LSAT 147 | Section 1 | Logical Reasoning: Q12

LR Question 12 Explanation

QUESTION TEXT: Ampicillin and other modern antibiotics kill a…

QUESTION TYPE: Strengthen

CONCLUSION: Newer antibiotics such as ampicillin will likely lead to drug resistant bacteria.

REASONING:

1. Ampicillin kills many more types of bacteria than penicillin does. 
2. Greater profits from Ampicillin manufacturing may lead to a penicillin shortage.

ANALYSIS: The argument has only told us one bad thing about Ampicillin: it kills more bacteria than penicillin does. More bacteria than necessary to cure the disease.

To support the conclusion, we should say “Killing more types of bacteria than necessary can cause antibiotic resistance”

(If you got this wrong, don’t feel bad. I did too. I picked E,  and knew it was uncertain, but for some reason didn’t come back to review this, despite my misgivings)

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1. CORRECT. If this is true, then we see how Ampicillin can lead to drug resistance. By killing more bacteria than necessary, Ampicillin creates the absence of competition that helps drug-resistant bacteria.
2. This suggests penicillin is safe. But it tells us nothing about why Ampicillin would lead to drug resistance where penicillin didn’t.
3. This weakens the argument. It suggests that any penicillin shortage would be limited: manufacturers would see the higher prices and produce more penicillin.
4. Expense doesn’t matter. We only care about the effects the new drugs have on bacteria.
5. I picked this. I think my reasoning was “if Ampicillin is overused, maybe bacteria will develop resistance to it”. That’s speculative. We need an answer which tells us how antibiotic resistance develops, and this answer doesn’t do that.