Antibiotics and Resistance

Question 1

When the body’s normal defences cannot prevent or overcome a disease, it can be treated by

Answer 1

chemotherapy with antimicrobial drugs

Question 2

How do antimicrobial drugs act?

Answer 2

By killing or by interfering with the growth of the microorganisms

Question 3

What is the important principle of selective toxicity?

Answer 3

Antimicrobials must act within the host without damaging the host

Question 4

Who started modern chemotherapy and what was speculated about?

Answer 4

Paul Ehrlich - magic bullet

Question 5

Alexander Fleming observed inhibition of the growth of

Answer 5

Staphylococcus aureus by penicillin produced by penicillium notatum

Question 6

When did Alexander Fleming discover penicillin?

Answer 6

1928

Question 7

What is antibiosis?

Answer 7

The mechanism of inhibition of one microorganism by another

Question 8

What is an antibiotic?

Answer 8

A substance produced by microorganisms which inhibits another microorganism

Question 9

Antibiotics are rather easy to discover but few antibiotics are of

Answer 9

medical and/or commercial value

Question 10

Give an example of the commercial use of an antibiotic

Answer 10

As a supplement in animal feed rather than for treating diseases

Question 11

Which species produces the majority of our antibiotics and where is it found?

Answer 11

Streptomyces in the soil

Question 12

A few antibiotics are produced by endospore forming bacteria such as

Answer 12

Bacillus

Question 13

Some antibiotics are produced by ______, mostly the genera penicillium and ceplasporium

Answer 13

Molds/fungi

Question 14

Antibacterial drugs do not affect the eukaryotic cells of humans. why?

Answer 14

Cell types differ substantially
e.g. presence/absence of cell walls, struc of ribosomes
Selective toxicity has many targets

Question 15

Why are antimicrobials targeting protozoans or helminths difficult to use?

Answer 15

The drug that targets these pathogens usually damages the host too
They are more similar to the human cell on a cellular level

Question 16

Some drugs have a narrow spectrum of microbial activity. What does this mean?

Answer 16

They have a narrow range of different microbial types they effect

Question 17

Penicillin G has a narrow spectrum of microbial activity, how?

Answer 17

Affects gram-positive bacteria, but very few gram negative bacteria

Question 18

What are broad-spectrum antibiotics?

Answer 18

Antibiotics that affect a broad range of gram positive and gram negative bacteria

Question 19

For an antibiotic to affect a gram negative bacterium, what are two key requirements

Answer 19

Drugs that pass through the porin channels must be relatively small and preferably hydrophilic
Drugs that are lipophilic (affinity for lipids)o r especially large do not enter the Gram -ve bacteria readily

Question 20

What is an opportunistic pathogen?

Answer 20

An opportunistic infection is an infection caused by bacterial, viral, fungal, or protozoan pathogens that take advantage of a host with a weakened immune system or an altered microbiota (such as a disrupted gut flora). Many of these pathogens do not cause disease in a healthy host that has a normal immune system.

Question 21

Bacteria may become opportunistic pathogens. How?

Answer 21

The antibiotic destroys competitors of normal microbiota

Question 22

What is a superinfection?

Answer 22

The growth of a target pathogen.

Also the term applied to the growth of a target pathogen that has developed resistance to the antibiotic

Question 23

What does bactericidal mean?

Answer 23

Kills microbes directly

Question 24

What does bacteriostatic mean?

Answer 24

The prevention of microbes from growing

Question 25

Bacteriostatic often results in the death of the microbes, how?

Answer 25

The host’s own defences, such as phagocytosis and antibody production destroy the microorganism

Question 26

There are _ major modes of action of antimicrobial drugs

Answer 26

5

Question 27

What are the major modes of action of antimicrobial drugs?

Answer 27

1. Inhibition of cell wall synthesis
2. Inhibition of protein synthesis
3. Inhibition of nucleic acid replication and transcription
4. Injury to plasma membrane
5. Inhibition of synthesis of essential metabolites

Question 28

How does penicillin act as an antimicrobial?

Answer 28

Inhibits cell wall synthesis
Prevents synthesis of intact peptidoglycan layers
Cell wall weakened
Cell undergoes lysis

Question 29

Name three antibiotics which kill bacteria by inhibiting protein synthesis.

Answer 29

1. Chloramphenicol
2. Streptomycin
3. Tetracycline

Question 30

How does Chloramphenicol kill bacteria?

Answer 30

By the inhibition of protein synthesis

Binds to the 50S portion and inhibits formation of peptide bond

Question 31

How does streptomycin kill bacteria?

Answer 31

By the inhibition of protein synthesis

Changes the shape of 30S portion causing code on mRNA to be read incorrectly

Question 32

How does tetracycline kill bacteria?

Answer 32

By the inhibition of protein synthesis

Interfere with attachment of tRNA to mRNA-ribosome complex

Question 33

Certain antibiotics bring about changes in the permeability of the plasma membrane, what does this result in?

Answer 33

The loss of important metabolites from the cell.

Question 34

Name two antifungal drugs that combine with sterols in the fungal plasma membrane to disrupt the membrane

Answer 34

Miconazole and ketaconzazole

Question 35

How can the synthesis of essential metabolites be inhibited?

Answer 35

By competitive inhibition