Antibugs

Question 1

Which antibiotics affect cell wall synthesis?

Answer 1

B lactams (penicillins, cephalosporins, carbapenems)
Glycopeptides (vanc, teic)

Question 2

How do b lactams work

Answer 2

Rely on the integrity of the b lactam ring for bacteriocidal activity
Bind to and inhibit the enzyme that catalyzes the cross linking btw polymer chains in the cell wall, causing weakening followed by cell lysis

Question 3

How do glycopeptides work

Answer 3

Bind the the peptidoglycan chains preventing formation of peptide x linking

Question 4

WHich antibiotics inhibit protein synthesis

Answer 4

MAcrolides
TEtracyclines
aminoglycosides
Licosamides
Chloramphenicol

Question 5

What is the difference btw bacterial and mammalian ribosomes

Answer 5

bacterial- 50s + 30s subunits
Mammalian have a 60s and 40s

Question 6

How do macrolides (erythromycin) work

Answer 6

Bind to the 50s subunit inhibiting peptide chain translocation

Question 7

How do tetracyclines work

Answer 7

Bind to the 30 s subunit and inhibit binding of aminoacyl-tRNA

Question 8

How do aminoglycosides work?

Answer 8

Also bind to the 30s subunit and cause misreading of mRNA

Question 9

Lincosamides MOA ?

Answer 9

eg clindomycin
Disrupt the function of the 50s subunit

Question 10

How does chloramphenicol work?

Answer 10

Inhibits peptidyl transferase activity of the 50s subunit, stopping transpeptidation

Question 11

Which abx inhibit nucleic acid synthesis?

Answer 11

Trimethoprim
Quinolones
metronidazole
Rifampacin

Question 12

HOw does trimethoprim work?

Answer 12

Inhibits dihydrofolate reductase needed in purine/pyrimadine synthesis (bacteriostatic)

Question 13

How do quinolones work?

Answer 13

Inhibit DNA gyrase, the enzyme that compresses DNA into coils

Question 14

How does metronidazole work?

Answer 14

INhibits and damages dna synthesis (unclear exact MOA)

Question 15

How does rifampacin work?

Answer 15

Prevents rna transcripton by inhibiting DNA dependent RNA polymerase

Question 16

WHen is it important to use a bacteriocidal agent?

Answer 16

In the immunosuppressed

Question 17

Bacteriostatic drugs?

Answer 17

MAcrolides
licosamides
chloramphenicol
tetracyclines
trimethoprim

Question 18

Characteristics of penicillins?

Answer 18

Low toxicity, short half life, renal excretion unchanged
HYpersensitivity in 10%, anaphylaxis in 1
Side effects incl encephalopathy and didarrhoea
Tissue penetration good, but meninges need to be inflammed to cross the BBB

Question 19

CHaracteristics of cephalosporins

Answer 19

Less susceptible to b lactamases
broader spec
Excreted unchanged in urine (bar cefotaxime which is 50% metabolsied in the liver)

Question 20

What is different about ceftriaxone c.w. other cephalosporins

Answer 20

Highly protein bound (95%) with a long half life (6-12 hr) only given OD

Question 21

How are cephalosporins divided?

Answer 21

Three generations, increasingly more gram negative cover whilst positive cover is maintained

Question 22

Second generation cephalosporins examples and use

Answer 22

Cefuroxime
More stable b lactam ring used for prophylaxis in bowel surgery, lack anaerobic cover

Question 23

Third generation cephalosporins examples

Answer 23

cefotaxime, ceftriaxone, cepftazidime

Question 24

Carbapenem cover

Answer 24

broad- positive, negative, aerobic and anaerobicUS

Question 25

Uses of carbapenems

Answer 25

Neutropenic and multiresistant gram neg sepsis.

Question 26

What do carbapenems not work on

Answer 26

MRSA, E faecalis and some pseudomonas

Question 27

WHy is imipenem combined with cilastatin

Answer 27

Prevent renal metabolism and increase plasma conc.

Question 28

S/E of carbapenems

Answer 28

generally well tolerated but can cause convulsions. Excreted unchanged

Question 29

GLycopeptide cover

Answer 29

gram positive spectrum and used in MRSA + endocarditis. GRam negative cover limited as large polar molecules cannot penetrate the outer lipd wall

Question 30

DIfference between teic and vanc?

Answer 30

TEic is more potent, longer duration of action, better tissue penetration and better tolerated. More resistance about

Question 31

CHaracteristics of glycopeptides

Answer 31

Toxicity common- nephro/oto/neutropenia. monitoring required. ELimination unchanged in urine Minimal absorption from gut Can cause red man syndrome- IV vanc can lead to histamine release

Question 32

MAcrolide spectrum

Answer 32

SImilar to penicillin, mainly gram positive organisms SPecific activity against mycoplasma and legionella

Question 33

What is good about azithromycin

Answer 33

increased gram negative cover with a v long half life (40-60 hrs)

Question 34

CHaracteristics of macrolides

Answer 34

Well tolerated metabolised and excreted by the liver potent inhibitors of the CYP450 enzymes

Question 35

Side effects of macrolides?

Answer 35

GI (erythromycin is a prokinetic), prolonged QT< thrombophlebitis

Question 36

Cover of aminoglycosides?

Answer 36

Mainly gram negative, including pseudomonas. First line for serious gram negative infections

Question 37

Pharmacokinetics of AMinoglycosides?

Answer 37

LArge, polar molecules needing active transport into the cell. Renally excreted IV required due to low lipid solubility

Question 38

Why do aminoglycocides work well with penicillins?

Answer 38

Penicillins break down the cell wall, giving aminoglycosides better cellular access

Question 39

S/E aminoglycosides

Answer 39

Toxic to kidneys and cn8 with narrow therapeutic range Impair transmission at NMJ by decreasing prejunctional release and reducing post junctional sensitivity to Ach

Question 40

Quinolones uses?

Answer 40

Broad spec so often gastroenteritis or multiple resistant infetions Tends towards covering gram neg, but some pos

Question 41

Difference between cipro and levofloxacin?

Answer 41

Levo has increased pneumococcal cover, useful for LRTI

Question 42

Characteristics of quinolones?

Answer 42

Good oral absorption wide distribution with good cns penetration excreted unchanges low toxicity INhibits cyp450

Question 43

S/E quinolones

Answer 43

nausea, vomiting, convulsions, prolonged qtc

Question 44

WHat is metronidazole good for?

Answer 44

Anaerobic bacteria- these predominate in abscesses so useful here

Question 45

Characteristics of metronidazole

Answer 45

Well tolerated Distributes in csf, prostate and pleural fluid Excreted unchanged in urine

Question 46

Rare side effects of metronidazole

Answer 46

rash pancreatitis peripheral neuropathy Flushing and hypotension with alcohol

Question 47

Why are quinolones bad in epilepsy?

Answer 47

GABA antagonism