lec 7 - persisters

Question 1

most common chronic infection

Answer 1

tb

Question 2

persister cells

Answer 2

dormant variants of bacterial cells
antibiotic resistant
responsible for chronic disease

Question 3

add antibiotics at stationary phase

Answer 3

more persistent phenotypes seen emerging

Question 4

altruistic behaviour

Answer 4

beneficial to recipient

cooperative behaviour

Question 5

western blot

Answer 5

analytical technique used to monitor protein expression and detect specific proteins
uses probe and antibodies against the proteins
electrophoresis often used

Question 6

stochastic fluctuation

Answer 6

formation of persister cells is a random process

Question 7

what controls expression of persister genes

Answer 7

external evironment

Question 8

identifying persisters

Answer 8

kill off susceptible population
isolate persister cells
dye cells 
red cell debris shows dead cells
add antibiotics
remove antibiotics - growth of persister cells seen

Question 9

what part of the cells will show dye

Answer 9

intact cellular membranes

Question 10

fluorescent activated cell sorting - FACS

Answer 10

separates cells on size and colour

smaller and less coloured cells are persister population - not expressing RNA

Question 11

ribosomal RNA promoter

Answer 11

GFP downstream of promoter for ribosomal gene

healthy cells express this to make proteins

Question 12

effect of up-regulation of toxin/antitoxin molecules

Answer 12

cell in growth arrest

Question 13

toxin-antitoxin (TA) systems

Answer 13

2 linked genes combine
1 encodes a protein ‘poison’
1 encodes a corresponding ‘antidote’

constant non-activity of toxin, unless antitoxin is degraded

Question 14

over expression of toxin

Answer 14

generation of more persister cells

Question 15

quorum sensing

Answer 15

regulation of gene expression in response to fluctuations in cell-population density

essential for generating persister cells

Question 16

persister cells are not genetically resistant

Answer 16

they are a sub-population of antibiotic-tolerant bacteria

Question 17

growth of persister cells

Answer 17

slow growing or in growth arrest
have decreased metabolic activity
able to resume after lethal stress

Question 18

why are persisters a public health concern

Answer 18

antibiotic resistance

treatment failure

Question 19

asymptomatic persistent infections

Answer 19

can be caused by latent growth-arrested bacteria

are associated with relapses of acute symptomatic infections

Question 20

symptomatic persistent infections

Answer 20

characterised by long period of clinical manifestations

Question 21

repetitive use of antibiotics

Answer 21

-ve effects on health
deplete resident microbiota
increase antibiotic-resistant strains

Question 22

why do infections persist

Answer 22

ineffective clearance by host

inability of immune system to detect a pathogen

Question 23

formation of biofilms

Answer 23

can block complement-mediated and cell-mediated killing in many persistent infections

Question 24

cefotaxime

Answer 24

causes many antibiotic-susceptible bacteria to die rapidly
results in large initial decrease in colony forming units (CFUs)
persister cells remain viable

Question 25

if cells have an intermediate growth rate…

Answer 25

bacteria may be able to grow without being killed by the antibiotic

Question 26

effect of mutations

Answer 26

can increase the lag time of bacteria or probability of persisters
therefore antibiotic resistance

Question 27

factors enhancing persister cell formation

Answer 27

nutrient limitation
extreme pH
DNA damage
bacteria-rich environments e.g. biofilms/macrophages

Question 28

bistability

Answer 28

explains how growing and growth arrested cells can live in the same clonal population

Question 29

pore-forming toxins

Answer 29

can reduce proton motive force and decrease the rate of ATP synthesis within a cell

Question 30

how do persister cells become tolerant to antibiotics?

Answer 30

through target inactivity due to a decrease in growth and metabolism or reduced drug uptake

Question 31

persister cell regrowth

Answer 31

either all together

or spontaneously as soon as external stress is removed

Question 32

conditional cooperativity

Answer 32

autoregulation of some toxin-antitoxin molecules where they can only form complexes at some ratios