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Infection > Introduction To Antibiotics & Resistance > Flashcards

Introduction To Antibiotics & Resistance Flashcards

1
Q

What are the different anti microbials?

A

Antibacterial

Antifungal

Antiviral

Antiprotozal agents

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2
Q

What are antibiotics also known as ?

A

Antibacterials

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3
Q

Do antibiotics treat viruses?

A

They do not treat viral infections

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4
Q

How do we classify antibiotics ?

A

1) Bactericidal or bacteriostatic
2) broad spectrum / narrow spectrum
3) target site of antibiotic - mechanism of action
4) chemical structure of antibacterial class.

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5
Q

What does bactericidal mean ?

A

Lethal to bacteria - kills the bacteria

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6
Q

What does bacteriostatic mean ?

A

Stops growth and reproduction of bacteria

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7
Q

What does an antibiotics having a broad spectrum mean ?

A

It can attack a wide range of bacteria for example gram positive and gram negative bacteria.

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8
Q

What questions do we consider when choosing an antibiotic?

A
  1. Does it even reach the site of infection?
  2. Is it available for the right formulation ( IV vs oral)
  3. What is the half life of the drug ? - this helps to decide dosing frequency
  4. Does it interact with any other drugs the patient is taking ?
  5. Is there toxicity issues - some drugs have a narrow therapeutic range
  6. Does it require therapeutic drug monitoring ?
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9
Q

What are the three methods to measure antibiotic activity ?

A

1) disc testing
2) broth microdilution to generate a minimum inhibitory concentration ( MIC)
3) MIC- E test

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10
Q

Outline the method of disc testing to measure antibiotic activity

A

1) lawn bacteria on your agar plate.
2) Add your paper discs with antibiotics
3) incubate and leave overnight for 18 hours,
4) the antibiotic would diffuse out of the paper disc.
5) you would obtain a zone of clearance from each antibiotic - larger the zone of clearance the more effective the antibiotic

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11
Q

How to obtain a minimum inhibitory concentration using broth microdilution?

A

1) all wells contain broth.
2) Put increasing concentration of antibiotics into the wells.
3) leave overnight - 18 hrs
4) first well that is clear - would be the minimum inhibitory concentration.

Also do a sterile control and growth control

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12
Q

How to obtain a minimum inhibitory concentration using an E test ?

A

1) lawn plate of agar with bacteria
2) Put E test strip ( at the bottom of the strip there would be the lowest concentration of antibiotic and at the top there would be the highest concentration of antibiotic )
3) leave over night
4) You would obtain a zone of clearance - where the first number where you get no growth of bacteria is the minimum inhibitory concentration.
- this method is much quicker than a broth microdilution

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13
Q

What are the 4 main mechanisms of action for antibiotics ?

A

1) inhibit cell wall synthesis
2) inhibit protein synthesis
3) inhibit cell membrane function
4) inhibit nuclei acid synthesis

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14
Q

Give examples of the classes of antibiotics that work by inhibiting cell wall synthesis ?

A

Beta-lactams ( eg penicillins , cephalosporins)

Glycopeptides

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15
Q

Give examples of antibiotics that work by inhibiting cell membranes function ?

A

Polymixins ( eg. Colistin)

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16
Q

Give examples of antibiotics that work by inhibiting protein synthesis z.

A

Tetracyclines

Aminoglycosides

Macrolides

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17
Q

Give examples of antibiotics that work to inhibit nucleic acid synthesis ?

A

Quinolones

Trimethoprim

Ridampicin

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18
Q

Beta-lactate antibiotics

A

An umbrella group that encompasses four families of antibiotics

  • penicillin
  • cephalosporins
  • carbapenems
  • monobactams
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19
Q

What are beta-lactate mechanism of of action ?

A

They inhibit cell wall synthesis

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20
Q

What are important pencillins to remember ?

A

1) benzylpenicillin ( usually referred to as just penicillin)
2) amoxicillin
3) co-amoxiclav
4) flucoloxacillin - cellulitis

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21
Q

What does amoxicillin works against ?

A

Mainly gram positive bacteria

  • has some activity against gram negative bacteria
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22
Q

What does penicillin work against ?

