NCLEX : Other Microbiology Concepts

Study concepts, example questions & explanations for NCLEX

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Example Questions

Example Question #1 : Other Microbiology Concepts

What mold produces aflatoxin, a common contaminant in peanuts, peanut butter, pistachios, brazil nuts, and corn products?

Possible Answers:

Cladosporium

Aspergillus

Mucor

Penicillium

Correct answer:

Aspergillus

Explanation:

Aspergillus flavus is a mold species commonly found in peanut butter and many other foods. It produces aflatoxin, a toxin linked to increased risk of liver cell cancer. The other mold species listed are not considered to be related to liver cancer. Cladosporium species are rarely harmful to humans. Penicillium species produce antibiotics, which we commonly use to treat infections. Mucor species cannot grow in warm temperatures, and are unable to infect humans, with the exception of certain heat-tolerant strains, which may cause some zygomycosis.

Example Question #2 : Other Microbiology Concepts

Which of the following is a fungus that may be responsible for certain cases of diaper rash? 

Possible Answers:

Blastomyces dermatitidis

Pneumocystis jirovecii

Sporothrix schenckii

Aspergillus fumigatus

Candida albicans

Correct answer:

Candida albicans

Explanation:

Candida albicans is a fungus present in the normal flora of humans. An overgrowth of this fungus may cause yeast infections of the skin, vagina, or mouth. After a child receives antibiotics, they may contract a mycotic diaper rash due to Candida albicans overgrowth since the normal bacterial flora have been eliminated by the antibiotics. Pneumocystis jirovecii may cause pneumocystis pneumonia. Blastomyces dermatitidis and Aspergillus fumigatus may cause lung infection if the spores are inhaled. Lastly, Sporothrix schenckii may cause a skin infection called Sporotrichosis after it enters through a break in skin integrity.

Example Question #3 : Other Microbiology Concepts

Which of the following human body systems are prions most likely to affect?

Possible Answers:

The cardiovascular system

The reproductive system

The nervous system

The endocrine system

The gastrointestinal system

Correct answer:

The nervous system

Explanation:

Prions are infectious protein particles that affect proteins, misfolding them and causing loss of function. They are most commonly found in the brain. Prion diseases are also called transmissible spongiform encephalopathies (TSEs) and include diseases such as mad cow disease and Creutzfeldt-Jakob disease.

Example Question #4 : Other Microbiology Concepts

Which of the following regarding fungi is false?

Possible Answers:

Fungi are similar to plants in that they contain chlorophyll

Fungi are present as normal flora in the human body

A disease caused by a fungus may be termed a mycotic infection

Yeasts are considered fungi

Thrush is an example of a fungal infection

Correct answer:

Fungi are similar to plants in that they contain chlorophyll

Explanation:

Fungi are similar to plants in that they both have cell walls (fungi have chitin cell walls and plants have cellulose cell walls) but they do not contain chlorophyll. Fungi such as Candida albicans are present in the normal flora of the human body. An overgrowth of fungi can cause mycotic infections such as a vaginal yeast infection, or orally as in thrush.

Example Question #5 : Other Microbiology Concepts

The virus responsible for causing AIDS (HIV) is classified as a retrovirus. Many of the drugs used to treat HIV infection take advantage of a unique sequence of events involved in the replication of retroviruses.

In order for HIV to replicate, which of the following steps must occur first?

Possible Answers:

The viral RNA must be degraded

A DNA polymerase must be synthesized from the RNA template

The host cell must synthesize reverse transcriptase

New viral RNA molecules must be synthesized by the viral RNA polymerase

The viral RNA must be converted to DNA

Correct answer:

The viral RNA must be converted to DNA

Explanation:

A retrovirus is an infectious particle consisting of an RNA genome packaged in a protein capsid, surrounded by a lipid envelope. This lipid envelope contains polypeptide chains, including receptor-binding proteins that link to the membrane receptors of the host cell, initiating the process of infection. In order to replicate, its genetic material (RNA) must first be converted to a DNA molecule by the enzyme reverse transcriptase. This enzyme, which is found in the virus particle, is a DNA polymerase that uses an RNA molecule as a template to synthesize DNA, resulting in an RNA/DNA double helix.

Further enzyme action leads to the synthesis of a DNA double helix using the RNA/DNA template. This DNA helix can then integrate into the host chromosome and be transcribed into RNA molecules coding for capsid proteins, envelope proteins, and the reverse transcriptase. This integration into the host DNA is carried out by the viral integrase. Integration into the host chromosome is required for the synthesis of new viral RNA molecules. A host cell RNA polymerase is responsible for this transcription. Many new virus particles are then assembled containing the RNA molecule and the enzyme reverse transcriptase.

Example Question #6 : Other Microbiology Concepts

An immunologist studying macrophages performs a series of experiments to study the pathophysiology and immunology of macrophages exposed to viral attack.

Which of the following activities in macrophages is counterproductive for cellular defense against viral attack?

Possible Answers:

Cytokine-initiated antiviral activity

Reduction of viral infection/replication in other cells

Phagocytic activity

Virus reservoirs in mononuclear phagocytes

Antigen presentation

Correct answer:

Virus reservoirs in mononuclear phagocytes

Explanation:

Mononuclear phagocytes (MNPs), which consist of blood monocytes, tissue macrophages, and dendritic cells, are the main cellular elements responsible for elimination of viral pathogens. At the same time, MNPs are the targets and reservoirs for many viruses. Most noteworthy, the MNPs utilize phagocytosis as the first battle armament against the onslaught. This greatly diminishes the quantity of virus until other aspects of the immune system can be activated.

Utilizing a number of antimicrobial mechanisms, macrophages can prevent infection or replication of the virus in other cells, representing an additional protection mechanism. Antibodies produced in response to viral infection may lead to either neutralization or lysis of the target cells. This is partially governed by the macrophage, functioning nonspecifically as an effector cell for antibody dependent cellular cytotoxicity. In addition, both macrophages and monocytes can either activate or be activated upon by cytokines to further increase their antiviral vigilance.

The uptake, processing, and delivery of viral antigens to T cells in the lymph nodes referred to as antigen presentation rounds out the defense mechanisms utilized by macrophages. Monocytes and dendritic cells also function as antigen presenting cells.

 

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