Lecture 10 - Antibiotics

Question 1

What are the methods for controlling bacterial growth?

Answer 1

1. Sterilisation and disinfection
2. Antibiotics
3. Antibiotics resistance

Question 2

What is Sterilisation?

Answer 2

1. Absence of any pathogens
2. Absence of any microorganisms
3. Reduction of microorganism numbers to safe levels
4. The absence of any microorganisms including spores

Question 3

What are methods of sterilisation?

Answer 3

1. Moist heat
2. Filtration
3. Ionisation Radiation
4. Chemicals such as alcohols or chlorine compounds, Flaming

Question 4

How do you use Moist heat?

Answer 4

1. 121*C for 15min in autoclave chamber.

2. Air replaced by steam

Question 5

What is ionisation radiation

Answer 5

Disrupts microbial DNA and prevents reproduction

1. Beta radiation (high speed electrons)
2. Gamma radiations (high energy photons)
3. Instruments such as scalpels and syringees

Question 6

What is filtration?

Answer 6

1. Electrostatic filters can be used to sterilise liquids such as vitamins, preparations, that can be damaged by heat
2. Filters are made of nitrocellulose nets with pore sizes small enough to filter out viruses

Question 7

What is disinfection and examples?

Answer 7

1. The reduction of numbers of microorganisms so that pathogens are not present
2. Example: Boiling Water kills most vegetative bacteria
3. Method does not kill bacterial spores

Question 8

How do disinfectants work?

Answer 8

1. Damage the microbial cell such as the membrane lipids, DNA and proteins
2. Antispetics are disinfectants that can be applied to skin and wounds, do not kill spores

Question 9

What was the first Antibiotic?

Answer 9

Penicillin

Question 10

What is an antibioitic?

Answer 10

1. A chemical that controls the growth of microorganisms
2. Kills bacteria only
3. Anti-Microbial
4. Bactericidal
5. Bacteriostatic

Question 11

What’s the difference between Batericidal and Bacteristatic?

Answer 11

1. Bactericidal Kills

2. Bacteristatic: Prevents growth

Question 12

Antibiotics are specific, what targets are unique to bacteria?

Answer 12

1. Cell wall
2. Cell membrane
3. Protein synthesis
4. Nucleic Acid Synthesis

Question 13

How does Antibiotics target the cell wall? For example with Penicillin?

Answer 13

1. Inhibits enzymes that build up cross-linkages between the molecules that make up the bacterial cell wall
2. Penicillin binding proteins

Question 14

How does Antibiotics disrupt the cell membrane?

Answer 14

1. Polymyxin B binds to phospholipids in the cell membrane of Gram negative bacteria, intervenes with it’s function as selective barrier

Question 15

How does Antibiotics affect Nucleic Acid?

Answer 15

1. Rifampin
2. Interfere RNA synthesis by bacteria to a subunit of RNA polymerase
3. Bacteriocidal or bacteriostatic depending on concentration

Question 16

How does antibiotics affect Protein Synthesis

Answer 16

1. [Molecules] bind to bacterial ribosomes inhibiting protein syntehesis
2. Produced by Gram +ve bacteria
3. Streptomycin was the first effective treatment for TB
4. Most needed medicine on WHO list

Question 17

What is the Mechanisms of Resistance?

Answer 17

1. Alteration of target site, producing a molecule which functions normalyl but does not bind the drug
   e. g. Ribosomes, RNA polymerase
2. Production of enzymes that break down the antibiotic
   e. g. B lactamases interactive cephalosporins
3. Restricted Transport of antibiotic intro cell
   e. g. Glycopeptides
4. Mechanism of removing antibiotic from cell by efflux pumps
5. Protection of Target Site by Bacterial protein

Question 18

How does bacterial resistance happen?

Answer 18

1. Mutation followed by natural selection
2. Some strains of bacteria secrete the enzyme penicillinase (breaks down penicilin)
3. Use of Penicillin will kill off all non-resistant bacteria, leaving only resistant strains.