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What is the pathogen?

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kacey Witter - Daye

on 28 March 2015

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Transcript of What is the pathogen?

Case Study Six

The Temperature Tells the Tale

What is the pathogen?
This particular pathogen as evidence presented by its symptoms is
Salmonella enterica
serovar Typhimurium
What microbiological tests were done to test for this organism?
Laboratory Tests for Salmonella Typhimurium
How could this outbreak have been prevented?
To have prevented the outbreak of salmonella among the school population, adequate preparation and storing technique should have been taken into consideration. When defrosting frozen chicken, the chicken should be placed in the refrigerator to thaw out not in water. Salmonella don’t grow very well in colder areas, that is why it is important to keep things that salmonella like to grow on like (raw chicken) in the fridge. By doing this, it slows down the growth of the salmonella bacteria, so that it is more likely to kill all the bacteria when the chicken is being cooked. However, failure to apply this method will result in salmonella dividing about once every 20 minute, when defrosted at room temperature.
The fact that there were leftovers, the chicken should have been quickly cooled by placing them in a refrigerator after stem stop rising. If the chicken was properly cooked the first time to 177 degree Celsius and the leftovers quickly cooled down, then they can heat up leftovers. Cooking or reheating foods to a safe internal temperature use a meat thermometer, to make sure foods are cooked to a safe temperature.
What is meant by cytochrome oxidase negative and lactose negative?
Cytochrome oxidase negative is a test to see if an organism is an aerobe, therefore a cytochrome oxidase negative means that the result of the organism is negative, meaning that it does not produce cytochrome c oxidase.

Lactose negative is a non-lactose fermenting bacterium such as Salmonella that does not produce lactase hence it cannot ferment lactose.

What microbiological tests were done to test for this organism?
Samonella species are gram-negative flagellated facultatively anaerobic bacilli identified by by O, H, and Vi antigens. Microbiological test that could be done to identify the genus salomella is done by biochemical tests; the serologic type is confirmed by serologic testing.

Feaces and blood could be plated on several nonselective or selective agar media, such as (Blood, MacConkey, EMB, Salmonella-Shigella agars) as well as enintoenrichment broth such as Selenite orTethrathionate. Any growth in enrichment broth is subsequently subcultured onto the agars. The biochemical reactions of suspicious colonies are then determined on triple sugar iron agar and lysine-iron agar and a speculative identification made. Recently biochemical test of Salmonella as been simplified by tests that allows the rapid testing of 10-20 different biochemical parameters simultaneously. The presumptive biochemical identification of salmonella then can be confirmed by antigenic examination of O and H antigens using polyvalent and specific antisera.

What is S. Typhimurium ?
Salmonella typhimurium is a Gram-negative, rod-shaped bacterium. Salmonella bacteria were first discovered by an American scientist, Dr. Daniel E. Salmon in 1884. Dr. Salmon isolated the bacteria from the intestines of a pig and called it Salmonella
. The genus Salmonella is divided into two species,
S. enterica
S. bongori
. Salmonella enterica are rod shaped Gram-negative bacteria. They are facultative anaerobes. They are very commonly found in raw meat, chicken, and egg shells. Another one of its' habitats is in contaminated water. Once it enters the host, it resides in the intestinal tract of the human or animal. Research done on the genomic sequencing of S. enterica can aid in the effectiveness of medications and vaccinations in treating disease. It is usually isolated on a selective medium such as MacConkey agar and XLD agar.

Kacey Witter 1306380
Daniel Dennis 1401208
Patricia Grant 1104634
Kamoy McCala 1405645
Storing and Preservating
When storing the leftover chicken, chill the chicken promptly after the steam as stopped rising from it. When warm food slowly cools to room temperature, the bacteria can growth quiet quickly at the intermediate temperature which is 37 0C. The longer the chicken sits at room temperature the more likely the bacteria will flourish, the incubation period is 12-72 hours, (overnight is way too long).
The fact that the chicken was reheated twice and left out in room temperature to cooled, the chicken should have been disposed, by this time there would have been maximum growth on the meat.

Citrate Test
SIM Test
Catalase test
Voges Proskauer Test
Urea Hydrolysis Test
Oxidase test
Indole test

Reference List
Salmonella Outbreak: 5 Tips for Cooking Chicken Safely. (n.d.). Retrieved from http://www.livescience.com/40376-salmonella-outbreak-chicken-cooking-tips.html

Salmonella | FoodSafety.gov. (n.d.). Retrieved from http://www.foodsafety.gov/poisoning/causes/bacteriaviruses/salmonella/

Salmonella.org/faq.Retrieved from www.salmonella.org/faq.html

Baron, E., and S Finegold. 1990. Bailey and Scott’s diagnostic microbiology, 8th ed. The Mosby Company, St. Louis, MO.

MacFaddin, J. F. 2000. Biochemical tests for identification of medical bacteria, 3rd ed. Lippincott Williams and Wilkins, Philadelphia, PA.

Vasanthakumari, R. (2007). Textbook of Microbiology. New Delhi, India: BI Publications Pvt Ltd, 2007.

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