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Medical Micro > lec 8-9 antibiotics > Flashcards

lec 8-9 antibiotics Flashcards

(62 cards)

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1
Q

bacteriostatic

A

stops bacteria from reproducing without killing them
inhibits protein synthesis
e.g. macrolides

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2
Q

bacteriocidal

A

kills bacteria

e.g. fluorouquinolones

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3
Q

bacteriolytic

A

destruction of bacteria by damaging their DNA or cell wall

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4
Q

broad spectrum antibiotics

A

act against a wide range of disease-causing bacteria including gram +ve and -ve

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5
Q

types of antibiotic

A

macrolides
fluoroquinolones
cephalosporins

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6
Q

macrolide structure

A

12-16 macrolactone rings with amino sugars attached

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7
Q

macrolide binding site

A

large 50S ribosomal subunit

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8
Q

macrolide functions

A

inhibit protein synthesis
if protein cannot exit via tunnel in ribosome, then translation is inhibited
leads to cellular growth and arrest

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9
Q

why are gram +ve bacteria difficult to target

A

thick peptidoglycan layer

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10
Q

fluoroquinolone structure

A

bicyclic core structure

bacteriocidal

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11
Q

fluoroquinolone function

A

targets DNA gyrase and Topoiosomerase IV
commonly used for urinary infections
causes irreversible damage

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12
Q

entry of fluoroquinolones into gram +/-ve bacteria

A

passive diffusion into gram +ve bacteria and via outer membrane porins in gram -ve

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13
Q

examples of fluoroquinolones

A

ciproflaxin

oxoflaxin

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14
Q

cephalosporins

A

broad spectrum
semi-synthetic beta-lactam antibiotic
derived from mould cephalosporium
chemically related to penicillins

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15
Q

function of cephalosporins

A

interfere with bacterial cell wall synthesis

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16
Q

clostridium difficile

A

pathogen that disrupts GI tract

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17
Q

dysbiosis

A

disruption of gut microbiota

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18
Q

bacteriophages as antimicrobials

A

use of phages (virus) to treat pathogenic bacterial infections

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19
Q

advantages of using bacteriophages as antimicrobials

A

specific

cheap

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20
Q

disadvantages of using bacteriophages as antimicrobials

A

narrow spectrum

bacterial resistance

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21
Q

stages of infection of bacteriophage into bacteria

A
  1. adsorption to specific receptor
  2. DNA injection
  3. peptidoglycan degradation - DNA transferred to cell
  4. redirection of host metabolism to phage DNA replication and phage protein sythesis
  5. assembly of phage particles
  6. bacterial cell lysis and phage progeny release
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22
Q

which bacteriophage late proteins are responsible for host cell lysis

A

lysins
holins
murein synthesis inhibitors

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23
Q

anti-virulence stratgies

A

inhibiti specific mechanisms
targeting toxins
inhibiting seccretion systems

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24
Q

UPEC mechanism

A

binds and invades cell
replicates inside cell and forms biofilm
biomass disperses and exits cell
spreads to new cells

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25
synergistic effect
when interaction causes an increase in the effects of one or both of the drugs
26
synergistic drugs
suppress drug-susceptible populations more the single-drug therapies
27
antimicrobial resistance
resistance of a microorganism to an antimicrobial drug that was originally effective for treatment of infections caused by it
28
2 methods to measure resistance
increase in minimum inhibitory concentration (MIC) minimal bacterial concentration (MBC)
29
minimum inhibitory concentration (MIC)
lowest concentration of antimicrobial that will inhibit visible growth of microorganism overnight
30
limitation of MIC
micro bacteria takes 4 weeks to grow, too slow to change overnight
31
minimum bactericidal concentration (MBC)
lowest concentration of an antimicrobial that will kill bacteria in vitro
32
how do we know how much antibiotic to administer
break points
33
break points
chosen concentration defining whether bacteria is susceptible or resistant to antibiotic
34
if minimum inhibitory concentration (MIC) is more than the susceptibility break point...
.. then bacteria is intermediate or resistant to antibiotic
35
if MIC is less than or equal to the susceptibility break point ...
..then bacteria is susceptible to the antibiotic
36
bacteriostatic agent
stops bacteria from reproducing reaches MIC levels in blood/tissues
37
bactericidal agent
kills bacteria reaches cidal levels in blood/tissues
38
broad spectrum agent
low MICs for many different bacteria types - very weak concentration of antimicrobial would kill many bacteria
39
narrow spectrum agent
low MICs for just a few bacterial types
40
susceptible (sensitive) microbe
inhibited by an agent at a low MIC
41
resistance microbe
only inhibited by agents at a high MIC (takes higher dose to kill them)
42
molecular mechanisms of resistance
1. degradation of drugs by enzymes 2. modification of drugs by enzymes 3. alteration of drug target site 4. drug efflux pumps
43
beta-lactamase mechanism
degradation break down beta lactam ring e.g. cephalosporins - interfere in cell wall synthesis - bactericidal
44
common antibiotic resistance
MRSA
45
methicillin
in MRSA | is a beta-lactam antibiotic so broken down by beta-lactamases
46
penicillin binding protein (PBP)
penicillin binding proteins join peptide bridges in peptidoglycan layer and facilitate cell wall synthesis inhibited by beta-lactam antibiotics
47
what prevents penicillin from binding to a protein
pencillin binding proteins bind to beta-lactam antibiotics, preventing cell wall synthesis therefore lactam ring is broken down
48
streptomycin
aminoglycoside protein synthesis inhibitor targets ribosome 30S subunit modifies drug by phosphorylation prevents drug from binding
49
modifying membrane permeability of transport systems...
prevents entrance of drug into a cell
50
drug efflux pumps
important for mediating resistance to many antibiotics protein secretion system rids of toxic products from inside cytoplasm to outside outer membrane
51
RND family transporters
used by drug efflux pumps | powered by electrochemical gradient
52
transposons
transposable elements can change their position within a genome can create or reverse mutations and alter a cell's genetic identity mediators of resistance
53
vertical gene transfer
- spontaneous mutant resistant strain - apply antibiotic and only individual resistant strain will survive and reproduce - all susceptible bacteria will die - you have to wait for selection pressure (antibiotic) to occur
54
horizontal gene transfer
- transfer of genetic material between mature cells - no increase in number of cells but increase in number of resistance cells - transformation, conjugation and transduction
55
spread of antibiotic resistance genes
horizontal and vertical gene transfer
56
transformation
manipulation of a bacteria enabling it to take up DNA protein secretion system (type 6) used to kill surrounding cells and uptake their DNA natural transformation mediated by competence proteins
57
conjugation
resistance gene moves with replicating plasmid into a new cell (no replication involved)
58
transduction
resistance gene hijacks and integrates host cell plasmid with bacteriophage DNA
59
R plasmids
important in resistance | have genes for conjugation fertility factor
60
conjugation plasmid
a plasmid that is transferred from one bacterial cell to another during conjugation.
61
conjugation fertility factor
allows genes to be transferred from a bacterium carrying the factor to a bacterium lacking the factor by conjugation
62
origin of transfer
short sequence of genes necessary for DNA transfer from bacterial hst to recipient during bacterial conjugation cis acting - oriT is found on same DNA that is transferred

Medical Micro (10 decks)

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