Chapter
24
1. The patient is suffocating because of
an inflamed epiglottis. What is the etiology of the symptoms?
Haemophilus
2. The
patient has a sore throat. What is the etiology of the symptoms?
The answer cannot be determined based on
the information provided
3. It is common for a normal, healthy
individual to carry potentially pathogenic organisms in their upper respiratory
tract.
TRUE
4. Which of the following diseases has a
cutaneous form, especially in individuals over 30 years of age?
Diphtheria
5. The patient is suffocating because of
the accumulation of dead tissue and fibrin in her throat. What is the etiology
of the symptoms?
Corynebacterium
6. A patient has a paroxysmal cough and
mucus accumulation. What is the etiology of the symptoms?
Bordetella
7. All
of the following are true of the common cold EXCEPT
early treatment will drastically reduce
the disease symptoms
Concept
Map: Tuberculosis
1. Tuberculosis is the name of the
___________ caused by the _________ Mycobacterium tuberculosis.
Disease; bacterium
2. What can you deduce from the
treatment strategy for M. tuberculosis infection?
The organism has some innate resistance
to antibiotics.
**It is rare that you have to treat an
infection with multiple antibiotics for such a long period of time.
3. Which of the following could be true
of tuberculosis of the kidney?
All of the above could be true
**TRUE:
The disease could be subsequent to a
normal primary infection.
The disease could be subsequent to a
reactivated latent infection.
The patient would likely be infected
with MDR TB or XDR TB.
The patient would likely have a positive
skin test.
Chapter
24
1. Which of the following is mismatched?
Mycoplasma
– gram-positive pleomorphic rod
2. Which of the following statements
regarding tuberculosis is FALSE?
Nearly 1/3 of the worlds population
shows symptoms of tuberculosis
3. A patient has fever, difficulty
breathing, chest pains, fluid in the alveoli, and a positive tuberculin skin
test. Gram-positive cocci are isolated from the sputum. The patient most likely
has
pneumococcal pneumonia
4. Which one of the following produces
small "fried-egg" colonies on medium containing horse serum and yeast
extract?
Mycoplasma
5. The
most common causative agent of bacterial pneumonia is Streptococcus pneumoniae.
TRUE
6. A positive tuberculosis skin test
indicates that the patient has active tuberculosis.
FALSE
7. The primary victims of the influenza
pandemic of 1918-1919 were
young adults
8. Vaccination with the influenza
vaccine confers lifelong immunity to influenza virus.
FALSE
9. Microscopic examination of a lung
biopsy shows thick-walled cysts. What is the etiology of the symptoms?
Pneumocystis
10. Which
statement regarding influenza (flu) is true?
Antigenic shift can occur because the
genome is in several pieces.
Diseases
in Focus Chapter 24 – Male, age 78
MEDICAL
HISTORY (Hx)
The
patient is a male, age 78. He was admitted to the hospital for fever, chills,
chest pain, and a productive cough. He lives in Houston, Texas, and is an
aspiring author and retired investment banker. He spends much of his retired
life golfing, or working on his novel. He is sexually active, and in a
non-monogamous relationship. He and his partners are consistent with their use
of birth control. He lives in a loft apartment by himself, and owns a dog. He
is allergic to peanuts, but does not have any special concerns that would
affect your ability to treat him. His family history does not suggest any
factors associated with genetic disease. He smokes regularly (1 pack/day), and
reports drinking alcohol (5+ drinks) 3 times a week, on average. He does not
use drugs of abuse. Two weeks ago, he traveled to Seattle for two days to meet
with his editors. Within the last five days he began to feel unusually tired
with a persistent dry cough. As time passed, his cough worsened, and he
developed a fever and chest pains. He also had several bouts of loose, watery
diarrhea. Upon admission to the hospital, he seems clumsy and uncoordinated,
with a fever of 40.8∘C.
Differential
Diagnoses
Differential
diagnosis is the process of identifying a disease from a list of possible
diseases that fit the information derived from examining a patient. Your job
will be to synthesize information from a patient whose main presenting symptoms
are consistent with a microbial disease of the respiratory system. Use the
"Diseases in Focus" 24.1, 24.2, and 24.3 tables and your knowledge about microbial
diseases of the respiratory system to identify the patient's risk factors and
symptoms, evaluate diagnostic evidence, formulate and test a diagnosis about
the pathogen responsible for the patient's woes, and suggest a course of
treatment.
1. Identify relevant information
Review the patient's medical history,
and then identify risks and concerns that could be relevant to your diagnosis
(and the patient's treatment).
