Microbiology Ch 14 –

Which of the following statements concerning pathology, infection, and disease is true?

A. The majority of microorganisms are pathogenic.
B. Microorganisms that make up the normal microbiota of an individual never cause disease.
C. Pathology refers to the study of structural and functional changes that occur in the body as a result of a disease.
D. The term infection is synonymous with the term disease.

C. Pathology refers to the study of structural and functional changes that occur in the body as a result of a disease.

Which of the following is an example of the symbiotic relationship known as mutualism?

A. a tapeworm in the gastrointestinal tract of a human
B. E. coli within the large intestine
C. saprophytic Mycobacterium of the ear
D. Corynebacterium on the surface of the eye

B. E. coli within the large intestine

Koch’s postulates established criteria for proving that a specific organism causes a specific disease. Which of the following is NOT one of the criteria given by Koch’s postulates?

A. The pathogen must be isolated from inoculated animals and must be different from the original organism.
B. The pathogen must be isolated from the diseased host and grown in pure culture.
C. The pathogen isolated from a pure culture must cause the disease in a healthy lab animal.
D. The same pathogen must be present in every case of the disease.

A. The pathogen must be isolated from inoculated animals and must be different from the original organism. This is not one of the criteria. According to Koch’s postulates, the pathogen isolated from the inoculated animals must be the same as the original organism.

Which of the following is classified as a latent disease?

A. tuberculosis
B. infectious mononucleosis
C. shingles
D. influenza

C. shingles

A patient acquires an infection by touching a contaminated door handle. Which mode of transmission best describes this scenario?

A. direct contact transmission
B. vehicle transmission
C. droplet transmission
D. indirect contact transmission

D. indirect contact transmission

A dog develops a diarrheal disease after drinking water from a creek during a hike with his owner. Which of the following best describes this method of disease transmission?

A. vehicle transmission
B. vector transmission
C. contact transmission
D. There is not enough information to determine the mode of transmission.

A. vehicle transmission

Plague is transmitted through the bite of an infected flea. Which of the following best describes this mode of transmission?

A. direct contact transmission
B. vehicle transmission
C. vector transmission
D. indirect contact transmission

C. vector transmission

Which of the following is a fungal zoonosis that can be transmitted by direct contact?

A. tapeworm
B. West Nile encephalitis
C. ringworm
D. Lyme disease

C. ringworm

Which of the following would be an example of disease transmission via INDIRECT contact?

A. Mr. Smith sneezes on an airplane, and the person sitting beside him catches his cold.
B. A student sneezes on her test booklet. The instructor grades it and catches her cold.
C. A restaurant worker has diarrhea caused by Norovirus. He fails to wash his hands adequately before preparing the salad, and his customers get sick.
D. A tick that is infected with Lyme disease bites a hiker, and the hiker gets Lyme disease.

B. A student sneezes on her test booklet. The instructor grades it and catches her cold.

According to the animation, surgical infections account for what percentage of nosocomial infections?

8%
40%
15%
20%
11%

20%

What type of nosocomial infection is likely to arise from intravenous catheterizations?

A. Lower respiratory
B. Bacteremia
C. Urinary tract
D. Surgical
E. Cutaneous

B. Bacteremia

How might a patient who is not being treated with an antibiotic still be exposed to an antibiotic?

A. Antibiotics can be used in aerosols, thereby entering the environment.
B. Visitors currently being treated with antibiotics can pass them on to the patient.
C. Health care workers being treated with antibiotics may pass the antibiotic on to the patient.

A. Antibiotics can be used in aerosols, thereby entering the environment.

Why are invasive procedures likely to increase the risk of nosocomial infections?

A. Invasive procedures require long term hospital stays, thereby increasing the number of visitors seen by the patient.
B. These procedures allow microbes from the skin to enter the bloodstream of the patient.
C. These procedures are carried out by health care workers, who carry resistant microbes.
D. Invasive procedures must use antibiotics.

