Microbiology Exam 3

Rhinovirus:

researchers have identified a set of core genes that are common to all rhinoviruses. If a vaccine can be made against a protein product from this core set, perhaps disease prevention will be possible. Antibiotics will not prevent or cure a cold. Antihistamines can sometimes be used to treat the symptoms of a cold; however, they do not shorten the length of the illness. Because rhinoviruses spread by respiratory droplets, washing hands remains an important hygiene measure to decrease transmission of the viruses.

What does virion mean?

A completely assembled and infectious virus outside its host cell is known as a virion.

How are viruses classified and named?

A taxonomic scheme for all viruses has yet to be universally adopted - The International Committe on Taxonomy of Viruses (ICTV) is developing a classification system. The measles virus and poxviruses, for example, are named after the disease they cause; The Ebola and Marburg viruses after the location from which they were originally isolated; The Epstein- Barr virus after the researchers who studied it. Others are named after morphologic factors— the coronaviruses ( corona = " crown") have a crown- like capsid and the picornaviruses ( pico = " small"; rna = " ribonucleic acid") are very small viruses with an RNA genome.

What does virus host range refer to?

A virus' host range refers to what organisms ( hosts) the virus can infect and it is based on a virus' capsid structure. Most viruses have a very narrow host range. -A specific bacteriophage, for example, only infects specific bacterial species, the smallpox virus only infects humans, and the poliovirus infects only humans and primates. -A few viruses may have a broader host range, as the rabies viruses infect humans and most warm- blooded animals.

What is West Nile encephalitis or meningitis?

About one in 150 people infected with WNV will develop West Nile encephalitis or meningitis that affects the central nervous system. Symptoms can include high fever, headache, stiff neck, stupor, disorientation, coma, convulsions, muscle weakness, vision loss, numbness, and paralysis. These symptoms may last several weeks to over a year, and the neurologic effects may be permanent. Death can result.

Adenoviruses:

Adenoviruses (family Adenoviridae) are a group of over 50 types of nonenveloped, icosahedral virions having double-stranded DNA. The viruses take their name from the adenoid tissue from which they were first isolated (the pharyngeal tonsil located in the upper rear of the pharynx). Some adenoviruses are frequent causes of acute URT infections often symptomatic of a common cold in infants and young children. Transmitted through respiratory droplets, the viruses most often cause distinctive symptoms because the fever is substantial, the throat is very sore (acute febrile pharyngitis), and the cough is usually severe. In addition, the lymph nodes of the neck swell and a whitish-gray material appears over the throat surface. New military recruits may suffer acute respiratory disease (ARD) as a result of adenovirus transmission in crowded locations which can progress to viral pneumonia. The most common cause of laryngitis is a viral infection of the URT caused by a common cold or flu virus.

What is unique about the paramyxovirus infections?

Affects the lower respiratory tract. Enveloped viruses consisting of many clinically important pathogens.

What is antigentic drift?

Antigenic drift involves small changes to the virus. These changes involve minor point mutations resulting from RNA replication errors. The mutations will be expressed in the new virions produced. Although such mutations may be detrimental, on occasion one might confer an advantage to the virus, such as being resistant to a host's immune system. For example, a spike protein might have a subtle change in shape (that is, the structural shape has "drifted") so immunity to the flu virus is incomplete. This is what happens prior to most fu seasons. The virus spikes are different enough from the previous season that the host's antibodies fail to properly recognize the new strain. Both influenza A and B viruses can undergo antigenic drift.

What is antigenic shift?

Antigenic shift is an abrupt, major change in structure to influenza A viruses. Antigenic shift may give rise to new strains that can now jump to another species, including humans. (that is, the spike structure has "shifted") to which everyone is totally defenseless, and from which a pandemic may ensue.

What is Arbovirial Encephalitis?

Arboviral Encephalitis is an acute inflammation of the brain. pain in the head and neck, convulsions, coma. Those who recover may have paralysis and mental disorders. Humans are dead-end hosts There are many forms, many transmitted by mosquitoes and ticks.

What does Arbovirus refer to?

