Hello everyone, today I am going to discuss the experiments performed in the laboratory on Thursday and Wednesday. Specifically, I am going to discuss my rectal sample, since most people in the class did not receive this particular bacterial species on their pre-prepared plates. For the rectal samples, we received four prepared plates, an SBA, a MAC, an XLD, and a CVA. My pathogenic isolate appeared as a clear colony on MAC, a gray colony on SBA, yellow colonies on XLD, and showed no growth on CVA. No growth on CVA revealed that my isolate was not Campylobacter since this plate is specific for Campylobacter. Clear growth on MAC revealed that my isolate was a non-lactose fermenting gram negative rod. The yellow colonies on the XLD confused me slightly at, since normal GI flora typically appear yellow on XLD. However, I remembered that Yersinia may appear clear to slightly yellow on XLD, so I began to suspect a possible Yersinia infection. I performed an API 20 E to confirm this. My API results yielded a perfect match for Yersinia enterocolitica, which can cause such diseases as mesenteric lymphadenitis, hemorrhagic enterocolitis, and terminal ileitis. Although I chose to perform an API 20 E to confirm my identification of Yersinia enterocolitica, I could have performed an entirely different set of tests and come to the same conclusion. If KIA, LIA, and Urea tests had yielded Alk/A, P/Y, and +/- and motility tests had been negative at 35° and positive at room temperature, I would have also come up with an ID of Yersinia.
Below is a transmission electron microscopic view of Yersinia enterocolitica. I had never seen an image quite like this, so I thought I would included it!
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