Micro Exam 4 Homework

Which of the following enzymes breaks down the "glue" that holds cells together?

Hyaluronidase

In the search for new antimicrobial drugs, to minimize resistance developing scientists should focus on

new targets of action found only in bacteria

Corynebacterium diphtheria and Bordetella pertussis cause respiratory diseases. Which statement below is true regarding these infections?

pertussis exotoxin causes tissue damage

Which of the following is an important virulence factor for dental caries?

polysaccharide adhesion

Ammong the recommendations from the Centers for Disease Control and Prevention to limit the development of antibiotic resistance are __________.

to treat with the oldest, effective antimicrobial

Certain traits that allow pathogens to create infection and cause disease are termed

virulence factors

Which of the following antibiotics are properly matched with their target of action?

Platensimycin-lipid biosynthesis

Which of the following statements regarding antigenic shift are true?

-little immunity to virus strains resulting from antigenic shift exists in the population. -viral strains resulting from antigenic shift contain RNA segments from different species. -antigenic shift results in a major change in the genetic composition of the virus

Patient with an infectious disease

-immunological assays to analyze a blood sample and search for antibodies or antigens using agglutination immunofluorescence, or EIA. - with the purpose to detect antibody against suspected pathogen

What are some of the current challenges to production of the influenza vaccine?

-in order to yield a vaccine, the virus must be produced in eggs -the virus undergoes antigenic changes on a regular basis

Predict which of the following are reasonable outcomes of the cytokine storm during the 1918 flu pandemic.

-increased fluid in the lungs and labored breathing -an excessive inflammatory response leading to extensive tissue damage

Which of the following explains why treatment of symptomatic tetanus requires an antitoxin and an antibiotic?

Because C. tetani bacteria excrete tetanus toxin, it is important to neutralize the toxin while also killing the bacteria that are producing more.

Penicillin and other β-lactam antibiotics inhibit cell-wall synthesis. What makes them effective at killing bacterial cells?

-Bacteria are generally hypertonic relative to their environment, so they burst when their cell wall is weakened by the action of these antibiotics.

what is meant by selective toxicity

-Chemotherapeutic agents should act against the pathogen and not the host

Why are chemotherapeutic agents that work on the peptidoglycan cell wall of bacteria a good choice of drug?

-Humans and other animal hosts lack peptidoglycan cell walls.

Why is polymyxin only used on the skin?

-It can also damage living human cell membranes, but the drug is safely used on the skin, where the outer layers of cells are dead.

One way to test if someone has immunity to a particular pathogen is to measure the antibody titer. What does it mean if someone has a positive antibody titer?

-Previous exposure to the pathogen (or through a vaccination) has caused B cells to produce memory B cells. When re-exposed to the pathogen, they rapidly produce antibodies against the antigen (resulting in a positive antibody titer

Predict which of the following would be outcomes of treatment with Tamiflu.

-an increase in the ability of the immune system to combat the infection -overall decrease in the replication rate of influenza -a decrease in the release of viral particles from the cell

Polymyxin

-antibacterial drugs -attach to phospholipids in the bacterial cytoplasmic membrane and interfere with its integrity -cell lysis -used only in the skin

Penicillin and its relatives block the formation of these peptide cross links

-block the formation of the cell wall - weakens the cell wall, and causes the cell to lyse

Salmonella is a gram-negative bacterium that is often capable of causing disease in humans. It does so through use of numerous different virulence factors.

-enterotoxin: diarrhea -siderophores: iron uptake -endotoxins in LPS layer: fever -type I fiambrie:adherance -flagellum: motility

symptoms of influenza infection

-fever -muscle pain -headache

Which of the following factors could have contributed to Barbara's development of shingles?

-her daughter and grandchildren moving into her house shortly after the death of her husband -her age, 68 -Many factors can contribute to reactivation of a latent virus. Research has yet to narrow it down to one thing, but stress, old age, and a change in the host's immune system have been linked to viral reactivation.

