I think Shigella is the most appropriate, as it is actually regarded as highly inflammatory. Yes, E. coli can be of the EHEC/STEC variety, but E. coli could also be of the ETEC variety or whatever other strains it has. Ergo, E. coli may be plausible, but it is not the 'most likely.' Bleh to these kinds of questions.
Shigella causes an inflammatory diarrhea; it produces a toxin and can invade tissue directly. In addition, it is resistant to acid, so it has a characteristically low infective dose (~10 organisms), which facilitates its fecal-oral (person-to-person) spread especially in settings where hygiene may be compromised, such as in daycare or institutional housing. It can be differentiated from E. Coli (EHEC) because E Coli doesn't have as much person-to-person spread and only causes GI damage by the shiga-like toxin, not direct invasion. Therefore, EHEC wouldn't facilitate as strong of a neutrophilic response.
Apart from the line in FA referencing PMN infiltrate in Shigella, there is no way to differentiate here between it and E. Coli. Cheap shot.
Like many here, I was between E. Coli and Shigella but went with Shigella because of the daycare center history. I associate EHEC E. Coli with bad burger meat and it seemed unlikely to me that they would be whipping up burgers at the daycare (Usually everyone brings their own lunch to daycare) .
Shigella is the most likely causal organism over E. coli due to the vignette specifically stating the patient has had "bloody MUCOID stools with tenesmus."
Page 144 FA 2019 GI manifestations: Fever, crampy abdominal pain -> tenesmus, blood mucoid stools (bacillary dysentery).
Please correct me if I'm wrong, but I don't remember Sketchy mentioning bloody mucoid stools for E. coli and that detail doesn't seem to appear in FA.
sOn EMB Agar, isolated colonies of lactose-fermenting bacteria appear brown to blue-black in color. Escherichia coli appears as large, blue-black colonies, often with a green metallic sheen. Enterobacter spp. present as brown to blue-black, mucoid colonies with no sheen. Non-lactose-fermenting colonies, such as Shigella spp. and Salmonella spp., appear transparent and colorless.
We basically needed to correlate that โ no organisms seen but only neutrophils to being a lactose non-fermentor organism. Therefore the answer is Shigella and not E coli
the child was in a daycare, sonnei and rotavirus are the ones to keep in mind. sonnei can also be due to unwashed veggies too. and the inflammatory stool (neutrophils) also indicates sonnei. the lack of exposure (undercooked meat for EHEC) helps to rule out E.Coli. dirty water (ETEC and EIEC) aren't possible because of this kids bloody stool. Also for this to be HUS (the only possible E.Coli with bloody diarrhea), we should have seen the triad or at least something about it (anemia + thrombocytpoenia + Acute Renal Insuff.). Also, "mucoid stools" is right from the FA chart for shigella.
E. coli isn't an inflammatory diarrhea, Shigella is (think back to the flames in the Sketchy video). That alone is enough to rule out E. coli from answer choices.
Can someone help me out? I chose E.Coli too, and I'm too thick to understand the comments here. The question said fecal smear not special agar culture dishes...why are we talking about stain colors? and why would methylene blue stained fecal smear show no organism? I thought methylene blue stains just about any cells that has DNA/RNA. If the question is trying to tell us that there were NO ORGANISMS seen in the smear, why would Shigella not be seen? Is it because Shigella invades cells and considered more intracellular than E.Coli?
submitted by louisville(12)
Methylene-blue stained fecal smear reveled numerous neutrophils (but not any organisms). Shigella is colorless when stained with methylene blue; E coli stains blue with methylene blue because it ferments lactose.