9/9/2023
Antibiotics
Drugs : chemicals taken by the body and modifies chemical reaction inside the body
Social drugs
Medicinal drugs
Antibiotics
Is a chemical substance produce by micro
organisms mainly fungi …kill/ stop the
growth of bacteria
How antibiotics work ?
5
Either damage the cell wall of bacteria …causing the bacteria to lyse so kill bacteria
Preventing formation of cell wall ….prevent growth / reproduction of bacteria
Why antibiotics kills only bacteria?
Mainly antibiotics they interfere with cell wall Formation .
Where human cells , nor viruses have cell walls
Loop of DNA
No nucleus
No mitochondria
No endoplasmic reticulum
B
-
I
Cell wall
Made from murein
Cytoplasm
Plasmid
Small DNA Contain genes that makes
the bacteria resistant to certain
antibiotics
Smaller ribosomes
Flagellum
Cell membrane
Why complete the course of antibiotic :
1.
To make sure all bacteria have been killed
Bacteria become resistant
Bacteria become immunised and have memory cells
2. Otherwise remaining bacteria might reproduce / replicate
3. And recurrence of illness / continue of illness
4. To prevent bacteria from undergoing mutation and developing resistant strain to antibiotics
5. So antibiotics become no longer effective
6. So we have to develop new types of antibiotics
Why we shouldn’t use antibiotics too much ?
How can we limit antibiotic resistant form of bacteria?
Use antibiotics less often / don’t use antibiotics unless prescribed
Don’t use when you have viral infection
Complete the course of antibiotic
Don’t use same type of antibiotic many times
Isolation patients with antibiotic resistant infection
Good hygiene reducing spread of disease
Suggest
Some times we take antibiotics as a
prophylactic measurement to
prevent / protect the body from
secondary infection by bacteria .
Natural selection
1.
there is variation
2. Variation is due to meiosis , fertilisation and mutation .
3. Fav. Characteristic
2. Selection
will survive
pressure
4. Less fav
Food
char. Will die
Definition of mutation ( change in base sequence of a
gene / DNA producing a new allele coding for a favorable
characteristic ) .
Causes of mutation ( exposure to a mutagen )
3. Selection pressure ( example, food, predation ,
antibiotics , poison )
4. Those who have favorable characteristic are able to
6. Grow and reproduce
And pass on the fav. Trait / allele to the
1. Variation Cause is MFM
coming generation
2. Selection pressure
3. Fav. Characteristic
( factor that cause choice
between 2 options)
Poison
Poison
survive
will survive
4. Less fav char.
Will die
5. The one with resistant allele
will pass it to coming generations
1. Variation
5. Those who have less favorable characteristic will die
Cause is MFM
6. So survival of the fittest , those who have favorable trait
will grow and reproduce
7. Passing in the mutant / gene to the coming generation
Thus increasing the allele frequency
8. By natural selection
Resulting in new species with the ability to …….fav
characteristic
Resistant
2. Selection
pressure
Antibiotic
sensitive
How population of antibiotic resistant bacteria ( MRSA) develop?
1.
Variation ( resistant and non resistant bacteria )
2. Where bacteria undergo mutation
Dont study
Only use the steps of natural selection
in previous page and apply
3. Which is a change in base sequence producing a new allele
4. Selection pressure is the antibiotic ( frequent use of antibiotic )
5. Those are resistant to antibiotic will survive
6. Those who are non resistant will die
7. Survival of the fittest , resistant , who will replicate and pass on the
mutant allele (resistant ) allele to the coming generations .
8. Increasing frequency of resistant allele in population .
9. By natural selection
10. Resulting in a whole new population of resistant bacteria .
Variation
Mutation + definition
New allele
Selection pressure
Favorable characteristic survive
Breed and pass on mutant allele to coming generations
Change allele frequency
Natural selection
Bacteria ……..resistant
Not human
Understanding
X ray
Antibiotic sensitivity test
become resistant to
antibiotic
*
restur
is
Petridish
/
I
e
Bein
So not killed by antibiotic
Mutation and
⑤
A
Agar ( nutrients ) for growth of bacteria
Antibiotic diffuse down its concentration gradient in agar
2
& Paper discs soaked with different types
of antibiotics ( A, B , C, D)
Result shows that antibiotic D is the most effective antibiotic in
killing bacteria / bacteria is highly sensitive to this antibiotic
Where the antibiotic killed most of the bacteria ..leaving largest
Why carry this test ?
zone of inhibition ( clear area ) .
While being resistant to antibiotic A
1. Person might be infected with bacteria that are resistant to antibiotics
2. To find the most effective antibiotic
3. That kills all bacteria …thus preventing antibiotic resistance
Biology 0610
3
Drugs
Page 8 in marking scheme
October/ November 2010
Syllabus-0610
Paper 31
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&
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lG
ab
r
&
Percentage of population
Different 20 countries
iha
Enyt
O
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375
I
19 5
Dr
.
Percentage of
antibiotic resistance
⑧
I
⑮
-
Discuss
Dr. Nihal Gabr
463
3%.
-
50 %
kw 3%
-
30%
Biology 0610
Drugs
⑪ Positive correlation’
① Where as the percentage population using antibiotics increase,
the percantage of resistant bacteria increase.
