Antibiotics

Question 1

How do penicillins and cephalosporins work?

Answer 1

Inhibits bacterial cell wall synthesis by preventing cross linking between peptidoglycan chains

Question 2

What is amoxicillin used for?

Answer 2

Has activity against gram +ve (strep, staph) and gram -ve (H.influenzae, E.coli) bacteria. Commonly susceptible infections include UTIs, otitis media, sinusitis, uncomplicated CAP, salmonellosis, oral infections. Also used in combination in H.pylori eradication

Question 3

Which strains of bacteria would rule out amoxicillin (and other Beta lactam) use?

Answer 3

Bacteria that produce beta lactamase enzymes.

Question 4

What are the cephalosporin generation drugs?

Answer 4

1st gen - cefradine
2nd gen - cefuroxime
3rd gen - cefotaxime
Less activity against gram +ve bacteria the higher the generation. 2nd gen less susceptible to beta lactamase inactivation. 3rd gen greater activity against certain gram -ve bacteria

Question 5

What is a common side effect to be wary of when using the cephalosporins?

Answer 5

Antibiotic-associated colitis

Question 6

Interaction of cephalosporins with aminoglycosides?

Answer 6

Increased risk of nephrotoxicity

Question 7

How do antifolate antibiotics Trimethoprim and Sulfonamides work?

Answer 7

Inhibit folate synthesis. Trimethoprim inhibits dihydrofolate reductase, sulfonamides inhibit diaminopteroate synthetase. Combined as co-trimoxazole

Question 8

What is trimethoprim commonly used to treat?

Answer 8

UTIs. Can also be used in resp-tract infections, acne resistant to other Abx, prostatits, shigellosis, invasive salmonella

Question 9

What is the interaction of trimethoprim and sulfonamide use with methotrexate?

Answer 9

Increased risk of severe bone marrow depression

Question 10

Why is trimethoprim and sulfonamides use becoming a problem?

Answer 10

Resistance is common

Question 11

How does nitrofurantoin work?

Answer 11

Broad spec ABx that inhibits DNA, RNA, protein and cell wall synthesis

Question 12

What is nitrofurantoin used for?

Answer 12

UTIs. Effective against E. Coli, Enterobacter cystitis, Enterococcus, Klebsiella, and Staphylococcus aureus

Question 13

Contraindications to nitrofurantoin use?

Answer 13

Acute porphyrias, G6PD deficiency, infants < 3 months old

Question 14

Which strain of bacteria is completely resistant to nitrofurantoin?

Answer 14

All pseudomonas strains

Question 15

What type of antibiotic is doxyxycline?

Answer 15

Tetracyclines

Question 16

How does doxycycline work?

Answer 16

Protein synthesis inhibitor, inhibits RNA translation

Question 17

What is doxycycline used for?

Answer 17

Susceptible infections caused by chlamydia, rickettsia, mycoplasma

Question 18

Why should doxycycline use be cautioned with myasthenia gravis and SLE?

Answer 18

Can increase muscle weakness in myasthenia gravis and exacerbate SLE

Question 19

Why should doxycycline and other tetracyclines not be given to children under 12 or pregnant women?

Answer 19

Doxycycline deposits on teeth and bone, causing staining and dental hypoplasia

Question 20

Examples of aminoglycosides?

Answer 20

Gentamicin, streptomycin

Question 21

How does gentamycin work?

Answer 21

Protein synthesis inhibitor, binds to 30S subunit

Question 22

Indications for aminoglycoside use?

Answer 22

Serious aerobic gram -ve infections and staph. Gentamycin against P. aeroginosa, streptomycin against M. tuberculosis

Question 23

Why is aminoglycoside use contraindicated in those with myasthenia gravis?

Answer 23

NMJ transmission can be impaired

Question 24

Side effects to be wary of with aminoglycosides?

Answer 24

Ototoxicity and nephrotoxicity

Question 25

Why is drug monitoring essential when on aminoglycosides?

Answer 25

Narrow therapeutic index, also not normally used for more than 10 days due to toxicity risk

Question 26

What is often used in combination with aminoglycosides in streptococcal endocarditis/other serious infections in blind therapy?

Answer 26

Beta lactams such as penicillin

Question 27

What syndrome can be caused in neonates if aminoglycosides have been used?

Answer 27

Grey baby syndrome

Question 28

What type of antibiotic is erythromycin?

Answer 28

Macrolide

Question 29

How does erythromycin work?

Answer 29

Protein synthesis inhibitor, inhibits protein elongation

Question 30

Why is clarithromycin given BD whilst erythromycin is given QDS?

Answer 30

Clarithromycin has greater activity and better tissue availability

Question 31

What is erythromycin used for?

Answer 31

Similar spectrum to penicillins so used as alternative in pen allergic patients. Gram +ve (and some gram -ve) infections

Question 32

Why is erythromycin enteric coated?

Answer 32

It is adversely affected by gastric acid

Question 33

Why are only short courses of macrolides given?

Answer 33

Resistance is quite rapid, >14 days use increases risk of hepatic damage

Question 34

Example of quinolone?

Answer 34

Ciprofloxacin

Question 35

How does ciprofloxacin work?

Answer 35

Inhibits DNA gyrase and topoisomerase IV which are involved in DNA remodelling. (Humans don't have DNA gyrase)

Question 36

What is ciprofloxacin used for?

Answer 36

Broad spec. Particularly active against gram -ve bacteria (campylobacter, neisseria, pseudomonas)

Question 37

What type of weather should be avoided when on quinolones?

Answer 37

Excessive sunlight

Question 38

How does metranidazole work?

Answer 38

Broken down to toxic compounds within anaerobic microbes.

Question 39

What is metranidazole used for?

Answer 39

Anaerobic protozoal infections, H.pylori infection, rosacea, pseudomembranous colitis

Question 40

Why can't alcohol be consumed when using metranidazole?

Answer 40

Disulfiram-like reaction can occur (flushing/abdo pain/hypotension)

Question 41

What type of antibiotic is vancomycin?

Answer 41

Glycopeptides

Question 42

How does vancomycin work?

Answer 42

Inhibits cell wall synthesis

Question 43

What is vancomycin used for?

Answer 43

Gram +ve infections both aerobic and anaerobic including MRSA. Treatment of endocarditis and C.diff

Question 44

Why should vancomycin not be given PO for systemic infections?

Answer 44

Poorly absorbed

Question 45

Side effects of vancomycin?

Answer 45

Ototoxic and nephrotoxic, blood disorders, N, chills, fever, flushing of upper body 'red man' syndrome

Question 46

Which antibiotics are safe to use in pregnancy?

Answer 46

Penicillins and cephalosporins

Question 47

Which antibiotics are NOT safe to use in pregnancy?

Answer 47

Chloramphenicol, tetracyclines, fluouroquinolones, co-trimoxazole

Question 48

Tazocin is a combination of which drugs?

Answer 48

Piperacillin and tazobactam

Question 49

Vancomycin only has activity against which type of organism?

Answer 49

Gram +ve bacteria

Question 50

Aztreonam only has activity against which type of organism?

Answer 50

Gram -ve bacteria