Exam 4 Flashcards
what are some LRT infections
- bronchitis
- histoplasmosis
- influenza*
- pneumonia
- tuberculosis
what are some URT infections
- common cold
- diphtheria
- whooping cough
- strep throat
- ear infections
how are respiratory pathogens transmitted from human to human
- via indirect contact with respiratory droplets (common)
- less than 3ft; are heavier and need to be in
close contact with someone to transfer
- less than 3ft; are heavier and need to be in
- via airborne droplet nuclei (rare)
- are lighter and can travel in the air for a
longer amount of time
- are lighter and can travel in the air for a
true or false; some respiratory pathogens exist as part of the normal microbiota
true
does influenza start in the URT or LRT
starts in the URT and then moves to LRT
describe corynebacterium diphtheriae shape
- gram-positive rods
- often arranged side by side in “palisades”
- irregular staining
how is corynebacterium diphtheriae transmitted
- humans are the only known reservoir
- transmitted via contact with respiratory droplets
humans can have c. diphtheriae in their
oropharynx or on skin
what population is most likely to get c. diphtheriae
unimmunized children
describe diptherotoxin
- A-B exotoxin
- lysogenzied strains of C. diphtheriae causes Diphtheria
what is the function of diptherotoxin
inhibits protein synthesis
what are some signs/symptoms of diphtheria
- acute onset of sore throat
- pseudomembrane = dead cells, exudate, RBCs, and bacteria
- “bull neck” = enlarged cervical lymph nodes and edema in the neck
- fever
- systemic diphtheria = toxin gets into circulation (toxemia) and damages heart and kidneys
if someone were to have a sore throat, enlarged cervical lymph nodes, fever, and pseudomembrane - what would be their diagnosis?
diphtheria
would corynebacteria organisms be detected in the blood from a patient with systemic diphtheria?
no
- because the corynebacteria infect the URT, but the localized infection produces the toxin that would be systemic
c. diphtheria requires these two treatments
- antibiotics to arrest the infection, but toxins already absorbed are unaffected
- diphtheria antitoxin to neutralize toxin circulation
what vaccines work to prevent diphtheria, pertussis, and tetanus
DTaP and Tdap vaccines
- contains diphtheria toxoid = inactivated exotoxin
what are some signs/symptoms of a common cold and how long do they last
- sneezing, sore throat, runny nose, cough
- nasal secretions initially watery, then thicken,
finally become cloudy and greenish
- nasal secretions initially watery, then thicken,
- symptoms mostly gone within 7-10 days
what are some complications that can occur with a common cold
sinus congestion or earache
what are some signs/symptoms of the flu and how long do they last
- high fever; lasts 3-4 days
- early and prominent extreme exhaustion
- chest pain and severe cough
what are some complications that can occur with the flu
- bronchitis and pneumonia; can be life-threatening
how many times do adults vs children get a common cold and what is the causative agent?
- adults get ~ 2-4 a year
- children get ~ 9 colds a year
- causative agent = children don’t have as much immunity
what is the most common cause of the common cold
rhinovirus
describe rhinovirus
- naked virus with an RNA genome
- replicate best between 33C - 35C -> infect cooler tissues of the nose
what is the pathogenesis of common cold
- infects respiratory epithelial cells in the nasal mucosa
- inhibits the ciliary motion of infected cells; cells die
- damage leads to release of cytokines, inflammation
- nasal excess nasal secretions, congestions, sore throat, coughing, and sneezing
- fever is typically absent
how is rhinovirus transmitted
- direct contact = with hands contaminated with respiratory droplets
- indirect contact = respiratory droplets
- contaminated fomites (rhinoviruses are naked)
- only need a few virions to infect
describe bordetella pertussis
- tiny encapsulated gram-negative bacilli
- causes pertussis aka whooping cough
bordetella pertussis is the classic disease of
infants (<1 year)
- severe, life-threatening in babies
what is the epidemiology of bordetella pertussis
- human reservoir
- transmitted via contact with respiratory droplets
what is the pathogenesis of bordetella pertussis
- cells are inhaled, attach to ciliated cells of respiratory epithelium
- tracheal cytotoxin = toxic to ciliated epithelial cells -> disrupts mucociliary clearance
describe pertussis toxin (PTx)
- A-B exotoxin
- A subunit inactivates inhibitory regulatory G protein, causing increase in cAMP production
- increased cAMP yields increased mucus, decreased killing ability of phagocytes
what are the stages of pertussis disease
- incubation = 7-10 days; no symptoms; rising bacterial culture
- catarrhal = 1-2 weeks; rhinorrhea, malaise, fever, sneezing, anorexia; peak bacterial culture
- paroxysmal = 2-4 weeks; repetitive cough with whoops, vomiting, leukocytosis; falling bacterial culture
- convalescent = 3-4 weeks (or longer); diminished paroxysmal cough, development of secondary complications (pneumonia, seizures, encephalopathy); lowest point of bacterial culture
what is the treatment for pertussis
- primarily supportive
- antibiotics effective if treated early
what is the prevention of pertussis
- immunization with DTaP starting at two months
- subunits of B. pertussis are used in the vaccine
- requires boosters, Tdap
what does Tdap include
tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis
which type of vaccine do you think would result in longer lasting immunity?
