MMG 301 Exam 3

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.

Why are antibiotics often ineffective in treating food poisoning (food intoxication)?

Antibiotics target bacteria; they do not damage toxins.

Which type of vaccine could possibly cause a person to develop the disease?

Attenuated live vaccine.

"Bloodborne hepatitis" is caused by infection with hepatitis ________ virus.

B

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.

How does the protozoan Trypanosoma evade detection by the immune system?

It can change the surface antigens frequently, preventing the immune system from tracking it.

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.

It is a differential medium and a selective medium.

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.

Water supplies are treated with chlorine to kill pathogens. Chlorine reacts well with many other chemicals and bacterial cells because it is a strong oxidant. However, Legionella pneumophila can sometimes evade killing by residual chlorine. How does it do this?

Legionella tends to form biofilms and infect other microbial cells as intracellular pathogens.

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.

Some studies have indicated that the ID50 for Vibrio cholerae can be as high as 10^8 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.

What is the role of epidemiology?

To learn how to treat and prevent various diseases.

A patient with AIDS often dies of a variety of infections caused by opportunistic microorganisms.

True

Budding of virions from an infected host results in enveloped virus.

True

Which of the following microorganisms actually grows inside the macrophage?

Tuberculosis bacterium

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.

Which of the following was an emerging mosquito-borne disease in the early 2000s and has now spread to every state in the United States?

West Nile Fever

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.

In bubonic plague, buboes are swellings formed in the lymph nodes and filled with

Yersinia pestis.

Some viruses have plus sense RNA genomes. Which of the following could describe one of those viruses?

a virus that contains RNA with the same nucleotide sequence as the functional mRNA that its host cell will translate to produce viral products

Controlling most rickettsial diseases involves managing

the vector

Bacterial fermenters themselves are a significant source of nutrition for ruminants, but not for hindgut fermenters, because __________.

they pass through an acidic chamber and are digested

How is the syphilis spirochete initially transmitted?

through tiny breaks in the skin epithelial layer

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

transduction

Nucleic acid probes are used to detect the presence of particular sequences of DNA.

true

Soldiers or refuges in crowded unsanitary conditions are most susceptible to which rickettsial disease?

typhus

A patient is brought to the hospital with severe gastrointestinal distress, including cramps, dehydration and diarrhea. Which of the following symptoms would indicate that the pathogen is Vibrio cholerae?

voluminous, watery diarrhea

Which public health measure(s) is/are most effective against pathogens transmitted through common vehicles?

water purification and food safety regulations

Epidemiology is defined as the study of

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

Another name for pertussis is

whooping cough

Rickettsia are obligate intracellular parasites that are transmitted by arthropods. In which of the following places would you most likely find the parasites living in the host organism during the course of infection?

within macrophages

Deaths because of infectious disease are more common in developing countries, such as Africa, compared to the Americas because of __________.

-all of the listed responses are correct (inadequate sanitation, limited access to clean water, limited immunization programs)

Chickenpox, caused by a herpes virus, results in a systemic papular rash that quickly heals.

True

Emerging diseases are a problem worldwide, even in highly developed regions of the world.

True

The hantaviruses are occasionally spread by person-to-person transmission, although exposure to infected rodent excreta is the most common route of infection.

True

Lyme disease and syphilis are similar in that they __________.

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

The disk-diffusion test is used for

assessing antimicrobial activity.

A pathogen must __________ in order for it to cause disease.

attach and multiply

Which of the following can be used in creating a vaccine?

attenuated bacteria, inactivated viruses, or recombinant proteins

R-plasmids are most likely acquired via

bacterial conjugation.

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

bacterimia

The primary function of a phagocyte is to

both engulf and destroy pathogens.

Which of the following is a cause of drug-specific resistance in disease-causing organisms?

indiscriminate nonmedical use of antimicrobials

Human immunodeficiency virus (HIV) __________.

infects and replicates in macrophages and T-helper cells

Hantaviruses are most commonly transmitted by ________ of virus-contaminated rodent ________.

inhalation / excreta

Which of the following is most likely to cause disease?

injection of 105 cells of a highly virulent bacterial species into a mouse

The bodys non-inducible, preexisting ability to recognize and destroy a variety of pathogens or their products is called

innate immunity.