Arbovirus is a term used to refer to a group of viruses that are transmitted by arthropod vectors. The word arbovirus is an acronym(ARthropod-BOrne virus).

Viral Replication: Maturation

Assembly (Maturation). Once the phage parts are made, they are assembled into complete virus particles. The enzymes encoded by viral genes guide the assembly in step- by- step fashion. In one area of the host cytoplasm, phage heads and tails are assembled from protein subunits; in another area, the heads are packaged with DNA; and in a third area, the tails are attached to the heads.

Viral Replication: Attachment

Attachment. The first step in the replication cycle of a virulent phage occurs when phage and bacterial cells collide randomly. If sites on the phage's tail fibers match with a complementary receptor site on the cell wall of the bacterium, attachment will occur. The actual attachment consists of a weak chemical union between phage and receptor site. In some cases, the bacterial flagellum or pilus contains the receptor site.

How do we grow viruses if they are unable to grow using an auger plater?

Because viruses are parasites (requiring a live cell host), they will not grow on a nutrient agar plate the way bacterial cells do. Some other form for virus cultivation was needed. In 1931, Alice M. Woodruff and Ernest W. Goodpasture described how fertilized chicken eggs could be used to cultivate some viruses. The shell of the egg was a natural culture dish containing nutrient medium, and viruses multiplied within the chick embryo tissues.

Viral Replication: Biosynthesis

Biosynthesis. Having entered the cytoplasm, production of new phage genomes and capsid parts begins. As phage genes code for the disruption of the host chromosome, the phage DNA uses bacterial nucleotides and enzymes to synthesize multiple copies of its genome. Messenger RNA molecules transcribed from phage DNA appear in the cytoplasm, and the biosynthesis of phage enzymes and capsid proteins begins. Bacterial ribosomes, amino acids, and enzymes are all enlisted for biosynthesis. Because viral capsids are repeating units of capsomeres, a relatively simple genetic code can be used over and over.

Virus and Cancer:

Cancer results, in part, from the uncontrolled reproduction (mitosis) of a single cell. The cell escapes the cell cycle's controlling factors and as it continues to multiply, a cluster of cells soon forms. Normally, the body will respond to a tumor by surrounding it with a capsule of connective tissue. Such a local tumor is designated benign because it usually is not life threatening. Cancer is an uncontrolled growth and spread of cells. A tumor is a clone of abnormal cells. A benign tumor, normally, the body surrounds a tumor with a capsule of connective tissue. A malignant tumor, Tumor cells can break free from the capsule and spread to other tissues of the body (metastasis).

What is HSV-1?

Cold sores are contagious sores caused by HSV-1. After the acute (primary) infection, the viruses enter the sensory neurons and become latent in the nearby sensory ganglia. Viral reactivation and movement to the epithelia can trigger another round of cold sores. Reactivation of the dormant viruses often occurs after some form of trauma, often in response to stressful triggers, such as fever, menstruation, or emotional disturbance. Even environmental factors like sunburn (exposure to ultraviolet light) can trigger reactivation.

What do Human Papillomavirus infections cause?

Common warts are usually benign skin growths resulting from a strain of HPV. Genital warts (condylomata) are often transmitted through sexual contact.

What is complex symmetry?

Complex Symmetry: a combination of helical and icosahedral symmetry, a construction described as complex symmetry. Some bacteriophages, for example, have an icosahedral head with a collar and tail assembly in the shape of a helical sheath. Poxviruses, by contrast, are brick shaped, with submicroscopic filaments occurring in a swirling pattern at the periphery of the virus.

Temperate phages:

Do not lyse the host They insert their DNA into the bacterial chromosome as a prophage (lysogenic cycle)

How can EBV lead to lymphoma?

EBV in immunocompromised patients may lead to Burkitt lymphoma, a tumor of the connective tissues of the jaw that is prevalent in areas of Africa. In fact, EBV was the first human virus associated with a malignancy. In addition, there is growing evidence suggesting a possible link between EBV and Hodgkin disease, a lymphoma of the lymph nodes and spleen. Also, evidence is mount-ing for an association between EBV and an increased risk of developing multiple sclerosis, a muscle-weakening disease of the central nervous system.

