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Micro 121 > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

Abx Bactericidal

A

kills susceptible bacteria without host defenses
if immumocompromised you want these
the vast majority of ABx
use these if not too severe ONLY

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2
Q

ABX Bacteriostatic

A

inhibit bacterial growth
destruction of organism dependent on host defenses (still rely on host defenses)
inhibiting their role

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3
Q

abx work best on

A

actively dividing and growing bacteria.

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4
Q

BETA lactam abx mechanism

A

binds to transpeptidase enz complexand block the crosslinking of peptidoglycan.

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5
Q

beta lactam acts on what

and 2 of them

A

act on cell wall
pennicilin S
cephalosporins

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6
Q

vancomycin acts on

A

cell wall

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7
Q

vancomycin mechanism

A

stops the extension of peptidoglycan chain (NAM and NAG

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8
Q

vancomycin affects Gram __ bacteria only

A

+

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9
Q

vancomycin is a

A

glycopeptide

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10
Q

vancomycin administered via

A

IV

for more serious G+ infections.

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11
Q

inhibitors of protein synthesis

A 
bind to either 30S or 50S subunit of ribosome
inhibit:
activation
chain initiation
chain elongation
chain termination
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12
Q

nucleic acid inhibitors

A

prevent supercoiling of DNA (DNA Gyrase)

excellent drugs with broad spectrum

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13
Q

metabolic inhibitors

A

combo of trimethoprim/sulfonamides => bactrim

strong drug for UTI

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14
Q

sulfonamides

A

structural analog of PABA and competitively inhibits synthesis of dihydrofolic acid (precursor of tetrahydrofolic acid)

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15
Q

trimethoprim

A

Structural analog of dihydrofolic acid and competitive inhibitor of dihydrofolate reductase (final enz in pathway to tetrahydrofolic acid)

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16
Q

Spread of resistance (3)

A
  1. plasmid
  2. conjugation
  3. transformation
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17
Q

plasmid

A

circular dsDNA that can exist and replicate independent of chromosome
may integrate with host chromosome

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18
Q

conjugation

A

gene transfer and recombination in bacteria that requires direct cell-cell contact
Sex bridge - DNA can spread

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19
Q

Transformation

A

naked DNA taken up by a bacterial cell and incorporated into the recipient genome
must be a competent cell to take tup the DNA
usually in the gut - lots of bacteria

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20
Q

Maintaining resistance

A

Selective pressure

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21
Q

selective pressure

A

ensures the resistance gene is maintained

keep giving abx - keep having to continue producing PBP that is different and resistive

22
Q

selective pressure occurs from

A

common abx usage - ex kids ear infections
not completely finshing a prescription
using a leftover prescription
abx in animal feed

23
Q

Mechanisms of resistance

A

enzymes that inactivate the drug
target site alteration
ribosome alteration
efflux pumps

24
Q

enzymes that inactivate the drug

A

beta lactamase
aminoglycoside
ESBL - only been around for 3-5 Years

25
Q

beta lactamase

A

plasmid spread (rapid emergence)

26
Q

danger organism with ESBL

A

E. Coli

resistant to all beta lactam abx.

27
Q

target site alteration

A

pennicilin binding proteins

beta lactam abx can no longer bind

28
Q

2 examples with altered PBPs

A

MRSA

S. pneumoniae.

29
Q

gram negative cell extra aces

A

PBP changed
porin proteins
enzymes
once inside cell may not be able to bind.

30
Q

Metabolism mechanism of resistance

A

organism alters the metabolic pathway and overcomes the blocked pathway.

31
Q

Evolution of S. Aureus resistance

A

S. Aureus

  • pennicilin resistent aureus (1950)
  • methicilin (1980)
  • MRSA
  • Vancomycin (1997)
  • VRE (1990s)
  • VRSA (2002)
32
Q

MRSA

A

20% of Staph infections in canada

33
Q

MRSA tx

A

vancomycin

34
Q

vancomycin

A

hospital IV use

expensive

35
Q

Community acquired MRSA

A

found in common animals - not infected

but giving it back to humans once healed.

36
Q

control of CA MRSA

A

detergent

hot dryer

37
Q

Hospital screening programs MRSA

A

Nasal swab +/- perineum - 24 hours

Isolation room, contact precautions

38
Q

enterococci

A

relatively harmless bacteria found in the bowel (normal flora), skin, vagina, environment
occasionally causes infection.

39
Q

history of VRE

A

avoparcin (similar abx) used in animal feed - colonized animals - colonized humans
exponential growth in VRE colonization incidence (but not infection incidence)

40
Q

Screening for VRE

A

rectal swab

do not do it routinely anymore because so common

41
Q

VRE patients - we do this

A

contact precautions

42
Q

CDAD

A

clostridium difficile associated diarrhea

43
Q

background of c diff

A

abx associated diarrhea (AAD)

recognized as a pathogen in 70s

44
Q

epidemiology of c diff - how does it survive

A

spores - last months despite drying and disinfectants.

45
Q

Clinical disease options

A

asymptomatic
moderate diarrhea
lifethreatening colitis

46
Q

Life threatening c diff (2)

A

pseudomembranous colitis
toxic megacolon - emergency needs surgery
can lead to death ( 30% ).

47
Q

treatment of c diff

A

abx:
metronidazole
vancomycin - adds to selective P

48
Q

Fecal bacteriotherapy

A

stool sample liquified, filtered and given to patient - reestablishing normal gut flora to repopulate

49
Q

fecal bacteriotherapy route options

A
  1. enema
  2. gastric tube
  3. Colonoscope - most effective
50
Q

Fecal bacteriotherapy success

A

94% cure rate

normal bowel restoration in 24 hours.

Micro 121 (3 decks)

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