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Year One - Principles of Disease > Antimicrobial Chemotherapy > Flashcards

Antimicrobial Chemotherapy Flashcards

1
Q

What are the two types of antibiotics?

A

Bactericidal

Bacteriostatic

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2
Q

What are bactericidal antibiotics?

A

Kill bacteria

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3
Q

What are bacteriostatic antibiotics?

A

Inhibit the growth of bacteria

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4
Q

What is the M.B.C?

A

Minimal bactericidal concentration

The minimum concentration of a bactericidal antibiotic needed to kill a given organism.

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5
Q

What is the M.I.C?

A

Minimal inhibitory concentration

The minimum concentration of a bacteriostatic antibiotic needed to inhibit the growth of a given organism.

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6
Q

What are sensitive organisms?

A

Organisms that are inhibited or killed by the antibiotics

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7
Q

What are resistant organisms?

A

Organisms that are not inhibited or killed by the antibiotics

Unlikely to respond to attainable levels of the drug in tissues

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8
Q

What are the three ways that we can inhibit or kill bacteria?

A

Inhibit cell wall synthesis

Inhibit protein synthesis

Inhibit nucleic acid synthesis

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9
Q

What two groups of antibiotics inhibit cell wall synthesis?

A

Beta-lactams

Glycopeptides

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10
Q

What are beta-lactams?

A

Bactericidal antibiotics

Contain a beta-lactam ring

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11
Q

How do beta-lactams inhibit cell wall synthesis?

A

Disrupt peptidoglycan synthesis in the bacteria cell wall.

They do this by inhibiting penicillin-binding proteins, which are responsible for eh cross linkage of carbohydrate chains in the cell wall. This means that the cell wall can’t be synthesised as the peptidoglycan layer is not formed.

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12
Q

Name two beta-lactams

A

Penicillin

Cephalosporins

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13
Q

What type of bacteria do penicillins target?

A

Gram-positive

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14
Q

What are glycopeptides?

A

Bactericidal antibiotics

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15
Q

How do glycopeptides inhibit cell wall synthesis?

A

Inhibit the assembly of the peptidoglycan precursor, which inhibits the peptidoglycan layer from being formed.

They do this by binding to carbohydrate chains in the cell, which prevent penicillin binding proteins from binding and cross linking the chains

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16
Q

Name two glycopeptdes

A

Vancomycin

Teicoplanin

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17
Q

What is vancomycin?

A

A glycopeptide antibiotic

Highly toxic, so intravenously infused to avoid local tissue damage. It’s carefully monitored as a result

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18
Q

Why do glycopeptides and beta-lactams target bacterial cell walls not human cell walls?

A

Human cells don’t have cell walls

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19
Q

What five groups of antibiotics inhibit protein synthesis?

A

Aminoglycosides

Macrolides

Tetracyclines

Oxazolidinones

Cyclin lipopeptides

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20
Q

What are aminoglycosides?

A

Bactericidal antibiotics

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21
Q

How do aminoglycosides inhibit protein synthesis?

A

They bind to the codons on the mRNA strand which means that they are misread at the ribosome and that the tRNA anticodon is matched incorrectly

This can result in premature termination or the wrong portion being synthesised

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22
Q

Name an aminoglycoside

A

Gentamicin

Highly toxic so requires careful dosage regime and monitoring

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23
Q

What are macrolides?

A

Bactericidal or bacteriostatic

Useful alternative to penicillin in treatment of gram-positive infections in patients who are penicillin allergic

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24
Q

How do macrolides inhibit protein synthesis?

A

Prevent peptide transferase from adding the growing peptide attached to tRNA to the next amino acid

Inhibit ribosomal translation

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25
Q

Name a macrolide

A

Erythromycin

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26
Q

What are tetracyclines?

A

Bacteriostatic antibiotics

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27
Q

How do tetracyclines inhibit protein synthesis?

A

Block the attachment of tRNA to the ribosome

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28
Q

What are oxazolidinones?

A

Bactericidal or bacteriostatic antibiotics

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29
Q

How do oxazolidinones inhibit protein synthesis?

A

Inhibit synthesis of a ribosomal subunit

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30
Q

Name an oxazolidinone

A

Linezolid

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31
Q

What are cyclic lipopeptides?

A

Bactericidal antibiotics

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32
Q

Name a cyclic lipopeptide

A

Daptomycin

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33
Q

What group of antibiotics inhibit nucleic acid synthesis?

A

Fluoroquinolones

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34
Q

What are fluoroquinolones?

A

Bactericidal

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35
Q

How do fluoroquinoles inhibit nucleic acid synthesis?

A

Inhibit DNA synthesis directly by inhibit the wrapping of DNA

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36
Q

Name a fluoroquinole

A

Ciprfloxacin

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37
Q

How can we measure an organism’s antibiotic sensitivity?

