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ANTIBIOTICS > Y3 Antibiotics > Flashcards

Y3 Antibiotics Flashcards

1
Q

What two groups of bacteria are penicillins active against?

A

Staphylococci and Streptococci

gram-positive

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2
Q

How do penicillins work?

A

Inhibit the enzyme responsible for synthesising the bacterial cell wall (X-linking of peptidoglycan)

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3
Q

What is the active group on penicillins?

A

Beta-lactam ring

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4
Q

How do bacteria become resistant to antibiotics?

A

By synthesising the enzyme beta-lactamase

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5
Q

What are some of the simplest forms of penicillin?

A

Benzyl-penicillin and Phenoxymethypenicillin

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6
Q

What are BenPen and Phenoxymethypenicillin (penicillin V) used to treat usually?

A

STREP INFECTIONS: Pneumonia (in combination with macrolide)
Tonsilitis
Endocarditis
SSTIs +fluclox

CLOSTRIDIAL INFECTIONS:
Tetanus

MENINGOCOCCAL INFECTIONS:
Meningitis and septicaemia

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7
Q

Which penicillins have anti-pseudomonad properties?

A

TAZOCIN: tazobactam and piperacillin

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8
Q

What particular agent does tazocin have good action against?

A

Pseudomonas Aeruginosa

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9
Q

Why is tazobactam a useful addition? What agents does tazocin thus cover that other penicillins do not?

A

It is a beta-lactamase inhibitor and so fewer organisms are resistant to tazocin.

Staph. Aureus and gram-negative anaerobes

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10
Q

What sorts of infections is tazocin particularly useful in?

A

HCAIs (usually quite multi-resistant organisms:

  • HAP
  • Hospital acquire UTI
  • Intra-abdominal sepsis
  • SSTI
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11
Q

What are some adverse effects of tazocin?

A

Abx associated colitis

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12
Q

What are some examples of broad spectrum penicillins?

A

Amoxicillin and Co-amoxiclav

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13
Q

What makes amoxicillin more useful against gram-negative bacteria?

A

It has an amino chain attached to its beta-lactam ring

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14
Q

What can we do to make amoxicillin even more broad spectrum?

A

Add clavulanic acid to make co-amoxiclav

- Clavulanic acid is an example of a beta lactase inhibitor

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15
Q

What is one of the main uses of amoxicillin and why?

A

Empirical treatment for pneumonia? Covers the common gram positive causes: Strep Pneumoniae and the common gram negative causes: haemophilus influenzae

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16
Q

What are some of the less common uses for amoxicillin?

A

Empirical treatment for UTIs (usually trimethoprim and nitrofurantoin)
Part of treatment for an HCAI or intrabdominal sepsis
Part of treatment for H. pylori associated peptic ulcers

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17
Q

What are some penicillinase resistant antibiotics? How do they achieve this?

A

Flucloxacillin

Addition of an acyl group make them resistant to many lactase enzymes

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18
Q

What organism is flucloxacillin particularly useful against?

A

Staphylococcus aureus (NOT ALL STRANDS) MRSA is resistant to fluclox.

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19
Q

What sorts of infections is flucloxacillin particularly good at treating?

A

SSTIs

We can use it in combination with BenPen if particularly severe but can often cover alone

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20
Q

What are some of the less common infections that flucloxacillin can be used for?

A

Osteomyelitis and septic arthritis and endocarditis

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21
Q

How do cephalosporins and carbapenems work?

A

With a beta-lactam ring

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22
Q

How are cephalosporins and carbapenems different from penicillin?

A

Side groups (dihydrothiazine ring - cephs) and (hydroxyethyl ring - penems) make them less resistant to beta-lactamases

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23
Q

Are cephalosporins and carbapenems typical narrow or broad spectrum?

A

Broad. The newer ones even more so

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24
Q

What are some examples of cephalosporins?

A

Cefalexin, cefotaxime, cephradine

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25
Q

What are some examples of carbapenems?

A

Meropenem and ertapenem

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26
Q

What are some of the more common uses of cephalosporins?