Resident staphylococci are commonly found in the ________ and these seldom cause disease.

upper respiratory tract

Which of these is often used as a prophylactic measure to protect a person against future attack by a pathogen?

vaccination.

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

virulence factors

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

viruses require host cells to replicate themselves

Which of the following statements is TRUE about HIV infections?

1. The viral nucleocapsid of the virus enters the host cell when the viral and host membranes fuse. 2. The cDNA can integrate into the host chromosome. 3. T-helper cells are greatly reduced in number. (Answer = all)

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

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

Laboratories that work with extremely low risk pathogens are classified as

BSL-1

All of the following are Gram-positive genera typically found on the skin EXCEPT __________.

Bacteroides

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.

What is the function of boosters?

Boosters are injections that are given periodically to maintain immunity.

The causative agent of Lyme disease is ________, which is carried primarily by the ________.

Borrelia burgdorferi / Ixodes sp. (deer tick)

What is meant by selective toxicity?

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

Which of the following pathogens is spread by infected lice?

Rickettsia prowazekii

Quinolones and fluoroquinolones act against what bacterial target?

DNA gyrase

An important intestinal pathogen generally acquired from contaminated food or water is

Escherichia coli O157:H7.

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

Hyaluronidase.

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

Silent mutation

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.

Tetanus is highly contagious through person-to-person contact.

False

Viral hepatitis can result in acute kidney disease, followed by chronic kidney disease.

False

All microorganisms that live in the human body are harmful.

False.

Which of these microorganisms is most likely to be found in the human stomach?

Helicobacter pylori

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.

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.

Hantaviruses are related to viruses such as ________ and ________.

Lassa fever virus / Ebola virus

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).

Which of the following diseases causes an influenza-like illness that can progress to include pneumonia?

Q fever

Reverse transcriptase is a(n)

RNA-dependent DNA polymerase.

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

Staphylokinase

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

The bacterium is neither killed nor inhibited by the antibiotic.

How does a capsule help certain bacteria evade detection by the immune system?

The capsule is composed of polysaccharides that are similar to those found in the host; thus, the immune system does not recognize it as foreign.

The primary disease reservoir for plague is

rats

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.

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

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

Symbionts can be acquired by an individual host organism horizontally (from the environment) or vertically (from a parent). In humans, there is evidence that infants are largely colonized by their parents' microbes, and family members living in the same household have microbiomes that are more similar than those of individuals living nearby. However, no two humans have identical microbiota, and certain factors, such as diet and antibiotics, can alter the microbiome. This indicates that humans may be colonized by __________.

both vertical and horizontal transmission

Pattern recognition receptors are most directly used

by phagocytes to detect pathogens.

Once a person has been infected with Neisseria gonorrhoeae, the individual

can be reinfected immediately because of the diversity of strains and frequency of mutation.

A person who tests positive for the human immunodeficiency virus but shows no symptoms of AIDS would be termed a __________.

carrier

Staphylococcus aureus produces ________, an enzyme that results in the accumulation of fibrin around the bacterial cells.

coagulase

Obligate anaerobes are likely to be found in the __________.

colon

All students that ate in the school dining hall on Monday developed stomach cramps and diarrhea. The student clinic was overwhelmed with patients. However, by Thursday the number of patients seen in the clinic was back to normal. This could have been caused by a __________.

common-source epidemic

Legionella pneumophila is generally transmitted by

contaminated water in coolers, pools, and domestic water systems.

The damaged areas of teeth caused by organic acids produced by dental plaque are called

dental caries

Extensive microbial growth in a thick bacterial layer on the teeth is called

dental plaque.

The type of Escherichia coli that produces a verotoxin similar to the one produced by Shigella dysenteriae is ________ E. coli.

enterohemorrhagic

The human gastrointestinal tract includes all of the following EXCEPT the

epiglottis.

