Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Microbes, Immune Systems and their Interaction > Practical 1. Microbial Offence and Defense > Flashcards

Practical 1. Microbial Offence and Defense Flashcards

1
Q

What are bioassays used for ?

A

Used to estimate the concentration of antibiotics in a solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why do we need to be able to estimate the concentration of antibiotics in a solution ?

A
  1. During the manufacture of antibiotics

2. In a hospital setting, to measure the concentration of the antibiotic in a patients bloodstream

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Where does a zone of growth of inhibition occur ?

A

Around the well

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

When does the edge of the zone of growth of inhibition form ?

A

When the antibiotic is too dilute to inhibit growth of the bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does a more concentrated antibiotic in the well result in ?

A

A wider zone of growth of inhibition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What can the standard curve be used for ?

A

To determine the antibiotic concentration in an unknown sample

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What can antibiotics be synthesised by ?

A
  1. Fungi

2. Bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What did the discovery of antibiotics for chemotherapy result in ?

A

The emergence of resistant organisms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How would you determine the sensitivity of an organism to antibiotics ?

A

A disc diffusion method

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What must standardised methods for antibiotic disc diffusion consider the effects of ?

A
  1. Culture medium
  2. Inoculum density
  3. Antibiotic discs
  4. Incubation conditions
  5. Interpretation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does susceptible mean ?

A

Implies that an infection caused by the strain may be treated with the antibiotic at the dosage recommended for the type of infection and the infecting species of bacterium, unless otherwise contra-indicated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is meant by resistant ?

A

Encompasses strains incompletely inhibited within the usual therapeutic range

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is meant by the term intermediate ?

A

Strains exhibiting an in between diameter of zone of growth inhibition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How might resistance to antibiotics be acquired ?

A
  1. Chromosomal mutations

2. Transfer of plasmid determined resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What effect might a chromosomal mutation have on an antibiotic and give the example ?

A

Effect the functionality for example through alteration of the antibiotics target so that it is no longer susceptible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is still retained in a chromosomal mutation ?

A

The functionality of the target molecule is retained

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is Rifampicin ?

A

An antibiotic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How does Rifampicin work ?

A

Binds to the enzyme RNA polymerase and blocks the ability of the bacterium to transcribe DNA into mRNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

How do mutations in chromosomal genes and Rifampicin work ?

A

Mutations in the chromosomal genes coding for RNA polymerase result in an altered enzyme to which rifampicin no longer binds, while maintaining functioning of the enzyme

20
Q

Do chromosomal mutations occur frequently in bacteria populations ?

A

They occur spontaneously and at low frequencies

21
Q

How can rifampicin resistant mutants be distinguished from rifampicin sensitive cells ?

A

By plating on agar containing rifampicin

22
Q

Does plating on rifampicin containing media induce rifampicin resistant mutants ?

A

No, they are already present in the population

23
Q

How can the frequency of rifampicin resistant mutants be calculated ?

A

Number of rifampicin resistant mutant colonies per ml/ starting culture viability count

24
Q

What is another name for disc diffusion method ?

A

Kirby- Bauer Method

25
Q

What are the zones of growth inhibition for the test organism compared with in disc diffusion ?

A

Standard sensitive strain

26
Q

Why cant zones of growth inhibition obtained with different antibiotics be directly compared ?

A

Different antimicrobial agents diffuse at different rates

27
Q

What do the organisation such as EUCAST or CLSI do ?

A

The establish breakpoints to classify a microorganism as resistant or susceptible

28
Q

What is the purpose of testing an internal control or reference strain ?

A

This is to make sure that the technique is correct and the antibiotic disc load also since the profile of this strain is known

29
Q

What is E. coli strain R- ?

A

A sensitive strain, lacking a resistance plasmid

30
Q

What is E. coli strain R+ ?

A

A resistant strain, containing a resistance plasmid

31
Q

What is conjugation ?

A

The transfer of genetic material between bacterial cells by direct cell to cell contact

32
Q

What does the R plasmid carry ?

A

The gene for chloramphenicol resistance

33
Q

What does the gene for chloramphenicol resistance confer ?

A

Resistance to the antibiotic on bacteria harboring this mobile genetic element

34
Q

What is the host bacterium sensitive to ?

A

Nalidixic acid

35
Q

What does the recipient strain carry ?

A

A chromosomal mutation conferring nalidixic acid resistance

36
Q

What is plasma encoded chloramphenicol acetyltransferase responsible for ?

A

Chloramphenicol resistance in R factor bearing E. coli

37
Q

How does chloramphenicol acetyltransferase inactivate the antibiotic ?

A

It catalyses the 3-O-acetylation of chloramphenicol in the presence of acetyl coenzyme A

38
Q

What is nalidixic acid ?

A

A 4-quinolone antibacterial drug

39
Q

How does bacterial DNA exist ?

A

A supercoiled form

40
Q

What is the enzyme DNA glyrase responsible for

A

It is a topoisomerase that is responsible for introducing negative supercoils into the structure

41
Q

How does the nalidixic acid act ?

A

By inhibiting the activity of the bacterial gyrase, preventing the normal functioning of DNA

42
Q

What are quinolones ?

A

Broad spectrum agents that rapidly kill and are well absorbed after oral administration

43
Q

What is the minimum inhibitory concentration (MIC) ?

A

The lowest concentration of a substance that inhibits growth of an organism

44
Q

What is the agar dilution method convenient for ?

A

Simultaneously testing several strains or for testing different doses of bacteria

45
Q

In the clinical microbiology what dilutions are normally used ?

A

2 fold

46
Q

What is the end point of the titration affected by ?

A

The inoculum size

Microbes, Immune Systems and their Interaction (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions