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Clinical Microbiology > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

Which type of bacteria have a thick cell wall?

A

Gram positive

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2
Q

What separates the outer membrane from the cell wall of gram negative bacteria?

A

Periplasm

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3
Q

How do bactericidal agents achieve sterilisation?

A

By directly killing bacteria

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4
Q

How do bacteriostatic act?

A

Suppress growth but do not directly sterilise the infected site

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5
Q

What is the issue with the lysis of bacteria by bactericidal agents?

A

This can lead to the release of toxins and inflammatory material

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6
Q

What is meant by the ‘spectrum’ of an antibiotic?

A

This refers to the range of bacterial species which are effectively treated by the antibiotic

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7
Q

All antibiotics within an antibiotic class will have a similar spectrum. T/F?

A

False

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8
Q

What is the difference between broad and narrow spectrum antibiotics?

A

Broad spectrum antibiotics are active against a wide range of bacteria
Narrow spectrum antibiotics are active against a limited range of bacteria

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9
Q

Describe the guided therapy strategy for the use of antibiotics?

A

This depends on identifying the cause of infection, an agent is then selected for use based on sensitivity testing

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10
Q

What spectrum of antibiotics are used for guided therapy?

A

Narrow spectrum

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11
Q

In guided therapy there is as little impact on colonisation and resistance as possible. What is the pay off for this?

A

The antibiotic often has limited action on the bacteria causing the infection

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12
Q

In empirical therapy there is extensive action against the bacteria which might be causing the infection. What is the pay off for this?

A

There is a large impact on colonisation and resistance

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13
Q

What spectrum of antibiotics are used for empirical therapy?

A

Broad spectrum

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14
Q

Describe the empirical therapy strategy for the use of antibiotics?

A

Used when the initiation of therapy cannot wait for culture results. A best guess therapy is used based on clinical and epidemiological acumen.

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15
Q

What is prophylactic therapy?

A

Used to prevent infection before it begins

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16
Q

What is the result of overgrowth of yeasts which can occur with the use of antibiotics?

A

Thrush

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17
Q

What is the result of overgrowth of the bowel which can occur with the use of antibiotics?

A

Diarrhoea

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18
Q

Which antibiotics are particularly associated with the development of c.difficile?

A

Clindamycin
Co-amoxiclav
Cephalosporins
Ciprofloxacin

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19
Q

C.difficile forms spores which can be difficult to eradicate from hospitals. T/F?

A

True

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20
Q

C.difficile can be difficult to treat as it has developed resistance to common antibiotic classes. T/F?

A

True

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21
Q

How is an uncomplicated UTI defined?

A

A common condition where there are lower urinary tract symptoms without sepsis of evidence of upper tract involvement

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22
Q

In uncomplicated UTI, you need to use an antibiotic with systemic activity. T/F?

A

False - the antibiotic only needs to sterilise the urine so there is no need for systemic activity

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23
Q

What is the first line agent used to treat uncomplicated UTI?

A

Trimethoprim

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24
Q

Why is trimethoprim a good choice of antibiotic for uncomplicated UTI in men?

A

It penetrates well into the prostate

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25
Q

Nitrofuratoin is an excellent broad spectrum antibiotic which is concentrated in the urine so has no effect on other tissues. In what cases should it not be used?

A

In renal failure nitrofurantoin will fail to concentrate in the urine so should not be used in this case

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26
Q

Nitrofuratoin is relatively non-toxic in short courses. What can be caused with long term use?

A

Pulmonary fibrosis

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27
Q

What bacteria commonly cause uncomplicated UTIs?

A 
E.coli
Other coliforms
Pseudeomonas
Staphylococcus
Enterococcus
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28
Q

If there is a complicated UTI what is the best choice of antibiotic?

A

Ciprofloxacin

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29
Q

If a patient is severely unwell with a UTI then what antibiotics should be used?

A

Amoxicillin

Gentamicin

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30
Q

Beta lactase are safe for use in pregnancy. However, what is the risk of the use of broad spectrum beta-lactam agents in pregnancy?

A

These are associated with necrotising enterocolitis in premature infants

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31
Q

Why should tetracyclines should not be used in pregnancy?

A

These can cause bone and tooth abnormalities

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32
Q

Why should trimethoprim not be used in pregnancy?

A

Can cause neural tube defects in the first trimester

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33
Q

Why should nitrofurantoin not be used in pregnancy?

A

Can cause haemolytic anaemia in the third trimester of pregnancy

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34
Q

Why should aminoglycosides not be used in pregnancy?

A

Can cause ototoxicity in the second and third trimesters

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35
Q

Why should quinolones not be used in pregnancy?