Numerous barriers exist in human beings to prevent infection

-skin is a physical barrier and produces antimicrobial fatty acids and antibacterial peptides. Normal microbiota inhibit infection -stomach acidity ph2 inhibits microbial growth -flushing of urinary tract prevents infection -lysozyme in tears and other secretions dissolves bacterial cell walls -mucus and cilia lining the trachea suspend and move microorganism out of the body

The common methods to control the spread of West Nile virus include

-using insect repellents

tetracycline

30S ribosomal subunit

The respiratory tract has multiple systems to help protect against airborne diseases. Which of the following summarizes some of these systems

A mucociliary blanket to remove contaminants, secretion of lysozyme and other antimicrobial chemicals, and alveolar macrophages helps protect against airborne diseases.

antiviral drugs

A number of drugs are effective in interrupting the viral disease cycle. Some antiviral drugs include nucleoside or nucleotide analogs and protease inhibitors.

Which domain of the A-B toxin binds to cell surface receptors on the host cell?

B domain

Quinolones and fluoroquinolones act against what bacterial target?

DNA gyrase

Membrane transport proteins are required for which mode(s) of antibiotic resistance?

Efflux pumps, beta-lactamases, and modification of porins all utilize membrane transport proteins.

Since the majority of human papillomavirus (HPV) infections are asymptomatic, screening for this infection is

necessary because chronic infection can lead to cervical cancer

Clostridium tetani is an obligate anaerobe that can cause tetanus. When it enters the human body, it can produce tetanus toxin. Considering that C. tetani is an obligate anaerobe, which of the following explains how it can survive and cause disease in the human body?

Especially in deep wounds, C. tetani can sometimes survive in areas with damaged tissue that have become anoxic because of poor-to-no blood flow.

Most people experience several colds each year. Why is it that people do NOT develop immunity to the viruses that cause the common cold?

Even when only the colds caused by rhinoviruses are considered, there is enough variation in the antigens presented by these viruses that they are often not recognized by the immune system even in an individual who has only recently recovered from a cold.

Which of the following would be the first sign of an infection that resulted in the release of endotoxin?

Fever

Considering that they require an oxygen-free environment, how do obligate anaerobes survive in the human body?

They are able to survive in places where aerobic organisms quickly use the available oxygen. They can also survive in areas with impaired blood flow (reducing oxygen availability).

Why is a release of endotoxin into the bloodstream potentially deadly?

It can lower blood pressure and cause the patient to go into shock.

Immunoassays are techniques that use immunology to determine the presence of antigens, antibodies, or both. In one type of enzyme-linked immunoassay test, antibodies are attached to a matrix (such as the bottom of a microtiter plate). Next, the sample to be tested (such as patient serum) is added. An antibody-enzyme complex is then added. Finally, the enzyme substrate is added. The enzyme must catalyze a reaction that is visible (such as a color change), meaning that it is possible to see if the antibodies were present by seeing if there is a color change. The development of the colored product is proportional to the concentration of antibody. What would this sort of test be useful for?

It would be useful for detecting a virus in a patient's blood, as the antibody on the matrix would bind to the virus. The second antibody (attached to the enzyme) is able to bind because it is specific for the antigen.

Antifungal medications are often used topically. Why is this the case?

Like human cells, fungal cells are eukaryotic. To develop systemic fungal medications requires finding specific characteristics of fungal cells that can be targeted, such as the ergosterol in fungal cell membranes.

Endotoxins are also known as

Lipid A

Barbara is worried about spending time with her grandchildren while being treated for shingles. Can her grandchildren contract chickenpox or shingles from spending time with their grandmother?

No. Because of their ages, the grandchildren have most likely been vaccinated against the chickenpox. They are also safe from contracting shingles because they are young.

One group of medications used to treat HIV infections is the reverse transcriptase inhibitors. There are two types of these medications, nucleoside reverse transcriptase inhibitors (like AZT) and non-nucleoside reverse transcriptase inhibitors. AZT resembles thymine and is inserted into DNA during replication, leading to the termination of replication. Non-nucleoside reverse transcriptase inhibitors bind to reverse transcriptase and inhibit it in that manner. Non-nucleoside reverse transcriptase inhibitors tend to have fewer side effects. Which of the following best describes why this is the case?

