Antibacterials

Question 1

What are the different sites where antibiotics can act?

Answer 1

Cell wall synthesis
DNA synthesis
Protein synthesis

Question 2

Which types of antibiotics inhibits cell wall synthesis?

Answer 2

Beta lactams

Glycopeptides

Question 3

Which antibiotics inhibit DNA synthesis?

Answer 3

Quinolones

Folic acid antagonists

Question 4

Which antibiotics inhibitprotein synthesis?

Answer 4

Tetracyclines
Aminoglycosides
Macrolides

Question 5

What is an example of a beta lactam?

Answer 5

Penicillin
Cephalosporins
Carbapenems- eg meropenem

Question 6

What is an example of a glycopeptide?

Answer 6

Vancomycin

Question 7

What is an example of a quinolone?

Answer 7

Ciprofloxacin

Question 8

What are some examples of folic acid antagonists?

Answer 8

Trimethoprim

Sulphonamides

Question 9

What are the major indications for use of antibiotics?

Answer 9

Therapy of clinically significant bacterial infections- either empirical treatment of suspected infection or treatment of culture proven infection

Prophylaxis- eg peri op, short term meningitis contacts
Long term- asplenia, immunodeficiency

Question 10

What are the factors governing antibiotic choice accounting for likely infectious agent and patients to be used in?

Answer 10

Time of year
Anatomical site
Travel history
Duration of illness
PMH
Occupational history

Question 11

What are the common side effects of antibiotics?

Answer 11

Toxicities
Allergic reactions
Ecological effects- eg C.dificile infection
Drug reactions

Question 12

How does antibiotic resistance arise?

Answer 12

Chromosomal mutation

Horizontal gene transfer

Question 13

Why do some bacteria have resistance to beta lactams such as penicillins, cephalosporins and carbapenems?

Answer 13

All drugs in this class must have a B lactam ring which must be intact for them to be active. This is vulnerable to attack by beta lactamase attack.

Question 14

What is the mechanism of action of beta lactam antibiotics?

Answer 14

These bind to several penicillin binding proteins in bacteria. Some of these are transpeptidases that are required for cross linking of the peptidoglycan layer of the cell wall. This prevents it making an intact cell wall when it divides.

Question 15

What are the pharmacokinetics of penicillins?

Answer 15

Widely distributed across body. Short half lives due to rapid elimination by kidney.

Question 16

What are the clinical indications of penicillin G?

Answer 16

Active against many aerobic gram positive bacteria, a more limited range of gram negative bacteria such as gonococci and meningococci.

Question 17

Are gram negative bacilli sensitive to penicillin G?

Answer 17

No

Question 18

What is the clinical indication for flucloxacillin?

Answer 18

Beta lactamase resistant. Therefore reserved for beta lactamase producing staphylococci.

Question 19

What is the clinical indication for ampicillin and amoxicillin?

Answer 19

Gram negative bacilli. Less effective against gram positive cocci. Inactivated by B lactamase.

Question 20

What are the side effects of penicillins?

Answer 20

Nausea
Allergic reactions-fever, vasculitis, steven johnson syndrome, anaphylactic shock. 
Aminopenicillins commonly produce a non allergic maculopapular rash in people with glandular fever. Does not recur if another type of penicillin is given. 
Reversible neutropenia and eosinophilia
Encephalopathy
Diarrhoea
C. Dif related colitis
Cholestatic jaundice.

Question 21

What is the clinical indication of 3rd generation cephalosporins such as cefotaxime, ceftriaxone and cefixime?

Answer 21

Gram negative bacilli. Can cross blood brain barrier.

Question 22

What are the pharmacokinetics of cephalosporins?

Answer 22

2nd and 3rd generation must be given parenterally. Most are excreted by kidney and have short half lives.

Question 23

What are the side effects of cephalosporins?

Answer 23

Nausea, vomiting, abdo discomfort
Headache
Rashes
Similar allergic reactions to penicillins
C.dif related colitis

Question 24

Which antibiotic is commonly now being used more and more in place of trimethoprim for lower urinary tract infections?

Answer 24

Nitrofurantoin

Question 25

What is the mechanism of action of nitrofurantoin?

Answer 25

inhibits DNA synthesis.

Question 26

Which bacteria is nitrofurantoin active against?

Answer 26

Many gram positive cocci and E coli.

Question 27

What are some examples of macrolides?

Answer 27

Azithromycin, clarithromycin, erythromycin

Question 28

What are some examples of aminoglycosides?

Answer 28

Gentamicin, streptomycin

Question 29

What is the mechanism of action of aminoglycosides?

Answer 29

They bind to 30s ribosome subunit and prevent protein synthesis.

Question 30

What is the spectrum of activity of aminoglycosides?

Answer 30

Active against many gram negative bacteria and some gram positive bacteria. Inactive against anaerobes.

Question 31

What are the major side effects of aminoglycosides?

Answer 31

Ototoxicity

Nephrotoxicity

Question 32

What are some examples of tetracyclines?

Answer 32

Doxycycline, minocycline

Question 33

What is the mechanism of action of tetracyclines?

Answer 33

Inhibition of 30 s subunit of ribosomes.

Question 34

What is the spectrum of activity of tetracyclines?

Answer 34

Many G+ and G- bacteria. Also effective in chalmydia infections.

Question 35

What are the most common infecting organisms in sinusitis/ otitis media which has failed to resolve after 7 days?

Which antibiotics can be used to treat them?

Answer 35

H. Influenzae, S. Pnuemoniae, Moraxella catarrhalis.

Suitable drugs would include amoxicillin, doxycycline and clarithromycin.

Question 36

Which organisms commonly cause community acquired pneumonia?

Answer 36

S. Pneumoniae, H. Influenzae, staphylococci. Atypical micro organisms include legionella, mycoplasma pneumoniae or chlamydia pneumoniae.

Question 37

Which antibiotics would be a good choice for CAP?

Answer 37

Amoxicillin if pneumococcus is suspected
Clarithromycin will cover most organisms.

Severe CAP (high CURB 65 score) is treated with IV therapy including penicillin G with clarithromycin or doxycyclin.

Question 38

Which antibiotics are often used for hospital acquired pneumonia?

Answer 38

Cefuroxime, co amoxiclav used for early onset infections.
Ciprofloxacin for late onset infections. Aminoglycoside such as gentamicin can be added for severe infection if P. Aeruginosa is suspected.

Question 39

What are the bacterial causes of gastroenteritis?

Answer 39

E.coli, salmonella, campylobacter, V.cholerae, shigella.

Question 40

What treatment is commonly prescribed for bacterial gastroenteritis?

Answer 40

Fluid replacement.
If there are severe symptoms then- ciprofloxacin and clarithromycin are effective for campylobacter and shigella. Salmonella can be treated with ciprofloxacin.