21. Principles of Disease

Differentiate the terms in each of the following pairs:

a. etiology and pathogenesis

b. infection and disease

c. communicable disease and noncommunicable disease

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?

The emergence of new infectious diseases is probably due to all of the following except

a. the need of bacteria to cause disease.

b. the ability of humans to travel by air.

c. changing environments (e.g., flood, drought, pollution).

d. a pathogen crossing the species barrier.

e. the increasing human population.

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 one of the following diseases is not correctly matched to its reservoir?

a. influenza-animal

b. rabies-animal

c. botulism-nonliving

d. anthrax-nonliving

e. toxoplasmosis-cats

Which of the following is not a portal of entry for pathogens?

a. mucous membranes of the respiratory tract

b. mucous membranes of the digestive canal

c. skin

d. blood

e. parenteral route

Use the following information to answer questions 1 and 2. A 6-year old girl was taken to the physician for evaluation of a slowly growing bump on the back of her head. The bump was a raised, scaling lesion 4 cm in diameter. A fungal culture of material from the lesion was positive for a fungus with numerous conidia.

Besides the scalp, this disease can occur on all of the following except

a. feet.

b. nails.

c. the groin.

d. subcutaneous tissue.

e. The disease can occur on all of these areas.

Use the following information to answer questions 3 and 4. A 12-year old boy had a fever, rash, headache, sore throat, and cough. He also had a macular rash on his trunk, face, and arms. A throat culture was negative for Streptococcus pyogenes.

The boy most likely had

a. streptococcal sore throat.

b. measles.

c. rubella.

d. smallpox.

e. hand-foot-mouth disease.

Use the following information to answer questions 3 and 4. A 12-year old boy had a fever, rash, headache, sore throat, and cough. He also had a macular rash on his trunk, face, and arms. A throat culture was negative for Streptococcus pyogenes.

All of the following are complications of this disease except

a. middle ear infections.

b. pneumonia.

c. birth defects.

d. encephalitis.

e. All are complications of this disease.

A patient has conjunctivitis. If you isolated Pseudomonas from the patient’s mascara, you would most likely conclude all of the following except that

a. the mascara was the source of the infection.

b. Pseudomonas is causing the infection.

c. Pseudomonas has been growing in the mascara.

d. the mascara was contaminated by the manufacturer.

e. All of the above are valid conclusions.

You microscopically examine scrapings from a case of Acanthamoeba keratitis. You expect to see

a. nothing.

b. viruses.

c. gram-positive cocci.

d. eukaryotic cells.

e. gram-negative cocci.

Use the following choices to answer questions 7 through 9.

a. Pseudomonas

b. Staphylococcus aureus

c. scabies

d. Sporothrix

e. virus

Nothing is seen in microscopic examination of a scraping from the patient’s rash.

Use the following choices to answer questions 7 through 9.

a. Pseudomonas

b. Staphylococcus aureus

c. scabies

d. Sporothrix

e. virus

Microscopic examination of the patient’s ulcer reveals 10μm ovoid cells.

Use the following choices to answer questions 7 through 9.

a. Pseudomonas

b. Staphylococcus aureus

c. scabies

d. Sporothrix

e. virus

Microscopic examination of scrapings from the patient’s rash shows gram-negative rods.

Which of the following pairs is mismatched?

a. leading infectious cause of blindness—Chlamydia

b. chickenpox—shingles

c. HSV-1—encephalitis

d. Buruli ulcer—stomach acid

e. none of the above