Rheumatic fever is the most serious complication of

Question

Rheumatic fever is the most serious complication of streptococcal infection, but rheumatic fever is not itself an infection. Rheumatic fever occurs only when, in defending against streptococcal infection, the body's immunological system produces antibodies that also attack the cells of the heart and kidneys.

Which of the following, if true, would contribute most to an explanation of why only streptococcal bacteria give rise to rheumatic fever?

(A) Only certain strains of streptococcal bacteria are associated with rheumatic fever.
(B) The antibodies that the body produces to control a streptococcal infection can attack cells of the mucous membranes
(C) Antibiotics have not proved as effective against streptococcal infections as they have against some other bacterial infections. 
(D) Streptococcal bacteria are the only bacteria that are structurally similar to the cells of the body attacked in the rheumatic fever.
(E) Rheumatic fever can be misdiagnosed if it is not preceded by a serious streptococcal infection.

fluke · Accepted Answer

KarishmaB · Answer

S infection can sometimes lead to R fever. 
When antibodies against S infection start attacking the heart and kidneys too, it gives R fever.

We need to explain why ONLY S bacteria causes R fever. What is it about S bacteria infection and the antibodies produced against it that lead to R fever. Why other bacteria do not lead to R fever? What is so distinct about S bacteria?

(A) Only certain strains of streptococcal bacteria are associated with rheumatic fever.

This tells us that R fever happens only in case of some strains of S bacteria. But it doesn't explain why R fever happens only with S bacteria.

(B) The antibodies that the body produces to control a streptococcal infection can attack cells of the mucous membranes

We don't know the relation between mucous membranes and heart and kidney (R fever). This doesn't help explain anything.

(C) Antibiotics have not proved as effective against streptococcal infections as they have against some other bacterial infections.

Doesn't explain why only S infection causes R fever.

(D) Streptococcal bacteria are the only bacteria that are structurally similar to the cells of the body attacked in the rheumatic fever.

S bacteria are the only bacteria that are similar to the cells attacked in R fever (cells of heart and kidney). So now we know that S bacteria are structurally similar to cells of heart and kidney. Hence the antibodies against S bacteria end up attacking heart and kidney too and hence lead to R fever. This is the reason that R fever occurs in case of S bacteria only. 
Correct.

(E) Rheumatic fever can be misdiagnosed if it is not preceded by a serious streptococcal infection.

If a serious S infection doesn't happen, R fever can me misdiagnosed as say, viral fever or some other fever. So without a serious previous S infection, doctors may not be able to diagnose R fever correctly. Say if the S infection is mild, doctors may not come to know that it is there and the subsequent fever may not be diagnosed as R fever. But this doesn't explain why only S infection causes R fever.

Answer (D)

crazyfin · Answer

to which study guide does this question belong...i found it very tough and havent still understood the answer

crisnas · Answer

One more vote for D.
It correctly points out the cause-effect mentioned in the Q stem


Krishna

ranga41 · Answer

I choose E, I dont understand why so many people choose D, I rejected it readily, is there something i am not getting?

A) Only certain strains of streptococcal bacteria are associated with rheumatic fever.  (Does not support it very much) 

B) The antibodies that the body produces to control a streptococcal infection can attack cells of the mucous membranes  (but if heart and kidney are mucous membrane is out of scope of passage) 

C) Antibiotics have not proved as effective against streptococcal infections as they have against some other bacterial infections.  (out of scope) 

D) Streptococcal bacteria are the only bacteria that are structurally similar to the cells of the body attacked in the rheumatic fever.  (so the bacteria's structure is similar to structure of the cells that are getting attacked? that follows the assumption that a bacteria can attack a certain part of body if it has same structure as the cells of the part it attacks, this is not in the scope of the statement) 

E) Rheumatic fever can be misdiagnosed if it is not preceded by a serious streptococcal infection.  (if the person does not get the streptoco..infection rheumatic fever is misdiagnosed..which lends support to the argument)

crisnas · Answer

Hi Ranga,

I see a sense in what you say. But again, the stem says "Rheumatic fever occurs only when, in defending against streptococcal infection" which suggests that there is no chance of one actually having Rheumatic fever unless one is suffering from streptococcal infection. 
Doesn't this outline the assumption as such?

