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3rd yr- IWB- Microbiology > Antimicrobial agents > Flashcards

Antimicrobial agents Flashcards

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1
Q

Define antibiotics

A

They are the products f microbes that, in dilute solution, inhibit or kill other organisms

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2
Q

Define antimicrobial agents

A

These include antibiotics and synthetic compounds that have the same effect

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3
Q

What can we do to naturally occurring antibiotics

A

We can modify them to give semi synthetics derivatives

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4
Q

How can modified antibiotics differ from their parent compound

A

In they antimicrobial activity or their pharmacological properties

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5
Q

What 2 effects can antimicrobial agents have?

A
  1. They can inhibit microbial growth

2. They can kill microbes

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6
Q

Define static

A

Agents that inhibits microbial growth

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7
Q

Define cidal

A

Agents that kill microbes

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8
Q

How do we carry out susceptibility testing

A

We grow the bacteria in agar
Then we place disks with varying concentrations of antibiotic solution in the agar and see what reaction that causes with the bacterial culture

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9
Q

Name an alternative susceptibility test to the disk method

A

Absylum test strip (e test strip)

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10
Q

How does the absylum (e ) test strip work

A

It is a plastic strip with a carefully controlled gradient of the drug to be tested
The greater the area of inhibitor the greater the susceptibility the drug is to the bacteria

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11
Q

If you are doing a susceptibility test and you see small colonies of bacteria growing in the zones of clearing what does this mean?

A

It means those bacteria are resistant to the drug and require urgent further investigation

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12
Q

What does MIC stand for in microbiology

A

Minimum inhibitory concentration

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13
Q

What is the Minimum inhibitory concentration (MIC)

A

It is the lower concentration of antibiotic that prevents visible growth of a particular bacterium

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14
Q

What does MBC stand for in microbiology

A

Minimum bactericidal concentration

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15
Q

What is the minimum bactericidal concentration (MBC)

A

The lowest concentration of antibiotic that kill a particular bacterium

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16
Q

How are MIC and MBC values determined?

A

By using dilution methods

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17
Q

What do we mean when we describe drugs as being synergistic?

A

Means they work together

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18
Q

What do we mean when we describe drugs as being antagonistic?

A

They work against each other

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19
Q

Why are bacteria good targets for the activity go antimicrobial substances

A

As apexes of their metabolism are significantly different from that of humans

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20
Q

What provides the basis for the selective toxicity of antibiotics?

A

The fact that antibiotics may act up bacterial reaction that are not found in human cells

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21
Q

Why is selective toxicity important?

A

Important so that antibiotics target bacteria and not human cells

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22
Q

What are the problems with selective toxicity in the case of penicillin

A

Penicillin allergies arise due to the presence of the thiazolidine ring within the penicillin structure

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23
Q

Fungi and protist metabolism is closer to bacteria or humans?

A

Humans

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24
Q

What do viruses depend on to be able to replicate

A

Viruses are obligate intracellular parasites that depend almost exclusively upon human metabolism for their replication

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25
Q

Viruses are O________ I_______ P________

A

Obligate intracellular parasites

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26
Q

What is the problem with using drugs that affect viral replication and spread

A

They are too toxic for humans

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27
Q

List the key stages in the replication cycle of a virus

A
  1. Entry
  2. Uncoating
  3. Reverse transcription
  4. Integration
  5. Protease inhibition
  6. Virus replication and assembly
  7. Virus release
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28
Q

Name some antiviral agents

A
  1. Amantadine
  2. Rimantadine
  3. Acyclovir
  4. Gancyclovir
  5. Ribvarin
  6. Zidovudine
  7. Lamivudine
  8. Oseltamivir
  9. Zanamivir
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29
Q

What is amantadine used in?

A

Treatment and prevention of influenza A infection

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30
Q

What is Rimantadine used in?

A

Treatment and prevention of influenza A infection

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31
Q

How do amantadine and rimantadine work

A

By targeting the viral entry and uncoating process

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32
Q

What is Acyclovir and what is used to treat

A

It is a nucleoside analogue used to treat infections caused by the herpes virus (especially herpes simplex virus)

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33
Q

What is gancyclovir and what is used to treat

A

It is a derivative of acyclovir that is more active against CYTOMEGALOVIRUS

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34
Q

What is ribavirin and what is used to treat

A

It is a nuceloside analogue that has a broad spectrum of activity
It is used to treat respiratory syncytial virus

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35
Q

What is zidovudine (AZT) and what is used to treat

A

It is a revere transcriptase inhibitor

It is used to slow the progression of HIV when the patient has developed AIDs

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36
Q

What is lamivudine

A

It is an inhibitor for reverse transcriptase

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37
Q

Other than the virus itself what else can antiviral agents target?

