Antibiotics

Question 1

What does bactericidal refer to?

Answer 1

• bactericidal describes a type of method in which antibiotics work in
• bactericidal antibiotics destroy bacteria

Question 2

What does bacteriostatic refer to?

Answer 2

• bacteriostatic describes a type of method in which antibiotics work in
• bacteriostatic antibiotics prevent the multiplication of bacteria. The host’s own immune system can then destroy the pathogens
• (prevents bacteria from growing)

Question 3

What are the two types of antibiotics?

Answer 3

• antibiotics are classified into two types depending on their method of action:
• bactericidal
• bacteriostatic

Question 4

What are antibiotics?

Answer 4

antibiotics are chemical substances that inhibit or kill bacterial cells with little or no harm to human tissue
- they are drugs used to treat infections caused by bacteria and other microorganisms

Question 5

What does conjugation refer to?

Answer 5

• conjugation is a mechanism for the horizontal transfer of gene between bacterial cells

Question 6

What does gram negative indicate?

Answer 6

• gram negative bacteria have a high resistance to antibiotics
• gram negative bacteria have an outer membrane
• they have a thinner peptidoglycan cell wall

Question 7

What are Gram-positive bacteria?

Answer 7

• gram positive bacteria are a type of bacteria that have a thick cell wall
• this helps protect the bacteria from antibiotics and other substances that might damage them

Question 8

What is the difference between gram negative and gram positive bacteria? What colour do they go?

Answer 8

• gram positive bacteria show blue or purple after gram-staining in a laboratory test, they have thick cell walls
• gram negative bacteria show pink or red on staining and have thin walls
• they release different toxins

Question 9

How can bacteria evolve to become resistant to antibiotics?

Answer 9

• mutations arise in bacteria, some of the mutations may make them resistant to antibiotics (new antibiotic resistance alleles)
• antibiotics create a strong selection pressure. Bacteria that are susceptible to the antibiotic die, while those that are resistant survive

Question 10

Why are bacterial populations capable of evolving very quickly

Answer 10

• very fast reproduction (asexual which is faster than sexual)
• huge population size e.g. in the billions, so vast numbers of cells may have mutations
• some random mutations will be advantageous making some bacteria more likely to survive to reproduce and spread

Question 11

What can patients do when taking antibiotics to reduce the risk of bacteria becoming resistant?

Question 12

How can hospitals reduce the risk of MRSA

Question 13

Core practical questions

Question 14

How does penicillin work? Is it bactericidal or bacteriostatic?

Question 15

How does erythromycin work? Is it bactericidal or bacteriostatic?

Question 16

How does vancomycin work? Is it bactericidal or bacteriostatic?

Question 17

How does Neomycin work? Is it bactericidal or bacteriostatic?

Question 18

How do antibiotics provide another selection pressure

Question 19

What are the names of the different stages involved in evolution by natural selection?

Answer 19

Evolution by natural selection, antibiotic resistance:
- mutation leading to variation
- selection pressure and differential survival
- reproduction
- inheritance
- repeated over multiple generations

Question 20

What happens in the first stage of evolution by natural selection in antibiotic resistance? Mutation leading to variation

Answer 20

• mutations arise in the bacteria, some of the mutations may make them resistant to antibiotics (new antibiotic resistance alleles)

Question 21

What happens in the second stage
selection pressure and differential survival

Answer 21

• antibiotics create a strong selection pressure
• bacteria that are susceptible to the antibiotic die, while those that are resistant survive

Question 22

what happens in the third stage
reproduction

Answer 22

• the bacteria that survive reproduce
• all their competitors have been killed by the antibiotic meaning they have access to more resources in the environment favouring fast growth rates

Question 23

what happens in the fourth stage
inheritance

Answer 23

• the surviving bacteria have the antibiotic resistance allele meaning that all bacteria in the next generation will also have the allele (asexual reproduction - all new bacterial cells produced are clones)

Question 24

what happens in the fifth stage
repeated over multiple generations

Answer 24

• the frequency of the resistance allele increases