B. These procedures allow microbes from the skin to enter the bloodstream of the patient.

How can health care workers reduce the occurrence of nosocomial infections?

A. Limit the number of visitors who can see the patient
B. Administer all medications orally instead of through injections
C. Practice more stringent aseptic techniques
D. Reduce the number of times they visit a patient

C. Practice more stringent aseptic techniques

The health of the patient

A. should be the primary concern of the healthcare worker.
B. is secondary to the health of the healthcare worker.
C. is secondary to the health of co-workers in healthcare settings.

A. should be the primary concern of the healthcare worker.

How can surgeons help to limit nosocomial infections?

A. They should perform surgeries and invasive procedures only when absolutely necessary.
B. They should prescribe as many antibiotics as possible.
C. They should only operate on healthy individuals.
D. They should prescribe immunosuppressive drugs to their patients.

A. They should perform surgeries and invasive procedures only when absolutely necessary.

If a patient notices a healthcare worker not following suggested precautions,

A. they should leave the healthcare facility immediately.
B. they should immediately bring it to the attention of the healthcare worker.
C. they should immediately wash their hands.

B. they should immediately bring it to the attention of the healthcare worker.

Which of the following characteristics of a catheter should be considered, to help minimize the spread of nosocomial infections?

A. Reusable
B. Washable
C. Single-use
D. Inexpensive
E. Long

C. Single-use

Which of the following statements is true regarding hand washing?

A. Hand washing should be done frequently by patients.
B. Hand washing should be done frequently by healthcare workers.
C. Frequent and proper hand washing should be routinely done by patients and by healthcare workers, both prior to and after interaction.
D. Hand washing should be done before and after patient interaction.

C. Frequent and proper hand washing should be routinely done by patients and by healthcare workers, both prior to and after interaction.

Epidemiology is defined as the study of

A. where a disease occurs.
B. where and when a disease occurs, and how it is transmitted.
C. when a disease occurs.
D. how a disease is transmitted.

B. where and when a disease occurs, and how it is transmitted.

What is the role of epidemiology?

A. To learn which organisms cause disease.
B. To learn how to treat and prevent various diseases.
C. To learn what diseases can be caused by respiratory pathogens.
D. To learn which medicines are effective at killing pathogens.

B. To learn how to treat and prevent various diseases.

Expected prevalence of a disease is

A. the number of new cases of a disease over a period of time.
B. the total number of cases of a disease over a period of time.
C. the expected occurrence of a disease based on past observations.
D. the anticipated geographical spread of a disease based on past observances.

C. the expected occurrence of a disease based on past observations.

In the sixth segment of the animation, why is the disease epidemic in North America?

A. The disease has spread to North America from Europe.
B. The disease occurs at a lower rate than what would normally be expected in this region.
C. The disease occurs at a higher rate than what would normally be expected in this region.
D. Only a few cases are occurring in this region.

C. The disease occurs at a higher rate than what would normally be expected in this region.

In the last segment of the animation, how many regions of the world experience the pandemic during April of year four?

Four
Two
Six
Five

Five

In the last segment of the animation, when does the first epidemic occur?

A. April of year four
B. March of year two
C. January of year four
D. September of year three
E. January of year three

E. January of year three

If a disease occurs at a fairly stable rate, it is said to be

A. endemic.
B. sporadic.
C. epidemic.
D. pandemic.

A. endemic.

Which of the following would be considered a fomite?

A. A fly
B. A tick
C. Contaminated water
D. An infected toy

D. An infected toy

Which of the following would be considered a vector?

A. Saliva that is transmitted between individuals during kissing
B. A fly carrying disease from fecal matter to food
C. Water droplets that come from a sneeze from an infected individual
D. Water containing bacteria from fecal matter

B. A fly carrying disease from fecal matter to food

When aerosols containing pathogens spread disease from a distance of less than one meter, it is considered

A. vector transmission.
B. contact transmission.
C. airborne transmission.
D. waterborne transmission.

B. contact transmission.

Which of the following is considered a major category of transmission of disease?