Relevant:
Age-related risk of disease
Risk of sexually transmitted infection
Risk of vector-borne disease
Risk of travel-related disease exposure
Not Relevant:
Occupational risk of disease
Risk of drug-related disease exposure
Risk of genetic/familial disease
Special concerns for treatment
Risk of immunocompromised
**You have reviewed your patient's medical history, and you
recognize several factors that could be relevant to your diagnostic process.
His age, sexual habits, travel history, and pet dog all could increase his
exposure to diseases, pathogens, or vector organisms.
Your
first concern however, is that your patient's symptoms seem to include changes
in his mental state. He is clumsy and uncoordinated, which could potentially
signal a serious or life-threatening condition. He also has a high fever, a
productive cough, and occasional diarrhea. These latter symptoms are general
enough that they could apply to several different types of respiratory disease,
but your patient's fever and possible cerebral involvement up the ante enough
that you would like to begin treating him as soon as possible. You take a blood
sample and a nasal swab from your patient, and order smear preps from the
samples for Gram-staining and other diagnostics. While you wait for your
results, you order a chest x-ray for your patient.
X-ray
results
Your
patient's x-ray is shown here. You observe bilateral (both sides of the body)
basal (lower) pulmonary congestion, as well as pleural effusion, indicating
excess fluid between the two pleural layers. These results are compatible with
a diagnosis of pneumonia.
2. Interpret your results
Now that you have considered the
evidence at hand, you should start to build a hypothesis about what disease
your patient has. In the beginning of your diagnostic process you should try
and think broadly to help you consider any and all reasonable possibilities.
You can then narrow down these possibilities by performing diagnostics that can
support or refute your hypothesis.
A form of bacterial pneumonia
Melioidosis
Viral pneumonia, RSV
Coccidioidomycosis
**You have narrowed down the diseases you
suspect are responsible for your patient's condition to a form of bacterial or
viral pneumonia, melioidosis, influenza, or coccidioidomycosis. Now you must
wait for your initial diagnostics to return from the lab.
3. Interpret your results
After a day, you receive the following
results:
What does this tell you?
Your patient's samples show the presence
of a Gram-negative bacteria.
**Your initial results are positive for
the presence of a Gram-negative bacterium. You believe your patient has a form
of bacterial pneumonia!
4. Refine your hypothesis
Based upon these results, which of the
following could your patient have?
Haemophilus influenzae pneumonia
Legionellosis
Melioidosis
**Your patient's Gram-stained sample
does not show clear evidence for a Gram-positive pathogen, or for one with an
obligate intracellular habit. Thus, you suspect your patient has Haemophilus
influenzae pneumonia, legionellosis, or meliodosis.
5. Select a diagnostic
You
would now like to try and culture your pathogen. Shown are three different
types of media: A. Blood agar with gentamicin
B. Buffered charcoal-yeast extract agar
C. Chocolate agar with X and V factors
B. Buffered charcoal-yeast extract agar
C. Chocolate agar with X and V factors
Blood
agar with gentamicin – Burkholderia
pseudomallei
Buffered
charcoal-yeast extract agar – Legionella
pneumophila
Chocolate agar
with X and V factors – Haemophilus
influenza
After a five days, you observe the
following:
6. Diagnose the disease
What diseases could result from the
organism you cultured?
legionellosis
Pontiac fever
** Legionella pneumophila can cause
both Pontiac fever and legionellosis
7. Fill in the disease that best fits
your patient's symptoms.
Of
the two diseases caused by the pathogen you isolated,
legionellosis fits your patient's symptoms the best.
8. Treat the disease
How will you treat this disease?
Erythromycin
** You start your patient on a course of
erythromycin
9. Legionelllosis is a nationally
reportable disease, and you must notify the authorities of your finding. Before
you call in your diagnosis however, you want to try and identify how your
patient first contracted it. You decide to question your patient about his
possible exposure history in the ten days before his illness. You ask him if he
has been in, around, or used:
a decorative fountain
any form of respiratory therapy equipment
(e.g. sleep apnea, asthma devices)
a mall or other large enclosed shopping
venue
long-term care, senior, or assisted
living facility (e.g. nursing home, rehab facility)
a hospital (besides his current stay)
a shower (away from home)
construction or projects affecting,
plumbing and/or water lines
a hotel
a pool, hot tub, jacuzzi or whirlpool
spa
a doctor's or dentist's office
a steam room or sauna
grocery stores with misters for fruit
and vegetables
recreational misters
a humidifier
** Legionellosis can be
transmitted by almost any situation involving water conditions where the
bacteria can grow, particularly if they are able to form a highly resistant
biofilm. Legionella already exists in most water systems; however the
frequency of outbreaks still remains relatively low.