Nucleoside reverse transcriptase inhibitors may interfere with DNA replication by the host, not just by the virus.

Bacteria that are resistant to sulfonamide have enzymes that have a greater affinity for what?

PABA

Identification of a pathogen in a patient can be done without having to culture the pathogen using

PCR testing if a pathogen specific genetic sequence is known

Which antibiotic is overcome by beta-lactamases?

Penicillin

Why would an efflux pump for penicillin located on a bacterial cell membrane not be effective at providing resistance to the drug?

Penicillin disrupts the cell wall, which is located outside of the cell membrane.

How are superantigens different from other types of exotoxins?

Superantigens cause an overstimulation of the host immune system.

How might efflux pumps increase antibiotic resistance in bacteria?

Resistant bacteria can have more efflux pumps, and can have less specific efflux pumps.

Which of the following mutations would not result in antibiotic resistance?

Silent mutation

Autoimmune diseases sometimes develop shortly after an infection. This is the case with rheumatic fever. Which of the following is the most likely reason that there is often a relationship between autoimmune disorders and infection?

Some pathogens, like the rheumatogenic strains of S. pyogenes, contain antigens that resemble normal cell surface proteins. As the immune system responds to them, it attacks the cells with similar antigens as well.

Which of the following virulence factors would be found in Staphylococcus aureus?

Staphylokinase

Which of the following matches are correct regarding streptococcal infections?

Streptococcus pyogenes: scarlet fever

What is meant when a bacterium is said to become "resistant" to an antibiotic?

The bacterium is neither killed nor inhibited by the antibiotic.

Diptheria is caused by bacteria that have been infected by a bacteriophage. This bacteriophage is a lysogenic phage and contains the genes to produce the diphtheria toxin, which inhibits protein synthesis. Which of the following is the correct term for the phage while its genetic material is integrated into the bacterial chromosome?

The genetic material is called a prophage and the change in the host cell's properties is called lysogenic conversion.

the vaccination strategy for human rabies infections with that for measles.

The measles vaccine is given prophylactically to children as part of the MMR series. Measles is a highly infectious and rapidly developing respiratory disease. The high human-to-human communicability of this pathogen requires a substantial herd immunity to prevent epidemics. In contrast, the rabies vaccine is generally given to patients after they have been exposed to the pathogen. Rabies is not spread from person to person and has a low basic reproduction number in the animal reservoir population (R0 ~ 1.2). In addition, the rabies virus spreads slowly in the peripheral nerves. This provides enough time for post-infection vaccination to work.

Viremia

The suffix -emia refers to the blood. Viremia means the presence of viral particles within the blood.

Which of the following describes an example of antigenic shift?

The surface antigens of a virus become drastically changed as a result of the combining of genetic material from different viruses within one organism

The yellow fever virus replicates in lymph nodes and in other immune system cells. How does it arrive in lymph nodes?

The yellow fever virus is phagocytosed by white blood cells, and then travels through the lymph vessels. Lymph nodes contain white blood cells and filter lymph as it moves through the lymph vessels. White blood cells with yellow fever virus can become established there. Some viruses, like the yellow fever virus, can replicate inside of white blood cells like those in lymph nodes.

A patient who has been hospitalized with uncontrolled muscle spasms has probably been infected with bacteria that secrete a(n)

neurotoxin

How do fibrinolysins enhance a pathogen's virulence?

They break down fibrin proteins that are involved in clot formation, allowing the cells to penetrate deep into damaged skin.

Why is it difficult to find good chemotherapeutic agents against viruses?

Viruses depend on the host cell's machinery, so it is hard to find a viral target that would leave the host cell unaffected.

When would endotoxins be released from a bacterial cell?