Duta Where when the percentage of taking antibiotics was 2%...the
5
bacterial resistance was 14
......%yet
upon increasing the
.
percentage of population using antibiotics to 3%,, the % of
5
bacterial resistant increses to⑬7
....%
lG
ab
r
.
D Variation in % of resistance between countries at each percentage of antibiotic usage
Data
① Some are used for specific diseases
④ Some have undesirable side effects
Some are expensive
4
Dr
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iha
⑧ Some bacteria are already resistance to such antibiotics
Page7 in marking scheme
March 2015
Syllabus-0610
Dr. Nihal Gabr
464
Paper 32
8
4
When bacteria are spread onto agar in a Petri dish they form colonies. Each colony forms
from one bacterium. Fig. 4.1 shows an investigation into antibiotic resistance in a species of
bacterium that causes disease.
colonies of bacteria
no antibiotic
added to agar
transfer of
bacteria
culture to
dish A
agar
A
S TA R T O F P R O C E S S
ab
r
culture of bacteria
in a liquid medium
antibiotic
added
to agar
B
DR
.N
transfer of bacteria
culture from dish B to
liquid medium
iha
lG
transfer of
bacteria
culture to
dish B
transfer of bacteria
culture to dish C
after 24 hours
transfer of bacteria
culture to dish D
antibiotic
added
to agar
antibiotic
added
to agar
C
D
Fig. 4.1
© UCLES 2010
bacteria exposed
to X-rays
0610/32/M/J/10
For
Examiner's
Use
9
(a) Explain what is meant by the term antibiotic.
For
Examiner's
Use
drug / medicine(AW) / chemical / substance ;
produced by microorganisms ;
A ref to idea of synthetic analogues
kills / stops, growth of, bacteria / other microbes ;
[2]
(b) Explain why
(i) only a few bacteria grew in dish B compared with dish A,
(ii) more bacteria grew in C than in B.
ab
r
(most) were killed by the antibiotic ; ora
[1]
(only) antibiotic-resistant bacteria transferred from B / (only)
iha
lG
resistant bacteria in C / fewer resistant bacteria in B / non-
[1]
resistant bacteria were killed in B ;
(c) Fig. 4.1 shows the effect of an antibiotic on a species of disease-causing bacterium.
Suggest why antibiotics should not be used too often.
pressure ;
.N
resistant bacteria, survive / not killed / are selected for / selection
eventually, all / many, become resistant ;
DR
[2] ;
AVP ; e.g. any consequence of overuse / antibiotic no longer effective
(d) Explain the possible effect of the X-rays on the bacteria.
X-rays caused mutations ;
change in DNA ;
ref to, gene / allele ;
mutation causes antibiotic resistance ;
[3]
© UCLES 2010
0610/32/M/J/10
[Turn over
Biology 0610
May/ June 2020
MRSA
Syllabus-0610
Paper 43
.N
iha
l
Ga
br
5
Dr
7
Drugs
Dr. Nihal Gabr
562 of 871
Biology 0610
Drugs
Variation where some bacteria are resistant and others are not .
Resistance is due to mutation producing new allele ( resistant
allele )
Those with no resistance will be killed
Ga
reproduce
br
Survival of fittest , those with resistant allele will survive and
Passing on the mutant allele of resistance
By natural selection
Where the mutant resistant allele is transferred to another strain
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l
of bacteria through plasmid
Dr
Increase frequency all resistant allele in population .
Direct
Dr. Nihal Gabr
563 of 871
Biology 0610
Drugs
Oct/November 2021
8
Syllabus-0610
Paper 42
Dr
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iha
l
Ga
br
1
Dr. Nihal Gabr
564 of 871
Drugs
Ga
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Biology 0610
Fungal extract contains both amylase and pectinase
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iha
l
The presence of clear zone around D in both petri dishes indicates that
the substrate has been broken down .
Extract has a higher concentration than 1 % amylase
Clear zone around D in starch agar jelly is larger than that around A
Clear zone around D in pectin agar jelly is smaller than that around B
Dr
g
Extract has lower concentration than 1 % pectinase .
Extract contained enzymes , diffuse through agar to break down substrate…
where the higher the concentration of the enzyme in extract , the greater the clear
zone
Smaller clear zone
Dr. Nihal Gabr
565 of 871
Biology 0610
Antibiotic sensitivity test
March 2022
Syllabus-0610
Paper 42
Bacteria is sensitive to
.N
iha
l
antibiotic E …killed
Ga
br
4
Bacteria is
resistant to
antibiotic
A ..survived
replicated
Dr
9
Drugs
Dr. Nihal Gabr
566 of 871
Biology 0610
Drugs
It shows the biggest zone of inhibition indicating death /
Direct
1.
Ga
br
stop of growth of most bacteria.
Variation ( resistant and non resistant )
.N
iha
l
2. Due to mutation which is change in base sequence
3. Producing new allele which cause the bacteria to become
resistant
4. the frequent use of antibiotic act as a selection pressure
5. Those who are resistant will survive
Dr
6. And pass on the mutant allele to coming generations
7. Increasing frequency of resistant allele in population
8. By natural selection
Complete the course of antibiotic
Dr. Nihal Gabr
567 of 871