Question 1

Pathogenicity islands are

Accepted Answer

Pathogenicity islands are clusters of genes in bacterial chromosomes that have been horizontally acquired through mobile genetic elements and are responsible for a bacterium's virulence or pathogenicity. They contain genes that are not required for basic bacterial processes but are essential for virulence, including genes encoding toxins, adhesins, and immune system subversion proteins.

Question 2

Trichinella species spend their entire life within the body of a mammalian host, but can move from one species to another upon consumption of an infected animal.Which of the following statements regarding trichinosis is incorrect?

Accepted Answer

Ground pork is not safe, as the grinding process does not inactivate the Trichinella cysts.

Question 3

Which of the following statements regarding helminths causing intestinal distress plus migratory symptoms is incorrect?

Accepted Answer

The answer of Which of the following statements regarding helminths...

Question 4

The most dangerous outcome of a Taenia solium infection occurs when

Accepted Answer

When Taenia solium eggs are ingested, they can develop into larvae that migrate to various tissues, including the brain, causing neurocysticercosis, which is a serious and potentially life-threatening condition.

Question 5

The most dangerous outcome of a Taenia solium infection occurs when humans ingest tapeworm eggs rather than cysticerci.This type of transmission occurs by

Accepted Answer

Ingesting tapeworm eggs occurs through fecal-oral transmission, such as drinking water contaminated with feces from infected animals, leading to cysticercosis, a serious condition.

Question 6

Ascaris lumbricoides

Accepted Answer

All of the choices are correct. Ascaris lumbricoides is an intestinal roundworm that spreads to humans by ingestion of Ascaris eggs in contaminated food. The larvae penetrate into lymphatics and capillaries around intestines, migrate to the pharynx, get swallowed, and return to intestines to mature.

Question 7

Which of the following is not a helminth that causes intestinal symptoms accompanied by migratory symptoms?

Accepted Answer

Trichuris trichiura, also known as whipworm, primarily causes intestinal symptoms without migratory symptoms, unlike the other helminths listed.

Question 8

Which of the following is not true of schistosomiasis?

Accepted Answer

Schistosomiasis is a tropical disease that is transmitted via freshwater snails to humans. It is caused by blood flukes which can penetrate intact skin through hair follicles. The disease does not cover its outer surface with blood proteins to escape detection by the immune system. While schistosomiasis is currently not prevalent in the southern U.S., there is concern that warming waters due to climate change could lead to its introduction and spread.

Question 9

Which of the following statements concerning archaea in the microbiome is correct?

Accepted Answer

Methanogenic archaea are known to inhabit anaerobic environments such as the gut and gingival pockets. While some archaea do thrive in extreme conditions, others, like methanogens, are known to be commensal with humans. Option A is therefore incorrect. Option B is also incorrect as archaea can thrive in certain environments within the human body. Option D is incorrect as treatments for archaeal infections differ from those for bacterial infections.

Question 10

Which of the following helminths is correctly paired with its portal of entry?

Accepted Answer

Taenia solium is ingested through the consumption of contaminated food or water. Schistosoma species enter through the skin when exposed to contaminated water, Ascaris lumbricoides also enters through ingestion, and Enterobius vermicularis is transmitted through the fecal-oral route, not sexual transmission.

Question 11

Which of the following statements regarding tapeworms is incorrect?

Accepted Answer

Tapeworms do not produce toxins, instead, they absorb nutrients from their host's digestive tract.

Question 12

A metagenomic study from a never-before-seen type of gingival infection indicates the presence of large numbers of archaea.Which of the following would be a good practice to isolate this organism?

Accepted Answer

The presence of archaea suggests an anaerobic environment, so using an anaerobic medium and incubating in a sealed container would be the best practice for isolating this organism. The other options are not related to the preferred growth conditions of archaea.

Question 13

Identification of the causative microbe for a diarrheal infection often requires a stool culture.The best medium for this purpose is

Accepted Answer

A medium containing bile as a selective agent is the best choice for stool culture as it inhibits the growth of gram-positive bacteria and allows the growth of gram-negative bacteria that are commonly associated with diarrheal infections. This selective medium makes it easier to identify the causative microbe. A general purpose medium would not be selective enough and might allow the growth of normal gut microbiota that would interfere with identification. Using a broad-spectrum antibiotic would be counterproductive as it would kill the very bacteria that need to be identified. A medium containing mammalian blood would not provide any benefits over a selective medium, and a liquid medium would not be ideal as it would not allow for observation of colony morphology.

Question 14

Because of the complexity of the Schistosoma life cycle, there are several parts of the cycle that could be disrupted to halt the spread of the disease.Which of the following proposals is not likely to succeed in decreasing the prevalence of schistosomiasis?

Accepted Answer

A vaccine would not be effective against miracidia because they do not infect humans.

Question 15

The fact that Salmonella has a high ID₅₀ means that

Accepted Answer

A high ID₅₀ means that a relatively large number of organisms are needed to cause infection, so consuming just a few cells is unlikely to result in illness.

Question 16

Both Taenia and Trichinella can be found as cysts embedded in pork muscle.Which of the following statements about these organisms is incorrect?

Accepted Answer

The answer of Both Taenia and Trichinella can be found...

Question 17

From the surface to the interior of a tooth, the tissues in order are

Accepted Answer

The correct order of tissues from the surface to the interior of a tooth is enamel, dentin, and pulp. Enamel is the hard outer layer of the tooth, followed by dentin, which makes up the bulk of the tooth and is softer than enamel. The innermost layer is the pulp, which contains nerves and blood vessels. The other answer choices do not present the tissues in the correct order.

Question 18

Which of the following statements regarding schistosomiasis is incorrect?

Accepted Answer

Currently, there is no evidence to suggest that individuals who recover from a Schistosoma infection are protected by lifelong immunity. While it is possible that some level of immune protection may develop, reinfection is common in endemic areas, and individuals may become reinfected multiple times throughout their lives.

Question 19

Which of the following statements regarding trichinosis is incorrect?

Accepted Answer

Trichinosis is not transmitted by the fecal-oral route, but rather by consuming undercooked pork or wild game infected with the Trichinella larvae. The larvae then migrate from intestines to blood and various body tissues, where they encyst in skeletal muscle. Therefore, statement B is incorrect.

Question 20

Paramyxoviruses evade the host immune system by

Accepted Answer

Paramyxoviruses enter new cells by inducing syncytia formation, which involves merging of multiple infected cells and their membranes. This makes it difficult for the immune system to recognize and target the infected cells, allowing the virus to evade host defenses. None of the other options listed accurately reflect how paramyxoviruses evade the host immune system.

Quiz 22: Infectious Diseases Affecting the Gastrointestinal Tract