Question from a student 20170503d

Q:

I have some questions concerning 2014-2015 Past Paper B2.

I think the implicated microorganism should be Staphylococcus aureus but the incubation period of 11-40 hours is not so consistent with that of the Staphylococcus aureus. Does it mean that as long as the calculated incubation period is longer than the incubation period of the microbe itself, it can be considered as consistent?

And the difference in attack rate of roast turkey is also quite high and there are also Clostridium perfringens detected in the roast turkey. The incubation period also matches. Can we also deduce it is the agent that cause the outbreak?

One more question is that if the microbes mentioned in the questions do not fit in the analysis, we can suggest some possible microbes by ourselves?

And may I also ask if Listeria monocytogens can grow at 40C? If yes, that means heat treatment at 40C is not effective in suppressing its growth?

A: 

The incubation period is a little too long. You have to discuss this point when you answer the question. But the pizza has the highest attack rate difference, which is an important factor for the implicated food. The roast turkey can also be a suspected food but it is less likely than the pizza. 

If the microbes resulted from the investigation do not fit totally with the deduction, you can of course suggest other possibilities.

Listeria can grow at 40C, so 40C is not effective in suppressing its growth