On Thursday night you are up late studying for your microbiology exam the next d
ID: 132740 • Letter: O
Question
On Thursday night you are up late studying for your microbiology exam the next day (even though you know that cramming the night before is NOT the correct way to study for this class).
Your lab partner stops by and the two of you decide to order a pepperoni pizza. By 1 A.M. you are exhausted. One piece of the pizza is left but you are too tired to wrap it up and put it in the refrigerator, so you leave it in the box on your desk and go to bed. While closing the lid of the box you sneeze and deposit 1000 Staphylococcus aureus cells onto the pizza. At room temperature this organism has a generation time of 30 minutes.
In the morning you wake up, still exhausted, and realize you already late for your 8:30 A.M. class. Too late to get breakfast, you grab the left over pizza and rush to class.
Should you expect to feel sick later in the day? If so, what symptoms would you have? (Use internet or library reference book to determine these.) (5pts) (1 source minimum!)
Explanation / Answer
Staphylococcus aureus is a gram-positive bacterium that can cause skin illnesses such as pimples, boils, carbuncles, abscesses etc. It can cause respiratory illnesses. However, it can produce enterotoxins that can cause food poisoning if ingested. It can produce around 9 different toxins.
The S .aureus was sneezed on the pizza. If it is a pathogenic strain, it can cause food poisioning if ingested. S. aureus has a generation time of around 30 min. It can grow in foods that contain milk and cheese. The leftover pizza contains cheese and meat. Hence, the bacterium would be able to grow on the pizza. The early symptoms of food poisoning can take less than 30 min of ingestion. Typically, symptoms would occur with 2-8 hours of ingestion. As the doubling time is only 30 min, the 1000 bacteria would have grown by 8: 30 am in to a sizable number (around 3.5*107 cells).
Generation time= time/number of generations
30 minutes= 450 minutes/ 3.3*log N/1000
3.3*log N/1000= 450/30= 15
3.3 (log N-Log 1000) = 15
3.3 (log N-3) =15
3.3 Log N- 9.9= 15
3.3 log N= 15+ 9.9= 24.9
Log N= 24.9/3.3= 7.55
N= 107.55= 35481338= 3.5*107 cells
Hence, the food ingested will have enterotoxin produced by S. aureus.
The person will exhibit symptoms by 2-8 hrs, indicating that you will feel sick by 10:30 am -4:30 pm. Symptoms will include nausea, violent vomiting, abdominal cramping, with or without diarrhea. The disease is self limiting in healthy people. However, in infants and old people, hospitalization may be required. Dehydration may result in case of severe water loss.
The enterotoxins possibly stimulate the vagus nerve in the abdominal viscera and signal the vomiting center in brain. The toxins also penetrate gut lining and activate immune responses. Inflammatory mediators such as histamine, leukotrienes, and neuroenteric peptide substance P may causes vomiting. The toxins produced cannot be destroyed by heating. Pyrogenic toxins cause superantigenic activity. This activity leads to immunosuppression and nonspecific T-cell proliferation. As less as 0.1 microgram of enterotoxin can cause food poisioning.
I cannot include references, as it is not permitted by the Chegg’s rules.
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