Pre-Lecture Quiz 9

Lance's physician administered a tuberculin test to determine whether Lance had been infected during his flight from South Africa. How was this test performed?

A small amount of cell wall material from Mycobacterium tuberculosis was injected into Lance's forearm skin.

In the case of gastrointestinal disease, how can an intoxication be distinguished from an infection?

An intoxication is usually apparent shortly after ingestion, while an infection takes longer.

What area of the country has the highest incidence of Rocky Mountain Spotted Fever?

The Appalachian mountains and Ozarks

How are patients typically infected with listeriosis?

Contaminated food or drink

Which component of a Gram-negative cell wall can cause fever, vasodilation, inflammation, shock, and blood clotting?

Lipid A

How is tuberculosis transmitted?

aerosol droplets released by a cough or sneeze

Dr. Smith assures Scott that although inflammation may sound scary, there are several possible options for treating Scott's moderate acne. Which of the following would be the most appropriate for Scott's case?

topical treatment with a product containing benzoyl peroxide an oral antibiotic such as erythromycin

Which of the findings listed below support the hypothesis?

Increasing levels of sodium, potassium, bicarbonate, and chloride ions, as well as water, are secreted as toxin concentrations are increased from 25, 50, 100, and 150 units. Protein levels within the ileum loop fluid are increased up to 1000 units of toxin. Histological observation indicates that morphological alteration and sloughing of epithelial cells occurs up to a maximum of 1000 units.

An indirect immunofluorescence assay is described as the CDC "gold standard serological test" for RMSF. Keeping in mind the principles behind indirect fluorescent-antibody (indirect FA) testing, which of the following characteristics contributes to its choice as the gold standard?

Indirect FA is more sensitive than direct immunofluorescent testing. Indirect FA will detect R. rickettsii-specific antibodies present in the patient's serum. Indirect FA uses an antibody that reacts with any human antibody. Indirect FA is rapid, sensitive, and specific.

__________ is the treatment of choice for C. trachomatis.

Erythromycin

Most microbes that reside in the intestines are facultative or obligate anaerobes. Describe the growth of facultative anaerobes in the presence of and also in the absence of molecular oxygen.

Facultative anaerobes can grow without molecular oxygen, but grow faster in its presence.

Which is the vector of Rickettsia rickettsia?

a tick

The nutritional requirement to oxidize amino acids and Kreb's cycle intermediates means Rickettsias are __________.

obligate intracellular parasites

In 90% of cases, a spotted non-itchy rash forms on the __________, particular to rickettsiosis.

palms and soles

What part of the United States is endemic for RMSF?

the Appalachian region (North Carolina, Kentucky)

What is the word used to refer to diseases transmissible from animals to humans?

zoonoses

As an epidemiologist, Dr. Thompson is interested in determining the frequency with which a specified event occurs within a particular population at a certain instant or during a particular period. This measure is known as a rate. In epidemiologic practice, an attack rate is the most commonly used method of determining the extent or frequency with which a disease is experienced by a population of individuals. In this instance, Dr. Thompson is interested in knowing what percentage of the individuals who attended the July 4 celebration became ill. The attack rate is the number of individuals treated and/or had symptoms divided by the number of attending individuals. What is the attack rate of food poisoning among the group who attended the July 4 celebration?

105/150(100)= 70.0%

Although cholera can be treated with antibiotics, data suggest that antibiotic treatment alone is NOT the most effective therapy. Which of the following statements describes the most likely reason for supplementing antibiotic therapy?

Antibiotic therapy addresses only the growth of V. cholerae; it doesn't address the extreme dehydration suffered by a person infected with V. cholerae

What is the most likely cause of this couple's disease?

Campylobacter jejuni

Into which type of cell are the Rickettsia introduced in the human host?

Endothelial cells

The name Propionibacterium is derived from the fact that the organism produces propionic acid during fermentative metabolism. Which of the following statements about fermentative metabolism is true?

Fermentation produces significantly less ATP than aerobic respiration; however it generates NAD+, which can be used in glycolysis.

The BCG vaccine is available to immunize people against tuberculosis. Had Lance been vaccinated, he would not have been concerned about becoming infected on the airplane. Why was he NOT vaccinated?

Immunized patients have a positive skin reaction when tested, even if they have not been infected with Mycobacterium tuberculosis. Such "false positive results" hinder the work of epidemiologists trying to track the spread of the disease.

From the preliminary analysis, it would appear that individuals who consumed barbecue with Bubba-Qs sauce had the highest attack rate, followed by the dry-rubbed barbecue. Some of the individuals who said they ate the barbecue with the sauce did not become ill. Which one of the following is the most likely explanation for such an occurrence?

Individuals who became ill may have consumed larger quantities of the food than individuals who did not become ill.

Drag each of the structures to the appropriate bin to indicate whether it is found in prokaryotes only, in eukaryotes only, or in both.

Prokaryote: capsule Eukaryote only: golgi complex, mitochondria, nucleus, rough ER Both: cytoplasm, plasma membrane, flagella, ribosomes

Which of the following is a characteristic of biological transmission from Dermacentor to a human host?

R. rickettsii is transmitted to the human host during a bite, when tick saliva enters the wound.

What disease does Paul suspect Ron might have contracted?