A. Vehicle transmission
B. Contact, vehicle, and vector transmission
C. Vector transmission
D. Contact transmission

B. Contact, vehicle, and vector transmission

Which is an example of vehicle disease transmission?

A. Touching a telephone with cold viruses on its surface
B. The transmission of MRSA from skin to skin contact
C. The bite of a mosquito containing malaria
D. The presence of Listeria on undercooked chicken served for dinner

D. The presence of Listeria on undercooked chicken served for dinner

The following choices list several types of diseases, along with factors that may contribute to their emergence. Which disease and associated factor do NOT match?

A. Increased incidence of Lyme disease: increases in deer populations
B. increased incidence of malaria: global warming
C. spread of cholera to new regions: modern travel
D. emergence of avian influenza A (H5N1): use of antibiotics

D. emergence of avian influenza A (H5N1): use of antibiotics

As a health care worker, I am keenly aware of how important it is to avoid harming my patients. I worry about inadvertently transmitting an infectious disease to an already compromised individual. According to the CDC, what is the MOST important thing I can do to avoid this?

A. Shave my head.
B. Wear a lab coat.
C. Wear shoe covers.
D. Wash my hands before interacting with any patient.

D. Wash my hands before interacting with any patient.

Which of the following statements about the development of infectious diseases is correct?

A. The period of decline is the time when the infected individual’s health rapidly deteriorates.
B. The prodromal period is characterized by very severe symptoms.
C. During the incubation period, the infected individual exhibits obvious signs of sickness.
D. The period of convalescence is the time during which the person regains health and fully recovers (back to the pre-disease state).

D. The period of convalescence is the time during which the person regains health and fully recovers (back to the pre-disease state).

Malaria is an infectious disease caused by infection with a protozoan. In certain tropical regions, malaria is constantly present. We would say that malaria is a(n) _________ disease in these regions.

A. sporadic
B. epidemic
C. pandemic
D. endemic

D. endemic

One effect of washing regularly with antibacterial agents is the removal of normal microbiota. This can result in

A. body odor.
B. no bacterial growth because washing removes their food source.
C. increased susceptibility to disease.
D. fewer diseases.
E. normal microbiota returning immediately.

C. increased susceptibility to disease.

During a six-month period, 239 cases of pneumonia occurred in a town of 300 people. A clinical case was defined as fever 39°C lasting >2 days with three or more symptoms (i.e., chills, sweats, severe headache, cough, aching muscles/joints, fatigue, or feeling ill). A laboratory-confirmed case was defined as a positive result for antibodies against Coxiella burnetii. Before the outbreak, 2000 sheep were kept northwest of the town. Of the 20 sheep tested from the flock, 15 were positive for C. burnetii antibodies. Wind blew from the northwest, and rainfall was 0.5 cm compared with 7 to 10 cm during each of the previous three years.

The etiologic agent of the disease in the situation is

A. wind.
B. sheep.
C. soil.
D. pneumonia.
E. Coxiella burnetii.

E. Coxiella burnetii.

A commensal bacterium

A. does not infect its host.
B. does not receive any benefit from its host.
C. is beneficial to its host.
D. may also be an opportunistic pathogen.
E. is beneficial to, and does not infect, its host.

D. may also be an opportunistic pathogen.

Which of the following statements is TRUE?

A. At least one member must not benefit in a symbiotic relationship.
B. At least one member must benefit in a symbiotic relationship.
C. Symbiosis refers to different organisms living together and benefiting from each other.
D. A parasite is not in symbiosis with its host.
E. Members of a symbiotic relationship cannot live without each other.

B. At least one member must benefit in a symbiotic relationship.

Transient microbiota differ from normal microbiota in that transient microbiota

A. are present for a relatively short time.
B. cause diseases.
C. are always acquired by direct contact.
D. are found in a certain location on the host.
E. never cause disease.

A. are present for a relatively short time.

Which of the following is NOT an example of microbial antagonism?

