Mastering Microbiology Chapter 12

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What is the key difference between yeast and mold?

Yeast is unicellular, while mold is multicellular.

You are given an unknown, pure sample of a eukaryotic organism. Which of the following tests would allow you to determine if the sample contains algae?

Place the sample in a clear container filled with media containing no sugars, and leave it in a sunny window. After a few weeks, look for growth of the organism.

Which of the following new chemicals would NOT be effective against Giardia?

a chemical that inhibits the formation of cell walls

Which phylum of protozoa contains organisms that are nonmotile obligate intracellular parasites? (Hint: They cause a well-known tropical disease.)

Apicomplexa

Humans are the definitive host for __________, which is a type of __________.

Taenia saginata; tapeworm

Which of the following organisms requires an additional nonhuman host to complete its life cycle?

Plasmodium species

The term dermatophyte is typically used for fungi that cause which of the following?

cutaneous mycoses

Helminthic diseases are usually transmitted to humans by

gastrointestinal route.

All of the following are characteristic of the Platyhelminthes EXCEPT that they

have highly developed digestive and nervous systems.

The encysted larva of the beef tapeworm is called a

cysticercus.

A definitive host harbors which stage of a parasite?

adult

What do tapeworms eat?

intestinal contents

Seventeen patients in ten hospitals had cutaneous infections caused by Rhizopus. In all seventeen patients, Elastoplast bandages were placed over sterile gauze pads to cover wounds. Fourteen of the patients had surgical wounds, two had venous line insertion sites, and one had a bite wound. Lesions present when the bandages were removed ranged from vesiculopustular eruptions to ulcerations and skin necrosis requiring debridement. Fungi are more likely than bacteria to contaminate bandages because they

can tolerate low-moisture conditions

In mid-December, a woman with insulin-dependent diabetes who had been on prednisone fell and received an abrasion on the dorsal side of her right hand. She was placed on penicillin. By the end of January, the ulcer had not healed, and she was referred to a plastic surgeon. On January 30, a swab of the wound was cultured at 35°C on blood agar. On the same day, a smear was made for Gram staining. The Gram stain showed large (10 µm) cells. Brownish, waxy colonies grew on the blood agar. Slide cultures set up on February 1 and incubated at 25°C showed septate hyphae and single conidia. The most likely cause of the infection is a

dimorphic fungus

Ringworm is caused by a(n)

fungus

Yeast infections are caused by

Candida albicans.

Which of the following is the most effective control for malaria?

eliminate Anopheles

You see acid-fast oocysts in a fecal sample from a patient who has diarrhea. What is the MOST likely cause?

Cryptosporidium

In the malaria parasite life cycle

humans are the intermediate host and mosquitoes are both the definitive host and the vector.

Which of the following arthropods does NOT transmit diseases by sucking blood from a human host?

houseflies

Which of the following pairs is mismatched?

mosquito - Pneumocystis

Based on the lab results, which organism is most likely causing Tori's new symptoms?

Candida albicans

Which of the following best explains why Tori developed a new series of symptoms?

The antibiotics that treated Tori's primary respiratory infection also removed some of her normal bacterial flora, resulting in an overgrowth of other organisms.

Which of the following could Tori's physician choose as a treatment for her yeast infection?

-a single oral dose of fluconazole
-a topical over-the-counter ointment, such as clotrimazole or miconazole

Which of the following infections are also caused by C. albicans?

-fulminating disease
-oral thrush

Which of the following statements best describes why the treatment for Tori's fungal infection may result in side effects to her own cells?

Fungal cells and human cells have a nucleus, multiple organelles, and 80S ribosomes for protein synthesis.

How do blastoconidia and chlamydoconidia produced by yeast differ from bacterial endospores?

Blastoconidia and chlamydoconidia are spore structures produced by budding in yeasts, whereas bacterial endospores are produced by bacteria under extreme conditions.

How do pseudohyphae in yeasts differ from vegetative hyphae in filamentous fungi?

Yeasts use pseudohyphae to produce new daughter cells, whereas filamentous fungi use their vegetative hyphae to distract immune cells in the human host.

Why does Dr. Clark request stool samples for examination?

-He will have the laboratory prepare the samples for an ova and parasite (O&P) exam. Fresh or preserved stool samples can be observed microscopically for the presence of parasites or their eggs/cysts.
-Tapeworms are pathogens of the gastrointestinal tract; as a natural progression of digestion some of the tapeworm pieces will be expelled along with fecal matter.

Which of the following represents the MOST LIKELY route of transmission for Michael's infection?

Foodborne - Eating undercooked, unwashed, or otherwise contaminated food that contained parasitic propagules

Which of the following organisms is most likely the causative agent of Michael's tapeworm infection?

Taenia solium

Compare the anatomy of the tapeworm (Image C) to the anatomy of the roundworm (Image D). Given that both are parasitic worms, which of the following reasons best explains why the tapeworm is flat?

Tapeworms utilize diffusion to absorb nutrients from the host's digestive system.

What is the correct sequence of events for the life cycle of the pork tapeworm, T. solium?

1. eggs are produced by adult tapeworms living in the definitive host
2. eggs are released to the environment in the feces
3. pigs eat grass contaminated, or fertilized, with human feces.
4. inside the intermediate host, the eggs mature into larvae and encyst in the hosts muscles
5. the definitive host ingests the eggs and becomes infected

Why do we see an increase in the levels of IgE antibody in Michael's serum?

IgE is the class of antibodies involved in hypersensitivities such as allergies and parasitic infections.

What is the treatment that Dr. Clark will most likely recommend?

Praziquantel or albendazole, drugs that target eukaryotic parasites with minimal side effects in the host.

Why was Dr. Clark worried about tapeworm infection in other body sites?

-When tapeworm larvae escape the stomach, they can travel to other parts of the body such as muscles, the liver, the eye, and even the brain to form cysticerci.
-The presence of T. solium in the brain can result in neurocysticercosis, a serious condition which has symptoms resembling those of brain tumors or epilepsy.

In humans, beef tapeworm infestations are acquired by ingesting

cystycerci of Taenia saginata in undercooked meat.

All of the following pertain to pinworm infections EXCEPT

it is most commonly transmitted by cysts in water

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