Symptoms of rabies?

Fever, headache, and increased muscle tension develop. Patients become alert and aggressive, followed by paralysis and brain degeneration. Death from respiratory paralysis occurs within days. Brain degeneration, together with an inability to swallow, increases the violent reaction to the sight, sound, or thought of water. The disease therefore has been called hydrophobia— literally, the fear of water. Death usually comes within days from respiratory paralysis.

What is HSV-2?

Genital herpes is a common STD, caused usually by HSV-2. Symptoms include: itching and throbbing in the genital area. followed by blisters.

What is a helical virus?

Helical Viruses: rabies and tobacco mosaic viruses, exist in the form of a helix and are said to have helical symmetry. The helix is a tightly wound coil resembling a corkscrew or spring.

Influenza and what type of two spikes do they contain?

Hemagglutin (H) helps the virion attach and penetrate host cells. Neuraminidase (N) helps release virions from the host cell after replication and assembly.

What is Hepatitis A?

Hepatitis A is an acute inflammatory disease of the liver most commonly transmitted by food or water contaminated by the feces of an infected individual. Hepatitis A is a highly contagious liver infection caused by the hepatitis A virus. The virus is one of several types of hepatitis viruses that cause inflammation and affect your liver's ability to function. Hepatitis A virus (HAV) belongs to the Picornaviridae family.

What is Hepatitis D?

Hepatitis D is caused by two viruses: HBV and the hepatitis D virus ( HDV). The latter virus con-sists of a protein fragment called the delta antigen and a segment of RNA, and can only cause liver damage when HBV is present. HDV requires the outside coat of HBV to infect cells. Therefore, one cannot become infected with hepatitis D unless he or she already is infected with HBV. Chronic liver disease with cirrhosis is two to six times more likely in a co- infection.

What are two types of rabies?

In animals: Furious rabies involves violent symptoms like: wide eyes. drooling. unprovoked attacks. Animals with dumb rabies are docile and lethargic.

What is unique about Lassa fever?

Infection leads to severe fever, exhaustion, and patchy blood- filled hemorrhagic lesions of the throat. The fever persists for weeks and profuse internal hemorrhaging is common. Overall, only about 1% of infections result in death. Transmission of Lassa fever is primarily through aerosol or direct contact with excreta from infected rodents, or from contaminated food.

What is herpes keratitis?

Infection of the eye is called herpes keratitis. It can cause scarring of the cornea and blindness.

What is the Rotavirus?

Infections can be a deadly infection in children. Transmission occurs through ingestion of contaminated food or water. The viruses invade the small intestine, inducing diarrhea. Treatment is oral rehydration therapy. Two vaccines are available.

What is unique about the Epstien-Barr virus (infectious mononucleosis)?

Infectious mononucleosis is a blood disease, especially of antibody- producing B lymphocytes ( a type of mononuclear white blood cell) in the lymph nodes and spleen. The name infectious mononucleosis ( or " mono") is familiar to young adults because the disease is common in this age group. It is sometimes called the " kissing disease" because it is spread by contact with saliva. It is a latent virus.

What is unique about measles (rubeola)?

Is a highly contagious disease Transmission occurs through respiratory droplets. Koplik spots are red patches with white grain-like centers that appear along the gum line. The characteristic red rash Vaccine is given in the MMR inoculation. Complications can be subacute sclerosing panencepalitis or Paget's disease of the bone One is subacute sclerosing panencephalitis (SSPE), a rare brain disease characterized by a decrease in cognitive skills and loss of nervous function. It can occur anytime from 1 month to 25 years after clinical measles (usually within 7 to 10 years).

What is Smallpox's?

Is contagious, and sometimes fatal. Pink-red macules appear on the face and trunk. They then become papules, and fluid-filled vesicles. The vesicles become pustules that break open and emit puss, leaving pitted scars (pocks).

What is unique about chickenpox's?

Is no longer a prevalent disease in the United States. A vaccine using attenuated viruses became available in 1995. It is a highly communicable disease caused by the varicella-zoster virus (VZV). It is transmitted by skin contact and respiratory droplets. A red, itchy rash spreads across the entire body and turns into fluid-filled vesicles which break open and yield highly infectious virus-laden fluid. The most common complication is bacterial infection of the skin.

