Question from a student 20170423

TO BE ANSWERED IN REVIEW SESSION 2 ON 24/4/2017 MONDAY

From CCCCC, a question on the exercise..........................

The student requested email answer and not on the blog. So I deleted her email here and I will work the question in the review session with you students and then I will send my answer via email to the student.

The exercise is as follows:

	a.	45 of the patients joined a company picnic together with another 115 employees.  Lunch was served during the picnic: Menu—Pizza (with toping of  ham, olive, pineapples, and green pepper), shrimp salad, roasted turkey, and bread.
	b.	Lunch in the picnic was served at 12:00 noon on Saturday.
	c.	45 patients started to have diarrhea at  2:00pm on Saturday followed by severe vomitting.  They went to the hospital immediately.  The last patient went to the hospital at 4:00pm on Saturday.
	d.	The hospital laboratory detected low levels of Salmonella enterica subspecies typhimurium (serotype O14) from the feces of 15 patients.
	e.	The laboratory of the Health Department detected low levels of Salmonella enterica subspecies typhimurium (serotype O14) and low levels of Staphylococcus aurues from the shrimp salad that was left over from the food served during the picnic and then refrigerated after lunch.  Low  levels of Clostridium perfringens  spores were found in the vegetable stock, part of  which was used to make the turkey stuffing.  No bacteria or spores were found from bread or pizza.
	f.	The laboratory traced the sources of the food.  Some dough was collected from the pizza house which supplied the pizzas for the picnic.  No bacteria were found in the dough.
	g.	The turkey and bread was prepared in the morning and transported to the picnic area without refrigeration.  The shrimp salad was also made in the morning, stored in a foam box with some ice and transported to the picnic area.  The pizzas were baked right before lunch time and transported to the picnic area while they were kept at 65-70°C.
	h.	Most of the patients recovered after one day of rest.

        

i.	The foods consumed at breakfast and lunch and the illness records are listed in the following table, calculate the attack rates.  Which food would be the suspected food?  Explain briefly.                                                                                                       (4 marks)

Foods served	Ate				Did not Eat
	Well	Ill	Total	Attack rate	Well	Ill	Total	Attack rate
Pizza	78	10	88		37	35	72
Shrimp salad	56	33	89		51	10	61
Roast turkey	78	25	103		30	20	50
Bread	96	40	136		19	5	24

ii.	Using the information provided,  suggest a hypothesis to describe the outbreak.  Describe the implicated microorganism(s) involved, their transmission, food implicated, and events that caused the outbreak.  Explain your answer.                                 (12 marks)

iii.	How could the outbreak be prevented?                                                                  (4 marks)