A
  • active against gram positive bacteria - mainly stroptococci
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23
Q

What does flucloxacillin work against ?

A

Active against staphylococci and streopcocci ( gram positive bacteria)

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24
Q

What does co-amoxiclav work against ?

A

Combination of amoxicillin and cluvulanic acid ( a beta lactamase inhibitor)

  • amoxiccilins efficacy against some bacteria such as staphylococcus aureus can be reduced by an enzyme these bacteria produce such as beta lactamase which reduced antibacterial efficacy as it breaks down the antibiotic preventing it from working against the bacteria.
  • cluvulanic acid inhibits beta lactamase allowing amoxicillin to function for longer before it is broken down.
  • this makes co-amoxiclav effective against staphylococci , streptococci , gram negative bacteria - and an effect on anaerobic bacteria too.
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25
Q

How many generations are there of cephalosporins?

A

5

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26
Q

What is the mechanism of action of cephalosporins?

A

Inhibiting cell wall synthesis

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27
Q

What are cephalosporins active against z.

A
  • they have quite a broad spectrum , they have however NO activity against anaerobic bacteria.
  • can attack both gram negative and gram positive bacteria depending on the generations
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28
Q

What class of cephalosporins is used to treat bacterial meningitis?

A

Cetriaxone because of its good level of activity in the CSF due to ability to easily cross the blood brain barrier

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29
Q

What is a common concern over cephalosporins?

A

It often causes clostridium difficult infection.

  • C.diff is a commensals bacterium found in your normal gut microbiota that competes for nutrients with other flora. The constant competition prevents overgrowth of C.diff.
  • cephalosporins can eliminate some of the natural gut flora as well as the pathogenic organism causing the infection. This reduces competition allowing for C.diff to proliferate and over grow.
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30
Q

If an antibiotic begins with a C , what does it usually carry the risk of ?

A

C.diff infection

THIS IS NOT TRUE FOR ANTIBIOTICS STARRING WITH ‘CO’

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31
Q

What is the main carbapenems ?

A

Meropenem

There is also ertapenem, impenem.

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32
Q

How does meopenem work ?

A

Works by inhibiting cell wall synthesis.

  • against gram positive and gram negative bacteria - it is active against anaerobic bacteria.
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33
Q

Why would you not prescribe meropenem to someone who has a history of penicillin alllergy

A

Because it has a similar structure to penicillin , but nowadays it is considered safe.

34
Q

What is meropenem strongest against ?

A

E.Coli

Pseudomonas aeruginosa

Staphylococcus aureus

35
Q

What antibiotic out of the B-lactams is considered the reserve antibiotic for gram negative infections ?

A

Carbapenems

36
Q

Mechanism of action of glycopeptides?

A

Inhibits cell wall synthesis

37
Q

What is the main glycopeptides ?

A

Vancomycin

38
Q

What is vancomycin active against ( this is a g, glycopeptides)

A

Aerobic and anaerobic bacteria.

Gram +ve

39
Q

What is a limitation of using vancomycin? ( a glycopeptides)

A

It has a very narrow therapeutic window , so the patient needs to have a therapeutic drug monitoring to ensure the drug does not come toxic.

40
Q

What is the method of administration for vancomycin?

A

IV especially for systemic infections because it isn’t absorbed via the gut.

41
Q

What is the exception for giving IV vancomycin?

A

In the case of a C.diff infection whereby it is given orally because the target is the GIZ TRACT.

42
Q

What is another glycopeptides other than vancomycin?

A

Teucoplanin

43
Q

What is the advantage of teicoplanin relative to vancomycin?

A

Teicoplanin has a larger therapeutic index and is therefore much easier to monitor with the risk of toxic dose being less likely.

44
Q

What are the two types of tetracyclines?

A

Doxycycline and tetracyclines

45
Q

Are tetracyclines /doxycycline bacteriostatic or bactericide?

A

Bacteriostatic because they inhibit protein synthesis of the bacteria which holds them In the stationary phase of the growth cycle - instead of killing them outright .

46
Q

What is a good choice of medication for people with penicillin allergy ?

