Which of the following statements is false?
a. E. coli never causes disease
b. E. coli provides vitamin K for its host
c. E. coli often exists in a mutualistic relationship with humans
d. A disease-causing strain of E. coli causes bloody diarrhea

Distinguish symptoms from signs as signals of disease.

Define symbiosis. Differentiate commensalism, mutualism, and parasitism, and give an example of each.

All members of a group of ornithologists studying barn owls in the wild have had

salmonellosis (Salmonella gastroenteritis). One birder is experiencing her third infection. What is the most likely source of their infections?

a. The ornithologists are eating the same food.

b. They are contaminating their hands while handling the owls and nests.

c. One of the workers is a Salmonella carrier.

d. Their drinking water is contaminated.

Which of the following is not one of Koch's postulates?

a. The same pathogen must be present in every case of the disease.

b. The pathogen must be isolated and grown in pure culture from the diseased host.

c. The pathogen from pure culture must cause the disease when inoculated into a healthy, susceptible laboratory animal.

d. The disease must be transmitted from a diseased animal to a healthy, susceptible animal by direct contact.

e. The pathogen must be isolated in pure culture from an experimentally infected lab animal.

Among hospital patients who have infections, one-third did not enter the hospital with the infection but rather acquired it in the hospital. How do they acquire these infections? What is the method of transmission of these infections? What is the reservoir of infection?

Indicate whether each of the following conditions is typical of subacute, chronic, or acute infections.

a. The patient experiences a rapid onset of malaise; symptoms last 5 days

b. The patient experiences cough and breathing difficulty for months

c. The patient has no apparent symptoms and is a known carrier