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  #1  
Old 12-25-2011
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Listening Micro question

A 3 yr old male experiences several episodes of otitis media. Middle ear exudate cultures grow H.influenzae although the patients immunizations are upto date. Which of the following explains H.influenzae infection in this patient despite immunizations?
A. No vaccine is effective against H.influenzae
B. The strains responsible for this patients disease produce exotoxin
C. The strains responsible for this patients disease do not produce capsule
D. H.influenzae infections despite immunizations means defective cellular immunity
E. H.influenzae infections despite immunizations signifies defective neutrophil function.

Post ur answers with explanations plz......!!!!!
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  #2  
Old 12-25-2011
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Default

C.

its caused by non typable H.influenza they do not have a capsule.so no vaccination for non typeable H.influenza.

also non typable H.influenza can cause otits media ,sinusitis and bronchitis.

Gluck
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Old 12-26-2011
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c.
nontypal h.influenza
__________________
if ur ready to learn......world is ready to teach...take d leap!!
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Old 12-26-2011
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Smile yup ans is C

But my doubt is can it be D.
Since HiB vaccine is a conjugate vaccine, the purpose of conjugation of H.influenzae vaccine with diptheria or tetanus toxoid is to get an T-cell dependent response which would develop a memory B cell clone. Development of immunity this way is long lasting compared to just H.influenzae capsular polysaccharide. So if we assume the patient suffers from T cell defect, this would lead to a poor memory response and hence inadequate immunity which would result in frequent infections????????
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Old 12-26-2011
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Quote:
Originally Posted by daulath singh View Post
But my doubt is can it be D.
Since HiB vaccine is a conjugate vaccine, the purpose of conjugation of H.influenzae vaccine with diptheria or tetanus toxoid is to get an T-cell dependent response which would develop a memory B cell clone. Development of immunity this way is long lasting compared to just H.influenzae capsular polysaccharide. So if we assume the patient suffers from T cell defect, this would lead to a poor memory response and hence inadequate immunity which would result in frequent infections????????
the infx is not caused by H.influenza type B for which there is vaccine as u pointed Hib conjugate vaccine.

this pt disease caused by non typable H.influenza which do not possess capsule so HiB vaccine not effective against it .

Two major categories of H.influenza-
encapsulated H. influenzae: a, b, c, d, e, and f
Unencapsulated strains are termed nontypable (NTHi)

most common is tybe b H.infuenza

option D is distractor

hope it helps !
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Old 12-26-2011
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Quote:
Originally Posted by daulath singh View Post
But my doubt is can it be D.
Since HiB vaccine is a conjugate vaccine, the purpose of conjugation of H.influenzae vaccine with diptheria or tetanus toxoid is to get an T-cell dependent response which would develop a memory B cell clone. Development of immunity this way is long lasting compared to just H.influenzae capsular polysaccharide. So if we assume the patient suffers from T cell defect, this would lead to a poor memory response and hence inadequate immunity which would result in frequent infections????????
I agree with u answer can be both c and d.
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Old 12-26-2011
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Quote:
Originally Posted by step_enhancer View Post
the infx is not caused by H.influenza type B for which there is vaccine as u pointed Hib conjugate vaccine.

this pt disease caused by non typable H.influenza which do not possess capsule so HiB vaccine not effective against it .

Two major categories of H.influenza-
encapsulated H. influenzae: a, b, c, d, e, and f
Unencapsulated strains are termed nontypable (NTHi)

most common is tybe b H.infuenza

option D is distractor

hope it helps !
Thanks for the info.....i agree with u....Since the boy suffers from frequent infections, the possibility of immunodeficient state has to be kept in mind....I feel D could also be the answer.
Lets see if anyone can clarify it in greater detail.......
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Old 01-24-2012
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Default Its C

I think that the reason for not being D is because when children have multiple mucosal infections (otitis, pharyngeal etc) they should tell you specifically or give you clues for either selective IgA deficiency or variable immunodeficiency.
In the question stem they specifically tell you that he is having infections secondary to H.influenza eventho he is vaccinated; Knowing that the most common causes of otitis media are in this order.
S.pneumo
H.Influenzae (Not HiB)
Moraxella

If they didnt mention that the child already had the vaccine for HiB then D would be correct, however, they put it for a reason.

One trick I do is dont overthink the question and just answer from the info given. If they would told me that the child had been suffering from multiple infections not only in the middle ear, but in the throat as well and even putting some more organisms then for sure i would pick D.
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Old 01-24-2012
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Default

there was a similar question in Kaplan Qbank.

according to its answer, 95% of invasive disease (epliglottitis, meningitis) is due to H.Influenzae caused by type B that has a polyribitol phosphate capsule. But Otitis Media is usually caused by a strain with out the capsule, which is why even though you've been vaccinated you can still get otitis media.
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