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Week 102 > Antibiotics > Flashcards

Antibiotics Flashcards

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1
Q

What is the MOA of beta lactams?

A

Cell wall synthesis inhibitors –> high osmotic pressure inside bacteria draws fluid in –> bacteria swells and lysis occurs. AB-enzyme complex also stimulates release of autolysins which cause autodigestion of the bacteria.

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2
Q

How does cell wall synthesis occur in bacteria?

A

NAG + NAM + 5 AAs = PG precursor
PG precursor leaves cell and binds with cell wall acceptor molecules outside of cell, and transglycosylation and transpeptidation are catalysed by PENICILLIN BINDING PROTEINS (PBPs): transpeptidase and D-alanine carboxypeptidase.

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3
Q

Which type of bacteria are beta lactams most effective against and why?

A

Gram positives because they have a thick outer cell wall

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4
Q

Are beta lactams bactericidal or bacteriostatic?

A

Bactericidal as AB-enzyme complex causes release of autolysins -> autodigestion

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5
Q

What are the different classes of beta lactams?

A

Penicillins, cephalosporins, carbapenems

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6
Q

Name some penicillins

A

Benzylpenicillin (Pen G)
Phenoxymethylpenicillin (pen V)
Flucloxacillin
Co-amoxiclav (amoxicillin + clavulanic acid)

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7
Q

Uses of penicillins?

A

Gram +ve but not beta lactamase, gram -ve. AEROBES.

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8
Q

Uses of benzylpenicillin

A

Strep inc strep pneumonia (pneumococcal)
Meningococcal (N. meningitidis) - not first line anymore
Gonococca (N. gonorrhoea)

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9
Q

Which penicillin has inherent beta lactamase resistance?

A

Flucloxacillin

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10
Q

Which AB causes cholestatic jaundice?

A

Flucloxacillin

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11
Q

What is particular indication of flucloxacillin?

A

Beta lactamase producing staph

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12
Q

What is the role of clavulanic acid?

A

Extends spectrum of amoxicillin by inactivating beta-lactamase; coamoxiclav

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13
Q

What is the toxicity of penicillins?

A

Generally safe; hypersensitivity reactions can occur.

Cholestatic jaundice in _______

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14
Q

Name some cephalosporins

A

ceftriaxone, cefataxime… cef______

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15
Q

What is the spectrum of cephalosporins

A

Broad spectrum - similar to penicillin but increased potency; active against gram + and -, but greater against +ve due to cell wall.
Beta lactamase - effective against beta lactamase producing staph

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16
Q

Indication of cephalosporins

A

Serious life threatening infections with unknown cause e.g. thought to be due to pneumonia, meningitis, septicaemia

Beta lactamase producing staph infections

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17
Q

Toxicity of cephalosporins

A

Similar to penicillins; hypersensitivity

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18
Q

Use of cephalosporins in penicillin allergic patients?

A

No, as the hypersensitivity is related to the beta lactam ring and so often HS to both

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19
Q

What is the only synthetic beta lactam?

A

carbapenems

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20
Q

Name some carbapenems

A

Imipenem, ertapenem, carbapenem

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21
Q

Spectrum of carbapenems?

A

V broad spectrum; +ve, -ve, anaerobes

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22
Q

Indications of carbapenems?

A

Nosocomial infections thought to be due to multi resistant organisms or a mixed bag

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23
Q

Toxicity of carbapenems

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A

Increased risk of AEs due to commensal bacteria disruption e.g. colitis, superinfection such as C diff, candida

24
Q

Name drugs that inhibit bacterial cell wall synthesis

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A

Beta lactams:
Penicillins; benpen (G), phenoxymethyl (V), amoxi, coamoxiclav, fluclox
Cephalosporins; ceftriaxone, cef_____
Carbapenems; imipenem, ertapenem, carbapenem

