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Microbiology > Beta-lactams (Antibiotics Part 1) > Flashcards

Beta-lactams (Antibiotics Part 1) Flashcards

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Biology 101 flashcards
1
Q

What are the components of the wall in a gram positive bacteria?

A

Cell membrane

Peptidoglycan cell wall

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2
Q

What is the structure of the wall of gram negative bacteria?

A

Cell membrane
Peptidoglycan cell wall
Outer membrane
Periplasm

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3
Q

Name four areas of a bacterium that an antibiotic may target.

A

Cell wall peptidoglycan
Metabolism within the bacterium
DNA
Ribosomes

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4
Q

Describe bactericidal antibiotic action.

A

Achieve sterilisation of the infected site by directly killing bacteria.
- lysis of bacteria can lead to release of toxins and inflammatory material

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5
Q

Describe bacteriostatic antibiotic action.

A

Suppresses growth but does not directly sterilise the infected site
- requires additional factors to clear bacteria-immune mediated killing

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6
Q

What is an antibiotic spectrum.

A

Spectrum refers to the range of bacterial species effectively treated by the antibiotic

  • can vary widely even within the same antibiotic class
  • be aware of difference between lack of activity and resistance
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7
Q

Name a broad spectrum antibiotic.

A

Meropenem - active against almost all gram positive and gram negative species
- resistance is rare except for MRSA

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8
Q

Name a narrow spectrum antibiotic.

A

Benzyl-penicillin - highly active against streptococci

- most other disease causing bacteria are resistant

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9
Q

Describe broad spectrum antibiotics.

A

Antibiotics that are active against a wide range of bacteria
- treat most causes of infection, but also have a substantial effect on colonising bacteria

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10
Q

Describe narrow spectrum antibiotics.

A

Antibiotics that are active against a limited range of bacteria
- have a much more limited effect on colonising bacteria

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11
Q

When a narrow spectrum antibiotics useful, and when are broad spectrum antibiotics.

A

Narrow - useful when you know the cause of the infection

Broad - when someone is very acutely ill, and you don’t know which bacteria is causing it

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12
Q

Name 2 anaerobes that may infect a patient.

A

Bacteroides

Clostridium

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13
Q

Name 4 gram positive bacterial groups.

A

Clostridium
Steptococcus
Enterococcus
Staphylococcus

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14
Q

Name 6 gram negative bacterial groups.

A 
Bacteroides
Pseudomonas
Haemophilus
Neisseria 
Other coliforms
E.Coli
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15
Q

Describe guided therapy use in regards to antibiotic treatment.

A

Depends on identifying cause of infection and selecting an agent based on sensitivity testing
Gold standard - but means you have to wait 48hrs for the lab results, which isn’t always possible in very ill patients

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16
Q

Describe empirical therapy in regards to antibiotic treatment.

A

Best (educated) guess therapy based on clinical acumen

Used when therapy cannot wait for culture

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17
Q

Describe prophylactic therapy in regards to antibiotic treatment.

A

Preventing infection before it begins, e.g. in immunocompromised patients.

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18
Q

Antibiotic associated harm. Overgrowth of yeast and bowel flora leads to…..?

A

Yeast - thrush

Bowel flora - diarrhoea

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19
Q

How does antibiotic use lead to development of C.diff colitis.

A

Antibiotics unbalance the natural flora and resistant organisms already in the local environment colonise

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20
Q

Compare the impacts of narrow and broad spectrum antibiotics on colonisation.

A

Narrow - achieve clinical cure with as little impact on colonisation and resistance as possible
- penetration can be limited to site of infection
Broad - accept that impact on colonisation and resistance may be greater
- penetration broadly throughout the body (don’t know where the infection is)

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21
Q

What is the largest class of antibiotics?

A

Beta-lactams

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22
Q

Name the four sub-classes of antibiotics within beta-lactams?

A

Penicillins
Cephalosporins
Carbapenems
Monobactams

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23
Q

List some of the most important beta-lactam antibiotics.

A 
Penicillins
- Benzylpenicillin
- Flucoloacillin
- Amoxicillin 
Cephalosporins
- Ceftriaxone
Carbapenems
- Meropenem
Monobactams
- Aztereonam
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24
Q

What are the components of Augmentin and Tazocin?

A

They are both combination beta-lactams.
Augmentin - amoxicillin/clavulanic acid
Tazocin - piperacillin/tazobactam

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25
Q

Describe the mechanism of action of beta-lactams.

A

Beta-lactam motif analogue of branching structure of peptidoglycan. This inhibits cross-linking of cell wall peptidoglycan, and lysis of bacteria
Bacteriostatic

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26
Q

What do beta-lactamases target?

A

The ring of the beta-lactam antibiotics

27
Q

Which bacteria most commonly secrete beta-lactamases?

A

Gram negatives and S.aureus.

28
Q

How are beta-lactams usually administered?

A

IV (poorly absorbed by GI tract and normally excreted unchanged into urine and bile)
Some are given orally (causes vomiting)

29
Q

Which beta-lactams can be given orally?

A

amoxicillin and flucloxacillin

30
Q

What are the possible adverse effects of giving beta-lactams?

