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Pom 2 > .anti microbial therapies > Flashcards

.anti microbial therapies Flashcards

1
Q

What type of antibiotic is Prontosil

A

Sulphonamide

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2
Q

Was prontosil bactericidal or bacteriostatic?

A

Bacteriostatic

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3
Q

Was prontosil synthetic or natural?

A

Synthetic

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4
Q

What conditions can prontosil be used to treat?

A

UTIs, prophylaxis for HIV+, RTIs

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5
Q

Why is Prontosil becoming more common and what despite?

A

Due to resistance to other antimicrobials, despite some host toxicity

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6
Q

What condition was Prontosil used to treat to do with childbirth and what bacteria caused this?

A

Childbed fever (puerperal sepsis), cause by S. pyogenes

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7
Q

What type of bacteria was Prontosil affective against?

A

Gram positive

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8
Q

How do beta lactam antibiotics work?

A

Interfere with the synthesis of the peptidoglycan component of the bacterial cell wall, by binding to penicillin-binding proteins.
PBPs catalyse a number of steps in the synthesis of peptidoglycan.

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9
Q

What are examples of beta lactam antibiotics?

A

Penicillin and methicillin.

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10
Q

What is an antibiotic?

A

An antibiotic is an antimicrobial agent produced by a microorganism that kills or inhibits other microorganisms.

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11
Q

What are most antibiotics in use today are produced by?

A

Most antibiotics in use today are produced by soil-dwelling fungi (Penicillium and Cephalosporium) or bacteria (Streptomyces and Bacillus).

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12
Q

What is an antimicrobial?

A

A chemical that selectively kills or inhibits microbes

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13
Q

What is an antiseptic?

A

chemical that kills or inhibits microbes that is usually used topically to prevent infection

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14
Q

What are the 2 types of effects antibiotics create?

A

Bactericidal and bacteriostatic

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15
Q

define Minimal inhibitory concentration (MIC)

A

the lowest concentration of AB required to inhibit growth

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16
Q

What is the breakpoint?

A

Highest clinically-achievable concentration

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17
Q

What happens if an antibiotic concentration is required that is higher than the breakpoint?

A

The bacteria is resistant to that antibiotic

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18
Q

How does proportion of resistant bacteria increase in a population?

A

Antibiotics act as a selection pressure, so resistant bacteria outcompete non resistant

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19
Q

Name 3 misconceptions when antibiotics were first discovered?

A

Resistance against more than one class of antibiotics at the same time would not occur.
Horizontal gene transfer would not occur.
Resistant organisms would be significantly less ‘fit’ (sometimes true, sometimes not).

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20
Q

Why does antibiotic resistance lead to increased mortality, morbidity and cost?

A

Increased time to effective therapy.
Requirement for additional approaches – e.g. surgery.
Use of expensive therapy (newer drugs).
Use of more toxic drugs e.g. vancomycin.
Use of less effective ‘second choice’ antibiotics.

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21
Q

Are aminoglycosides bactericidal or bacteriostatic?

A

Bactericidal

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22
Q

How do aminoglycosides work\?

A

Target protein synthesis (30S ribosomal subunit), RNA proofreading and cause damage to cell membrane.

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23
Q

Name 2 aminoglycosides

A

Gentamicin, streptomycin.

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24
Q

Why is there limited use of aminoglycosides, and why is use increasing?

A

Toxicity has limited use, but resistance to other antibiotics has led to increasing use.

25
Q

Is Rifampicin bactericidal or bacteriostatic?

A

Bactericidal

26
Q

How does Rifampicin work?

A

Targets RpoB subunit of RNA polymerase.

27
Q

What type of resistance to Rifampicin is frequent?

A

Spontaneous resistance is frequent.

28
Q

What about Rifampicin affects compliance?

A

Makes secretions go orange/red

29
Q

Is Vancomycin bactericidal or bacteriostatic?

A

bactericidal

30
Q

How does Vancomycin work?

A

Targets Lipid II component of cell wall biosynthesis, as well as wall crosslinking via D-ala residues

31
Q

Why is there limited use of Vancomycin , and why is use increasing?

A

Toxicity has limited use, but resistance to other antibiotics has led to increasing use e.g. against MRSA

32
Q

Is Linezolid bactericidal or bacteriostatic?

A

Bacteriostatic

33
Q

How does Linezolid work?

A

Inhibits the initiation of protein synthesis by binding to the 50S rRNA subunit.

34
Q

What type of bacteria does Linezolid work on?

A

Gram positive

35
Q

Is Daptomycin bactericidal or bacteriostatic?

A

bactericidal

36
Q

How does Daptomycin work?

A

Targets bacterial cell membrane.

37
Q

What type of bacteria does Daptomycin work on?

A

Gram positive

38
Q

Why is dosage of Daptomycin limited?

A

Toxicity limits dose

39
Q

What type of toxicity to antibiotics have?

A

Selective toxicity

40
Q

Antibiotic resistance occurs via 4 distinct mechanisms. What are they?

A

Altered target site.
Inactivation of antibiotic.
Altered metabolism.
Decreased drug accumulation

41
Q

How does an altered target site arise?

A

Can arise via acquisition of alternative gene or a gene that encodes a target-modifying enzyme.

42
Q

How does MRSA achieve resistance through altered target site?

A

Methicillin-resistant Staphylococcus aureus (MRSA) encodes an alternative PBP (PBP2a) with low affinity for beta-lactams.

43
Q

How does Streptococcus pneumoniae become resistant to erythromycin through alteration of target site?

A

acquisition of the erm gene, which encodes an enzyme that methylates the AB target site in the 50S ribosomal subunit.

44
Q

How does inactivation of antibiotic occur?

A

Through enzymatic degradation or alteration

45
Q

What are 2 enzymes that cause antibiotic inactivation?

A

beta-lactamase (bla) and chloramphenicol acetyl-transferase (cat).

46
Q

What are 2 ways altered metabolism stops antibiotic working?

A

Increased production of enzyme substrate can out-compete antibiotic inhibitor
Bacteria switch to other metabolic pathways

47
Q

How does decreased drug accumulation stop effects of antibiotic?

A

Reduced penetration of AB into bacterial cell (permeability) and/or increased efflux of AB out of the cell – drug does not reach concentration required to be effective.

48
Q

How do macrolides work?

A

Targets 50S ribosomal subunit preventing amino-acyl transfer and thus truncation of polypeptides

49
Q

What are 2 examples of macrolides?

A

Erythromycin, azithromycin

50
Q

What bacteria are macrolides affective against?

A

Gram-positive and some Gram-negative bacteria

51
Q

Are quinolones bactericidal or bacteriostatic?

A

Bactericidal

52
Q

Are quinolones natural or synthetic?

A
53
Q

What do quinolones target in gram positive bacteria?

A

topoisomerase

54
Q

What do quinolones target in gram negative bacteria?

A

DNA gyrase

55
Q

What are 3 sources of antibiotic resistant genes?

A

Plasmids, transposons, naked DNA

56
Q

How are plasmids a source of AB resistant genes?

A

extra-chromosomal circular DNA, often multiple copy. Often carry mutliple AB res genes – selection for one maintains resistance to all

57
Q

How are transposons a source of AB resistant genes?

A

Integrate into chromosomal DNA. Allow transfer of genes from plasmid to chromosome and vice versa.

58
Q

What is naked DNA?

A

DNA from dead bacteria released into environment.

59
Q
A

Pom 2 (5 decks)

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