10. As you read off the above questions
to your patient, you start to get a feeling for the ubiquity of Legionella
pneumophila in water sources. If Legionella is so common, then why
doesn't everyone get sick? Generally, the risk of contracting legionellosis is
low for an immunocompetent person; however there are some factors that seem to
increase the likelihood of contracting the disease. Which of the following
factors specific to your patient do you think played a role in whether or not
he got sick once exposed to the bacterium?
His age
His cigarette and alcohol consumption
His travel history
** Men over the age of 50 are the most
likely to contract legionellosis, especially if they are heavy smokers or
drinkers.
Conclusion
Your
patient answers your questions one by one. In Seattle, he stayed at a hotel
with a decorative fountain in the lobby. He swam in the hotel's pool once, and
spent roughly thirty minutes each night (for two nights) in the hotel's
jacuzzi. He also took a shower in his room's bathroom. Subsequent analysis of
the water sources throughout the hotel and his room were negative for Legionella.
Once back at home, your patient recalls going shopping at a local grocery store that uses misters to keep vegetables fresh. He also brought his dog to a grooming salon, where he opted to bathe the animal himself. He spent an hour bathing the dog, and was often splashed by the water from the grooming sink. Lastly, he visited the dentist for to get a filling replaced shortly before he took ill.
Water sources and lines were analyzed at every location he visited. The water at the grocery store and the dentist's was negative for Legionella; however the water at the dog grooming salon tested positive! The salon was immediately shut down, and all recent clients were contacted regarding a possible outbreak.
Your patient makes a full recovery on your course of erythromycin, and further spread of the disease was prevented by your speedy diagnosis!
Once back at home, your patient recalls going shopping at a local grocery store that uses misters to keep vegetables fresh. He also brought his dog to a grooming salon, where he opted to bathe the animal himself. He spent an hour bathing the dog, and was often splashed by the water from the grooming sink. Lastly, he visited the dentist for to get a filling replaced shortly before he took ill.
Water sources and lines were analyzed at every location he visited. The water at the grocery store and the dentist's was negative for Legionella; however the water at the dog grooming salon tested positive! The salon was immediately shut down, and all recent clients were contacted regarding a possible outbreak.
Your patient makes a full recovery on your course of erythromycin, and further spread of the disease was prevented by your speedy diagnosis!
Influenza:
From the Great War to Today
It
was the spring of 1918, and the world was at war. In Haskell County, Kansas, an
epidemic of influenza was underway. Public health officials in Washington, D.C.
were notified; however, no investigators were sent. Meanwhile, soldiers from
all across Kansas were reporting to Camp Funston in training for the war. In
hindsight, it appears that a soldier from Haskell County brought influenza with
him to Camp Funston. By the middle of March, there was an epidemic in the camp.
Ultimately, about 1100 soldiers were infected and 38 died during the outbreak.
Unfortunately, the reporting methods at that time were not particularly good.
The epidemic at Camp Funston essentially went unnoticed by public health
officials. Within only a few months, the country would be caught in an epidemic
that no one could ignore.
During
the initial epidemic at Camp Funston, the infection was characterized by
several of the typical symptoms of influenza infection.
1. Which of the following are symptoms
of influenza infection?
Headache; fever; muscle pain
** After the person is exposed to the
flu virus, there is a short incubation period—only about one day—before
symptoms of infection appear. Influenza infection commonly causes muscle aches
and headache. These are most likely due to the fever that is part of the normal
immune response to infection. As fever raises the body temperature, cellular
demand for water will increase. At the same time, the person’s appetite and
thirst are typically depressed, leading to decreased consumption of water.
These two factors contribute to dehydration and an electrolyte balance, which
typically manifest as general malaise and headache.
The structure of the influenza virus is
central to its ability to cause disease in susceptible hosts. The structure of
the virus is relatively simple (compared to that of a prokaryotic or eukaryotic
cell); however, each component has an important role to play in the infectious
cycle of influenza.
2. Drag each one of the labels onto the
figure to identify the function of each structure.
** During infection, the structure of
influenza plays a vital role. Hemagglutinin (HA) mediates attachment to the
host cells, after which the lipid envelope fuses with the host cell membrane.