  • GI toxicity
  • Hypersensitivity
  • Infection
  • Rare
A

GI toxicity - nausea, vomiting, diarrhoea and cholestasis.
Hypersensitivity - type 1, type 4, interstitial nephritis
Infection - candidiasis, C.diff and resistant bacteria
Rare - seizure, haemolysis and leukopenia

31
Q

What are the complications of type 1 hypersensitivity reactions?

A

Urticarial rash - itchy and rasied

Anaphylaxis

32
Q

Why must you be careful when a patient claims to be allergic to an antibiotic?

A

They usually mean there are GI symptoms or there is a therapeutic failure, rather than a hypersensitivity reaction

33
Q

Can a patient with an allergy to a penicillin be given other antibiotics?

A

They will usually be allergic to other penicillins.

But cross-reactivity with other antibiotic classes are much lower (e.g. other beta-lactams)

34
Q

What is the first choice antibiotic for serious streptococcal infections?

A

Benzylpenicillin

  • IV route
  • narrow spectrum (not good at treating anything other than streptococcus)
35
Q

Describe how amoxicillin is a semi-synthetic penicillin.

A

As resistance towards it increased, scientists modified a small area on one of the side chains.
- amino penicillin

36
Q

Is amoxicillin broad or narrow spectrum?

A

Broad

  • good action against most gram positives (except staphylococcus)
  • good action against haemophilus and neisseria (gram negative)
37
Q

For what conditions is amoxicillin normally given?

A

Chest infections

  • COPD flare up
  • pneumonia
38
Q

Which penicillin was developed to be resistance against beta-lactamase produced by staphylococcus?

A

Flucloxacillin

39
Q

What is Flucloxacillin active against?

A

Staphylococcus aureus (not MRSA)
Steptococci
No gram negative action

40
Q

Name the two beta-lactamase inhibitors

A

Clavulanic acid

Tazobactum

41
Q

What is the purpose of co-administering beta-lactamases with penicillin?

A

Greatly broadens the spectrum of penicillins that work against gram negatives and S.auerus.

42
Q

Which penicillins are clavulanic acid and tazobactum co-administered with? (respectively)

A

Clavulanic acid and amoxicillin = co-amoxiclav

Tazobactum and piperacillin = tazocin

43
Q

Which bacteria are co-amoxiclav active against?

A 
Gram positives (not MRSA)
Gram neagtives (not Pseudomonas)
44
Q

Which bacteria are tazocin active against?

A 
Gram positives (not MRSA)
Gram negatives
45
Q

What is the go to antibiotic for very ill patients?

A

Tazocin

46
Q

Which drug is more susceptible to beta-lactamases, cephalosporins or penicillins?

A

Cephalosporins

- and they have good activity against gram positives and gram negatives

47
Q

Multiple generations of cephalosporins have been adapted as people have adapted over time. What happens to the spectrum with each generation?

A

Gram negative spectrum increases, with some loss of gram positive activity.
Latest generation is MRSA active

48
Q

Name a cephalosporin

A

Ceftriaxone

49
Q

What is Ceftriaxone active against?

A 
Gram positive (not MRSA or enterococcus)
Gram negative (not pseudomonas)
50
Q

Are cabapenems active against beta-lactamases?

A

Yes, but there are new beta-lactamases emerging which can lyse carbapenems

51
Q

Do carbapenems have a good spectrum of treatment?

A

Excellent spectrum against gram positives and negatives - ultra broad spectrum antibiotics

52
Q

Describe which bacteria Meropenem is active against?

A

EVERYTHING

- except MRSA

53
Q

Why isn’t Merpenem used more often?

A

It’s very effective, so we don’t want bacteria to develop resistance too quickly

54
Q

What is the only member of Monobactam class?

A

Aztreonam - being used more as doctors avoud using Merpenem

55
Q

What bacteria are Aztreonam active against?

A

Good activity against gram negative bacteria, and no effect at all against gram positive

56
Q

What class does Vancomycin belong to?

A

Glycopeptide class

57
Q

What is the mechanism of action of Vancomycin?

A

Inhibits cell wall formation in gram positives only (can’t fit though the thicker wall in gram negatives)

58
Q

Why does Vancomycin work on MRSA?

A

Not dependent of penicillin binding proteins - so it’s effective against resistant organisms

59
Q

How is Vancomycin administered?

A

Not absorbed from GI tract - must be given IV
If C.diff present in the gut needs treatment - should be given orally (doesn’t need to pass the gut wall to encounter the bacteria)

60
Q

What are the possible effects of Vancomycin toxicity?

A

Nephrotoxicity - more likely with higher doses
Red-man syndrome if injected too rapidly
- anaphlactoid reaction (rare)
Ototoxicity

61
Q

What is the main clinical issue with Vancomycin?

A

Underdosing - people are worried about toxicity

62
Q

Which antibiotic mentioned somewhere in these flashcards requires therapeutic drug monitoring?

A

Vancomycin

  • narrow therapeutic range
  • concentration is higher in severe illness
63
Q

For what conditions is Flucloxacillin normally given?

A

Soft tissue injury

  • Wound infection
  • Cellulitis

Microbiology (21 decks)

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