Antimicrobial chemotherapy

Question 1

• Describe those factors important in deciding when to use IV or oral antimicrobials.
• Describe the spectrum of action of different antimicrobial groups and the ad- vantages/disadvantages of broad and narrow spectrum antibacterials used singly or in combination.
• Explain the place of monitoring drug levels in antibacterial usage.
• List the commonly encountered adverse effects of antimicrobials.
• Explain the role of the laboratory in influencing antimicrobial choice.
• Describe the use of antiviral and antifungal agents in contemporary infection practice.

Answer 1

.

Question 2

Methods of testing antibiotic resistance

Answer 2

Disk diffusion test

Etest - measure MIC

Question 3

4 main mechanisms of resistance

Answer 3

Enzymatic inactivation of drug
Modified targets for drugs
Reduced permeability to drug
Efflux of drug

Question 4

Bacteria divide by what process

Answer 4

Binary fission - DNA replicates, cell elongates then splits into 2

Question 5

Resistance is mediated in what 2 ways

Answer 5

Chromosomally mediated - mutation in gene coding for where drug binds

Plasmid mediated - bacterial conjugation allows bacteria to transfer resistance genes

Question 6

Medically important resistant organisms

Answer 6

MRSA

VRE (vancomycin resistant enterococci)

ESBL (Extended Spectrum Beta Lactamase)

CPE (Carbapenemase Producing Enterobacteriaceae)

Clostridium difficile

Question 7

MRSA is resistant to what penicillin

Answer 7

Flucloxacillin

Question 8

VRE (Vancomycin resistant enterococci) are only sensitive to 1 or 2 antibiotics such as

Answer 8

Linezolid

Question 9

VRE (Vancomycin resistant enterococci) colonise those who are exposed to

Answer 9

multiple antibiotics

Question 10

ESBL (Extended Spectrum Beta Lactamase) are very resistant because they confer a range of resistance mechanisms that are developing faster than new antibiotics are designed

What antibiotics are they resistant to

Answer 10

Beta-lactams

Question 11

Alternatives for those resistant to penicillin

Answer 11

Quinolones, e.g. ciprofloxacin
Macrolides
Aminoglycosides
Licosamides, e.g. clindamycin
Co-trimoxazole
Glycopeptides, e.g. vancomycin
Daptomycin
Tetracycline

Question 12

Reasons for failure of antibiotic course

Answer 12

Inadequate dose of antibiotic

Inappropriate route

Non-compliance

Bacteria walled off in abscess cavity

Foreign bodies, eg surgical implants/prosthesis

Poor penetration of drug to site of infection, e.g. brain, bone

Question 13

Antibiotics with good biofilm activity

Answer 13

Rifampicin
Daptomycin
Ceftobiprole

Question 14

What is antibiotic stewardship

Answer 14

Set of coordinated strategies to improve the use of antibiotics with the goal of enhancing patient health outcomes, reducing resistance to antibiotics, and decreasing unnecessary costs

Question 15

Consider switching patients from IV to oral antibiotics after 48hrs, if…

Answer 15

The patient is improving clinically
AND
is able to tolerate an oral formulation

Question 16

When not to switch to oral antibiotics from IV

Answer 16

If oral route compromised, e.g. vomiting

Continuing sepsis

Specific cases, e.g. endocarditis, meningitis, deep abscesses

Question 17

What are alert antimicrobials

Answer 17

Ones of last resort; specialist use only