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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
Name a macrolide
Erythromycin
26
What are tetracyclines?
Bacteriostatic antibiotics
27
How do tetracyclines inhibit protein synthesis?
Block the attachment of tRNA to the ribosome
28
What are oxazolidinones?
Bactericidal or bacteriostatic antibiotics
29
How do oxazolidinones inhibit protein synthesis?
Inhibit synthesis of a ribosomal subunit
30
Name an oxazolidinone
Linezolid
31
What are cyclic lipopeptides?
Bactericidal antibiotics
32
Name a cyclic lipopeptide
Daptomycin
33
What group of antibiotics inhibit nucleic acid synthesis?
Fluoroquinolones
34
What are fluoroquinolones?
Bactericidal
35
How do fluoroquinoles inhibit nucleic acid synthesis?
Inhibit DNA synthesis directly by inhibit the wrapping of DNA
36
Name a fluoroquinole
Ciprfloxacin
37
How can we measure an organism's antibiotic sensitivity?
Laboratory test
38
Name the two types of resistance
Natural (inherent) Acquired (intrinsic)
39
What is natural resistance? Is laboratory sensitivity relevant?
When all strains of a given species are naturally resistant to an antibiotic No
40
What is artificial resistance? Is laboratory sensitivity relevant?
Results from an external source. May be present in some strains but not others Yes
41
How can artificial resistance be gained?
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
42
How can the genes that code for resistance spread through organisms within the same generation?
Genes are carried on the plasmids in bacteria. These structures can be transferred horizontally between bacteria in the same generation
43
What are plasmids?
Extra chromosomal packages of DNA
44
How can bacteria become resistant to beta-lactam antibiotics?
They can produce beta-lactase, which is an enzyme that cleaves the beta-lactam ring, making it inactuive
45
What bacteria is commonly resistant to beta-lactams?
Staphylococcus aureus
46
What are the two ways that we can combat beta-lactam resistance?
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
What is the second way in which bacteria can become resistant to beta-lactams?
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
What are resistant staphylococcus aureus called?
MRSA
49
What can we use to treat MRSA?
Vancomycin
50
What is benzyl pencillin used to treat?
Gram-positive bacteria Pneunmococcal meningococcal and strep pyogenes
51
What is amoxicillin used to treat?
Gram-negative bacteria Streptococci and some coliforms
52
What is flucloaxcillin used to treat?
Staphylococcal infections
53
What is co-amoxiclav used to treat?
Beta-lactamase producing coliforms
54
What seven side effects can patients experience from antibiotics?
Allergic reaction Gastroointestinal effects Thrush Liver toxicity Renal toxicity Neurological toxicity Haematological toxicity
55
What group of antibiotics are patients most likely to have an allergic reaction towards?
Beta-lactams True penicillin hypersensitivity is rare.
56
What two types of allergic reactions can patients experience towards antibiotics? What are the symptoms experienced?
Immediate - minutes after administration. Symptoms - itching, nausea, vomiting and wheezing Delayed - hours or days after administration. Symptoms - rashes, fever, vomiting and erythema nodosum
57
How can we tell if a patient is experiencing gastrointestinal effects to an antibiotic?
Nausea, vomiting and diarrhoea, as toxin production may occur.
58
What bacteria often causes gastrointestinal effects? How can we detect this bacteria? What do we treat it with?
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
How can antibiotics cause oral and vaginal thrush in patients?
Can result in the overgrowth of a specific form of yeast
60
What group of antibiotics are associated with thrush?
Beta-lactams
61
What effects can antibiotics have on the liver?
Increase liver enzymes and cause severe hepatitis
62
What two drugs are associated with liver toxicity?
Tetracyclines and anti-TB drugs
63
What patients are more susceptible to liver toxicity as a result of antibiotics?
individuals with pre-exsisting liver disease Individuals who are pregnant
64
Why is the kidneys often affected by antibiotics?
They are important route of excretion
65
What patients are more susceptible to renal toxicity as a result of antibiotics?
Individuals who have pre-existing renal disease
66
What two drugs are associated with liver toxicity?
Aminoglycosides Vancomycin
67
What drugs are associated with ototoxicity?
Aminoglycosides Vancomycin
68
What drugs are associated with optic neuropathy?
Ethambutol
69
What drugs are associated with peripheral neuropathy?
Metronidazole and nitrofurantoin
70
What drugs are associated with encephalopathy?
Beta-lactams
71
What is haematological toxicity?
Toxic effects on the bone marrow, which results in selective depression of one cell or unselective depression of all bone marrow cells
72
What is the name given to selective depression?
Neutropenia
73
What is the name given to unselective depression?
Panctyopenia
74
What drugs are associated with haematological toxicity?
Linezolid Co-trimaxazole
75
How can we minimise side effects?
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
Why might antimicrobials be prescribed?
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
Whom should we take care with when prescribing antibiotics?
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
What are empirical antimicrobial therapies? What should these therapies take into account? When should treatment be reviewed?
When the organism causing infection is not known. The site and type of infection, likely causative organisms When culture tests become available
79
How can we decide if the antibiotic will be effective against the known or likely causative agent?
Carry out sensitivity test
80
Why are combination therapies used?
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
What are the possible outcomes of combination therapy?
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
What combination of drugs usually leads to an antagonistic effect?
One bactericidal and one bacteriostatic
83
What combination of drugs usually leads to an additive or synergistic effect?
Two bactericidal or Two bacteriostatic
84
Should antimicrobials be able to penetrate the site of infection?
Yes
85
What is the standard course of therapy?
7 days
86
How long is IV therapy for staph. aureus infections?
14 days
87
What can we use to treat UTIs? How long do we prescribe this drug for?
Trimethoprim 3 days
88
Why do we monitor serum levels of antimicrobials?
Ensure therapeutic ranges have been achieved Ensure the levels of the drug are not too high that toxic results are produced
89
Why might the blood and serum levels of a drug differ?
Depends on the drugs ability to penetrate the site of infection
90
What two drugs are commonly monitored
Vancomycin and gentamicin
91
How can we measure the M.I.C? What do these measures involve?
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
What are the four groups of anti-fungal drugs?
Polyenes Azoles Allylamines Echinocandins
93
What are polyenes?
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
What are polyenes sometimes toxic?
Can also bind to other sterols, like cholesterol
95
Name two examples of polyenes
Amphotericin B and nystatin
96
What are azoles?
Drugs that inhibit the synthesis of ergesterol
97
Name an azole
Fluconazole
98
What are allylalamines?
Drugs that inhibit the synthesis of ergesterol
99
Name an allylalamine
Terbinafine
100
What are echinocandins?
Inhibit the synthesis of gluten polysaccharides
101
Name an echinocandin
Caspofungin
102
What are all viral drugs?
Virustatic
103
What are nucleoside analogues?
Drugs that interfere with nucleic acid synthesis
104
Name a drug used to treat herpes?
Aciclovir Nucleoside analogue drug
105
What type of therapy is commonly used to treat HIV?
Combination therapy with at least three drugs Used for prophylaxis following occupational or sexual exposure to HIV positive bodily fluids
106
Name a drug used to treat HIV
Zidovudine
107
Name a drug used to treat hepatitis B and C
Interferon-a
108
Name a drug used to treat viral respiratory infections (influenza)
Zanamivir

Year One - Principles of Disease (15 decks)

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