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Antibiotics Flashcards

(61 cards)

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1
Q

What is the mode of action of penicillins?

A

Inhibit cell wall synthesis by preventing cross-linking of peptidoglycan

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2
Q

Are penicillins bactericidal?

A

Yes

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3
Q

What are the side effects of penicillins?

A

Very few

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4
Q

What is the spectrum of penicillins?

A

Narrow to broad spectrum

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5
Q

How are penicillins excreted?

A

Via the kidneys

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6
Q

Are penicillins safe in pregnancy?

A

Yes

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7
Q

What are the five types of penicillins?

A
  1. penicillin
  2. flucloaxacillin
  3. amoxicillin
  4. Peperacillin/tazobactam
  5. co-amoxiclav
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8
Q

What is flucloxacillin used to treat?

A

Only staphylococci and streptococci infections

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9
Q

How is amoxicillin absorbed?

What destroys amoxicillin?

A

Best absorbed orally

B-lactamase

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10
Q

What is the spectruum of Piperacillin/Tazobactam?

A

Broad spectrum

Will treat mostly anything even pseudomonas

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11
Q

How is piperacillin/tazobactam administered?

A

IV

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12
Q

What is Co-amoxiclav a mixture of?

A

Amoxicillin

Clavulanic acid (B-lactamase inhibitor)

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13
Q

What is the method of action for cephalosporins?

A

Inhibits cell wall synthesis by preventing cross-linking of peptidoglycan

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14
Q

Are cephalosporins bactericidal?

A

Yes

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15
Q

What are the unwanted actions of cephalosporins?

A

Kill off normal gut bacteria & allow overgrowth of C.diff causing nasty gastroenteritis

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16
Q

What spectrum to cephalosporins work across?

A

Broad spectrum, each generation is becoming progressively broader spectrum

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17
Q

How are cephalosporins excreted?

A

Via the kidneys

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18
Q

Are cephalosporins safe in pregnancy?

A

Yes

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19
Q

How do glycopeptides work?

A

Cell-wall active antobiotics, binds to the end of the growing peptide chain during synthesis of peptidoglycan & prevents cross-linking: weakening the bacterial cell wall.

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20
Q

Are penicillins bactericidals?

A

Yes

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21
Q

What is an unwanted effect of vancomycin?

A

Builds up to toxic levels in patients who have kidney failure, causing further damage.

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22
Q

What spectrum do glycopeptides work across?

A

Only active against organisms with a gram +ve cell wall

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23
Q

How are glycopeptides excreted?

A

Via the kidneys

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24
Q

How are glycopeptides administered?

What is the exception?

A

Have to be given IV

Vancomycin can be given orally in the treatment of C.diff as this way it has effect on the gut lumen.

