Antimicrobial Chemotherapy

Question 1

What are indications for antimicrobials?

Answer 1

Therapy; empiric or directed

Prophylaxis; primary or secondary

Diagnosis of infection; clinical, lab or none

Severity assessment; sepsis/septic shock

Question 2

What is important to consider when prescribing antimicrobials?

Answer 2

Severity

Patient characteristics; age, renal function, liver function, immunocompromised, pregnancy, known allergies etc.

Question 3

Describe antimicrobial selection

Answer 3

Should be based on

• guidelines
• likely organisms
• empirical/result based
• bactericidal vs bacteriostatic
• single agent or combo
• potential adverse effects

Question 4

What drives antibiotic resistance?

Answer 4

A natural phenomenon

Bacteria adapt to survive, rapidly multiply and generate resistance very quickly

4 main mechanisms

• enzymatic inactivation of drug
• modified targets for drugs
• reduced permeability to drug
• efflux of drug

Also genetics; chromosomally mediated resistance, plasmid mediated

Question 5

Describe chromosomally mediated antibiotic resistance

Answer 5

• Mutation in gene coding for drug target or membrane transport system
• much lower than frequency of acquisition of plasmids
• basis for using multi-drug therapy

Question 6

Describe plasmid mediated antibiotic resistance

Answer 6

• replicate independent of cell chromosomes

- carry genes for enzymes which degrade antibiotics and modify membrane transport systems

Question 7

What resources can be used to support antibiotic prescribing?

Answer 7

Disk diffusion method for sensitivity testing

Etest; gradient strip w/different concentrations to check minimum inhibitory concentration; generally the lower the MIC the better

Question 8

What is antimicrobial stewardship?

Answer 8

Refers to a set of co-ordinated strategies to improve the use of antimicrobial medications with the goal of enhancing patient health outcomes, reducing resistance and decreasing unnecessary costs

Question 9

Describe the strategies involved in antimicrobial stewardship

Answer 9

• using right antibiotic for right indication for right duration
• use antibiotic only if suspected or proven bacterial infection
• Use per guidelines and review with microbio results
• review prescriptions regularly and stop ASAP
• limit use of broad-spectrum blind antibiotic therapy to seriously ill patients