Week 4: Biofilms - antimicrobial tolerance

Question 1

Why tolerance and not resistance?

Answer 1

resistance is the genetic resistance, methods encoded in their genome

tolerance, ability to withstand a pressure

Question 2

Why do microbes have increased tolerance to antimicrobials?

Answer 2

• First recall the distinction between antibiotic or antimicrobial resistance and tolerance.
• For tolerance there are strategies such as:
• Slow growth and persistent cell state in the low nutrient areas of the biofilm.
• Cells not susceptible to antibiotics that challenge active growth processes
• Spatial structure leads to lower concentrations of antibiotics in regions and selects for resistance
• Some antimicrobials (eg disinfectants or toxic metals) don’t make it into the biofilm as they react with the polysaccharide (e.g. aminoglycosides) are chelated, degraded by enzymes etc.
• Note that small uncharged antimicrobials can have uninhibited diffusion

Question 3

What is an example of microbes losing tolerance?

Answer 3

if you take the genetically same microbes in a biofilm.

remove them from that environment and grow in e.g. liquid culture

lose tolerance

emergent quality, gained by the fact they are in that biofilm, living in biofilm.

Question 4

Why are microbial infections hard to treat in a clinic?

Answer 4

• when you culture the microbe and screen for conditions where the ab might work.

in different environment (body) the tolerance may be decreased in the microbe.

due to different gene expression.

physiologically a different state, antibiotic state fails.

antibiotic not compatible for the lifestyle of the microbe in that environment.

Question 5

How do you test the antibiotic someone might need?

Answer 5

culturing them

putting them in the compliantonic type condition

screen for things and where the antibiotics might work.

Question 6

What do antibiotics rely on?

Answer 6

active growth of microbes

target processes like transcription, cell division

spatial structure an gradient mean some antibiotics cant get in.

biofilm microbes, change gene expression. upregulate efflux pumps so if an antibiotic does get it, its pumped out faster.

Question 7

Why may you need a repeat prescription of antibiotics?

Answer 7

antibiotic bound by polysaccharides at the surface and cant get into the material.

others cant.

non-growing regions of the biofilms, the antibiotics wont work as regions of the biofilm wont incorporate.

might tolerate antibiotics by entering non-growing state.

Question 8

How would you describe biofilms interacting with one another?

Answer 8

COLLECTIVE

Question 9

Can microbes in biofilm effective treatment?

Answer 9

YES as they work a a collective