Self limited diarrhea in a 4 year old

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Self limited diarrhea in a 4 year old

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macintosh
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03/12/08 - 03:36 AM

Stool cultures of a 4 year old boy with self limited diarrhea and abdominal cramps grow non-lactose fermenting gram negative rods on MacConkey's agar. Organisms do not produce gas on fermentation of glucose and do not produce H2S on TSI agar. Which of the following is the most important pathogenic mechanism for the infection caused by this bacterium?

A. Exotxin production

B. Mucosal invasion

C. Intestinal colonization

D. Bacteremia

E. Proliferation in lymph nodes

(Please explain your answer, as I am confused.)

pr20
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03/12/08 - 10:23 AM

A. Exotoxin production??

Non-lactose fermenting Gm-ve rods are:-

Shigella,Yersinia(both are nonmotile and non-H2S producers)

Salmonella,Proteus(both are motile and H2S producers)

Usually Shigella causes more severe dysentery.So finally left with Yersinia enterocolitica.

Yersinia entercolitica causes enterocolitis mimicking appendicitis through the production of enterotoxin(which is a type of exotoxin).

Pls post the correct answer.

yarab99
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03/12/08 - 01:14 PM

B-mucosal invasion

this is shigella...as pr20 said we are left with shigella and yerisinia...and shigella is more common,besides yerisenia will present mimicing appendicitis

shigella`s pathogenic mechanism is by mucosal invasion it enters by M cells in Payer patches so it escapes phagosomes,then releases its toxins,exotoxin production is Right but it cant be done with out invasion first,which is THE MOST IMPORTANT MECHANISM

Tiff
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03/12/08 - 02:00 PM

yarab99 wrote:
B-mucosal invasion

this is shigella...as pr20 said we are left with shigella and yerisinia...and shigella is more common,besides yerisenia will present mimicing appendicitis

shigella`s pathogenic mechanism is by mucosal invasion it enters by M cells in Payer patches so it escapes phagosomes,then releases its toxins,exotoxin production is Right but it cant be done with out invasion first,which is THE MOST IMPORTANT MECHANISM

Agree

macintosh
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03/13/08 - 06:17 AM

The correct answer, as stated in USMLE World is choice "B" (i.e. mucosal invasion). But personally I favour choice "A" to be correct, as I agree with the explanation provided by pr20.

Based on my understanding after reading the relevant topic from Kaplan Microbiology Lecture Notes, Shigella causes the most sever form of hemorrhagic dysentery. I can not understand how the most severe of dysentery is actually very "self limited". Additionally while reading the topic of Yersinia enterocolitica, I find that the diarrhea it causes may occur without symptoms of apendicitis (pseudoappendicits), in at least the very young. It is however not mentioned how young, would the very young be. Any ideas any one?

bactitech
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04/26/08 - 08:10 PM

I have had Shigella flexneri personally. It rips up your guts and causes bloody diarrhea. It is self limiting only because Shigella does not invade the blood stream, whereas Salmonella can and does. The latter can also invade tissues and become a systemic infection. I have seen Salmonella in sputum, a shoulder aspirate, and in blood cultures over my career where as Shigella are only in stool specimens. I was sicker than a dog with Shigella and lost 15 lbs. in the course of 2 weeks. Do NOT equate self-limiting to "not serious." A little child with this organism would have had to be in the hospital on IV's to survive the diarrheal and tenesmus onslaught.

I have only seen Yersinia growing in cultures a couple of times. They were both in young children but I cannot remember the age. I don't know anything about the cases either but know that they came from our hospital clinic's family practice group. It is not very common. Shigella really isn't either, although I'm told there is a current outbreak in Indiana. We see Campylobacter and Salmonella MUCH more often.

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