A. bacteria competing for nutrients
B. acid production by bacteria
C. bacteria causing disease
D. bacteriocin production
E. bacteria occupying host receptors

C. bacteria causing disease …

The yeast Candida albicans does not normally cause disease because of ______.

A. the transient microbiota
B. parasitic bacteria
C. other fungi
D. the normal microbiota

D. the normal microbiota

The major significance of Robert Koch’s work is that

A. diseases can be transmitted from one animal to another.
B. microorganisms cause disease.
C. microorganisms can be cultured.
D. microorganisms are present in a diseased animal.
E. microorganisms are the result of disease.

B. microorganisms cause disease.

Koch observed Bacillus anthracis multiplying in the blood of cattle. What is this condition called?

A. focal infection
B. septicemia
C. local infection
D. systemic infection
E. bacteremia

B. septicemia

Which of the following is NOT a verified exception in the use of Kochs postulates?

A. Some human diseases have no other known animal host.
B. Some pathogens can cause several disease conditions.
C. Some diseases are not caused by microbes.
D. Some diseases are noncommunicable.
E. Some diseases have poorly defined etiologies.

D. Some diseases are noncommunicable.

Which of the following definitions is INCORRECT?

A. endemic: a disease that is constantly present in a population
B. pandemic: a disease that affects a large number of people in the world in a short time
C. incidence: number of new cases of a disease
D. sporadic: a disease that affects a population occasionally
E. epidemic: a disease that is endemic across the world

E. epidemic: a disease that is endemic across the world

Focal infections initially start out as

A. local infections.
B. systemic infections.
C. septicemia.
D. bacteremia.
E. sepsis.

A. local infections.

The rise in herd immunity amongst a population can directly attributed to

A. None of the answers is correct.
B. improved handwashing.
C. antibiotic-resistant microorganisms.
D. vaccinations.
E. increased use of antibiotics.

D. vaccinations.

Which of the following is NOT a communicable diseases?

A. AIDS
B. typhoid fever
C. malaria
D. tetanus
E. tuberculosis

D. tetanus

Symptoms of disease differ from signs of disease in that symptoms

A. always occur as part of a syndrome.
B. are changes observed by the physician.
C. are specific for a particular disease.
D. are changes felt by the patient.
E. None of the answers is correct.

D. are changes felt by the patient.

Which of the following definitions is INCORRECT?

A. secondary infection: a long-lasting illness
B. chronic: a disease that develops slowly and lasts for months
C. acute: a short-lasting primary infection
D. primary infection: an initial illness
E. inapparent: infection characteristic of a carrier state

A. secondary infection: a long-lasting illness

the figure shows the incidence of influenza during a typical year. Which letter on the graph indicates the endemic level?

a
b
c
d
The answer cannot be determined based on the information provided.

D

In the figure, when is the prevalence the highest?

A. February
B. The answer cannot be determined based on the information provided.
C. March
D. July
E. January

A. February

A disease in which the causative agent remains inactive for a time before producing symptoms is referred to as

A. latent.
B. acute.
C. subclinical.
D. subacute.
E. zoonotic.

A. latent.

The graph in the figure shows the incidence of polio in the United States. The period between 1945 and 1955 indicates a(n)

A. communicable disease.
B. epidemic level.
C. pandemic.
D. sporadic infection.
E. endemic level.

B. epidemic level.

Which of the following is NOT a predisposing factor of disease?

A. genetic background
B. None of the answers are correct; all of these are predisposing factors of disease.
C. lifestyle
D. occupation
E. climate

B. None of the answers are correct; all of these are predisposing factors of disease.

In which of the following diseases can gender be considered a viable predisposing factor?

A. tetanus
B. anthrax
C. salmonellosis
D. urinary tract infections
E. pneumonia

D. urinary tract infections

In which of the following patterns of disease does the patient experience no signs or symptoms?

A. decline
B. prodromal
C. convalescence
D. incubation
E. incubation and convalescence

E. incubation and convalescence

If a prodromal period exists for a certain disease, it should occur prior to

A. convalescence.
B. decline.
C. illness.
D. incubation.

C. illness.

Which of the following diseases is NOT spread by droplet infection?

