AAMC 10 #127. Testing the urease necessity for H. pylori

[Monkeymaniac]

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The question states "Which of the following experiments would best test the hypothesis taht urease is necessary for teh colonization of the stomach by H. pylori"?

A) Exposing ulcer patients to antobodies to urease
B) Exposing uninfected individuals or animals to a strain of H.p. that lacks urease
...

I chose A but the answer is B.

Kaplan's solution states that the reason why A can't be answer is

"Urease is an enzyme that converts urea to ammonia and carbon dioxide; it could not cause an infection or colonize anything because it is not a form of life. This does not have anything to do with H. pylori colonization of the stomach."

But I've seen from TBR immunology practice passags that antobodies could be produced against molecules (protein) other than pathogens, membrane receptors for instance. So I don't understand why A can't be answer. Wouldn't getting rid of all the urease, when the patient is cured, suggest that the urease was indeed needed for H. pylori to survive? Thanks in advance.

 

[Monkeymaniac]

Anyone please?

 

[vsl5]

The question states "Which of the following experiments would best test the hypothesis taht urease is necessary for teh colonization of the stomach by H. pylori"?

A) Exposing ulcer patients to antobodies to urease
B) Exposing uninfected individuals or animals to a strain of H.p. that lacks urease
...

I chose A but the answer is B.

Kaplan's solution states that the reason why A can't be answer is

"Urease is an enzyme that converts urea to ammonia and carbon dioxide; it could not cause an infection or colonize anything because it is not a form of life. This does not have anything to do with H. pylori colonization of the stomach."

But I've seen from TBR immunology practice passags that antobodies could be produced against molecules (protein) other than pathogens, membrane receptors for instance. So I don't understand why A can't be answer. Wouldn't getting rid of all the urease, when the patient is cured, suggest that the urease was indeed needed for H. pylori to survive? Thanks in advance.

Because if dont have urease (eg. knockout strain), and you cannot infect, this proves that urease was necessary for infection. In answer A, if you use antibodies to a strain that HAS urease, you will kill H. pylori but this only proves that H. pylori produced urease, not that it was necessary for infection.

 

[ahamdi2]

the question here is asking to identify if urease is "necessary" to the growth of the a colony. keep it simple, grow H. pylori with out urease and see !!!

of course its hard to think that way on the actual test, we always look for prof that the other choices aren't correct. dont feel bad i also choose answer A.