A

2nd and 3rd line treatment for UTIs and LRTIs

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27
Q

What sorts of infections are cephalosporins and carbapenems used for?

A

Cephalosporins and carbapenems are usually reserved for very severe or very complicated infections because they have such broad spectrum activity.
They are able to cover most infections

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28
Q

How does trimethoprim work?

A

it inhibits folate synthesis and thus stops bacteria from being able to replicate DNA

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29
Q

Is trimethoprim broad or narrow spectrum?

A

BROAD. Especially against gram negative enterobacteria e.g. E.coli

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30
Q

What can we add to trimethoprim to make it even broader spectrum? How does this work?

A 
A sulphonamide (sulphamethoxazole). Another type of folate inhibitor but it works in a different way and so their effects can be additive.
CO-TRIMOXAZOLE
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31
Q

What are some common uses of trimethoprim?

A

First line for UTI. 200mg PO BD.

Alternative are nitrofurantoin and piperacillinam

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32
Q

What is a common use for co-trimoxazole?

A

Pneumocystis pneumonia in people with immunosuppression e.g. HIV

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33
Q

What are some of the contra-indications for trimethoprim?

A

FIRST trimester of pregnancy (neural tube defects)

34
Q

How does nitrofurantoin work?

A

It is metabolised by bacteria and the active form Nitrofuran is produced which damages bacterial DNA

35
Q

What organisms is nitrofurantoin useful against?

A

Gram positive and gram negative agents that commonly cause UTI

36
Q

What organisms is nitrofurantoin less useful against?

A

Ones that have reduced activity of nitrofuran reductase

37
Q

What is the most common reason for using nitrofurantoin?

A

Uncomplicated UTI

38
Q

What are some of the contraindications of nitrofurantoin?

A

Do not use in pregnancy at all or in the first 3 months of life.

39
Q

How do tetracyclines work?

A

They inhibit protein synthesis by binding to 30s sub-units and are hence bacteriostatic

40
Q

What are some examples of tetracyclines?

A

Doxycycline and Lymecycline

41
Q

Are tetracyclines broad or narrow spectrum?

A

Relatively broad

42
Q

How do bacteria develop resistant to tetracyclines?

A

Develop an efflux pump to pump them out

43
Q

What are some of the adverse effects of tetracyclines?

A

GI symptoms but they are some of the lowest risk for C Diff

44
Q

What are some of the most common uses for tetracyclines?

A

Acne Vulgaris: particularly when there are inflamed papule caused by propionibacterium acnes

LRTI including infective exacerbation of COPD and atypical pneumonias

Chlamydial infection including PIFD

Typhoid, Anthrax, malaria and lyme disease

45
Q

What are some of the contraindications for tetracylines?

A

Bind teeth and bones during development so do not give during pregnancy

46
Q

How do aminoglycosides work?

A

Similarly to tetracyclines - they bind irreversibly to 30S subunits and hence inhibit protein synthesis

47
Q

Are aminoglycosides bactericidal or bacteriostatic?

A

Bactericidal - they have other mechanisms of action which are largely not-understood. It is likely one of these which causes them to be bactericidal

48
Q

What are some examples of aminoglycosides?

A

Gentamicin and Streptomycin

49
Q

Which organisms are aminoglycosides useful against?

A

Gram negative aerobic bacteria (neisseria meningitides and gonorrhoea and campylococci, staphylococci and mycobacteria

50
Q

How do aminoglycosides enter the bacterium cell?

A

Via OXYGEN-dependent channels (hence anaerobes innately resistant)

51
Q

How do some aerobes develop resistance against aminoglycosides?

A

Changing the permeability of their membranes

52
Q

How can we attempt to overcome aerobe resistance to aminoglycosides?

A

If we give them with penicillins then penicillins can help to weaken the cell membrane and again improve the permeability

53
Q

What are some contraindications of aminoglycosides?

A

They are nephrotoxic and ototoxic

54
Q

Through what route to we give aminoglycosides?

A

Always IV. They do not cross lipid membranes and so cannot be given orally.