What is Hepatitis C?

Is transmitted by blood Few symptoms are associated with primary infection. Most cases develop a symptomless chronic infection cirrhosis is the primary cause of liver transplants in the US HCV damage is the primary reason for liver transplants in the United States. Damage is accelerated by alcoholism and drug use. No vaccine is available

What is an isocahedral virus?

Isocahedral viruses: herpes simplex and polioviruses, have the shape of an icosahedron and hence, icosahedral ( icos = " twenty," edros = " side") symmetry. The icosahedron then has 20 triangular faces and 12 corners.

What is unique about Respiratory syncytial (RS) disease?

It commonly affects children under 1 year of age. It infects the bronchioles and alveoli of the lungs, causing cells to fuse together into syncytia.

What is Rabies?

It has the highest mortality rate of any human disease once symptoms have begun. It enters the body through a skin wound contaminated with a bodily fluid from an infected animal.

What is unique about Fifth disease?

It is caused by human parvovirus B19 Transmission occurs through respiratory droplets. Symptoms include a fiery red rash on the cheeks and ears, and trunk. It disappears within a few days. Adults can experience symptoms similar to those of rheumatoid arthritis.

What two individuals are accredited with discovering vaccines to Polio?

Jonas Salk grew large quantities of the viruses and inactivated them with formaldehyde to produce the first polio vaccine in 1955. Albert Sabin's group subsequently developed a vaccine containing attenuated ( weak-ened) polioviruses. This vaccine was in widespread use by 1961 and could be taken orally ( OPV) as compared with Salk's vaccine, which had to be injected ( IPV).

Lytic and Lysogenic Cycle in relation to viruses:

Lysogenic cycle - the phage DNA integrates into the bacterial chromosome as a prophage. Bacteriophages participating in this cycle are known as temperate phages. The bacterial cell survives the infection and continues to grow and divide normally. As the bacterial cell undergoes DNA replication and binary fission, the prophage is copied and vertically transferred to daughter cells as part of the replicated bacterial chromosome. Thus, as cells divide, each daughter cell is " infected"; that is, it contains the viral genome as a prophage. Such binary fissions can continue for an undefined period of time. Usually at some point, the bacterial cells become stressed ( e. g., lack of nutrients, presence of noxious chemicals). This triggers the prophage to excise itself from the bacterial chromosomes and switch to a lytic cycle, lysing the bacterial cells as new phage are released.

What is the purpose of spikes projecting from an enveloped virus?

Many enveloped viruses also contain spikes projecting from the envelope. These proteins also function for attachment and host cell penetration.

What antibodies do patients develop one week after the onset of infection by EBV?

Many patients develop heterophile antibodies. (Heterophile antibodies: Antibodies nonspecifically reacting with proteins or cells from unrelated animal species.) The antibodies peak at weeks two to five and may persist for several months to one year.

What is the Norovirus?

Norovirus infections are the most likely cause of nonbacterial gastroenteritis in adults. Noroviruses ( formerly called the Norwalk- like viruses) are transmitted primarily through the fecal- oral route, either by consumption of contaminated food or water, or by direct person- to- person spread especially through aerosols produced from a vomiting episode.

What are Oncogenic viruses and Protooncogenes?

Oncogenic viruses transform infected cells. Epstein-Barr virus is linked to Burkitt Lymphoma, a tumor of the jaw. Human papilloma virus (HPV) is associated with cervical cancer. There is now a vaccine against some HPV. Protooncogenes, are the forerunners of oncogenes. Protoncogenes may have important functions as regulators of growth and mitosis (they must be important in cell metabolism, perhaps as growth regulators). protooncogenes can be converted to oncogenes by: -radiation, -by chemical carcinogens, -by chromosomal breakage and rearrangement, or -by viruses after which tumor formation begins.

