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[ ESA 3- Infection and Immunity > Antimicrobials > Flashcards

Antimicrobials Flashcards

1
Q

What can antimicrobials be classified into?

A

Antibacterials
Antifungals
Antivirals
Antiprotozoals

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2
Q

How can antibacterials be classified?

A

Bactericidal or bacteriostatic
Broad or narrow
Target site
Chemical structure

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3
Q

What do bactericidal antibacterials do?

A

Kill bacteria

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4
Q

What do bacteriostatic antibacterials do?

A

Mainly inhibit

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5
Q

What does the target site of an antibacterial depend on?

A

The mechanism of action

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6
Q

What are the ideal features of an antimicrobial agent?

A 
Selectively toxic
Few adverse effects
Reach site of infection
Oral and IV formulation
Long-half life
No interference with other drugs
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7
Q

Why should an antimicrobial be selectively toxic?

A

So it is minimally toxic

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8
Q

Why should an antimicrobial have a long half life?

A

Allows for infrequent dosing

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9
Q

What are the classes of mechanism of action of antibacterials?

A

Affect cell wall synthesis
Affect protein synthesis
Affect cell membrane function
Affect nucleic acid synthesis

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10
Q

Give two examples of classes of antimicrobials that affect cell wall synthesis

A

Beta-lactams

Glycopeptides

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11
Q

Give three examples of classes of antimicrobials that affect protein synthesis

A

Tetracyclines
Aminoglycosides
Macrolides

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12
Q

Give an example of a class of antimicrobial that affects cell membrane function?

A

Polymixins

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13
Q

Give an example of a polymixin

A

Colistin

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14
Q

Give an example of a class of antimicrobial that affects nucleic acid synthesis

A

Quinolones

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15
Q

Give two examples of quinolones

A

Trimethoprim

Rifampicin

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16
Q

What are the most important classes of antibacterials?

A

Those that affect cell wall synthesis and those that interfere with protein synthesis

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17
Q

What class of antibacterial is penicillin?

A

Beta-lactam

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18
Q

What is penicillin binding protein?

A

A bacterial protein that physiologically cross-links the cell walls in bacteria

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19
Q

What is the mechanism of action of penicillin?

A

It binds to penicillin binding protein and inhibits it from cross-link the cell wall

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20
Q

What class of antimicrobial is vancomycin?

A

Glycopeptide

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21
Q

What is the mechanism of action of vancomycin?

A

It sits on the cross-links of the forming cell wall and stops penicillin binding protein from attaching, preventing cross-links from being attached to each other by the cell wall cross-linking enzyme

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22
Q

What class of antimicrobial are fluoroquinolones?

A

Quinolone

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23
Q

What is the mechanism of action of fluoroquinolones?

A

Interferes with the action of DNA gyrase during bacterial growth

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24
Q

What does DNA gyrase do?

A

Physiologically catalyses the supercoiling of DNA

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25
Q

How do fluoroquinolones interfere with the action of DNA gyrase?

A

Binds to both the enzyme and DNA to form a ternary (three molecule) complex, inhibiting the rejoining step and thus causes cell death

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26
Q

What are the mechanisms of antimicrobial resistance?

A

Drug inactivating enzymes
Altered target
Altered uptake

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27
Q

Give two examples of antimicrobials affected by drug inactivating enzymes

A

Beta-lactamases

Aminoglycosides

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28
Q

What happens in the altered target mechanism of antimicrobial resistance?

A

Target enzyme has a lowered affinity for antibacterial

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29
Q

Give three examples of antimicrobials affected by the altered target mechanism of resistance

A

Methicillin
Macrolides
Trimethoprim

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30
Q

What is caused by antibiotic resistance to methicillin?

A

MRSA

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31
Q

How can altered uptake be achieved in antibiotic resistance?

A

Decreased permeability

Increased efflux

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32
Q

Give an example of an antimicrobial affected by the decreased permeability mechanism of resistance

A

Beta-lactams

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33
Q

Give an example of an antimicrobial affected by the increased efflux mechanism of resistance

A

Tetracyclines

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34
Q

How can antibiotic resistance be genetically obtained?

A

Chromosomal gene mutation

Horizontal gene transfer

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35
Q

How does a chromosomal gene mutation result in antimicrobial resistance?