A

Viruses may produce polyproteins that are hydrolysed by specific proteases
These proteases can be targeted by antiviral drugs

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38
Q

What are antiviral drugs that target proteases called?

A

Protease inhibitors

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39
Q

Give an examples of a protease inhibitor

A

Nelfinavir

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40
Q

What is combination therapy

A

When a range of drugs with different modes of action are used to teat a disease

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41
Q

What does HAART stand for and what is it used to control

A

Highly Active Antiretroviral Therapy

Used to delay the emergence of a drug resistance of HIV

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42
Q

How can we defat emergence of resistance?

A

By using drugs with different modes of action

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43
Q

What is AZT

A

zidovudine

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44
Q

What is the trade name for oseltamivir?

A

Tamiflu

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45
Q

What is the trade name for zanamivir?

A

Relenza

46
Q

What are oseltamivir and zanamivir

A

They are neuraminidase inhibitors that prevent release of influenza virus from infected cells

47
Q

When was oseltamivir used a lot

A

During the H1N1 influenza pandemic

48
Q

What has happened due to the heavy use of oseltamivir during the H1N1 influenza pandemic

A

Has led to the emergence of distant strains of the H1N1 influenza virus

49
Q

What type of organism are fungi?

A

Eukaryotic organism that share similar metabolic processes with humans

50
Q

Why are there only a relatively small number of anti fungal drugs?

A

As we can only use a small number of them safely with out damaging human cells

51
Q

Give examples of classes anti fungal drugs we can use safely

A
  1. Polyenes
  2. The azoles
  3. Miscellaneous
52
Q

How do polyenes work?

A

By binding with sterols in eukaryotic membranes causing their destabilisation

53
Q

Give examples of polyenes

A

1, Nystatin

  1. Amphotericin B
  2. 5 flucytosine
54
Q

What are nystatins used to treat?

A

Oral and genital candida infections

55
Q

What is Amphotericin B used to treat

A

Used for treatment of systemic mycoses

56
Q

What is the problem associated with Amphotericin b and how do we overcome this problem

A

It is potentially toxic to humans and is often given with a second anti fungal or in a lipid preparation

57
Q

What is Amphotericin B often administered with?

A

5 flucytosine

58
Q

Why is Amphotericin B usually given with 5 flucytosine

A

As combining these 2 drugs allows a lower dose of Amphotericin B to be used

59
Q

What is 5 flucytosine (5-FC)

A

It is a synthetic pyrimidine that is metabolised in fungi to 5 flurouracil

60
Q

What is 5 flucytosine used against?

A

Primarily active against pathogenic yeasts

61
Q

How does 5 flucytosine work

A

Works by interfering with the synthesis of nucleic acids

62
Q

What are azoles

A

They are a large group of synthetic compounds that inhibit ergosterol synthesis

63
Q

What happens if ergosterol synthesis is inhibited?

A

Membrane leakage occurs

64
Q

Name the 2 families of azoles

A
  1. Imidazoles

2. Triazoles

65
Q

Give examples of imidazoles

A
  1. Clotrimazole
  2. Miconazole
  3. Exonazole
  4. Ketoconazole
66
Q

Give examples of triazoles

A
  1. Fluconazole
  2. Itraconazole
  3. Voriconazole
  4. Pasoconazole
67
Q

How are imidazoles used?

A

They are used topically to treat fungal infections

68
Q

Why are imidazoles only used topically

A

As they are too toxic to treat systemic infections

69
Q

How are triazoles used?

A

They have a wide variety of applications

70
Q

What is Fluconazole active against?

A

Only active against yeast and dimorphic fungi

71
Q

Name some miscellaneous anti fungal agents

A
  1. Terbinafore

2. Griseofulvin

72
Q

What is Terbinafore

A

A synthetic anti fungal agent

73
Q

What is Terbinafore sued to treat

A

Skin and nail infection

74
Q

How does Terbinafore work

A

By inhibits ergosterol biosynthesis

75
Q

What is Griseofulvin?

A

A naturally occurring compound

76
Q

How does Griseofulvin work

A

It binds to the portion involved in microtubule formation and prevents separation of chromosomes at mitosis

77
Q

What is Griseofulvin used to treat

A

Ring worms and other fungal infections of the skin or nails

78
Q

The fact that Griseofulvin is naturally occurring means it is what?

A

It is a try antibiotic with fungal properties

79
Q

What are protists?

A

They are unicellular eukaryotes

80
Q

What is difficult to achieve when we are making anti protist agents and why?