A

Laboratory test

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38
Q

Name the two types of resistance

A

Natural (inherent)

Acquired (intrinsic)

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39
Q

What is natural resistance? Is laboratory sensitivity relevant?

A

When all strains of a given species are naturally resistant to an antibiotic

No

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40
Q

What is artificial resistance? Is laboratory sensitivity relevant?

A

Results from an external source. May be present in some strains but not others

Yes

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41
Q

How can artificial resistance be gained?

A

Spontaneous mutation - results in the structure or function of the bacteria changing so not it no longer allows the antibody to act upon it

Natural selection - when a spontaneous mutation in one bacterium results in it having a selective advantage over other bacteria and survived under selection pressures. This allows it reproduce until all strains are resistant

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42
Q

How can the genes that code for resistance spread through organisms within the same generation?

A

Genes are carried on the plasmids in bacteria. These structures can be transferred horizontally between bacteria in the same generation

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43
Q

What are plasmids?

A

Extra chromosomal packages of DNA

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44
Q

How can bacteria become resistant to beta-lactam antibiotics?

A

They can produce beta-lactase, which is an enzyme that cleaves the beta-lactam ring, making it inactuive

45
Q

What bacteria is commonly resistant to beta-lactams?

A

Staphylococcus aureus

46
Q

What are the two ways that we can combat beta-lactam resistance?

A

We can modify the antibiotic side chain to produce new antibiotics = co-amoxiclav and flucloaxcillin

We can also alter the penicillin binding protein target site

47
Q

What is the second way in which bacteria can become resistant to beta-lactams?

A

They can alter the structure fo their penicillin binding protein target sites, which means that the beta-lactams are not Abel to bind to them

48
Q

What are resistant staphylococcus aureus called?

A

MRSA

49
Q

What can we use to treat MRSA?

A

Vancomycin

50
Q

What is benzyl pencillin used to treat?

A

Gram-positive bacteria

Pneunmococcal meningococcal and strep pyogenes

51
Q

What is amoxicillin used to treat?

A

Gram-negative bacteria

Streptococci and some coliforms

52
Q

What is flucloaxcillin used to treat?

A

Staphylococcal infections

53
Q

What is co-amoxiclav used to treat?

A

Beta-lactamase producing coliforms

54
Q

What seven side effects can patients experience from antibiotics?

A

Allergic reaction

Gastroointestinal effects

Thrush

Liver toxicity

Renal toxicity

Neurological toxicity

Haematological toxicity

55
Q

What group of antibiotics are patients most likely to have an allergic reaction towards?

A

Beta-lactams

True penicillin hypersensitivity is rare.

56
Q

What two types of allergic reactions can patients experience towards antibiotics? What are the symptoms experienced?

A

Immediate - minutes after administration. Symptoms - itching, nausea, vomiting and wheezing

Delayed - hours or days after administration. Symptoms - rashes, fever, vomiting and erythema nodosum

57
Q

How can we tell if a patient is experiencing gastrointestinal effects to an antibiotic?

A

Nausea, vomiting and diarrhoea, as toxin production may occur.

58
Q

What bacteria often causes gastrointestinal effects? How can we detect this bacteria? What do we treat it with?

A

C.difficile

Overgrow normal flora in GI tract and produce toxins. These toxins cause diarrhoea and infection.

Carrying out an immunoassay test with the patient’s stool

Vancomycin or metronidazole

59
Q

How can antibiotics cause oral and vaginal thrush in patients?

A

Can result in the overgrowth of a specific form of yeast

60
Q

What group of antibiotics are associated with thrush?

A

Beta-lactams

61
Q

What effects can antibiotics have on the liver?

A

Increase liver enzymes and cause severe hepatitis

62
Q

What two drugs are associated with liver toxicity?

A

Tetracyclines and anti-TB drugs

63
Q

What patients are more susceptible to liver toxicity as a result of antibiotics?

A

individuals with pre-exsisting liver disease

Individuals who are pregnant

64
Q

Why is the kidneys often affected by antibiotics?

A

They are important route of excretion

65
Q

What patients are more susceptible to renal toxicity as a result of antibiotics?

A

Individuals who have pre-existing renal disease

66
Q

What two drugs are associated with liver toxicity?

A

Aminoglycosides

Vancomycin

67
Q

What drugs are associated with ototoxicity?

A

Aminoglycosides

Vancomycin

68
Q

What drugs are associated with optic neuropathy?

A

Ethambutol

69
Q

What drugs are associated with peripheral neuropathy?

A

Metronidazole and nitrofurantoin

70
Q

What drugs are associated with encephalopathy?

A

Beta-lactams

71
Q

What is haematological toxicity?

A

Toxic effects on the bone marrow, which results in selective depression of one cell or unselective depression of all bone marrow cells

72
Q

What is the name given to selective depression?