A. botulism
B. diphtheria
C. the common cold
D. measles
E. tuberculosis

A. botulism

Biological transmission differs from mechanical transmission in that biological transmission

A. involves fomites.
B. works only with noncommunicable diseases.
C. involves specific diseases.
D. requires direct contact.
E. requires an arthropod.

C. involves specific diseases.

Which of the following is NOT a reservoir of infection?

A. a healthy person
B. a sick animal
C. a sick person
D. a hospital
E. None of the answers is correct; all of these can be reservoirs of infection.

E. None of the answers is correct; all of these can be reservoirs of infection.

Which of the following is a fomite?

A. pus
B. water
C. a hypodermic needle
D. insects
E. droplets from a sneeze

C. a hypodermic needle

Which of the following statements about biological transmission is FALSE?

A. The pathogen reproduces in the vector.
B. Houseflies are an important vector.
C. The pathogen may require the vector as a host.
D. The pathogen may enter the host in the vector’s feces.
E. The pathogen may be injected by the bite of the vector.

B. Houseflies are an important vector.

Which of the following pairs is mismatched?

A. malaria – vector
B. influenza – droplet infection
C. salmonellosis – vehicle transmission
D. syphilis – direct contact
E. None of the pairs is mismatched.

E. None of the pairs is mismatched.

A cold transmitted by a facial tissue is an example of which form of disease transmission?

A. droplet transmission
B. vector
C. vehicle transmission
D. indirect contact transmission

D. indirect contact transmission

A needlestick is an example of

A. fomite.
B. direct contact.
C. vector.
D. vehicle transmission.
E. droplet transmission.

A. fomite.

During a six-month period, 239 cases of pneumonia occurred in a town of 300 people. A clinical case was defined as fever 39°C lasting >2 days with three or more symptoms (i.e., chills, sweats, severe headache, cough, aching muscles/joints, fatigue, or feeling ill). A laboratory-confirmed case was defined as a positive result for antibodies against Coxiella burnetii. Before the outbreak, 2000 sheep were kept northwest of the town. Of the 20 sheep tested from the flock, 15 were positive for C. burnetii antibodies. Wind blew from the northwest, and rainfall was 0.5 cm compared with 7 to 10 cm during each of the previous three years.

the situation is an example of

A. a focal infection.
B. a zoonosis.
C. a nonliving reservoir.
D. human reservoirs.
E. a vector.

B. a zoonosis.

During a six-month period, 239 cases of pneumonia occurred in a town of 300 people. A clinical case was defined as fever 39°C lasting >2 days with three or more symptoms (i.e., chills, sweats, severe headache, cough, aching muscles/joints, fatigue, or feeling ill). A laboratory-confirmed case was defined as a positive result for antibodies against Coxiella burnetii. Before the outbreak, 2000 sheep were kept northwest of the town. Of the 20 sheep tested from the flock, 15 were positive for C. burnetii antibodies. Wind blew from the northwest, and rainfall was 0.5 cm compared with 7 to 10 cm during each of the previous three years.

The method of transmission of the disease in the situation was

A. droplet.
B. vector-borne.
C. indirect contact.
D. vehicle.
E. direct contact.

D. vehicle.

Which one of the following is NOT a zoonosis?

A. rabies
B. Hantavirus pulmonary syndrome
C. tapeworm
D. cat-scratch disease
E. None of the answers is correct; all of these are zoonoses.

E. None of the answers is correct; all of these are zoonoses.

A nosocomial infection is

A. always caused by pathogenic bacteria.
B. only a result of surgery.
C. always caused by medical personnel.
D. acquired during the course of hospitalization.
E. always present, but is inapparent at the time of hospitalization.

D. acquired during the course of hospitalization.

Which one of the following does NOT contribute to the incidence of nosocomial infections?

