stratagies

A

uses phage to deliver a protein that interferes with an essential bacterial process rendering the bacteria more susceptible to antibiotic- causing bacterial cell lysis- very specific, will only attach to the pathogen and not the animal cell

31
Q

anti-virulence strategies

A

inhibit specific mechanisms that promote infection and are essential to persistence in a pathogenic cascade and or cause of disease

32
Q

anti-virulence strategies offer

A

a reduced selection pressure for drug resistant mutations

33
Q

benefits of anti-virulence strategies

A

avoids undesirable dramatic alterations of the host microbiota that are associated with current antibiotics e.g. UPEC

34
Q

UPEC

A

chemical structures of anti-adhesive carbohydrate ligans- ligand for the FmH adhesion and (D) PapG adhesion.
e.g. if the bacteria cannot get into the cell it can not cause damage e.g. e.coli

35
Q

anti-virulence strategies- inhibiting secretly systems

A

both type 3 and 6 secretory systems inject proteins (15-30). Many bacteria inject proteins which manipulates the actin cytoskeleton-herby forcing uptake. Gram negative bacteria have complex protein translocation mechanisms

36
Q

it is thought that genes found in faecal extracts inhibit

A

salmonella rowth

37
Q

faecal extracts inhibit the growth of salmoenlla

A

62 genes were unregulated during growth in the faecal extract, whereas 76 genes were downgrade. Of the 76 genes repressed by faecal extracts, 29 (38.2%) are involved in salmonella host invasion- demonstrating major effect of the gut micro biome in repression f invasion

38
Q

problems with antibiotic usage

A

synergistic drugs suppress drug susceptible subpopulation more than single drug therapy, however this eliminates competitors of the drug resistant cells wo grow more rapidly than the non resistant cells would have done at weaker synergies- thus greater singer can increase population densities.

39
Q

example of what new antimicrobial drugs are developing to beat B-lactam resistance

A

INACTIVATION OF B-LACTAMASE INHIBITORS

40
Q

some phages develop

A

specific enzymes degrading exopolysaccharide structures (capsule, slime), masking or covering a targeted receptor.

41
Q

phages as antimicrobials: advantages

A

specific and cheap

42
Q

phages as antimicrobials: disadvantages

A

narrow spectrum/ bacterial resistance

43
Q

phage as antimicrobials

A

where pages attach to certain active sites on the outside of human cells e.g. mannose receptors–> if an inhibitor is added that has a higher affinity to the phage, then they won’t attach to the outside of the cell and inject their DNA- causing disease

44
Q

Stages of phage infection

A
  • adsorption to specific receprot- phage attachment is highly specific
  • DNA injection, after peptidoglycan degradation and pore formation in the bacterial cell
  • redirection of host metabolism to phage DNA replication and phage protein synths
  • assembly and packaging of phage particles
  • bacterial cell lysis and phage progeny release
  • virions burst into the environment
45
Q

phages can be used to fight

A

bacterial infection

Medical and general microbiology (36 decks)

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