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3 - Infection & Immunity > Antibacterials > Flashcards

Antibacterials Flashcards

1
Q

What are the 4 categories of antimicrobial agents?

A

Antibacterial, antiviral, antifungal and antiprotozoal

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2
Q

What is the difference between a bactericidal and bacteriostatic antibacterial agent?

A

Bactericidal - destroy bacteria

Bacteriostatic - inhibit bacterial replication

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3
Q

What do we mean by “spectrum” when referring to antibacterials?

A

Antibacterials can be broad or narrow spectrum. Broad spectrum antibacterials work against multiple types of bacterial species. Narrow spectrum antibacterials may be serotype, species, genus, or gram specific

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4
Q

What are the ideal features of antimicrobial agents?

A 
Selective toxicity
Minimal adverse affects
Reach site of infection
Oral/IV formulation
Long half-life
No interference with other drugs
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5
Q

What do the 4 classes of antibacterials target as their mechanism of action?

A

1 - cell wall synthesis (stability)
2 - protein synthesis (growth)
3 - nucleic acid synthesis (replication)
4 - cell membrane function (survival)

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6
Q 
Class 1 antibacterials target what bacterial function?
Give the 2 main types of class 1 antibacterial
A

Cell wall synthesis

Beta-lactams and glycopeptides

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7
Q 
Class 2 antibacterials target what bacterial function?
Give the 3 main types of class 2 antibacterial
A

Protein synthesis

Tetracyclines, aminoglycosides and macrolides

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8
Q 
Class 3 antibacterials target what bacterial function?
Give the main type of class 3 antibacterial
A

Nucleic acid synthesis

Quinolones

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9
Q 
Class 4 antibacterials target what bacterial function?
Give the main type of class 4 antibacterial
A

Cell membrane function

Polymixins

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10
Q 
What class of antibacterial and type of this class is penicillin?
How does penicillin produce its antibacterial effect?
A

Class 1 beta-lactam
Binds to penicillin binding protein inhibiting the cross-linking of cell wall peptidoglycans, causing the cell wall to destabilise and fragment

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11
Q 
What class of antibacterial and type of this class is vancomycin?
How does vancomycin produce its antibacterial effect?
A

Class 1 glycopeptide
Vancomycin sits on the cross-linking site sterically preventing the formation of cross-links causing the cell wall to destabilise and fragment

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12
Q

What class of antibacterial and type of this class are fluoroquinolones? How do they produce its antibacterial effect?

A

Class 3 Quinolones
Interfere with DNA replication by binding to topoisomerase IV and DNA gyrase so bacterial chromosomes can’t be unraveled and transcribed

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13
Q

What are the 3 main mechanisms of antibiotic resistance?

A

Drug inactivating enzymes - Beta-lactamases

Altered targets - D-lactate in vancomycin resistance, penicillin-binding protein with a lower affinity for beta-lactams in methicillin resistance

Altered drug uptake - decreased permeability (beta-lactams), increased efflux (tetracyclines)

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14
Q

By what 2 general mechanisms can antibiotic resistance be obtained?

A

Chromosomal gene mutation

Horizontal gene transfer

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15
Q

What are the 3 main forms of horizontal gene transfer?

What are the 3 main types of bacterial genetic information?

A

Conjugation, transduction, transformation

Chromosomes, plasmids, transposons

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16
Q

What 2 methods can be used to test antibiotic activity?

Describe each briefly

A

Disc sensitivity testing - An agar plate has a bacterium containing solution spread over it then a ring of antibiotic discs are laid out upon it. The radius of the ring where colonies fail to grow indicates the efficacy of that antibiotic.

Minimum inhibitory concentration - An antibiotic is serially diluted (2ml, 1ml, 0.5ml etc) in tubes and lined up, compare tubes to a positive and negative control and last dilution before appearance of bacteria in broth indicates minimum

17
Q

What are the 4 main types of beta-lactams?

A

Penicillins
Cephalosporins
Carbapenems
Monobactams

18
Q

Describe where each of these penicillins are most effective:
Penicillin
Amoxicillin
Flucloxacillin

A

Penicillin - streptococci (most now resistant)
Amoxicillin - gram positives and some gram negatives
Flucloxacillin - staphylococci and streptococci

19
Q

Describe where each of these beta-lactamase inhibitor combinations are most effective:
Co-amoxiclav
Piperacillin

A

Co-amoxiclav - staph, strep, anaerobes and more gram negatives
Piperacillin - staph, strep, anaerobes and even more gram negatives inc. pseudomonas

20
Q

What microbes are the cephalosporins effective against?

What microbes are they not effective against?

A

Gram negatives

Anaerobes

21
Q

Which cephalosporin would be used to treat meningitis and why?

A

Cetriaxone

Good activity in CSF

22
Q

What concern is associated with cephalosporins?

A

Increased incidence of C Diff infection

23
Q

What is the most useful group of broad spectrum antibiotics? Name one of these.
What microbes are they effective against?

A

Carbapenems
Meropenem
Most gram negatives inc. anaerobes

24
Q

Carbapenems are useful for patients with what condition?

A

Penicillin allergy

25
Q

What microbes are the glycopeptides effective against?
Which glycopeptide is used to treat C Diff and why?
What concerns should you have when prescribing this?

A

Most gram positives
Vancomycin - orally administered it is not absorbed in the GI tract
Narrow therapeutic window

26
Q

Describe the antibiotic effects of tetracycline and how it is administered.
Name 3 patient conditions in which you would consider tetracycline.
To what patients must tetracycline not be prescribed?

A

Broad spectrum against gram positives administered orally

Penicillin allergy, pneumonia caused by atypical pathogens, chlamydia

Children under 12

27
Q

What is the most common aminoglycoside used?
What microbes is it effective against?
What concerns do we have when prescribing it?
On what occasion is it generally used?

A

Gentamicin
Gram negative bacteria
Nephrotoxicity and ototoxicity
Severe gram negative sepsis

28
Q

Name a macrolide and the bacteria it is effective against.

What positive attributes does this macrolide have?

A

Erythromycin
Gram positives
Well distributed inc. intracellular penetration

29
Q

What is the most commonly prescribed quinolone and what is its target?
What bacteria is it effective against?
What concerns do we have regarding this antibiotic?

A

Ciprofloxacin
Inhibits DNA gyrase
Gram negatives and atypical pathogens
Increasing resistance and risk of C Diff

30
Q 
What class of antibiotic is trimethoprim?
What does trimethoprim inhibit?
In what conditions is trimethoprim prescribed?
A

Class 3
DNA synthesis and folic acid synthesis
UTIs, middle ear infections and traveller’s diarrhoea

31
Q

What antibiotic is trimethoprim combined with to produce co-trimoxazole?
In what conditions is it prescribed?

A

Sulfamethoxazole

Pneumocystis pneumonia in HIV, MRSA, UTIs

3 - Infection & Immunity (7 decks)

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