- whole cell vaccine
- subunit (acellular) vaccine
whole cell vaccine
describe the symptoms of and how long the immunity for killed whole-cell vaccine, DTP
- fever, agitation, febrile seizures
- long term immunity
what are the symptoms and duration of immunity for acellular vaccines, DTaP
- fewer, milder side effects
- waning immunity
during which weeks should pregnant women get a dose of Tdap vaccine and why
- during the early part of gestational weeks 27 through 36
- helps mother from passing pertussis onto infant and provides passive immunity to infant
what is the route of infection of bacterial pneumonia
- the infection of the lungs elicits inflammation
- the alveoli fill with fluids and WBCs (consolidation)
- air exchange becomes impaired and patients experiences respiratory distress
describe klebsiella penumonia
- gram-negative rods
- large capsule is its major virulence factor
- produces big mucoid colony when cultured on agar
what are some symptoms of klebsiella pneumonia
lung necrosis and abscess formation resulting in bloody “currant jelly” sputum
klebsiella pneumonia is the leading cause of
hospital-acquired pneumonia
how is klebsiella pneumonia transmitted
- transmitted via contact with respiratory droplets or contaminated medical equipment (eg ventilators)
true or false - klebsiella penumoniae may be part of the microbiota in pharynx and GI tract, and do not typically cause respiratory disease in healthy individuals
true
what populations are at most risk for klebsiella pneumonia
- those with preexisting lung conditions
- patients with invasive medical devices
- alcoholics and diabetics
what is the treatment for klebsiella pneumonia
- carbapenem antibiotics (beta lactam antibiotic)
- though it is hard to treat klebsiella pneumonia because of its antibiotic resistance
new strains encoding klebsiella pneumonia have emerged carbapenemase (KPC) and they belong to a family of bacteria called
carbapenem-resistant enterobacteriaceae (CRE)
describe mycoplasmal pneumonia
small, easily deformed bacteria lacking cell wall (no peptidoglycan)
mycoplasmal pneumonia is the leading pneumonia of
college students, common among military recruits, and children 5-15 years of age
how is mycoplasmal penumonia transmitted
through contact with respiratory droplets
- not part of the microbiota
mycoplasmal penumonia use specialized attachment organelle to bind to
ciliated cells
- this causes epithelial cells to be damaged and ciliary motion is hindered
what are some signs/symptoms of mycoplasmal pneumonia
- generally mild “walking pneumonia” or “atypical pneumonia”
- onset is gradual
- initial symptoms are fever, headache, muscle pain, and fatigue
- dry persistent cough and sputum may be produced later
describe haemophilus influenzae penumonia
- gram-negative coccobacillus
- nonencapsulated strains, which cause pneumonia
- colonizes the nasopharynx in majority of healthy children
- elderly is the high risk group
how is haemophilus influenzae transmitted
- via contact with respiratory droplets
- infect alveoli -> inflammation -> exudate rich in neutrophils -> cough and shortness of breath
antibiotic resistance is a big challenge for treatment of
haemophilus influenzae
- no vaccine against the nonencapsulated strains
describe histoplasmosis (spelunker’s disease)
- dimorphic fungus (ie mold and yeast forms)
- exists in soil contaminated with bat or bird droppings
how is histoplasma transmitted
- reservoir: birds and bats
- acquired through inhalation of mold spores from soil (often soil contaminated with bird and bat droppings)
- airborne transmission = the spores become airborne during cleanup or demolition projects
- non-communicable
what are some signs/symptoms of histoplasma
- headache, weakness, chest pain, and in severe cases -> extensive pulmonary infiltration and dissemination to other organs
what other diseases may occur from histoplasmosis
serious lung disease (TB-like illness) may occur in immunocompromised people or elderly or infants
what does antigenic drift mean
when envelope proteins continually mutate
- resulting from RNA replication errors
- RNA polymerase has low fidelity
- gradual
- occurs with influenza A, B, and C
what does antigenic shift mean
major changes caused by genetic reassortment
- coinfection with two viruses in same cells allow mixture of 8 RNA segments
- abrupt
- occurs with influenza A only
if someone has a low grade fever, runny nose, sneezing and cough but feels well enough to work or class, which disease do they most likely have?
