May 7, 2020
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There was a question in the AAMC bio q pack 2, number 12: How is A not correct? The explanation states that "Antibiotics are unlikely to have been the source of the mutations"

What? I thought the whole idea behind superbugs, and antibiotic resistance problems in hospitals was that bacteria are able to mutate and become resistant to antibiotics. How is this incorrect?

I was stuck between A and D because they both seemed likely. Is antibiotic resistance as developed through mechanisms suggested by A something that takes a long period of time to happen? And thus why A might not be a good answer? His initial stay in the hospital was a few weeks.




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There was a question in the AAMC bio q pack 2, number 12: How is A not correct? The explanation states that "Antibiotics are unlikely to have been the source of the mutations"

What? I thought the whole idea behind superbugs, and antibiotic resistance problems in hospitals was that bacteria are able to mutate and become resistant to antibiotics. How is this incorrect?

I was stuck between A and D because they both seemed likely. Is antibiotic resistance as developed through mechanisms suggested by A something that takes a long period of time to happen? And thus why A might not be a good answer? His initial stay in the hospital was a few weeks.
You are correct in saying that bacteria are indeed able to mutate and develop resistance to antibiotic(s).

The most likely mechanism here to confer such resistance would be spontaneous mutation in e.coli or horizontal gene transfer i.e. genes acquired from other neighboring bacteria.

Mutations can confer resistance to antibiotics, but it is not reasonable to assume that the antibiotics themselves cause mutations. Unless the passage details some mutagenic effect from antibiotic use, I'd scrap A. While some antibiotics may have mutagenic properties, that's outside the scope of the question frankly.

B doesn't make sense.
C it's not really gradual resistance; typically all or nothing, the e. coli has the gene needed for resistance of a particular antibiotic used in treatment or it doesn't and dies. C doesn't make complete sense unless we're considering a long-term event of HGT. Doesn't seem likely during active treatment.
D looks good, see above logic; these cells were resistant to the antibiotics prior to this particular hospital say.

Many ways that can happen - from natural mechanisms to misuse of antibiotics, but the presence of antibiotic is not sufficient in cases of natural resistance.

For example, you can have contracted gonorrhea only once and still have contracted the "superbug" strain to which resistance has become increasingly futile - even if you have never taken ciprofloxacin.

Hope that helps!
 
May 7, 2020
192
18
Status
Pre-Medical
You are correct in saying that bacteria are indeed able to mutate and develop resistance to antibiotic(s).

The most likely mechanism here to confer such resistance would be spontaneous mutation in e.coli or horizontal gene transfer i.e. genes acquired from other neighboring bacteria.

Mutations can confer resistance to antibiotics, but it is not reasonable to assume that the antibiotics themselves cause mutations. Unless the passage details some mutagenic effect from antibiotic use, I'd scrap A. While some antibiotics may have mutagenic properties, that's outside the scope of the question frankly.

B doesn't make sense.
C it's not really gradual resistance; typically all or nothing, the e. coli has the gene needed for resistance of a particular antibiotic used in treatment or it doesn't and dies. C doesn't make complete sense unless we're considering a long-term event of HGT. Doesn't seem likely during active treatment.
D looks good, see above logic; these cells were resistant to the antibiotics prior to this particular hospital say.

Many ways that can happen - from natural mechanisms to misuse of antibiotics, but the presence of antibiotic is not sufficient in cases of natural resistance.

For example, you can have contracted gonorrhea only once and still have contracted the "superbug" strain to which resistance has become increasingly futile - even if you have never taken ciprofloxacin.

Hope that helps!
Thanks. What threw me off was that, in the passage, they say this
1589483956073.png

He "received massive doses of the antibiotics". I know that hospitals are wary of using large doses of antibiotics, because it promotes development of bacterial resistance.

I'm still not understanding what you mean here, "Mutations can confer resistance to antibiotics, but it is not reasonable to assume that the antibiotics themselves cause mutations."

What is the difference between the mutations of bacteria in response to antibiotics and the antibiotics themselves causing mutations? This sounds like it's describing the same concept.
 
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Apr 25, 2020
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Thanks. What threw me off was that, in the passage, they say this
View attachment 306281

He "received massive doses of the antibiotics". I know that hospitals are wary of using large doses of antibiotics, because it promotes development of bacterial resistance.

I'm still not understanding what you mean here, "Mutations can confer resistance to antibiotics, but it is not reasonable to assume that the antibiotics themselves cause mutations."

What is the difference between the mutations of bacteria in response to antibiotics and the antibiotics themselves causing mutations? This sounds like it's describing the same concept.
Mutations are RANDOM. They are not due to a response to anything, it just happened that the bacteria had antibiotic resistance (which is a termed a beneficial mutation). Therefore, antibiotics do not cause mutations because mutations are a random event. I hope that makes sense.
 
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Cornfed101

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Mutations are RANDOM. They are not due to a response to anything, it just happened that the bacteria had antibiotic resistance (which is a termed a beneficial mutation). Therefore, antibiotics do not cause mutations because mutations are a random event. I hope that makes sense.
This.

Antibiotics do not cause mutations, they just allow the bacteria that are already resistant (through random mutations) to have an advantage and therefore replicate. The AAMC knows this and they are trying to catch you in a trap with answer A. It is fundamentally wrong.
 
Feb 5, 2020
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You should be careful about understanding what AAMC is saying. Choice A says the mutation was caused by the antibiotics. In reality, the antibiotics just killed all the bacteria, except those who happened to have the genetic mutation that gave them an advantage. It's safe to assume that you'll see more problems like this because I've been seeing more problems about gut microbiome and fecal transplantation, which are all about competition among bacterial species and which species has the upper hand for survival.
 
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