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"In fact, it is prolonged exposure to antibiotics that provides the selective pressure to drive antimicrobial resistance;" I've never understood why a longer c

by ars 6y ago

"In fact, it is prolonged exposure to antibiotics that provides the selective pressure to drive antimicrobial resistance;" I've never understood why a longer course of antibiotics would kill a resistant bacteria, while a shorter one won't. It's either resistant or it's not. Bacteria multiply far far too fast for them to notice multi-day courses of treatment, a bacteria only "notices" the current conditions before it either multiplies or dies. By prolonging medication you wipe out all the susceptible bacteria leaving only the resistant ones. It seems to me that instead we should use just enough antibiotic to keep the patient alive (to turn the corner) and then let the patients immune system do the rest. If I'm wrong about any of the above, I would love responses explaining why.

arn 6y ago
Resistance is not as black and white as you suggest. https://litfl.com/minimum-inhibitory-concentration/ https://litfl.com/minimum-inhibitory-concentration/ It’s more of a spectrum of concentrations. A resistant bacteria is one that doesn’t grow above a certain threshold. But longer exposure or higher concentration will change the effectiveness.
pdonis 6y ago
> It's either resistant or it's not. Resistance is not a binary thing. Often it simply means that a population of "resistant" bacteria takes longer to be completely eliminated, not that they are completely unaffected. It would be better if a different term were used to describe bacteria that are completely unaffected by a given antibiotic; perhaps "invulnerable" would do. If you are in fact dealing with bacteria that are invulnerable to a particular antibiotic, then you need to switch antibiotics, yes. > Bacteria multiply far far too fast for them to notice multi-day courses of treatment Bacteria multiply far too fast under ideal conditions. But the whole point of giving an antibiotic is to make the conditions as far as possible from ideal. > a bacteria only "notices" the current conditions before it either multiplies or dies Bacteria are not mayflies. They don't have to either multiply or die within a short period of time. > It seems to me that instead we should use just enough antibiotic to keep the patient alive (to turn the corner) and then let the patients immune system do the rest. Antibiotics suppress the patient's immune system, so once you have started them, you need to finish the job with them. If you are going to try to let the patient's immune system fight the infection, then I would think you would not give antibiotics at all; instead you would focus on maximizing supportive care for the patient's immune system (for example, they probably need to eat a lot of protein since the immune system needs protein to make antibodies, T-cells, etc.), and for the patient generally (make sure they stay hydrated, etc.).
wizzwizz4 6y ago
> I've never understood why a longer course of antibiotics would kill a resistant bacteria, while a shorter one won't. It's either resistant or it's not. The thing you're missing is that bacteria share genes. So if you have a high proportion of resistant bacteria, but non-resistant bacteria are still around, the genes survive and spread. But if only the (few) resistant ones are around, the (weakened) immune system can kill them and the genes don't. (And also, “it's either resistant or it's not” is an oversimplification in many real-world cases.)

by ars 6y ago

arn 6y ago

Resistance is not as black and white as you suggest. https://litfl.com/minimum-inhibitory-concentration/ https://litfl.com/minimum-inhibitory-concentration/ It’s more of a spectrum of concentrations. A resistant bacteria is one that doesn’t grow above a certain threshold. But longer exposure or higher concentration will change the effectiveness.

pdonis 6y ago

> It's either resistant or it's not. Resistance is not a binary thing. Often it simply means that a population of "resistant" bacteria takes longer to be completely eliminated, not that they are completely unaffected. It would be better if a different term were used to describe bacteria that are completely unaffected by a given antibiotic; perhaps "invulnerable" would do. If you are in fact dealing with bacteria that are invulnerable to a particular antibiotic, then you need to switch antibiotics, yes. > Bacteria multiply far far too fast for them to notice multi-day courses of treatment Bacteria multiply far too fast under ideal conditions. But the whole point of giving an antibiotic is to make the conditions as far as possible from ideal. > a bacteria only "notices" the current conditions before it either multiplies or dies Bacteria are not mayflies. They don't have to either multiply or die within a short period of time. > It seems to me that instead we should use just enough antibiotic to keep the patient alive (to turn the corner) and then let the patients immune system do the rest. Antibiotics suppress the patient's immune system, so once you have started them, you need to finish the job with them. If you are going to try to let the patient's immune system fight the infection, then I would think you would not give antibiotics at all; instead you would focus on maximizing supportive care for the patient's immune system (for example, they probably need to eat a lot of protein since the immune system needs protein to make antibodies, T-cells, etc.), and for the patient generally (make sure they stay hydrated, etc.).

wizzwizz4 6y ago

> I've never understood why a longer course of antibiotics would kill a resistant bacteria, while a shorter one won't. It's either resistant or it's not. The thing you're missing is that bacteria share genes. So if you have a high proportion of resistant bacteria, but non-resistant bacteria are still around, the genes survive and spread. But if only the (few) resistant ones are around, the (weakened) immune system can kill them and the genes don't. (And also, “it's either resistant or it's not” is an oversimplification in many real-world cases.)