But yes, (after looking at ur explanation) I have started doubting the validity of choice D.

I guess the OA/OE is required here.

Krishna

popew626 · Answer

Let me give it a shot, ranga41. Hopefully, I'm not wrong and you're not going to blow me up like you do at math

Okay, so Rheumatic Fever (RF) is caused by the body attacking itself. The conclusion, given in the question, is that ONLY strep. bacteria can cause RF. We have to find the choice that explains why this is. In other words, how does only strep, and not some other infection, cause RF? Only D explains why the body attacks itself and causes RF. E supports the evidence that strep needs to be present before RF can happen but doesn't explain why strep causes RF.

sheeler · Answer

I guess D is it.. applying the KISS rule.

ranga41 · Answer

No blowing up man...

Can you please eloborate on how D explains why the body attacks itself and causes RF, I am surely missing something.

I choose E for the same reason u have given, if strep needs to be present before RF can happen, then it probably causes it....

popew626 · Answer

The way I see it is that since RF is caused by the body attacking itself D tells you why it does. 

The body develops antibodies to attack the strep bacteria. Then, the antibodies attack some of the body's cells because these cells resemble the structure of the strep bacteria. Since the cells and the bacteria are so close in identity the body can't tell the difference so it attacks its own cells thinking that the cells are the bacteria.

D tells us that ONLY strep bacteria is similar to the cells of the body that are attacked in RF.

aquaguy, what's the OA anyway?

ranga41 · Answer

Makes sense but one shuld be a medicine major to answer this question...there is a big jump of concept here "the antibody generated by the body to attack the strep bacteria mistakes the human body cells for the bacteria and attacks it.......", the statement does not provide any cluse as to how antibodies recognises their enemies....

Darth_McDaddy · Answer

Ah!! D for me too. But, then again, D happens to be the most logical choice. Here is why. The question stem states that "Rheumatic fever occurs only when, in defending against streptococcal infection", and that the body attacks cells of heart and kidney. D clearly explains that the bacteria is structurally similar to the body cells attacked by the immune system. D implies that the body mistook healthy cells to be Streptococcal bacteria, thus attackign healthy cells. 

Ranga, E does not state the reason why the body attacks healthy cells. 

Thus D

gmataquaguy · Answer

Yeah me too. I found this question very difficult to comprehend. Had to read the passage a couple of times. It belongs to an ETS paper. So its a legit GMAT question.

rahulraao · Answer

hey popew626, hopefully is almost always wrong remember!! :wink:

Im sure you meant IT IS HOPED THAT!!! :lol:

OH GMAT ENGLISH!!

kuttingchai · Answer

D seems to be the best ans, as it is clear from the argument that body cannot differentite between human hart and kidney cells and bacteria , so assumption can be made that the bacteria can have similar structure as that of human cell.

dentobizz · Answer

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jlgdr · Answer

We need to strengthen the fact that SB will cause RF. Well if SB are the only baceteria structurally similar to the cells attachked in RF then this will clearly strengthen the fact that they are the ones causing it. Pretty clear to me D

Just my 2c

Cheers
J

Just my 2c

Cheers
J

semwal · Answer

streptococcal bacteria lead to streptococcal infection which give rise to rheumatic fever.........
ANTIBODIES ATTACK THE bacteria and similarly structured body cells........

hence "d"

dcummins · Answer

RF occurs during defense of the bodies heart and kidneys against antibodies produced in response to SI

Rheumatic fever is the most serious complication of streptococcal infection, but rheumatic fever is not itself an infection. Rheumatic fever occurs only when, in defending against streptococcal infection, the body's immunological system produces antibodies that also attack the cells of the heart and kidneys.

What would most explain why SI gives rise to RF?
(A) Only certain strains of streptococcal bacteria are associated with rheumatic fever.
I incorrectly chose A thinking that since ONLY certain strains are associated with RF then SI must be the cause. Thinking about this, perhaps this could insinuate similarly that there are other causes since ONLY certain strains are the cause.

So D is perhaps a clearer link.

Rheumatic fever is the most serious complication of

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Rheumatic fever is the most serious complication of

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