Viral Replication: Penetration

Penetration. Following attachment, the tail of the phage releases lysozyme, an enzyme that dissolves a portion of the bacterial cell wall. The tail sheath then contracts and the tail core drives through the cell wall. As the tip of the core reaches the cell membrane below, the DNA is ejected through the hollow tail core and on through the cell membrane into the bacterial cytoplasm. The ejection process takes less than two seconds and the capsid remains outside.

What is the polio virus?

Polio (poliomyelitis) infects the gray matter of the spinal cord and brain. Polioviruses enter the body through contaminated food and water Polioviruses multiply in: tonsils. lymph tissue. gastrointestinal tract. Rarely, the virus causes paralysis of the arms, legs, and body trunk which could lead to paralytic polio-myelitis.

Describe the resistance level of Hepatitis A virus (HAV)?

The hepatitis A virus ( HAV) is very resistant to chemical and physical agents, and several minutes of exposure to boiling water may be necessary to inactivate the virion.

Viral Replication: Release

Release. Mature phage particles now burst out from the ruptured bacterial shell. For some phages, lysozyme, encoded by the bacteriophage genes late in the replicative cycle, degrades the bacterial cell wall. The mature bacteriophages are set free to infect more bacterial cells.

What are retroviruses?

Retroviruses are replicated indirectly through a DNA intermediate using an reverse transcriptase enzyme. Although usually grouped with the RNA viruses, the retroviruses are replicated indirectly through a DNA intermediate ( RNA- to- DNA- to- RNA). Each virion contains two copies of strand RNA. During the infection process, a DNA intermediate will be formed using a reverse transcriptase enzyme carried within the virion. As a rule, RNA virus genomes are smaller than DNA virus genomes and depend more heavily on host cell proteins and enzymes for replication.

What is congenital rubella syndrome?

Rubella is dangerous to the developing fetus in a pregnant woman. Called congenital rubella syndrome, transplacental virus transmission to the fetus can lead to destruction of the fetal capillaries, and blood insufficiency follows. The organs most often affected are the eyes, ears, and cardiovascular organs, and children may be born with cataracts, glaucoma, deafness, or heart defects.

What is unique about S.A.R.S.?

SARS-CoV can be spread through close person-to-person contact by touching one's eyes, nose, or mouth after contact with the skin of someone with SARS. Spreading also comes from contact with objects contaminated through coughing or sneezing with infectious droplets by a SARS-infected individual. Whether SARS can spread through the air or in other ways remains to be discovered. Bats are the reservoir of SARS-CoV.

What is unique about smallpox's?

Smallpox is caused by a brick-shaped double-stranded DNA virus of the Poxviridae family. It is one of the largest virions, approximately the size of chlamydiae. The nucleocapsid is surrounded by a series of fiber-like rods with an envelope.

What is a provirus?

Some DNA viruses and retroviruses insert their genome into the host chromosome as a provirus.

What are newly emerging viruses?

Some, like Hantavirus, West Nile virus, and others are just new to certain populations or geographical areas. Others, like HIV, have crossed host ranges and resulted in the development of new human diseases. Genetic recombination allows different influenza viruses to reassort genome segments. The " swine flu" that broke out in Mexico in 2009 was the result of the reassortment of genome segments from a strain of avian flu virus, a human flu virus, and a swine flu virus. This produced a virus with the capability of infecting humans. When a single nucleotide is altered ( point mutation) in an RNA virus genome in the host cytoplasm, there is no way to " proofread" or correct the mistake during replication. Occasionally, one of these mutations may be advantageous. In the case of HIV, a beneficial mutation could gener-ate a new virus strain resistant to an antiviral drug. Emerging viruses are not really new. They are simply evolving from existing viruses and, through human changes to the environment, are given the opportunity to spread or to increase their host range.

What is the structure of an enveloped viruses?

The nucleocapsids of many viruses are surrounded by a flexible membrane known as an envelope; the viruses are referred to as " enveloped" viruses. The envelope is composed of lipids and protein, similar to the host cell membrane; in fact, it is acquired from the host cell during replication and is unique to each type of virus. These viruses may lose their infectivity if the envelope is destroyed. Also, when the envelope is present, the symmetry of the capsid may not be apparent because the envelope is generally a loose- fitting structure over the nucleocapsid.

What does the T.O.R.C.H. acronym stand for?