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25
How do antibiotics that inhibit protein synthesis work?
* Attatch to bacterial ribosomes which are structurally different to mamalian ribosome
26
Are macrolides bacterocidal?
NO they are bacterostatic: this means they inhibit bacterial growth but do not kill the bacteria, the bacteria are then killed by white blood cells.
27
What is the exception to bacteriostatic antibiotics?
The aminoglycoside group, they are bacteriosidal
28
How are macrolides excreted?
By the liver, through the biliary tree and into the gut
29
How do macrolides enter bacterial cell walls?
They are lipophillic and can do so easily
30
What are macrolides useful in treating?
* infections where the bacteria enter the hosts cells * intracellular organisms (*legionella*) * Organisms without a proper cell wall (*mycoplasma, chlamydia)* * penicillin sensitive patients
31
Name some macrolides?
Erythromycin Clarithromycin Azithromycin
32
Name an aminoglycoside?
Gentamicin (IV)
33
How are aminoglycosides excreted?
Excreted in urine
34
How do aminoglycosides work?
Binds to ribosomes by inhibiting protein synthesis **BUT they are bactericidal** The must be given IV and very occasionally IM
35
What are aminoglycosides active against?
Mainly gram negative aerobic organisms such as coliforms and pseudomonas aerginosa
36
What are aminoglycosides used for?
Used in hospital for treating life threatening gram negative infection
37
What is the limiting factor with aminoglycosides?
They have a narrow therapeutic index; ## Footnote *there is a narrow margin between giving enough antibiotic to treat and enough to overdose*
38
What is an unwanted side effect of aminoglycosides?
Causes damage to the kidneys and the VIII cranial nerve; resulting in * renal (kidney failure) * deafness and disturbance of balance
39
Name two antibiotics that inhibit protein synsthesis but do not fit into a class
Clindamycin Chloramphenicol
40
What is clindamycin used for?
2nd line treatment of staphylococcal and streptococcal infections Active in true anaerobes
41
What is Chloramphenicol used for?
Mainly used as a tropical treatment for eye infection
42
How do tetracyclines work?
They inhibit bacterial protein synthesis by attatching to ribosomes and are bacteriostatic
43
How are tetracyclines excreted?
Via the biliary system: gut
44
What is doxycyline used for?
Tetracycline used in Tayside For infections with no proper cell wall For penicillin allergic patients
45
Name three antibiotics that work on DNA?
Metronidazole Trimethoprim Fluoroquinolone
46
How does metronidazole work?
It acts by causing strand breakage of bacterial DNA.
47
What is metronidazole used for?
Infection caused by **true anaerobes** (*bacteria that will only grow when there is no oxygen present in the atmosphere*) i.e. C.diff Some infections caused by protozoa (*organisms that are single-celled parasites*)
48
How can trimethoprum be given?
Can be given **on its own orally** OR Can be given **in combination with sulphamethoxazole**= co-trimoxazole
49
What is trimethoprum active against?
Some gram +ve and some gram -ve organisms
50
How is trimethoprum excreted?
In the urine
51
Is trimethoprum safe in pregnancy?
From 4th month onward.
52
How do fluoroquinolones work?
Interacting with topoisomerases (*enzymes responsible for the coiling of DNA*): bacteria can no longer replicate.
53
Are fluoroquinolones bactericidal?
Yes
54
Why is the use of fluoroquinolones restricted?
As they are broad spectrum and may increase the risk of *c.difficile infection*
55
What is the unique factor regarding fluoroquinolones?
They are the **only oral antibiotic** for **pseudomonas**
56
What are the two main quinolones and what are they used for?
1. Ciprofloxacin (IV, oral) * complicated UTI infection 2. Levefloxacin (IV **only**) * **Severe CAP** in **penicillin allegic** patients
57
How do bacteria acquire resistance?
1. Genetic Mutation * misreading of DNA 2. Transfer of DNA that codes for antibiotic resistance from one bacterium to another by * transformation * conjugation * Transduction
58
What is transformation?
When bacteria die and cells break apart, '**free-floating DNA**' released into the surrounding environment may be '**scaveneged**' **by** other **bacteria** and **incorporated into their DNA**. This **DNA** may contain genes that **code** for **antibiotic** **resistance** and benefit the cell.
59
What is conjugation?
Bacteria often carry DNA in plasmids Some plasmids may carry genes that confer resistance to antibiotics When two bacteria are in close proximity to each other **a hollow bridge like structure, known as a pilus forms between** the two cells The **plasmid** **replicates** and one copy is transferred via the pilus to the other bacterium This enables a previously susceptible bacterium to acquire the antibiotic resistance
60
What is transduction?
Bacterial DNA is transferred from one bacterium to another inside a virus that infects bacteria. These viruses are called **bacteriophages** or **phages** When a phage infects a bacterium it takes over the bacterias genetic process to produce more **phage** During this process, bacterial DNA *which may code for antibiotic resistance* may be accidentaly **incorporated into the phages DNA** When the host cell dies and the phages are released from the dead cell, they will then contain DNA from the host bacterium that can be transferred to other bacterial cells
61
What are the three mechanisms of antibiotic resistance?
Altered antibiotic target binding site Destruction or inactivation of the antibiotic Increased efflux

Pharmacology (4 decks)

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