- strep throat
- a cold
- flu
a cold
what are some symptoms of influenza “the flu”
fever, headache, muscle aches/pains, fatigue, sore throat and cough
how is influenza transmitted
- contact with respiratory droplets
- airborne via respiratory droplet nuclei
- contact with fomites contaminated with respiratory droplets
describe influenza virus
- enveloped
- (-) ss RNA genome
- segmented genoma
what is the pathogenesis of “flu”
- the virus attaches to and infects epithelial cells in the URT
- replicates inside the cells, damaging the cells (recovery of the mucociliary escalator may take weeks)
- spreads to LRT and sometimes secondary bacterial infections occur
what are influenza’s glycoproteins “spikes”
- hemagglutinin (HA)
- neuraminidase (NA)
what is the function of hemagglutinin
- facilitates viral entry
- binds to sialic acid on host cells which act as receptors
what is the function of neuraminidase
- facilitates virion release from the cell by cleaving sialic acid
- degrades mucin layer of respiratory tract
why does influenza cause annual epidemics and periodic pandemics
viral evolution
flu pandemics are caused by the emergence of a virus that is “novel” which means there is a new
HA or NA subtype
HA and NA surface antigens change as influenza
replicates
which types of genetic change is primarily responsible for pandemics
- antigenic drift
- antigenic shift
- both are equally as likely to contribute to the emergence of a pandemic viral strain
antigenic shift
swine is susceptible to which two strains
avian and human influenza strain
true or false - influenza A can infect animals other than humans
true
in the 1918 pandemic influenza, were people with the strongest or weakest immune systems affected
strongest
what helped contain the 1918 flu pandemic
non-pharmaceutical interventions (NPI)
- isolation, quarantine
what is another name for avian H5N1 influenza
bird flu
is avian H5N1 influenza highly virulent in humans
yes
what are the three qualities that made 1918 influenza pandemic so severe
- everyone was susceptible because it was a novel strain
- spreads easily from person-to-person (airborne transmission)
- virus was unusually virulent (mortality rate = ~10%)
evidence so far suggests that H7N9 and H5N1 influenza cannot be transmitted from
human to human
what is the treatment for influenza antivirals
- supportive treatment (rest and fluids)
- there are four FDA-approved antiviral drugs recommended by CDC to treat flu
- three of which are NA inhibitors
- needs to be given early
what is the prevention of the four influenza strains
flu vaccines
- takes about six months to produce a flu vaccine
- vaccines are protective if the vaccine strains are closely related to circulating strains
describe flu vaccines
- contain three or four different viruses (mix of A subtypes and a B strain)
- about 50-70% effective, new one required each year because of antigenic drift
what are the two types of flu vaccine
- inactivated vaccine (flu shot)
- live attenuated vaccine (nasal spray)
what are the inactivated influenza vaccine recommendations
- routine annual influenza vaccination is recommended for all persons aged >_ 6 months who do not have contraindications
- exceptions: egg allergies and pervious adverse reactions to vaccine
infected people who are asymptomatic or mildly symptomatic can transmit influenza virus to
persons at high risk for complications from influenza
what is a coronavirus
- large family of enveloped viruses
- ss RNA genome
- cause a range of illnesses from mild to severe
which types of diseases are caused by coronaviruses
- common cold
- SARS (severe acute respiratory syndrome)
- MERS (middle east respiratory syndrome)
how is coronavirus transmitted
- contact with respiratory droplets (most)
- airborne transmission via droplet nuclei (less common)
- fomites: contaminated with respiratory droplets
when are people most infectious with COVID-19
2-3 days before symptoms and first 7 days of illness
what populations are more at risk for COVID
- people older than 65
- people with underlying medical conditions
what is the structure of SARS CoV-2
- ss (+) RNA genome
- enveloped
why do S-proteins bind to ACE2
triggers either viral endocytosis or membrane fusion and viral entry
- contributes to high rate of infectivity
S protein is coated in ____ which disguise it from the immune system
glycans
if SARS CoV-2 is not blocked by the immune system what will happen
virions will migrate to the LRT where they infect type 2 pneumocyte cells that are rich in ACE2 proteins
- will eventually lead to apoptosis and death of alveolar cells
in critical cases, a “cytokine storm,” an overreaction by the immune system, causes immune cells to cause damage to
healthy tissues
SARS CoV-2 once it infects the alveoli of the lung, may cause hypoxemia. What is hypoxemia?
- low hemoglobin in the blood
- loss of surfactant
- low oxygen in the blood
- septic shock
- elevated oxygen in the blood
low oxygen in the blood
what are the three stages of COVID-19
- asymptomatic state
- upper airway and conducting airway response
- hypoxia, progression to acute respiratory distress syndrome (ARDS) within 8 to 12 days
what happens in stage 1 of COVID
- incubation time - average is 5 days, range 2 to 14 days
- virus shed by the host in droplets
- virus propagates, mild innate immune response initiated
what happens in stage 2 of COVID
- robust immune response
- clinical manifestations of disease appear on average 5 days post-exposure and include cough, fever, shortness of breath, sore throat, loss of taste and/or smell
- up to 80% of COVID-19 cases will either be asymptomatic or will arrest at this stage
what happens in stage 3 of COVID
- critical care/hospitalization necessary
- manifestations include pneumonia, etc
- oxygen levels fall (SpO2 < 94%) as lungs become filled with fluid, WBCs, mucus, and cellular debris
- leading cause of death is hypoxic respiratory failure complicated by ARDS