A

Can cause bone and joint abnormalities

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36
Q

What are the four subclassifications of beta lactase antibiotics?

A

Penicillins
Cephalosporins
Carbapenems
monobactans

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37
Q

What is the brand name for the combination of amoxicillin and clavulanic acid?

A

Augmentin

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38
Q

What is the brand name for the combination of piperacillin and tazobactam

A

Tazocin

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39
Q

What is the mechanism of action of beta lactam antibiotics?

A

Inhibit the cross linking of cell wall peptidoglycan to cause lysis of the bacteria

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40
Q

Beta lactams are bacteriostatic antibiotics. T/F?

A

False - these are bactericidal

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41
Q

What kind of organisms typically secrete beta lactamases?

A

Gram negative organisms

S.aureus

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42
Q

Total antibiotic failure is likely with beta lactamases. T/F?

A

True

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43
Q

By which route are beta lactams usually given?

A

IV

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44
Q

When beta lactam antibiotics are given orally, what usually limits the dose?

A

Vomiting

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45
Q

What are the possible adverse effects of beta lactams?

A 
Nausea and vomiting
Diarrhoea
Cholestasis
Type 1 hypersensitivity 
Type 4 hypersensitivity
Interstitial nephritis
Candidiasis (oral or vulvovaginal)
C.difficile infection
Selection of resistance bacteria
Seizure
Haemolysis
Leukopaenia
46
Q

What is the most common presentation of type one hypersensitivity in patients on beta lactams?

A

Urticarial rash

47
Q

Patients who are allergic to a penicillin will usually be allergic to other penicillins. T/F?

A

True

48
Q

What organisms is Benzylpenicillin effective against?

A

Streptococcus
Clostridium
Neisseria

49
Q

What organisms is amoxicillin effective against?

A 
Streptococcus
Enterococcus 
Neisseria
Haemophilus
Clostridium
50
Q

What organisms is flucloxacillin effective against?

A

Streptococcus

Staphylococcus (not MRSA)

51
Q

How is Benzylpenicillin administered?

A

IV

52
Q

Flucloxacillin can be given orally. T/F?

A

True

53
Q

What organisms are cephalosporins effective against?

A 
Streptococcus
Staphylococcus (not MRSA)
E.coli
Neisseria
Haemophilus
Bacterioles
Clostridium 
Other coliform
54
Q

How does the spectrum of cephalosporins change with each generation?

A

With each generation of cephalosporins the gram negative spectrum increases with some loss of gram positive activity

55
Q

Give an example of a cephalosporin antibiotic?

A

Ceftriaxone

56
Q

What organisms are carbapenems active against?

A

Ultra-broad spectrum antibiotics active against most bacteria expect MRSA

57
Q

Carbapenems are resistant to beta lactamases. T/F?

A

True

58
Q

Give an example of carbapenem.

A

Meropenem

59
Q

What is the only monobactam currently in use?

A

Aztreonam

60
Q

Aztreonams can be given to those with a penicillin allergy. T/F?

A

True

61
Q

How is aztreonam administered?

A

IV

62
Q

What class of bacteria is vancomycin active against?

A

Gram positive organisms

63
Q

How is vancomycin administered?

A

IV

64
Q

Why is vancomycin effective against resistant organisms such as MRSA?

A

It is not dependent on penicillin binding proteins

65
Q

A loading dose of vancomycin is usually given. T/F?

A

True

66
Q

Drug monitoring is required for vancomycin. T/F?

A

True - it has a narrow TI

67
Q

What are the possible toxicities of vancomycin?

A

Nephrotoxicity

Ototoxicity

68
Q

What happens when vancomycin is injected too rapidly?

A

red man syndrome - anaphylactoid reaction

69
Q

What classes of protein synthesis inhibitors target the 50S ribosomes?

A

Macrolides
Clindamycin
Chloramphenicol

70
Q

What classes of protein synthesis inhibitors target the 30S ribosomes?

A

Aminoglycosides

Tetracyclines

71
Q

What ‘atypical’ organisms is clarithromycin effective against?

A 
Legionella
Mycoplasma
Coxiella
Chlamydia
Chlamydophila
72
Q

What is the spectrum of action of calrithromycin?

A

Active against gram positive and respiratory gram negative bacteria as well as ‘atypical’ bacteria

73
Q

Macrolides can be given orally even in severe infection T/F?

A

True

74
Q

Give examples of macrolides?

A

Erythromycin
Clarithromycin
Azithromycin

75
Q

What are the possible adverse effects of macrolides?

A 
Diarrhoea and vomiting
QT prolongation
Hearing loss (in long term use)
76
Q

Give examples of drugs which macrolides interact with?

