Viruses and Other Microorganisms - NCLEX-PN

The flu virus can be either live attenuated or inactivated. The center for disease control and prevention (CDC) recommends giving the flu virus annually to healthy adults, pregnant women, and children older than 6 months of age. The virus is different from year to year, and the vaccine each year represents the most common active forms of the virus. Vaccination is a type of primary prevention.

Viral replication takes place in several stages. Once the virus recognizes the target cell, it binds to the cell. The viral attachment protein present on the surface of virion interacts with the cell receptor. Following attachment the virus can penetrate the cell by process of endocytosis or fusion. In the step of uncoating the capsid the envelope is removed and viral nucleic acid is released inside the host cell, so the viral genes become available for transcription.

In the protein synthesis step the process differs according to type of virus and the structure of genome. RNA virus mostly replicates in the cytoplasm. Plus-strand RNA viruses initiate protein synthesis. Minus-strand RNA virus, double-stranded RNA viruses, and DNA viruses initiate nucleic acid synthesis. Protein synthesis in DNA virus replication is divided into early phase and late phase. Once the replication is over the newly synthesized viral protein and nucleic acid is assembled inside the cells. The capsomers are self assembled into capsid. In enveloped virus the viral envelope is added from the cell membrane and becomes associated with nucleocapsid. The newly assembled virus is released from the cell by budding or cell lysis.

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.

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.

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.

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.

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.

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.

Orchitis due to mumps has decreased significantly due to vaccination, but it is still a significant risk in unvaccinated individuals. Mumps-related orchitis can result in testicular failure later in life. None of the other microbial infections listed have an association with orchitis.

Individuals with hepatitis C have a much higher incidence of development of type II diabetes. This is thought to be due to increased levels of tumor necrosis factor (TNF)-alpha, which leads to insulin resistance. Gaucher's disease is a hereditary disorder of glucosylceramide accumulation that can affect the liver but is not caused by hepatitis C virus. Wasting syndrome is a general term for individuals who experience unintentional weight loss due to a disease such as cancer. Fabry disease is a rare liposomal storage disorder unrelated to any viral infection.

This question requires the student to distinguish between the rashes that are common in children; specifically those that may be present due to fear of immunizations. Measles begins with Koplik's spot in the mouth. Then the rash first appears on the forehead. Rubella first appears on the trunk, then spreads throughout the body. Chicken pox manifests as fluid-filled vesicles. Smallpox appears as blister-like lesions and this disease has been eradicated for a few decades.

All forms of warts are caused by the virus HPV, or human papillomavirus. In addition, HPV is the cause of a variety of dysplasias, including cervical dysplasia, vulvar dysplasia, and oropharyngeal cancer. None of the other viruses listed are associated with warts of any kind.

While all of the strains of HPV may cause condylomata acuminata, 90% of all cases of genital warts are caused by just two strains: 6 and 11.

Human papillomavirus has been associated with several forms of cancer, including cancers of the cervix, vulva, anus, and oropharynx. It is also associated with penile and vaginal dysplasias.

While HPV strains 31 and 33 have been associated with genital malignancies, more than 70% of cervical dysplasia is associated with HPV strains 16 and 18. Strains 6 and 11 are associated with genital warts, while 2 and 7 are associated with common warts.

While HPV 18 is associated with a large percentage of cervical dysplasia alongside HPV 16, HPV 16 is the strain associated with the majority of HPV-related anal cancer, cancer of the throat, tongue cancer, vaginal cancer, vulvar cancer, and penile cancer.

Infectious mononucleosis is associated with infection by Epstein Barr virus, a form of human herpes virus. Cytomegalovirus is associated primarily with congenital defects, parvovirus B19 is the cause of fifth's disease, also known as "slapped cheek syndrome." Herpes zoster is the virus responsible for both chicken pox and shingles.

There are more than 130 types of herpes viruses. Of those, 8 are known to infect humans. Some of the more common examples are herpes simplex 1 and 2, varicella / zoster, Epstein-Barr virus, and cytomegalovirus. Less common viruses include human herpes virus 6, human herpes virus 7, and Kaposi's sarcoma-associated herpesvirus. Rotavirus is not a herpes virus; rather, it is a double-stranded RNA virus in the Reoviridae family.

Rhinovirus, a type of picornavirus, is implicated in up to 50-80% of cases of the common cold. Other less common causes include human coronavirus (15% of cases), influenza (10%), and adenovirus (5%).

The majority of infectious vomiting and diarrhea in infants and young children is viral in origin, with the most commonly implicated virus being rotavirus. Norovirus is another common cause of viral gastroenteritis in individuals of all ages, though it is not as common in young children as rotavirus.