This allows the virus to be internalized, followed by release of the RNA genome
from the capsid. Viral proteins will be produced, assembled, and released from
the host cell. Release is mediated by neuraminidase (NA), and as the viral
particles leave, they take part of the host membrane, thereby creating their
envelope.
During the spring and summer of 1918,
cases of influenza began to emerge throughout Europe. Soldiers on both sides of
the front were struck down by this invisible pathogen. In contrast to the cases
seen at Camp Funston, these infections were much more severe, with symptoms
resembling those of pneumonia. As the months went on, the death toll continued
to rise.
3. The successful infection of a host,
and subsequent spread to another, results from a specific sequence of events
known as the replication cycle. Each of the statements below describes an
important step in the replication cycle of influenza.
Arrange the following statements in the
order that best describes the sequence of events involved in the replication of
influenza.
1.
Hemagglutinin (HA) spikes attach to host cells.
2.
Influenza enters the host cell.
3.
Nucleic acid enters the host cytoplasm.
4.
Influenza proteins are synthesized.
5.
Influenza nucleic acid is packaged in capsid.
6.
Influenza particles bud from the cell, releasing the virus into the surrounding
environment.
** After gaining entry to the host
respiratory system, influenza adheres to host cells. The virus then enters the
cells and begins the process of hijacking host machinery in order to produce
new viral particles. After all the components are synthesized, they are
assembled, and the virus leaves via budding. The newly released particles then
infect neighboring cells, perpetuating the infection.
It is thought that in Europe, the
influenza virus changed in such a way to make it more virulent in the human
population, resulting in increased severity of disease and increased mortality.
What changes could have led to the differences in pathology observed in Camp
Funston and in Europe? Research in recent years has led to our understanding
that these changes were due to the process known as antigenic shift.
4. Which of the following statements
regarding antigenic shift are true?
Viral strains resulting from antigenic
shift contain RNA segments from different species.
Little immunity to virus strains
resulting from antigenic shift exists in the population.
Antigenic shift results in a major
change in the genetic composition of the virus.
** Genetic analysis of the 1918 flu
revealed that it contained genetic material that was both avian and mammalian
in origin. This reassortment led to a deadly combination—a virus that was both
highly virulent and transmissible. These factors, coupled with the lack of
immunity in any population, led to the pandemic that impacted the entire world.
Research conducted in recent years on
the 1918 flu indicated that the high mortality rate and the severe pathology
associated with the disease were likely due to a cytokine storm that was
stimulated during infection. Recall that when they are released, cytokines
stimulate the production of more cytokines (positive feedback). Sometimes, this
feedback spins out of control, leading to an overproduction of cytokines known
as a cytokine storm.
5. Predict which of the following are
reasonable outcomes of the cytokine storm during the 1918 flu pandemic.
an excessive inflammatory response leading
to extensive tissue damage
increased fluid in the lungs and labored
breathing
** The cytokine storm during infection
with the 1918 influenza was extremely destructive. The massive release of
cytokines in the lungs led to an uncontrolled inflammatory response. As cells
moved into the lung tissue, the tissue was destroyed. Fluid entered the lungs,
and patients struggled to breathe. Furthermore, the ability to deliver oxygen
to the body was severely compromised, giving many patients a blue appearance.
As soldiers returned home to the United
States in the fall of 1918, they brought the deadly flu with them. The first
cases were noted in August of 1918. By September of that year, influenza
epidemics were reported in California, Texas, North Dakota, and Florida. The
disease would continue to spread throughout the fall and winter of 1918 and
into the spring of 1919. It is estimated that the 1918–1919 influenza pandemic
resulted in approximately 675,000 deaths in the United States and more than 20
million worldwide. Today, approximately 30,000 to 50,000 people die each year
from influenza infection. Several factors play a role in this relatively low
mortality rate. One factor is the availability of an influenza vaccine. But
although the vaccine does offer protection, its design and production are not
without their challenges.
6. 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.
** A vaccine for influenza has been
available since about 1945. The current vaccine generates protection against
the three strains most likely to cause infection during the flu season. The
vaccine is currently available in two forms: a nasal spray (made from live,
attenuated virus) and an injection (made from inactivated virus). Although both
offer protection, the effect is relatively short-lived and is specific only for
the three strains contained in the vaccine.
In addition to the vaccine, several
antiviral drugs are available to treat influenza infection. One of the most
prescribed treatments for influenza is Tamiflu (osteltamivir). Tamiflu works by
inhibiting the action of neuraminidase (NA).