A

Neutropenia

73
Q

What is the name given to unselective depression?

A

Panctyopenia

74
Q

What drugs are associated with haematological toxicity?

A

Linezolid

Co-trimaxazole

75
Q

How can we minimise side effects?

A

Antibiotics should only be used when indicated and in the minimum dose duration

Take care when prescribing to susceptible individuals

Monitor antimicrobials with a low therapeutic range - small difference between effective and toxic dose

Adverse reactions should be reported

76
Q

Why might antimicrobials be prescribed?

A

Prophylaxis - prevent future occurrence, useful in patients who have been exposed to others with infection or in patients who are about to undergo surgery with high post op-infection rates

77
Q

Whom should we take care with when prescribing antibiotics?

A

Children

Elderly

Patients with renal failure - antimicrobials are excreted by kidneys, so if they have failure they tend they tend to build up in the body which means doses need to be decreased proportionally

Patients with liver failure

Pregnant - can induce mutations in foetal chromosomes (mutagenic effects) or induce congenital abnormalities in the foetus (teratogenic effects)

78
Q

What are empirical antimicrobial therapies? What should these therapies take into account? When should treatment be reviewed?

A

When the organism causing infection is not known.

The site and type of infection, likely causative organisms

When culture tests become available

79
Q

How can we decide if the antibiotic will be effective against the known or likely causative agent?

A

Carry out sensitivity test

80
Q

Why are combination therapies used?

A

To cover a mixed infection caused by more than one organism

Two antimicrobials may have an enhanced effect together

Prevent development of resistant to one agent

81
Q

What are the possible outcomes of combination therapy?

A

Additive - combined effect is the same as the sum of their individual contributions

Anatgonistic - combined effect is less than the sum of their individual contributions

Synergisitic - combined effect is greater than the sum of their individual contributions

82
Q

What combination of drugs usually leads to an antagonistic effect?

A

One bactericidal and one bacteriostatic

83
Q

What combination of drugs usually leads to an additive or synergistic effect?

A

Two bactericidal

or

Two bacteriostatic

84
Q

Should antimicrobials be able to penetrate the site of infection?

A

Yes

85
Q

What is the standard course of therapy?

A

7 days

86
Q

How long is IV therapy for staph. aureus infections?

A

14 days

87
Q

What can we use to treat UTIs? How long do we prescribe this drug for?

A

Trimethoprim

3 days

88
Q

Why do we monitor serum levels of antimicrobials?

A

Ensure therapeutic ranges have been achieved

Ensure the levels of the drug are not too high that toxic results are produced

89
Q

Why might the blood and serum levels of a drug differ?

A

Depends on the drugs ability to penetrate the site of infection

90
Q

What two drugs are commonly monitored

A

Vancomycin and gentamicin

91
Q

How can we measure the M.I.C? What do these measures involve?

A

E-test or automated methods

E-test involves using a paper strip which has a gradient of antibiotic concentrations absorbed into it. The M.I.C of the organism can be read directly from the point where organism growth intersects the strip.

Automated methods involves measuring the growth of the organism in the presence of different concentration of the antibiotic

92
Q

What are the four groups of anti-fungal drugs?

A

Polyenes

Azoles

Allylamines

Echinocandins

93
Q

What are polyenes?

A

Bind to ergosterol which is present in the fungal cell wall, resulting in an increase in permeability of the cell wall

Active against both yeasts and filamentous fungi

94
Q

What are polyenes sometimes toxic?

A

Can also bind to other sterols, like cholesterol

95
Q

Name two examples of polyenes

A

Amphotericin B and nystatin

96
Q

What are azoles?

A

Drugs that inhibit the synthesis of ergesterol

97
Q

Name an azole

A

Fluconazole

98
Q

What are allylalamines?

A

Drugs that inhibit the synthesis of ergesterol

99
Q

Name an allylalamine

A

Terbinafine

100
Q

What are echinocandins?

A

Inhibit the synthesis of gluten polysaccharides

101
Q

Name an echinocandin

A

Caspofungin

102
Q

What are all viral drugs?

A

Virustatic

103
Q

What are nucleoside analogues?

A

Drugs that interfere with nucleic acid synthesis

104
Q

Name a drug used to treat herpes?

A

Aciclovir

Nucleoside analogue drug

105
Q

What type of therapy is commonly used to treat HIV?

A

Combination therapy with at least three drugs

Used for prophylaxis following occupational or sexual exposure to HIV positive bodily fluids

106
Q

Name a drug used to treat HIV

A

Zidovudine

107
Q

Name a drug used to treat hepatitis B and C

A

Interferon-a

108
Q

Name a drug used to treat viral respiratory infections (influenza)

A

Zanamivir

Year One - Principles of Disease (15 decks)

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