The antigen-binding site of an antibody accommodates a small portion of the antigen called a(n)

epitope.

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

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

Which of the following are properties of exotoxins?

exotoxins target specific cellular structures or molecules, very small amounts of exotoxin can be fatal, exotoxins are protein molecules.

The lower the basic reproduction number of a pathogen, the higher the percentage of immune individuals necessary to provide herd immunity.

false

An inanimate object that transmits infectious agents between hosts is most appropriately called a

fomite

Which of the following are NOT vectors important in disease transmission?

fomites

Illness that results from ingestion of pathogen-contaminated food is __________.

food infection

Severe cases of Staphylococcus aureus food poisoning may require treatment

for dehydration

Which of the following is NOT a public health measure used to control the transmission of disease?

genetic engineering

Staphylococcus aureus is a common causative agent of foodborne disease because it

grows on many foods, is present in some humans that work in food processing, and produces several heat-stable enterotoxins.

An attenuated strain of a pathogen

has lost its virulence, but may be used to create a vaccine.

For many years the CDC focused its seasonal influenza vaccination efforts on those groups in the population who suffered the highest influenza mortality rates, including the elderly aged 65 years and older. However, starting in 2008 the CDC shifted their focus to school-aged children and began recommending the vaccine for everyone aged at least 6 months. Research had shown no evidence for any protective effect of the vaccine in the elderly. By changing the recommendations for who should be vaccinated, the CDC planned to better protect the elderly by means of__________.

herd immunity

When squids that contain luminescent bacterial symbionts hatch, they do NOT contain a bacterial symbiont. Symbiont transmission in this symbiosis is

horizontal and involves specific selection of the symbiont from the environment.

Widespread antimicrobial drug resistance is usually passed by

horizontal gene transfer

A disease showing a relatively slow, progressive rise followed by a gradual decline in incidence is indicative of a(n)

host-to-host epidemic

The ability of humans to resist a disease is called

immunity.

The influenza vaccine is an example of a(n)

inactivated killed vaccine.

Disease ________ is measured by the total number of new reported disease cases within a population over a period of time.

incidence

Which stage of an acute infectious disease occurs between the time the organism begins to grow in the host and the appearance of disease symptoms?

incubation period

Toxic shock syndrome __________.

is life-threatening because of the superantigen toxin produced

The most heavily colonized human organ by bacteria is the ________, containing 10111012 bacterial cells per gram.

large intestine

Pus formation in skin lesions caused by Staphylococcus aureus infections is in part due to production of

leukocidin

Which of the following presents processed antigens to T cells?

major histocompatibility complex proteins

Aliivibrio fischeri symbionts benefit the Hawaiian bobtail squid by

mimicking the light of the moon, which helps the squid avoid nocturnal predators

In the first reported epidemiological study in 1854, John Snow attempted to discover the source of a London cholera epidemic by going house-to-house and recording deaths. When he mapped the results, he was able to identify the Broad Street water pump as the likely source of contaminated water. The data collected in this study was__________.

mortality

Which of the following would be the best strategy to prevent the spread of yellow fever and dengue fever into the southern United States?

mosquito avoidance and eradication

Viral size is generally measured in

nanometers

A frequent symptom of the common cold is

nasal discharge

When packaged in the virion, the complete complex of nucleic acid and protein is known as the virus

nuceocapsid

MHC I proteins are found

on all nucleated cells.

The human microbiome contains all

organisms present in and on the body.

A large number of cases of a particular disease observed in a relatively short period of time in an area that previously experienced only sporadic cases of the disease is known as a(n)

outbreak

Hepatitis B and C are transmitted via the

parenteral route.

An Etest® is a clinical tool used for the determination of

the minimum inhibitory concentration (MIC) value of an antimicrobial agent.

Pickling is a type of food preservation utilizing

weak acids

Of the following, which is the most common AIDS-associated opportunistic disease?

Pneumocystis jirovecti pneumonia

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

Practice more stringent aseptic techniques

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?

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

Which of the following are group A Streptococcus (GAS)?