A. gram-negative cell walls
B. lack of handwashing
C. lapse in aseptic techniques
D. lack of insect control
E. antibiotic resistance

A. gram-negative cell walls

Which of the following statements about nosocomial infections is FALSE?

A. They may be caused by drug-resistant bacteria.
B. They may be caused by opportunists.
C. They occur in compromised patients.
D. They may be caused by normal microbiota.
E. The patient was infected before hospitalization.

E. The patient was infected before hospitalization.

Which of the following can contribute to postoperative infections?

A. errors in aseptic technique
B. normal microbiota on the operating room staff
C. using syringes more than once
D. antibiotic resistance
E. All of the answers are correct.

E. All of the answers are correct.

Pseudomonas bacteria colonized the bile duct of a patient following his liver transplant surgery. This is an example of a

A. nosocomial infection.
B. latent infection.
C. sporadic disease.
D. communicable disease.
E. None of the answers is correct.

A. nosocomial infection.

Which of the following does NOT contribute to the emergence of infectious diseases?

A. Antibiotic resistance
B. Climatic changes
C. New strains of previously known agents
D. Ease of travel
E. The emergence of infectious diseases can be attributed to all of these

E. The emergence of infectious diseases can be attributed to all of these

Which of the following statements is FALSE?

A. Antimicrobial therapy for hemodialysis-associated infections increases antibiotic resistance.
B. The USA100 strain accounts for most hospital-acquired MRSA.
C. The USA300 strain accounts for most community-acquired MRSA.
D. The M in MRSA stands for mannitol.
E. S. aureus is differentiated from other mannitol+ cocci by the coagulase test.

D. The M in MRSA stands for mannitol.

The science that deals with when diseases occur and how they are transmitted is called

A. ecology.
B. communicable disease.
C. morbidity and mortality.
D. epidemiology.
E. public health.

D. epidemiology.

A researcher has performed a prospective study on the disease tetanus. To which specific kind of epidemiological study is this referring?

A. analytical
B. case control
C. experimental
D. descriptive
E. prodromal

D. descriptive

The CDC is located in

A. Atlanta, GA.
B. Washington, DC.
C. New York City, NY.
D. Las Angeles, CA.
E. Chicago, IL.

A. Atlanta, GA.

Which of the following best describes why West Nile Virus is considered to be an emerging infectious disease?

A. West Nile virus causes an infection and death in birds such as crows and blue jays.
B. West Nile virus causes a latent viral infection that can emerge later in life.
C. West Nile virus was first isolated in Uganda in 1937 and has caused significant outbreaks every year since then.
D. West Nile virus outbreaks have increased in number and affected areas since 1937.

D. West Nile virus outbreaks have increased in number and affected areas since 1937. West Nile virus was originally identified in 1937, when it caused a significant outbreak in Uganda. Following this initial outbreak, only minor occurrences in Egypt and Israel had been observed until 1999, when the virus reappeared with a significant outbreak in New York City. This appearance was important because it was the first time West Nile virus had been observed in the United States. Since then, West Nile virus has been declared an important pathogen to public health officials and those involved in veterinary medicine. In fact, in 2009, the CDC declared West Nile virus to be endemic in the United States.

During his research on West Nile virus, Bill learned that this virus is placed within a functional grouping known as arboviruses. What is meant by the term arbovirus?

Select all that apply.

– An arbovirus is an arthropod-borne virus.
– An arbovirus is a virus isolated in Ann Arbor, Michigan.
– An arbovirus is maintained in nature through biological transmission.
– An arbovirus is a virus that originated from plants.

– An arbovirus is an arthropod-borne virus. – An arbovirus is maintained in nature through biological transmission. Arboviruses get their name because they are typically arthropod-borne viruses that remain in nature because of biological transmission between susceptible hosts by blood-feeding arthropods, such as mosquitoes.

If mosquitoes are the mode of transmission for West Nile virus, why did the students in Bill’s virology class focus on finding the virus in the dead birds rather than collecting mosquitoes to examine?