A

Doxycycline and tetracycline ( classes of tetracycline)

47
Q

Tetracyclines / doxycycline are active against which bacteria ?

A

Gram positive

48
Q

Tetracyclines/doxycycline are effective against which illness especially?

A

Chlamydia

Rocky Mountain spotted fever

Typhoid fever

49
Q

Why should tetracycline/doxycycline not be used for streptococcal infections ?

A

Because unto 44% of S.pyogenes and 74% of S.faecalis have been found to be resistant to tetracyclines.

50
Q

Why can’t tetracycline be given to children younger than 12 years ?

A

It causes yellowing of the teeth among other adverse effects

51
Q

Why is tetracyclines given via IV instead of IM ?

A

Bioavailability of tetracycline is 100% via IVbut only49% via IM.

52
Q

What is the most common aminoglycosides ?

A

Gentamicin

53
Q

Gentamicin ( aminoglycosides) activity is targeted towards mainly what organisms ?

A

Gram negatives

54
Q

Mechanism of action of aminoglycosides?

A

Inhibiting protein synthesis

55
Q

Why is gentamicin ( aminoglycosides) normally reserved for gram negative sepsis ?

A

Because it has very good activity in the blood and urine.

  • good strength and lack of resistance .
56
Q

What are the side effects of gentamicin?

A

It is nephrotoxic

Ototoxicity

57
Q

What does nephrotoxic mean ?

A

It attacks cells of the proximal convulsed tubule in the kidney - but the cells do regenerate even if the drug is continued to be taken .

58
Q

What does otoxicity mean

A

Causes damage to the ear

It causes irreversible damage to the hair cells of the cochlea which leads to a loss of high frequency hearing .

59
Q

What are the two main macrolides ?

A

Erythromycin and carithromycin

60
Q

Mechanism of action of macrolides ?

A

Inhibits protein synthesis

61
Q

Why are macrolides good alternatives in patients with a penicillin allergy for mild gram positive infections ?

A

Similar spectrum of action

62
Q

What is erythromycin good in treating ?

A

Atypical pathogens in pneumonia

63
Q

Commonest example of quinolones

A

Ciprofloxacin - gram negative bacteria such as E. coli , shigella , salmonella

64
Q

Mechanism of action of quinolone

A

Inhibit DNA hyraxes

65
Q

What is used to treat UTIs?

A

Trimethoprim

66
Q

Mechanism of action of trimethoprim and sulphonamides?

A

Inhibitors of the folic acid cycle.

67
Q

Why shouldn’t trimethoprim and sulphonamides be given to pregnant women ?

A

Because they inhibit the folic acid cycle which is essential in pregnant women,

68
Q

When trimethoprim is combined with sulphonamides, sulfamethoxazole, what does it form ? And what is this combination often used to treat ?

A

Co trimoxazole which is used to treat pneumocystis pneumonia

69
Q

What are the two main families of antifungals ?

A

1) Azores

2) polyenes

70
Q

What are azoles active against ?

A

Yeasts

71
Q

Mechanism of action of azoles ?

A

Inhibit cell membrane synthesis

72
Q

An example of an azole and what is is used to treat

A

Fluconazole used to treat candida

73
Q

Polyenes mechanism of function

A

Inhibit cell membranes function

74
Q

Examples of polyenes

A

Nystatin and amphotericin

75
Q

What is nystatin used to treat a.

A

Topical treatment of candida

76
Q

What is amphotericin used to treat ?

A

IV treatment for systemic fungal infections eg aspergillus

77
Q

Two classes of anti virals

A

Aciclovirand osteltamivir

78
Q

Mechanism of action of aciclovir

A

When phosphorylates it inhibits viral DNA polymerase

79
Q

Outline the process of developing resistance from mutations

A

1) within a population of bacteria , a random mutation occurs. Some bacteria would develop antibiotic resistant traits.
2) on introduction to a selection pressure ie antibiotic , only these resistant cells will survive and thus selected for.
3) this causes resistant bacteria to reproduce which leads to a population which is entirely resistant to the antibiotic.

80
Q

What is another way antibiotic resistant genes may be transferred across a population of bacteria other than reproduction ?

A

Horizontal gene transfer

Infection (24 decks)

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