T for toxoplasmosis, O is for other diseases, such as syphilis; R for rubella, C for cytomegalovirus, and H for herpes simplex virus.

Bacteriophages of the T-even group:

T-even bacteriophages are virulent viruses that carry out a lytic cycle of infection in prokaryotes. 1.) Attachment by tail fibers 2.) Penetration 3.) Biosynthesis 4.) Maturation 5.) Release by lysis

What is a Monospot test?

The Monospot test is performed by first mixing samples of the patient's serum with a guinea pig tissue extract, which binds to and removes any closely related antibodies. Horse erythrocytes then are added and the red blood cells are observed for agglutination. Suitable controls ( not shown) must also be included.

What is unique about Ebola hemorrhagic fever (EHF)?

The ebolavirus damages endothelial cells, causing massive internal bleeding and hemorrhaging. Infection also suppresses the immune response. Thus, the patient bleeds to death internally before a reasonable immunologic defense can be mounted.

What is the next virus to be eradicated?

The polio virus may be the next infectious disease eradicated.

What is the Cytomegalovirus?

The virus takes its name from the enlarged cells ( cyto = " cell"; megalo = " large") found in infected tissues. Usually, these are cells of the salivary glands, epithelium, or liver. After the primary infection, CMV undergoes lifelong latency. CMV disease in a healthy individual may be among the most common diseases in American communities. Infection may be asymptomatic or produce a mononucleosis- like syndrome, involving fever and malaise. Most patients recover uneventfully. If a CMV- infected woman is pregnant, a serious congenital disease may ensue in 5% to 10% of infants if the virus passes into the fetal bloodstream and damages the fetal tissues.

What is dengue hemorrhagic fever and dengue shock syndrome?

Then, a condition called dengue hemorrhagic fever may occur. In this condition, the immune system reacts to the memory of the first dengue infection, allowing the new one to replicate unchallenged. A rash from skin hemorrhages appears on the face and extremities, and severe vomiting and shock ensue ( dengue shock syndrome) as blood pressure decreases dramatically.

What are the three types of influenza viruses?

There are three types of infuenza viruses, fittingly named infuenza A, influenza B, and influenza C. They all share similar structural features in that they are spherical shaped in culture, enveloped, and have a segmented genome consisting of several single-stranded (-strand) RNA molecules. Infuenza A is responsible for most cases of human flu

What is Dengue fever?

Transmission is by the S. aegypti mosquito and the tiger mosquito S. albopicta. Sudden high fever and prostration are early signs of infection. These are followed by sharp pain in the muscles and joints. Patients often report intense joint and muscle pain, sensations feeling like their bones are breaking; thus, the disease has been called breakbone fever. Prostration: Drained of strength.

What is Hepatitis B?

Virions consist of: a nucleocapsid surrounded by a core antigen (HBcAg). an envelope containing a surface antigen (HBsAg). Transmission usually involves direct or indirect contact with a bodily fluid.

What is the structure of a naked virus?

Viruses composed solely of a nucleocapsid are sometimes referred to as " naked" viruses.

What is West Nile Virus?

WNV causes a potentially serious illness. People typically develop symptoms between 3 and 14 days after they are bitten by the infected mosquito. Approximately 80% of people who are infected remain asymptomatic. Most of the remain-ing infected individuals display West Nile fever, consisting of a mild fever, headache, body aches, and extreme fatigue. They also may develop a skin rash on the chest, stomach, and back. Symptoms typically last a few days. There is no vaccine or specific treatment for West Nile fever.

What is tropism?

tropism ( tissue attraction) - the limitation to, even within its host range, only infect certain cell types or tissues within a multicellular plant or animal. For example, the host range for the human immunodeficiency virus ( HIV) is a human. In humans, HIV primarily infects a specific group of white blood cells called T helper cells because the envelope has protein spikes for binding to receptor molecules on these cells. The virus does not infect cells in other tissues or organs such as the heart or liver. Rabies virus is best at infecting cells of the nervous system and brain because its envelope contains proteins recognizing receptors only on these tissues. Therefore, a virus' host range and tissue tropism are linked to infectivity.