When the cell dies

The exotoxin that functions by destroying cell membranes is called

a cytolytic toxin

The hepatitis D virus is considered a defective virus because it lacks the genes to produce a component that is essential for viruses to function. Which of the following is this component?

a protein capsid

Tuberculosis continues to be an infectious disease of worldwide concern on account of __________.

an increase in multi-drug-resistant strain

Topical medications

are medications that are applied to a specific location, such as the surface of the skin.

R-plasmids are most likely acquired via

bacterial conjugation.

What disease does the human herpesvirus-1 cause?

cold sores or fever blisters -Cold sores or fever blisters are the painful, short-lived vesicles that form near the outer margins of the lips. It is transmitted via oral and respiratory routes. In the United States, a large percentage of the population is infected with this virus during infancy, when the virus is passed via respiratory droplets from family members.

Normal flora

compete with pathogens in the gut and on the skin

An exotoxin that has the ability to kill or damage host cells is referred to as a(n)

cytotoxin

Direct immunofluorescence

detection is due to labeled antibacterial antibody

Indirect immunofluorescence

detection is due to labeled secondary antibody binding antibacterial primary antibody

A pharmaceutical company that uses the Limulus amoebocyte lysate (LAL) assay to test water that is used to make sterile saline for intravenous administration is trying to detect small amounts of which of the following?

endotoxin

When treating a fungal infection, the best target for selective toxicity would be

ergosterol synthesis

West Nile Virus is an arbovirus that can be transmitted by birds because they develop viremia when infected. In contrast, infected humans cannot spread the disease because they do not develop viremia. Why is viremia associated with the ability to transmit the disease?

if there are no (or only very few) viral particles in the blood, then they are not picked up by vectors feeding on the blood in sufficient amounts to cause infection

Removal of particles

including microorganism by cilia in nasopharynx

Incidence of healthcare associated infections are

increased because patients are exposed to pathogen's that have increased drug resistance

Human immunodeficiency virus (HIV) __________.

infects and replicates in macrophages and T-helper cells

Blood and Lymph proteins

inhibits microbial growth

Rapid pH change

inhibits microbial growth

The diphtheria exotoxin is an A-B toxin that

is found only in Corynebacterium diphtheriae cells that have been infected with lysogenic bacteriophage β

Toxic shock syndrome

is life-threatening because of the superantigen toxin produced

The ability to cause disease is

pathogenicity

Mucus, antibacterial peptides, and phagocytes in lungs

prevent infection

Antigen assays

search for microbial or virus antigens using fluorescent antibody

Molecular assays

search for pathogen genes by gene amplification

An antimicrobial compound that targets a pathway or structure that is present in a pathogen but not in the host exhibits __________.

selective toxicity

The lowest number of pathogens or pathogen produced products that can be detected is a measure of

sensitivity

Which of the following best describes Barbara's condition?

shingles caused by the herpes zoster virus -As a child, Barbara was infected with the varicella virus and contracted chickenpox. Though she recovered from the chickenpox, the virus was able to enter the peripheral nerves and eventually the central nerve ganglion, where it persists as viral DNA hidden from her immune response. As a result of factors in her life, Barbara's virus was reactivated and traveled along the peripheral nerves to the cutaneous sensory nerves of the skin. This new outbreak produces the rash characteristic of a shingles infection. The occurrence of shingles is 10% to 20% in individuals who have had chickenpox.

A person who attended a picnic early in the day develops a very high fever and is unresponsive by the evening. This person most likely has been exposed to a(n)

superantigen

When a patient is treated with antibiotics,

the drug will kill or inhibit the growth of all of the sensitive bacterial cells

If a human is bitten by an animal that has rabies, then it is recommended that the human receive immune globin (human rabies antibodies) and a rabies vaccination (with inactive virus) as well. Which of the following is the best (and most specific) explanation for why both are recommended in this case?

the rabies antibodies provide a rapid response but short-lived response while the vaccination provides slower but longer-lasting protection.

Epithelial cells

throughout the body have tight junctions that inhibit pathogen invasion and infection

The process of acquiring antibiotic resistance by means of bacteriophage activity is called

transduction

It is difficult to attain good selective toxicity with antiviral drugs because of the fact that

viruses require host cells to replicate themselves