A. The students tried to isolate and identify West Nile virus from birds because they are large animals. It would be difficult to isolate West Nile virus from mosquitoes because they are small.
B. The students tried to isolate and identify West Nile virus from birds because they had access to dead birds that were known to be infected with West Nile virus.
C. The students tried to isolate and identify West Nile virus from birds because they are an amplifying host for the virus, making it more likely that the virus can be isolated from these animals.
D. The students tried to isolate and identify West Nile virus from birds because it is faster to isolate the virus from a bird than to isolate it from a mosquito.

C. The students tried to isolate and identify West Nile virus from birds because they are an amplifying host for the virus, making it more likely that the virus can be isolated from these animals. The students tried to isolate and identify the West Nile virus from the birds because there is a high probability that the birds were infected with the virus. Birds are considered to be an amplifying host for the West Nile virus, which means that the number of viral particles is increased dramatically within this host. Although house sparrows seem to be tolerant of this amplification process, studies had shown that crows and blue jays, both of which were specimens, were susceptible to death from this virus.

The brain tissue of the birds indicated the possibility of encephalitis. What is encephalitis, and why should this type of infection cause concern among health care professionals?

A. Encephalitis is an inflammation of the meninges. It is a concern to health care professionals because of how quickly the infection will spread to the rest of the body.
B. Encephalitis is an inflammation of the peripheral nervous system. It is a concern to health care professionals because of how quickly the infection will spread to the rest of the body.
C. Encephalitis is an inflammation of the brain tissue. It is a concern to health care professionals because an infection in the brain means the virus has breached protective measures.
D. Encephalitis is an inflammation of the spinal cord. It is a concern to health care professionals because the infection will spread to the brain.

C. Encephalitis is an inflammation of the brain tissue. It is a concern to health care professionals because an infection in the brain means the virus has breached protective measures. Encephalitis is an inflammation of the brain tissue. It is a concern to health care professionals because an infection in the brain means the virus has breached protective measures of the blood-brain barrier. Brain infections are serious because many are fatal because it is difficult to treat them with antimicrobials. Antimicrobials must be lipid-soluble in order to cross the blood-brain barrier. There is an exception, however. In some infections of the brain, the inflammation alters the permeability of the blood-brain barrier and may allow some antimicrobials to cross that would not be able to cross if the infection were not present.

Which of the following is the best mode of controlling the spread of West Nile infections?

A. Kill all mosquitoes to prevent the transmission of West Nile virus.
B. Kill all birds to prevent the amplification and transmission of West Nile virus.
C. Limit exposure to mosquitoes to prevent the transmission of West Nile virus.
D. Limit exposure to birds to prevent the transmission of West Nile virus.

C. Limit exposure to mosquitoes to prevent the transmission of West Nile virus. The best way to prevent West Nile virus infections is to limit exposure to the mosquitoes. This can be accomplished by using bug sprays, by staying indoors during times when mosquitoes are out (particularly in the summer months), and by wearing protective clothing outdoors if mosquitoes are present. Another preventative measure is to eliminate sources of water, especially stagnant water, where mosquitoes lay their eggs. This will help to decrease mosquito populations, reduce the possibility of exposure to the mosquito, and as a result limit the chance of infection with West Nile virus.

What features of West Nile virus make it an emerging disease of special concern?

Select all that apply.

– West Nile virus is an arthropod-borne virus transmitted by mosquitoes.
– West Nile virus has a high mortality rate in immunosuppressed humans and infects many species of birds in southern Europe, the Mediterranean basin, and North America.
– West Nile virus is maintained in nature through biological transmission between susceptible hosts by blood-feeding arthropods.
– West Nile virus has a positive, single-stranded RNA genome that is 11,000 to 12,000 nucleotides long.