Rocky Mountain spotted fever

Part of the reason for Scott's acne is the overproduction of sebum. Scott's initial instinct is that shutting down production of sebum would be the quickest route to eliminating his acne; however, sebum actually plays an important role in maintaining the skin as a first line of defense against pathogens. Which of the following best describes the role of sebum as a component of the first line of defense?

Sebum helps to keep the pH of the skin low, which inhibits the growth of microorganisms Sebum forms a protective layer over the skin.

Disease research and epidemiology bring together many different facets to help us better understand disease pathology and spread. Which of the following statements are true?

The interactions that occur between a microbe and host influence the evolution of both. Bacterial exotoxins can be altered to create toxoids, which can be used to produce protective immunity in a host. Some pathogens are able to cause disease within a host without penetrating the body.

Some studies have indicated that the ID50 for Vibrio cholerae can be as high as 108 organisms. Which of the following most likely explains the requirement for this relatively high ID50?

To establish infection, V. cholerae must survive the host immune response and the acidic environment of the stomach.

Which might be the best way to prevent getting infected by Rickettsia rickettsia?

Use tick repellents and remove ticks quickly

Which of the following are properties of exotoxins?

Very small amounts of exotoxin can be lethal. Exotoxins target specific cellular structures or molecules. Exotoxins are protein molecules.

The IV regimen administered by Ron's doctors is consistent with the CDC's recommendation that doxycycline be administered when RMSF is suspected. Apply your knowledge of RMSF to choose the most likely reasons behind this recommendation.

Without prompt treatment, RMSF can have a mortality rate as high as 20%. A delay in treatment can lead to complications that include respiratory, cardiac, and renal failure. Most tests that can definitively identify R. rickettsii are not very effective early in infection. The symptoms of RMSF are similar to those of several other infections, making definitive diagnosis difficult.

Which of the following symptoms is LEAST characteristic of Clostridium perfringens food poisoning?

moderate vomiting and fever

Acne is the result of the inflammatory response. In this case, the inflammation is resulting in acne that is very painful (physically and emotionally) for Scott. However, inflammation is a critical component of a normal immune response. What are the main functions of the inflammatory response?

repairing tissue damage resulting from inflammation "walling off" the site of injury or infection destroying and eliminating the invading pathogen

Rickettsia rickettsii is a gram-negative, obligate intracellular pathogen. Which of the following statements about the R. rickettsii life cycle is FALSE?

After entering a host, R. rickettsii multiplies to levels high enough to successfully invade cells and establish an infection.

How is the dormant form of Rickettsia rickettsii activated?

The bacteria are activated after the tick feeds on a host for several hours.

Which of the following findings are key to the cause of the outbreak?

The sauce was prepared on an overcrowded steam table and, as a result, did not reach an appropriate temperature to kill any organisms. Large quantities of meat were prepared and kept warm for a long time before they were served

Which of the following are true for the Chlamydia group of bacteria?

They all cause acutely life-threatening disease. They are all very small in size. They are all intracellular parasites. They are most reliably detected by fluorescent antibodies.

A jumbo jet finally takes off from the airport in Johannesburg, South Africa, and Lance relaxes in his business-class seat. The next stop, 16 hours later, will be Atlanta, Georgia. Lance has just spent six weeks interning with a South African law firm that specializes in human rights issues. His work took him to clients living in crowded conditions in several poor townships. Now Lance's thoughts turn to the upcoming fall term, when he will practically live in a study carrel, law books his constant companions. The deep coughing of a woman sitting beside him interrupts his reverie. He glances at her; she is thin and huddles against the armrest, looking pale and tired. She often rubs her chest as if it hurts. When the flight attendant offers the woman something to eat and drink, she turns everything down. Her loud, incessant coughing continues for the entire flight, interrupting Lance's sleep. Four weeks later, Lance opens a letter from the state department of health and learns that he may have breathed in a potentially deadly bacterium on that flight from South Africa. The letter advises Lance to have a physician administer a skin test to determine if he has been infected, but it also tells him that he must wait eight more weeks before being tested. An appropriately stained smear was prepared of a sputum specimen obtained from the sick woman on Lance's flight. Using oil-immersion magnification on your microscope, what would you observe that would aid in the diagnosis of tuberculosis?

acid-fast rods

Dr. Smith prescribes oral erythromycin for Scott. She also recommends that he consider using an over-the-counter gel or cream containing benzoyl peroxide. Although this regimen should be effective at treating Scott's acne, there are some possible side effects. Which of the following are possible side effects of Scott's treatment?

excessive drying of the skin gastrointestinal problems resulting from a reduction/elimination of normal intestinal flora Clear Light, a nonchemical, light-based system

The ability of Vibrio cholerae to cause disease depends on a number of factors. Which of the following are general requirements for any organism to cause disease within a host?

gaining access to the host via a portal of entry adherence to host tissues evasion of host defenses

Research has indicated that during the inflammatory response to P. acnes, both the classical and the alternative complement pathways are activated. Which of the following are outcomes of activating complement pathways?

inflammation cytolysis opsonization

How did this couple become infected with C. jejuni?

ingestion of contaminated, raw milk

Trachoma __________.

is an infection of conjunctiva is the leading cause of nontraumatic blindness in humans can be passed to a child during birth can be caused by introduction of bacteria into the eye via a fomite in adults