A

Selective toxicity is more difficult to achieve as protists are unicellular eukaryotes

81
Q

Give examples of antipritist agents

A
  1. Chloroquine
  2. Mefloquine
  3. Pyrimethamine
  4. Metronidazole
82
Q

What does metronidazole induce?

A

It induces strand breaks in the DNA of sensitive organisms and also disrupts membrane integrity

83
Q

What is metronidazole used to treat

A

Used to treat trichomonad vaginalis and entamoeba histolytic

84
Q

What can antibacterial agents target?

A
  1. The cell wall
  2. Membrane integrity
  3. Protein synthesis
  4. DNA metabolism
  5. DNA packaging
  6. RNA polymerase
85
Q

Cell wall inhibitors target what?

A

Peptidoglycan’s

86
Q

what is the benefit of cell wall inhibitors targeting Peptidoglycan

A

It is a unique biopolymer that contains both L and D amino acids
As it is unique to the cell wall it is the ideal target for agents that show selective toxicity

87
Q

Can antibiotics that interfere with the integrity of the cell wall be toxic to humans?

A

Yes some can eg Bacitracin

88
Q

Name some clinically useful cell wall inhibitors

A
  1. Cycloserine
  2. Fosfomycin
  3. Glycopeptides
  4. B-lactams
89
Q

What do all beta lactic antibiotics have in common

A

They have a 4 membered ring structure: the beta lactic ring

90
Q

Name the first rue antibiotic in clinical practice

A

Benzyl penicillin

91
Q

What is the significance of the beta lactic ring found in beta lactic antibiotics

A

The beta lactic ring forms a structural analogue of d alanyl d alanine
This acts by interferring with penicillin binding proteins like enzymes involved in the synthesis and maintained of peptidoglycan

92
Q

Give examples of FAMILIES of beta lactam antibiotics

A
  1. The cephalosporins
  2. Monobactams
  3. Cabepenems
93
Q

What are the cephalosporins

A

A family of broad spectrum antibiotics

94
Q

What are Monobactams active against

A

Gram negatie bacteria

95
Q

What are the Cabepenems

A

A family of broad spectrum agents

96
Q

Give examples of antibacterial antibiotics that affect membrane integrity

A
  1. Polymyxins
  2. Metronidazole
  3. Gramicidins
97
Q

Give examples of antibacterial antibiotics that affect DNA metabolism

A
  1. Para-aminobenzoic acid
  2. Folic acid
  3. Trimethoprim
  4. Sulphamethoxazole (a sulphonamide drug)
98
Q

Give examples of antibacterial antibiotics that affect DNA

A
  1. Nalidixic acid
  2. Metronidazole
  3. Ciprofloxacin
  4. Moxifloxacin
  5. Levoflocacin
99
Q

Give examples of antibacterial antibiotics that affect protein synthesis

A
  1. Aminoglycosides
  2. Tetracycline
  3. Chloramphenicol
  4. Macrolides
  5. Fusidic acid
  6. Linocosamides
  7. Mupirocin
  8. Linezolid
100
Q

What are the side effects of amino-glycosides

A

Damage to the 8th cranial nerve that can lead to deafness and balance problems in some individuals

101
Q

Give examples of amino-glycosides

A
  1. Streptomycin
  2. Gentamycin
  3. Kanamycin
102
Q

Give examples of antibacterial antibiotics that affect RNA synthesis

A
  1. Rifampicin

2. Nirofurantocin

103
Q

What Is Rifampicin used to treat

A

Tuberculosis and prophylaxis

104
Q

Benzyl penicillin was the first ______ _______ used in clinical practice

A

True antibiotic

105
Q

How do Polymyxins, Metronidazole and Gramicidins work?

A

By affecting membrane integrity

106
Q

How do Para-aminobenzoic acid, Folic acid, Trimethoprim and Sulphamethoxazolework

A

By affecting dan metabolism

107
Q

How do Nalidixic acid, Metronidazole, Ciprofloxacin, Moxifloxacin and Levoflocacin work

A

By affecting DNA

108
Q

How do aminoglycosides, Tetracycline, Chloramphenicol, Macrolides, Fusidic acid, Linocosamides, Mupirocin and Linezolid

A

By affecting protein synthesis

109
Q

How do Rifampicin AND Nirofurantocin work?

A

By affecting RNA synthesis

110
Q

Give examples of antimycobacterial antibiotics

A
  1. Streptomycin
  2. Ethambutol
  3. Pyrazinamide
  4. Isonlazid
  5. Rifampicin

3rd yr- IWB- Microbiology (12 decks)

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