– West Nile virus is an arthropod-borne virus transmitted by mosquitoes. – West Nile virus has a high mortality rate in immunosuppressed humans and infects many species of birds in southern Europe, the Mediterranean basin, and North America. – West Nile virus is maintained in nature through biological transmission between susceptible hosts by blood-feeding arthropods. Emerging infectious diseases are defined as ones that are new or changing, have increased in incidence in the recent past, or show a potential to increase in the near future. Given the increase in number of cases of West Nile virus encephalitis and avian death since it appeared in New York City in 1999, this virus meets the definition of an emerging infectious disease. Over half of known emerging infectious diseases are zoonotic, mainly of viral origin, and are likely to be vector-borne. West Nile virus is all of these things, and infections with this virus must be reported to the CDC for tracking. The CDC works along with the National Institutes of Health (NIH) and the World Health Organization (WHO) to address issues related to emerging infectious diseases. Together, these agencies have set goals for investigating, monitoring, and controlling emerging infectious diseases worldwide.

Student will identify Koch’s postulates for determining the etiology of infectious diseases.

Which of statements best describe Koch’s postulates?

Select all that apply.

– The pathogen must be isolated from the inoculated animal and must be shown to be the original organism.
– The pathogen must be isolated from the diseased host and grown in pure culture.
– The same pathogen must be present in every case of the disease.
– The microscopic properties of pathogens isolated from the original (diseased) and inoculated (also, diseased) animals should differ significantly.
– The pathogen from the pure culture must cause the disease when it is inoculated into a healthy, susceptible laboratory animal.

– The pathogen must be isolated from the inoculated animal and must be shown to be the original organism. – The pathogen must be isolated from the diseased host and grown in pure culture. – The same pathogen must be present in every case of the disease. – The pathogen from the pure culture must cause the disease when it is inoculated into a healthy, susceptible laboratory animal. You have correctly identified the four statements that describe Koch’s postulates. These experimental steps are used to systematically link a specific microbe to a specific infectious disease.

Students will be presented with experimental results obtained when testing a suspected pathogen, and will identify appropriate conclusions based on each scenario.

A rabbit was found to have Floppy Ear disease that causes long-ear infections, but its etiology (cause) is unknown. Unknown Microorganism X from the infected rabbit’s right ear was successfully isolated and cultured on laboratory growth media. The ear of a healthy laboratory mouse was then inoculated with isolated microorganism, and after a period of time, no disease is observed. Which of the following statements BEST describe the conclusion(s) that can be drawn from this experiment?

Select all that apply.

– Microorganism X is the etiologic agent for Floppy Ear disease since it caused infection in the diseased rabbit.
– A laboratory mouse might not be an appropriate, susceptible host; an experiment with a laboratory rabbit may be needed.
– Microorganism X might not be linked to Floppy Ear disease, since the inoculated mouse remained healthy.
– It is not possible to isolate and culture Microorganism X in the laboratory, since this microbe is found in nature.
– Microorganism X modified its cell wall structure while being cultured, and is no longer infectious to rabbits.
– Healthy laboratory organisms rarely show signs and symptoms of infection and disease.

– A laboratory mouse might not be an appropriate, susceptible host; an experiment with a laboratory rabbit may be needed. – Microorganism X might not be linked to Floppy Ear disease, since the inoculated mouse remained healthy. You have correctly identified two conclusions that can be drawn from this experiment. Koch’s postulates state that the pathogen must be isolated from the diseased host, grown in pure culture, cause disease in a healthy laboratory animal, and the re-isolated microorganism be the same as original pathogen. In this scenario, the suspected pathogen did not meet all of Koch’s postulates, since the laboratory mouse did not show signs of infection.

BENEFITS:

-The steps are designed to systematically link a pathogen to a specific infectious disease.
-Lab findings provide experimental evidence that support the germ theory of disease.
-Healthy susceptible animals can be used as model organisms when testing many types of infections, thus avoiding the unethical inoculation of healthy human hosts.

LIMITATION: -Different pathogens can produce the same signs and symptoms, making it difficult to determine which microorganism is causing a disease. -Some pathogens cause several different diseases, which makes it difficult to link one pathogen to one disease using Koch’s postulates. -Some infectious agents have specific growth requirements that prevent it from being artificially cultured in the lab.