Streptococcus pyogenes

The causative agent of streptococcal pharyngitis, also known as strep throat, is

Streptococcus pyogenes.

The Hepatitis B vaccine is which type of vaccine?

Subunit vaccine.

The unique antigen-reactive proteins of T cells are

T cell receptors.

Indirect EIA is used to detect

antibodies

Adaptive immune responses are directed at pathogen molecules called

antigens.

In 2011, the CDC reported a 28-state outbreak of Listeria monocytogenes that killed 33 people in the United States. The victims were found to have eaten portions of whole cantaloupe melons originating from a single farm in Colorado. The FDA traced the source of bacterial contamination to a piece of used equipment that had been recently purchased to wash the melons, nearby puddles of water, and a truck that hauled spoiled melons to a field to be fed to cattle. This would be an example of __________.

common-source transmission

Eradication of certain diseases is nearly impossible, because we cannot

control or immunize all vector and reservoir animals or eradicate organisms completely from the soil.

Individuals who have an active case of tuberculosis may spread the disease simply by ________ uninfected individuals.

coughing near

Diseases that suddenly become more prevalent are referred to as ________ diseases.

emerging

A disease that is constantly present in a population at low numbers is a(n) __________.

endemic

A disease that is present in unusually high numbers throughout the world is called a(n)

pandemic

The ability to cause disease is __________.

pathogenicity

Some antibiotics inhibit protein synthesis by disruption of translation through interactions with the

ribosome

Hantavirus pulmonary syndrome is a viral respiratory disease caused by contact with

rodents

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

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

sensitivity

A mechanism for penicillin resistance in bacteria is

splitting the β-lactam ring of the antibiotic.

Termites are capable of digesting cellulose and hemicellulose due to the presence of __________.

symbiotic bacteria in their gut.

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

syphilis

The rate of contaminant microbial growth during the exponential phase in food depends on

temperature, nutrient value, and water content.

The single most important physical sign of primary syphilis is

the chancre.

The most common infectious disease is

the common cold.

Saliva contains relatively few microbes compared to other body sites, because __________.

the concentration of antimicrobial enzymes limits their growth

When a patient is treated with antibiotics, __________.

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

During the early 20th century, pandemics typically took months to years to span the globe, while the 2009 H1N1 swine flu spread globally within weeks and had affected most countries within 6 months. This difference in the rate of spread is mainly due to__________.

the increased volume and speed of global transportation.

Tetanus develops from a puncture wound because

the organism's endospores germinate in anoxic conditions.

Which of the following is an example of humoral immunity?

the production of antibodies by B cells

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

20%

When a child begins to get its first teeth, what happens to the microbiota in the oral cavity?

The teeth are rapidly colonized by anaerobes, in particular Streptococcus, that are specifically adapted to growth in biofilms on the surfaces of the teeth.

What is the hallmark of a conjugated vaccine?

These vaccines contain weakly antigenic elements plus a more potent antigenic protein.

How are immune cells able to detect foreign pathogens?

They are able to detect structures on the surfaces of foreign cells that are not found in the host.

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).

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.

What is the drawback of live attenuated vaccines?

They can cause disease in some immunocompromised individuals.

Which is an example of acquisition of natural passive immunity?

a fetus protected from disease by its mothers antibodies

The causative agent of dengue fever is

a flavivirus

Antibody titer can be measured by

agglutination

With regards to mode of disease transmission, respiratory pathogens are generally ________, and intestinal pathogens are generally spread by contaminated ________.

airborne / food or water

Aphids that feed on carbohydrate-rich but nutrient-poor foods obtain ________ from their endosymbiotic bacterial partners.

amino acids.

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

an increase in multi-drug-resistant strains

The emergent H5N1 strain of avian influenza can occasionally be transmitted from birds to humans with a resulting 60% mortality rate (compared with a 2.5% mortality rate for the 1918 pandemic influenza). In 2012, after a single dead chicken in a wholesale market in Hong Kong tested positive for H5N1, all 17,000 chickens in the market and surrounding area were culled. This was an attempt to__________.

eliminate a reservoir.