7. Predict which of the following would
be outcomes of treatment with Tamiflu.
overall decrease in the replication rate
of influenza
an increase in the ability of the immune
system to combat the infection
a decrease in the release of viral
particles from the cell
** If taken within 30 hours of the
appearance of symptoms, Tamiflu is quite effective at inhibiting viral
replication. Because NA has been inhibited, the viral particles are unable to
bud from the infected cells. As a result, the infection isn’t perpetuated. This
slowing in the replication cycle gives the body enough time to mount an
effective immune response and eventually eliminate the infection.
Big
Picture Coaching Activity: Pertussis
Megan woke up this morning with a
feeling of dread. School was about to start, and Megan was due for her fifth
DTaP, her second MMR, and her second Varicella vaccinations. Her physician
explained that the DTaP vaccine would give her protection against diphtheria,
tetanus, and whooping cough. He also said that the MMR would protect her
against measles, mumps, and rubella, while the varicella shot would help
protect against the chicken pox.
1. Causative Agent of Whooping Cough
Bordetella pertussis
**
Whooping cough is caused by Bordetella pertussis, a small, obligately
aerobic, gram-negative coccobacillus.
2. Pathogens of the Bacterium
Lower respiratory system infections,
such as whooping cough, can lead to bronchitis or pneumonia due to the
inhibition of normal protective responses. Which of the following explains how
the pathogen overcomes normal protective responses of the respiratory system?
The bacteria attach to the ciliated
cells of the trachea, thus preventing mucus from being cleared.
** Bordetella pertussis attaches
to the ciliated epithelial cells of the trachea, which impedes the movement of
the cilia. Without being able to move, the cilia cannot clear the mucus from
the respiratory system and excess amounts accumulate.
While Megan was waiting for the
administration of her vaccines, she was looking at all of the posters on the
wall in the exam room. One of the posters was an information sheet on whooping
cough. This poster listed the characteristics of the organism, signs and
symptoms, the progression of infection, and finally the various vaccine options
for this organism.
3. Progression of infection
Megan learned from the poster that there
were three main stages of whooping cough. Place the following in order of how
they would occur during progression of the infection.
Catarrhal; Paroxysmal; Convalescence
** Catarrhal refers to the initial stage
of whooping cough that closely resembles a common cold. This may lead to misdiagnosis
or delay in treatment. Paroxysmal refers to the second stage of disease
progression when the patient, usually a child, suffers prolonged sieges of
coughing. This excessive coughing is a result of the body trying to clear the
mucus that has accumulated after the cilia were destroyed in the trachea. The
final stage of whooping cough is the convalescence stage and can last several
months.
4. Vaccine Effectiveness
The exam room poster for whooping cough
also listed the various vaccines that could be given. The three possible
vaccines were the DTP, the DTaP, and the Tdap. The DTP was made with
heat-killed whole cells of the bacterium B. pertussis, while the DTaP and the
Tdap were made with acellular pertussis components. Which of the following
statements regarding the vaccines explains why the DTP vaccine is no longer
used?
Bordetella
pertussis was not killed during
the heating process used on the DTP vaccine and could cause an active infection
**
Bordetella pertussis whole cells used in the vaccine were
heat-killed before being included in the vaccine. If the heating process was
not done properly, the cells were not killed. When this happened to an entire
batch of the vaccine, an epidemic of whooping cough resulted. It was determined
that the bacteria in the vaccines were living and capable of causing infection.
This led the health officials to determine that a safer vaccine was necessary.
The DTaP vaccine mentioned in the
previous question was created as a safer vaccine than the DTP. After this
vaccine was transitioned into use, epidemiologists were surprised to find that
whooping cough infection rates were still increasing, rather than decreasing.
5. Immune Response
Many possible explanations were given as
to why the numbers of pertussis infections were increasing, but the most likely
explanation was that the DTaP vaccine was not as effective as the DTP at
protecting children long-term. Which of the following best describes why this
is the case??
The DTaP vaccine is not made with
cellular components that would stimulate the immune system as effectively as
the DTP vaccine.
** Cellular components are more
effective at stimulating the immune response than non-cellular or acellular
components. The reason that the number of cases most likely rose after the
switch to the DTaP is that it did not offer the same long-term effectiveness
because it lacked cellular components. As a result, an additional booster
called the Tdap vaccine helps to provide protection after the memory has worn
off from the DTaP vaccine, but it is not recommended for teenagers and expectant
moms.