25
How do protein synthesis inhibitors work?
DNA is unwound and mRNA strands are formed in nucleus, then mRNA travels out to ribosomes in cytoplasm for translation to occur. tRNA bound to anticodon and AA recognise codons of mRNA bound to ribosome and form polypeptide chain. Protein synthesis inhibitors inhibit the protein synthesis by disturbing the ribosome at the 30s or 50s subunit, interrupting the protein synthesis by causing decreased protein synthesis or abnormal protein synthesis. They are therefore BACTERIOSTATIC
26
Are protein synthesis inhibitors bacteriocidal or bacteriostatic?
Bacteriostatic
27
Name some protein synthesis inhibitors
Aminoglycosides; -micins: gent, tobra (IV/IM), strep (TB), neo Tetracyclines; -cyclines: tetra, doxy Macrolides; -mycins: clarithro, azithro, erythro Chloramphenicol
28
Which work at 30s?
aminoglycosides; gentamicin, tobramicin | tetracyclines; doxycycline, tetracycline
29
Which work at 50s?
macrolides; erythromycin, azithromycin, clarithromycin | chloramphenicol
30
How does erythromycin work?
macrolide; at 50s subunit | prevents translocation of mRNA
31
How does doxycycline work?
tetracycline; at 30s subunit | competes with tRNA for binding with ribosome
32
How does gentamicin work?
aminoglycoside; 30s subunit causes conformational change of ribosome subunit leading to codon misreading and abnormal protein production
33
How does chloramphenicol work?
50s subunit inhibits transpeptidase
34
How is gentamicin administered?
parenteral; IV/IM
35
What are gentamicin's indications?
gram -ves e.g. kleb, e coli | staphs
36
streptamicin indications?
TB
37
toxicity of aminoglycosides?
gentamicin particularly i think: dose-related nephro/ototoxicity; monitoring needed
38
which antibiotic needs monitoring for signs of dose related nephrotoxicity?
IV/IM gentamicin
39
what is the spectrum of the tetracyclines?
broad spectrum; but increasing resistance means they're not used in much anymore chlamydia, mycoplasma, rickettsia, spirochetes
40
toxicity of tetracyclines?
stains teeth - not for children / pregnancy photosensitivity lupus / hepatitis
41
Which AB shouldnt be used in pregnant women due to effect on tooth development?
doxycycline (tetracyclines) due to staining
42
which AB causes photosensitivity
doxycycline (tetracyclines)
43
How should doxycycline be taken?
(tetracyclines in general) not with dairy as calcium lowers absorption
44
Which AB shouldnt be taken with dairy and why?
Doxycycline as calcium lowers absorption of the drug
45
Name some macrolides
-mycins: erythromycin, azithro, clarithro
46
MOA of macrolides?
interact with 50s subunit to prevent translocation of mRNA and inhibit protein synthesis
47
Spectrum of erythromycin?
Similar to penicillin; broad spectrum, affects gram -ve but not as well
48
What is a good alternative for patients with penicillin allergy?
Macrolides; erythromycin
49
Indications for erythromycin, clarithromycin (macrolides)
Penicillin allergies e.g. respiratory/skin/soft tissue infections
50
Indication for clarithromycin
Penicillin allergies, Hp triple therapy
51
Which AB is commonly used in Hp triple therapy
Clarithromycin
52
AEs of macrolides
Intestinal prokinetic properties -> D&V, abdo pain Cholestatic jaundice QTc prolongation -> ?TdP (serious)
53
MOA of chloramphenicol
50s subunit
54
Indications of chloramphenicol
Meningitis / typhoid alternative tx Very rarely used except in critically ill patients
55
toxicity of chloramphenicol
Can cause bone marrow suppression; very rare but high mortality so v rarely used except in critically ill patients
56
When should chloramphenicol not be used?
Premature babies / infants: inability to conjugate and excrete leads to accumulation and can cause circulatory collapse -> grey baby syndrome
57
Which AB can lead to grey baby syndrome and why?
Chloramphenicol; in premature babies they may have inability to conj/exc --> accumulation --> circulatory collapse --> "grey baby syndrome"

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