A

Statins

Warfarin

77
Q

Resistance to macrolides is common among ‘atypical’ pathogens’ but uncommon among ‘typical’ pathogens. T/F?

A

False - the opposite is true

78
Q

Clindamycin is given IV. T/F?

A

False - its has excellent oral absorption

79
Q

What organisms is clindamycin effective against?

A

Bacterioles
Clostridium
Staphylococcus
Streptococcus

80
Q

Why is clindamycin notorious for causing c.difficile?

A

Its effective on anaerobes means that is is particularly effective at disrupting colonic flora

81
Q

Clindamycin is highly effective at stopping exotoxin production. As such, what conditions is it used to treat?

A

Toxic shock syndrome
Necrotising fascitis
Other gram positive toxin mediated disease

82
Q

What are the possible toxic effects of chloramphenicol?

A

Bone marrow suppression
Aplastic anemia
Optic neuritis

83
Q

In what situations is chloramphenicol used?

A

Topical therapy to the eye

Bacterial meningitis with beta lactam allergy

84
Q

What are the possible toxic effects of amnioglycosides?

A

Hearing loss, loss of balance and oscillopsia
Neuromuscular blockade in patients with myasthenia gravis
Nephrotoxicity

85
Q

For how long is it appropriate to give a course of gentamicin?

A

3 days

86
Q

Describe the rationale behind the dosing regimen for gentamicin?

A

A high initial dose is given to take advantage of the rapid killing seen at high doses
A long dosing interval of 24-48 hours is left in order to minimise toxicity
In this time there is a prolonged post-antibiotic bacteriostatic effect

87
Q

What organisms are tetracyclines effective against?

A 
Streptococcus
Staphylococcus
Neisseria
Haemophilus
Enterococcus
Mycoplasma
Coxiella
Chlamydia
Chlamydophila
Rickettsia
88
Q

Give examples of quinolones

A

Ciprofloxacin

Levofloxacin

89
Q

Quinolones are always given by IV. T/F?

A

False - oral dosing can be used even in severe infection

90
Q

What organisms is levofloxacin affective against?

A

Streptococcus
Staphylococcus
Also some activity against gram negative

91
Q

What organisms is ciprofloxacin affective against?

A

Gram negative bacteria

Some action against streptococcus and staphylococcus

92
Q

What type of infections is ciprofloxacin used to treat?

A

UTI

Abdominal infections

93
Q

What type of infections is levofloxacin used to treat?

A

Respiratory tract infections

94
Q

What are the possible toxicities associated with quinolones?

A

GI toxicity
QT prolongation
Tendonitis
C.difficile infection

95
Q

In what situations is rifampicin used?

A

Tuberculosis

Serious gram positive (especially S.aureus) infection

96
Q

Why are drug interactions very important to consider when prescribing rifampicin?

A

Rifampicin is a potent CYP450 enzyme inducer

97
Q

What four antibiotics are used in standard short course therapy against TB?

A

Isoniazid
Rifampicin
Pyrazamide
Ethambutol

98
Q

What is the mechanism of action fo quinolones and rifampicin?

A

DNA and RNA biosynthesis inhibitors

99
Q

Trimethoprim causes an elevation inc creatine which doe not reflect a fall in GFR. T/F?

A

True

100
Q

What are some of the problems associated with the use of trimethoprim?

A

Causes an elevation in serum potassium (problematic in patients with chronic renal impairment)
Rash
GO disturbance

101
Q

Co-trimoxazole (a combination of trimethoprim and sulphamethoxazole) is commonly used. T/F?

A

False. - it is only used in specialist care due to its significant additional toxicity

102
Q

What type of bacteria is emtronidazole effective against?

A

Most anaerobic bacteria

103
Q

What type of infection is metronidazole used to treat?

A

Intra-adominal infections

104
Q

Metronidazole causes an unpleasant reaction with alcohol. T/F?

A

True

105
Q

Why folate synthesis inhibitor can cause peripheral neuropathy?

A

Metronidazole

106
Q

Which antibiotic is used to treat mild c.difficile infection?

A

Oral metronidazole

107
Q

Which antibiotic is used to treat severe c.difficile infection?

A

Oral vancomycin

108
Q

What is sepsis six?

A

A range of medical therapies used in the investigation/treatment of possible sepsis. This includes:
Titrate oxygen to sats >94%
Administer IV empiric antibiotics
Start IV fluid resuscitation
Take blood cultures to investigate source of infection
Measure serial serum lactases
Urine output measurement

109
Q

Lactate dehydrogenase is used as a generally marker of injury to cells. T/F?

A

True

110
Q

What is the benefit of lactase blood tests?

A

Helps to assess levels of hypoxia and lactic acidosis

Clinical Microbiology (17 decks)

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