A

A chromosome mutates to contain a gene that confers resistance.
An antibiotic is then applied and the resistant gene is selected for, as only the resistant bacteria will survive.
The surviving bacteria can then replicate to produce large numbers of bacteria the now carry the mutated resistance gene

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36
Q

What can antibiotic resistance genes be carried on?

A

Chromosomes
Plasmids
Transposons

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37
Q

How can antibiotic resistance genes be transferred?

A

Conjugation
Transduction
Transformation

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38
Q

How does antimicrobial resistance transfer by conjugation?

A

Resistant cell carries the gene on a plasmid or transposon that passes it on to another cell via pili

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39
Q

How does antimicrobial resistance transfer by transduction?

A

Resistant cell is infected by bacteriophage virus.
During replication of bacteriophages within resistant cell, bacterial DNA containing resistant gene is packaged into one of the phages
The bacteriophage then goes on to transfer the resistant gene to a non-resistant cell that incorporates it into its genes via recombination

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40
Q

How does antimicrobial resistance transfer by transformation?

A

Resistant cell carries the gene on a chromosome of plasmid
The resistant cell dies, and releases its DNA
The free DNA is picked up by the competent non-resistant cell, that has now acquired resistance

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41
Q

What happens once antimicrobial resistant is acquired by another cell?

A

It can go on to replicate so that it’s off-spring now possess the resistance gene

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42
Q

How can antibiotic activity be measured?

A

Disc sensitivity tests

Minimum inhibitory concentration

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43
Q

What happens in disc sensitivity tests?

A

Discs of antimicrobials are placed in a petri-dish containing clear agar, where a culture of bacteria is to be grown

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44
Q

How are the results of a disc sensitivity test interpreted?

A

The size of the clear agar around each disc correlates with its effectiveness

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45
Q

What happens in a minimum inhibitory concentration test?

A

There are two control test tubes, one with no antibacterials and bacteria, and one with no antibacterials and no bacteria.
The concentration of antibacterial is halved each test tube, and observe to see when no bacterial growth is observed- when the broth is not turbid

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46
Q

What are the types of beta-lactams?

A

Penicillins
Cephalosporins
Carbapenums
Monobactams

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47
Q

Give 5 examples of penicillins

A 
Benzylpenicillin
Amoxicillin 
Flucloxacillin 
Co-amoxiclav
Tazocin
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48
Q

What is co-amoxiclav?

A

Amox and clavulanate

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49
Q

What is tazocin?

A

Piperacillin + tazobactam

50
Q

Give an example of a cephalosporin?

A

Ceftriaxone

51
Q

Give an example of a carbapenum

52
Q

Give an example of a monobactam

53
Q

What is penicillin mainly active against?

A

Streptococci

54
Q

What is amoxicillin active against?

A

Gram +ve, some gram -ve

55
Q

What is flucloxacillin active against?

A

Staphylococci and streptococci

56
Q

Give two beta-lactamase inhibitor combinations

A

Co-amoxiclav

Tazocin

57
Q

What is co-amoxiclav active against?

A

Gram +ve
Anaerobes
More gram -ve than other penicillins

58
Q

What is Tazocin active against?

A

Same as co-amoxiclav, and even more gram negative, including pseudomonas

59
Q

How are cephalosporins organised?

A

Into generations

60
Q

How do each generation of cephalosporin differ?

A

Each generation has increased activity against gram -ve and decreased activity against gram +ve

61
Q

What is the advantage of cephalosporins over penicillin?

A

More broad spectrum drug

62
Q

What is the disadvantage of cephalosporins over penicillins?

A

No anaerobes activity

63
Q

Where does ceftriaxone have good activity?

A

In the CSF

64
Q

What are there concerns over regarding cephalosporins?

A

Association with C. Difficile

65
Q

What are the advantages of meropenum?

A

Very broad spectrum, including anaerobes
Active against most Gram -ve
Generally safe in penicillin allergy

66
Q

When are meropenum not safe in penicillin allergy?

A

Anaphylaxis

67
Q

What is vancomycin active against?

A

Most gram +ve

68
Q

What is the resistance situation regarding vancomycin?

A

Some enterococci are resistant

Resistance in staphs is rare

69
Q

What is the problem with vancomycin?

A

Not absorbed

Therapeutic drug monitoring

70
Q

When is vancomycin given orally?

A

C. Difficle only

71
Q

Why is therapeutic drug monitoring required for vancomycin?

A

Narrow therapeutic window

72
Q

What is the activity of teicoplanin similar to?

