Question 1

Only Gram-positive bacteria produce exotoxins.

Accepted Answer

Both Gram-positive and Gram-negative bacteria can produce exotoxins.

Question 2

Which of the following is NOT a likely reason why diseases caused by opportunists are becoming more frequent in the US population?

Accepted Answer

The other three choices all relate to specific groups of people with compromised immune systems, which would make them more vulnerable to opportunistic infections. However, choice D is about travel bringing in new pathogens that can infect otherwise healthy individuals. This is not related to immune system compromise and therefore is not a likely reason for the increase in opportunistic infections.

Question 3

A number of viruses often include a similar set of symptoms when they cause an infectious disease state (fever, headache, fatigue, runny nose). Why would they all cause the same symptoms if they're different viruses?

Accepted Answer

The symptoms are not caused by the viruses themselves, but rather by our immune response to the viruses. Our immune response is similar regardless of the type of virus, leading to similar symptoms.

Question 4

Home-canned foods should be boiled before consumption to prevent botulism. Considering that this treatment does NOT destroy endospores, why would it be helpful in preventing the disease?

Accepted Answer

Boiling the home-canned foods before consumption would denature the botulism exotoxin and inactivate it. The exotoxin is what leads to the disease symptoms, so this would make the food safer. While boiling does not destroy endospores, which can germinate into vegetative cells and produce new toxin, eliminating the exotoxin greatly reduces the risk of botulism.

Question 5

In two of Koch's postulates (#2 and #3), a pure culture of the organism is required. Which of the following would NOT be a possible consequence of using a contaminated culture?

Accepted Answer

Even though there's a contaminating microbe present, as long as the original suspect microbe is also present, the disease should still manifest in test animals and should be recoverable from test animals following infection. Therefore, there's really no consequence to using a contaminated culture.

Question 6

Why is it a good strategy for a microbe to adhere to a receptor that plays a critical function for a host cell?

Accepted Answer

If a receptor is critical for a host cell, the cell doesn't have a backup system to switch to. Therefore, the microbe benefits by putting that target out there, even though it makes it more susceptible to infection.

Question 7

The normal microbiota provides protection against potentially harmful organisms and stimulates the immune system. Why would the immune responses to members of the normal microbiota cross-react with pathogens?

Accepted Answer

Pathogens can often be closely related to members of the normal microbiota, and therefore the immune response may cross-react with them as they appear similar.

Quiz 16: Host-Microbe Interactions

Only Gram-positive bacteria produce exotoxins.

Which of the following is NOT a likely reason why diseases caused by opportunists are becoming more frequent in the US population?

A number of viruses often include a similar set of symptoms when they cause an infectious disease state (fever, headache, fatigue, runny nose) . Why would they all cause the same symptoms if they're different viruses?

Home-canned foods should be boiled before consumption to prevent botulism. Considering that this treatment does NOT destroy endospores, why would it be helpful in preventing the disease?

In two of Koch's postulates (#2 and #3) , a pure culture of the organism is required. Which of the following would NOT be a possible consequence of using a contaminated culture?

Why is it a good strategy for a microbe to adhere to a receptor that plays a critical function for a host cell?

The normal microbiota provides protection against potentially harmful organisms and stimulates the immune system. Why would the immune responses to members of the normal microbiota cross-react with pathogens?