Examples Of Unknown Microbiology

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Unknown #11:

My patient’s name is Cara, she is currently a freshman living in a dormitory with three friends. Just two weeks in, she catches the flu. Her roommates made her soup for the next couple of days from their shared pantry of foods. Cara however progressively becomes worse and now exhibits severe symptoms of nausea and diarrhea. This study was done by applying all of the methods that have been learned so far in the microbiology laboratory class for the identification of an unknown bacterium. The first step I took towards identifying my unknown was by using the given unknown broth and doing a streak plate to get single colonies by shaking the solution before taking my sample as well as using the aseptic technique to
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Using a wire loop, a small sample of the unknown test tube was plated on a nutrient agar using the streak method . The unknown test tube was then placed in a refrigerator to slow down any continued growth. The nutrient agar was labeled “VB TR1” and was placed in an incubator for 48 hours at 37 degrees Celsius. Following this procedure, I started to do research on microorganisms that presented the same type of symptoms (diarrhea and nauseous). After 48 hours, the plate was observed. There were multiple tiny whittish isolated colonies present, all of which showed the same growth pattern. Three colonies were chosen at random and Gram stains were performed on each (procedure for the Gram stain was used according to laboratory manual ex. 9). Each of the three Gram stains showed positive rods. After the Gram stain was determined, I began to do more research on microorganisms that had that identification and narrowing down all the possible tests to continue for identifying. Specific biochemical tests were performed. The biochemical tests performed were chosen based on the identification table that was given from the lab manual based on gram staining. The first test I performed was to check for endospore forming, my results came back positive the first time. However, it was difficult to verify if it was positive or not which had me test three more times resulting in non endospore forming. …show more content…
The Gram positive unknown was identified to be Listeria Monocytogenes. This conclusion was reached with several bits of evidence. Firstly, the Gram positive unknown was rod shape. This narrowed it down to seven different species. However, I felt it was important to perform a series of tests in order to confidently conclude that the Gram positive unknown was indeed Listeria Monocytogenes. So, the pre-constructed sequence of tests was still performed as if all seven of the Gram positive options were still possible. Secondly, the amounts of tests performed on the Gram positive unknown led to Listeria Monocytogenes as the only possible candidate. A non spore forming test removed all Bacillus and Clostridium species as a possibility. A positive catalase test removed Lactobacillus species as a possibility. A negative nitrate test removed mycobacterium species as a possibility. And, a positive phenol red arabinose test removed Kurthia species as a possibility. A Blood agar ( Beta hemolysis) test was resulted as negative which left only Listeria Monocytogenes. With performing the series of test I was able to come to the conclusion that my unknown is Listeria Monocytogenes. This microorganism causes listeriosis when someone ingests contaminated foods, symptoms starts with diarrhea and can progress to septicemia and meningitis mostly in high risk in pregnant women,

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