A

Vancomycin

73
Q

What is the advantage of teicoplanin over vancomycin?

A

Easier to administer

74
Q

What are the similarities between tetracyclines and doxycycline?

A

Similar spectrum

Oral only

75
Q

Where are tetracycline and doxycycline used?

A

Broad-spectrum, but specific use in penicillin allergy, usually from gram +ve
Atypical pathogens in pneumonia
Chlamydia and some protozoa

76
Q

Who shouldn’t tetracycline and doxycycline be given to?

A

Children under 12 years

77
Q

Why shouldn’t tetracycline and doxycycline be given to children under 12 years?

A

Stains teeth and bones

78
Q

What is the most common aminoglycoside?

A

Gentamicin

79
Q

What is gentamicin active against?

A

Profound activity against gram negatives

80
Q

Where does gentamycin have good activity?

A

In the blood and urine

81
Q

What is the problem with gentamicin?

A

Potentially nephrotoxic/ototoxic

82
Q

What is required with gentamicin?

A

Therapeutic drug monitoring

83
Q

What is gentamicin generally reserved for?

A

Severe gram -ve sepsi

84
Q

Give two macrolides

A

Erythromycin

Clarithromycin

85
Q

What is good about erythromycin?

A

Well distributed, including intracellular penetration

86
Q

Where is erythromycin used?

A

Alternative to penicillin for mild gram +ve infections

Active against atypical respiratory pathogens

87
Q

What is the most common example of quinolone?

A

Ciprofloxacin

88
Q

What is the mechanism of action of ciprofloxacin?

A

Inhibit DNA gyrase

89
Q

What is ciprofloxacin active against?

A

Very active against atypical pathogens

90
Q

What is the problem with ciprofloxacin?

A

Increasing resistance

Risk of C. Difficile

91
Q

What is the mechanism of action of trimethoprim and sulphonamides?

A

Inhibitors of folic acid synthesis

92
Q

When is trimethoprim used alone in the UK?

93
Q

What is co-trimoxazole?

A

Sulphamethoxazole and trimethoprim

94
Q

What is co-trimoxazole used for?

A

Treat PCP

Has activity against malaria

95
Q

What are the classes of antifungals?

A

Azoles

Polyenes

96
Q

What are azoles active against?

A

Yeasts, and sometimes molds

97
Q

What is the mechanism of action of azoles?

A

Inhibits cell membrane synthesis

98
Q

Give an example of an azole?

A

Fluconazole

99
Q

What is fluconzole used for?

A

Treat Candida

100
Q

What is itra/vori/posaconazole active against?

A

Aspergillus

101
Q

Give two polyenes

A

Nystatin

Amphotericin

102
Q

What is the mechanism of action polyenes?

A

Inhibit cell membrane function

103
Q

What is nystatin used for?

A

Topical treatment of Candida

104
Q

What is amphotericin used for?

A

IV treatment of systemic fungal infection, e.g. Aspergillus

105
Q

Give two antivirals

A

Aciclovir

Oseltamivir

106
Q

What is the mechanism of action of aciclovir?

A

When phosphorylated, it inhibits viral DNA polymerase

107
Q

What is aciclovir active against?

A

Herpes simplex

Varicella zoster

108
Q

Give two things caused by herpes simplex

A

Genital herpes

Encephalitis

109
Q

Give two things caused by varicella zoster

A

Chickenpox

Shingles

110
Q

What is the commercial name for oseltamivir?

111
Q

What is the mechanism of action of tamiflu?

A

Inhibits viral neuraminidase

112
Q

What does tamiflu treat?

A

Influenza A and B

113
Q

What conditions require specialist antivirals for treatment?

A

HIV
HBV
HCV
CMV

114
Q

What kind of antimicrobial is metronidazole?

A

Antibacterial and antiprotozotal

115
Q

What bacteria is metronidazole active against?

116
Q

What protozoa is metronidazole active against?

A

Amoebae
Giardia
Trichomonas

117
Q

What does amoebae cause?

118
Q

What does giardia cause?

119
Q

What does trichomonas cause?

120
Q

What is the purpose of antimicrobial stewardship?

A

Aims to guide practitioners on how to use antimicrobials in children, young people, and adults, with the outcome of slowing the progress of antimicrobial resistance. This will hopefully ensure that antimicrobials remain an effective treatment for infection

[ ESA 3- Infection and Immunity (15 decks)

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