Antimicrobials

Question 1

Which antibiotics affect protein synthesis? Give examples

Answer 1

Aminoglycosides -gentamicin
Macrolides - erythromycin
Tetracyclines - tetracycline, doxycycline

Question 2

Which antibiotics affect cell wall synthesis? Examples

Answer 2

Beta lactams

• penicillins
• cephalosporins
• carbapenems

Glycopeptides - vancomycin

Question 3

How can you work out the most likely cause of infection?

Answer 3

Anatomical site
Duration of illness
Past medical history
Occupational history
Travel history
Time of year
Age
Personal background

Question 4

What factors should be considered when deciding which antibiotics are the best choice?

Answer 4

Community or healthcare onset
Severity of infection
Immune status of patient
Baseline rate of resistance

Question 5

What are features of an ideal antibiotic?

Answer 5

Minimal impact on non-target commensal organisms
Clean kill of infecting bacteria
No resistance in any surviving pathogens
No effects on patient

Question 6

What are some general adverse effects of antibiotics?

Answer 6

Pharmacological - toxicities and drug reactions
Allergic reactions
Impact on normal flora leading to eg C diff

Question 7

What ADRs can gentamicin have?

Answer 7

Nephrotoxic

Auditory nerve - deafness and balance problems

Question 8

Give some examples of antibiotics which have to be monitored so they don’t reach toxic doses

Answer 8

Gentamicin

Vancomycin

Question 9

How is antibiotic activity measured?

Answer 9

Disc testing - antibiotic diffuses out onto bacteria in an agar plate
At some point, the antibiotic concentration will be too great for bacteria to grow

Question 10

How can antibiotic resistance be acquired?

Answer 10

Gene mutation which confers resistance

Horizontal gene transfer of plasmid

Question 11

What are some mechanisms of resistance?

Answer 11

Antibiotic inactivation eg beta-lactamase
Alteration of target site eg penicillin binding protein
Alteration of metabolic pathways
Reduce intracellular antibiotic accumulation by decreased permeability or active efflux

Question 12

Name some antibiotic resistant pathogens

Answer 12

MRSA
Glycopeptide resistant enterococci
Extended spectrum beta lactamase enterobacteriaceae (ESBLs)
Extensively drug resistant Klebsiella pneumonia (XDR-KP)

Question 13

What does antimicrobial stewardship involve?

Answer 13

Give the correct antibiotic
At the right time
At the right dose, frequency and duration
Via the right route

Question 14

How can the spread of resistant bacteria be stopped?

Answer 14

Isolation or cohorting
Hand hygiene
Decolonisation of patients

Question 15

How can the safety of an antibiotic be assessed?

Answer 15

Drug interactions 
Toxicity 
Allergies
Pregnancy or breast feeding 
Organ function
Administration route and efficacy

Question 16

Name the antibiotics which have been used for treating staph aureus

Answer 16

Penicillin
Methicillin (flucloxacillin)
Vancomycin

Question 17

Which values determine the effectiveness and potency of antibiotics?

Answer 17

Minimum inhibitory concentration

Minimum bactericidal concentration

Question 18

What is time-dependent killing?

Answer 18

When the major killing effect is how long the drug is bound to the receptor sites for - spend longer above the MIC

Question 19

What is concentration-dependent killing?

Answer 19

When the concentration determines how effecting an antibiotic is
Measure the Cmax to MIC ratio

Question 20

Give examples of antibiotics that work by time-dependent killing

Answer 20

Beta lactams

Macrolides

Question 21

Give examples of antibiotics that work by concentration-dependent killing

Answer 21

Aminoglycosides

Metronidazole

Question 22

Which antibiotics affect DNA synthesis?

Give an example

Answer 22

Quinolones

-ciprofloxacin