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Flashcards in Antibiotics and Resistance Deck (35):
1

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

chemotherapy with antimicrobial drugs

2

How do antimicrobial drugs act?

By killing or by interfering with the growth of the microorganisms

3

What is the important principle of selective toxicity?

Antimicrobials must act within the host without damaging the host

4

Who started modern chemotherapy and what was speculated about?

Paul Ehrlich - magic bullet

5

Alexander Fleming observed inhibition of the growth of

Staphylococcus aureus by penicillin produced by penicillium notatum

6

When did Alexander Fleming discover penicillin?

1928

7

What is antibiosis?

The mechanism of inhibition of one microorganism by another

8

What is an antibiotic?

A substance produced by microorganisms which inhibits another microorganism

9

Antibiotics are rather easy to discover but few antibiotics are of

medical and/or commercial value

10

Give an example of the commercial use of an antibiotic

As a supplement in animal feed rather than for treating diseases

11

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

Streptomyces in the soil

12

A few antibiotics are produced by endospore forming bacteria such as

Bacillus

13

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

Molds/fungi

14

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

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

15

Why are antimicrobials targeting protozoans or helminths difficult to use?

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

16

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

They have a narrow range of different microbial types they effect

17

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

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

18

What are broad-spectrum antibiotics?

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

19

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

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

20

What is an opportunistic pathogen?

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.

21

Bacteria may become opportunistic pathogens. How?

The antibiotic destroys competitors of normal microbiota

22

What is a superinfection?

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

23

What does bactericidal mean?

Kills microbes directly

24

What does bacteriostatic mean?

The prevention of microbes from growing

25

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

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

26

There are _ major modes of action of antimicrobial drugs

5

27

What are the major modes of action of antimicrobial drugs?

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

28

How does penicillin act as an antimicrobial?

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

29

Name three antibiotics which kill bacteria by inhibiting protein synthesis.

1. Chloramphenicol
2. Streptomycin
3. Tetracycline

30

How does Chloramphenicol kill bacteria?

By the inhibition of protein synthesis
Binds to the 50S portion and inhibits formation of peptide bond

31

How does streptomycin kill bacteria?

By the inhibition of protein synthesis
Changes the shape of 30S portion causing code on mRNA to be read incorrectly

32

How does tetracycline kill bacteria?

By the inhibition of protein synthesis
Interfere with attachment of tRNA to mRNA-ribosome complex

33

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

The loss of important metabolites from the cell.

34

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

Miconazole and ketaconzazole

35

How can the synthesis of essential metabolites be inhibited?

By competitive inhibition