55
Q

What are some of the most common uses for aminoglycosides?

A 
Severe sepsis (usually when the source has been identified
Pyelonephritis and complicated UTIs
Biliary and other intra-abdominal sepsis 
Endocarditis
56
Q

How do Macrolides work?

A

They inhibit protein synthesis by binding to the 50S sub-unit

57
Q

What are some examples of macrolides?

A

Erythromycin, Clarithromycin, Azithromycin

58
Q

Are macrocodes bacteriostatic or bactericidal?

A

Bacteriostatic

59
Q

Are macrocodes broad or narrow spectrum? Which ones are broadest?

A

Relatively broad

Clarithromycin and azithromycin have an even broader spectrum towards gram-negatives particularly heamophilus influenzae

60
Q

How do bacteria become resistant to macrolides?

A

Ribosome mutations

61
Q

What are some adverse effects? Which macrolides are most likely to cause them?

A

C. difficile overgrowth colitis.
Erythromycin is the most common abx to cause this

Can also cause ototoxicity and cholestatic jaundice
Prolong QT interval

62
Q

What are macrolides most commonly used for?

A

LRTI (Clarithromycin when penicillin is contraindicated due to allergy)
SSTI (when penicillin is CId because of allergy)
Severe pneumonia (added to penicillin to cover atypical e.g. legionella or mycoplasma)
Eradication of H.pylori (part of triple therapy with PPI and amoxicillin)

63
Q

How do quinolones work?

A

Inhibit DNA synthesis

64
Q

What are some examples of quinolones?

A

Ciprofloxacin, Levofloxacin

65
Q

Which organisms are quinolones most effective against?

A

Gram negative bacteria

66
Q

Which quinolone has a broader spectrum?

A

Levofloxacin - better effect against gram positives and so can be used for LRTIs.
Commonly used after tazocin in HAP

67
Q

How do organisms develop resistance against quinolones?

A

Decreasing permeability or increasing efflux to reduce the intra-cellular concentration

68
Q

What are some of the most common uses of quinolones?

A

UTI
Severe GI infection (shigella or campylobacter)
LRTI
Cipro is one of the only abx with use against pseudomonas aeruginosa

69
Q

What are some adverse effects of quinolones?

A

Can cause C.diff with hyper-virulent 027 strain

70
Q

How do glycopeptides work?

A

Inhibits growth and X-linking of peptidoglycan

71
Q

Which strains of bacteria are glycopeptides effective against?

A

Gram positives

72
Q

What is the most common example of a glycopeptide?

A

Vancomycin

73
Q

What are some of the most common adverse effects of vancomycin?

A

Thrombophlebitis at infusion site and in extreme cases Red-Man Syndrome (widespread anaphylaxis)
Nephrotoxic and ototoxic

74
Q

What are some of the most common uses of vancomycin?

A

Endocarditis (when severe or if MRSA)

Treatment for abx associated colitis due to C.diff (125mg PO for 10-14 days)

75
Q

What is an examples of an anaerobic anti microbial?

A

metronidazole

76
Q

How does metronidazole work?

A

Enters bacterium via passive diffusion and produce a NITROSO free radical during its metabolism. This binds to DNA and reduces synthesis

77
Q

Which organisms are resistant to metronidazole?

A

Aerobes - they cannot metabolise it and so are innately resistant

78
Q

What are some adverse effects of metronidazole? What are some warnings to give when prescribing?

A

GI upset as well as peripheral optic neuropathy, seizures and encephalopathy

DO NOT DRINK WITH ALCOHOL because enzyme acetylaldehyde dehydrogenase is inhibited (profuse vomiting, flushing and nausea)

79
Q

What are some contra-indications for giving metronidazole?

A

Liver disease (they are metabolised by the CYP450 system)

80
Q

What is metronidazole commonly used for?

A

Antibiotic associated colitis with c. diff
Oral infections (dental abscess or aspiration pneumonia)
Surgical and gynaecological infections
Protozoal infections including dysentry and giardiasis

ANTIBIOTICS (1 decks)

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