Test 4 - HW 8

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

viruses require host cells to replicate themselves

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

using insect repellents

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.

Borrelia burgdorferi is an interesting spirochete that is unusual when compared to other bacteria. Which of the following is the reason that it is so unusual?

it has a linear chromosome

Antibiotic resistance is a major concern as microbes can rapidly develop resistance when antibiotics are not used appropriately. Which of the following examples best describes how this occurs?

In any population of microbes, some individuals may have resistance genes. When exposed to an antibiotic, there is selection for the microbes that have these genes

Helicobacter pylori causes gastric ulcers on account of

autoimmune tissue destruction initiated by bacterial lipopolysaccharide (LPS)

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.

Bacillus anthracis is an endospore-forming bacterium. Which of the following is most likely?

B. anthracis spores can remain dormant for hundreds of years without needing nutrients, remaining capable of causing anthrax when they germinate.

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.

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

an increase in multi-drug-resistant strains

There are three forms of human anthrax. Which of the following forms are correctly matched with their description? intestinal: always fatal inhalation: least deadly form cutaneous: most severe form cutaneous: easily treatable

cutaneous: easily treatable

Which of the following correctly orders the successful application of epidemiology to control the emergence of SARS? 1. Sales restriction of civets and other wild food sources. 2. Containment and infection-control of virus in healthcare settings 3. Source of SARS traced to bats and civets. 4. Travel restricted to and from endemic areas. 5. Initial outbreak of SARS identified.

5, 3, 2, 4, 1

What might be a reason that it would be better to do a skin test for an infection rather than doing a blood test?

Antibody responses for some diseases are weak or undetectable, but inflammatory Th1 (helper T) cells may respond well.

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

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

Lactose-fermenting bacteria turn eosin-methylene blue medium from colorless to black or red. What causes this change?

Lactose fermentation generates lactic acid. Lactic acid lowers the pH of the medium, causing the medium to change colors

Meningococcal meningitis is definitively diagnosed from cultures isolated from nasopharyngeal swabs, blood, or cerebrospinal on Thayer-Martin medium, a selective medium for the growth Neisseria. However, preliminary diagnosis is often based on clinical symptoms, and treatment with antibiotics is started before culture tests confirm infection with N. meningitidis. Why?

Life-threatening symptoms can develop very rapidly

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

A clinical lab was not able to isolate any pathogenic bacteria from a patient suffering from a high fever and elevated white blood cell count. The physician suspects a viral infection may be to blame. What detection assay may the lab want to try next?

PCR followed by a nucleic acid hybridization technique to detect viral DNA or RNA

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

Pertussis exotoxin causes tissue damage

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)

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 matches are correct regarding streptococcal infections? Streptococcus pyogenes: lower respiratory infection Streptococcus pneumoniae: upper respiratory infection Streptococcus pneumoniae: glomerulonephritis Streptococcus pyogenes: scarlet fever

Streptococcus pyogenes: scarlet fever

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.

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

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)

Which of the following statements about hantaviruses is true?

They are similar in disease presentation to Ebola and other hemorrhagic viruses. Hantaviruses are an example of an emerging infectious disease. They are transmitted to humans by contaminated rodent droppings. (All of the listed responses are correct.)

Wild rodents are the major reservoir of the plague organism, Yersinia pestis, but pandemic plagues were historically associated with crowded, unsanitary urban areas. Why is this the case?

Yersinia pestis can be transmitted by fleas from wild rodents to urban rats, which quickly die of the disease. Humans are accidental hosts due to fleas seeking out blood meals after most rats have succumbed to the disease.

Which of the following is predicted to result in the largest disease outbreak?

a pathogen with a high R0 in an immunologically naïve (naive?) population

An animal disease transmitted to humans by direct contact, inhalation of aerosols, or bites is called

a zoonosis

Lyme disease and syphilis are similar in that they

are both caused by spirochetes and are chronic infections that involve the nervous systems

Which of the following is the correct progression of a herpes simplex 2 infection?

direct contact with infected tissue occurs; lesions develop; virus goes dormant in nerve cells; virus is reactivated to cause lesions

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

ergosterol synthesis

Incidence of healthcare associated infections are

increased because patients are exposed to pathogens that have increased drug resistance

Toxic shock syndrome (TSS)

is life-threatening because of the endotoxin produced

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

necessary because chronic infection can lead to cervical cancer

About half of the clinical cases of severe sore throat are due to Streptococcus pyogenes, and most of the rest are due to viral infections. Accurate and rapid diagnosis of a severe sore throat is important because untreated group A streptococcal infections can lead to

scarlet fever, rheumatic fever, acute glomerulonephritis, and streptococcal toxic shock syndrome

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

The sexually transmitted infection that can lead to infection of the central nervous system if not treated early is

syphilis

Herd immunity can protect

the elderly in a population

Among 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

Eosin-methylene blue agar inhibits the growth of gram-positive organisms while allowing gram-negative organisms to grow. Colonies of lactose fermenters turn a blackish color while nonfermenters are colorless. How would you classify EMB? Is EMB a differential medium or a selective medium? Think about the meaning of the terms differential and selective to choose your answer.

differential and selective