MICR 201 Microbiology for Health Related Sciences
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Transcript MICR 201 Microbiology for Health Related Sciences
Lecture 16: Microbial diseases of the respiratory system
Edith Porter, M.D.
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Respiratory systems: structure and normal microbiota
Upper respiratory tract infections
General: pharyngitis, tonsillitis, laryngitis, sinusitis, epiglottitis,
otitis media
Bacterial diseases
Viral diseases
Lower respiratory tract infections
General: bronchitis, bronchioliis, pneumonia
Bacterial diseases
Viral diseases
Fungal diseases
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Upper respiratory tract
Nasooropharynx
Gram+
Gram- anaerobes
Neisseria spec.
a-hemolytic streptococci
Haemophilus spec.
Lower respiratory tract
Mucociliary escalator
Scarcely populated
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Laryngitis: S. pneumoniae, S. pyogenes, viruses
Tonsillitis: S. pyogenes, S. pneumoniae, viruses
Sinusitis: Bacteria, fungi
Epiglottitis: H. influenzae
Sinusitis in right maxillary sinus in a CT scan (Ilana
Seligman)
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More common in young children
Small auditory tube which connects middle ear and throat
50% of all office visits to pediatrician
S. pneumoniae (35%)
H. influenzae (20-30%)
M. catarrhalis (10-15%)
S. pyogenes (8-10%)
S. aureus (1-2%)
Incidence of S. pneumoniae reduced by vaccineby 6
– 7%
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Streptococcus pyogenes
Group A streptococci
Resistant to phagocytosis
Streptokinases lyse clots
Streptolysins are cytotoxic
Diagnosis
indirect agglutination
ELISA
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Streptococcus pyogenes
Pharyngitis + exanthem
Erythrogenic toxin produced by lysogenized S. pyogenes
Tongue strawberry like
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Corynebacterium diphtheriae
Gram-positive rod, pleomorphic
Diphtheria (Greek: leather) membrane forms in throat
fibrin, dead tissue, and bacteria
Diphtheria toxin produced by lysogenized C. diphtheriae
Blocks protein biosynthesis
Infection is local but toxin may spread systemically
Kidney failure, heart failure
Prevented by DTaP and Td vaccine (Diphtheria toxoid)
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Over 200 different viruses capable of causing
common cold
Rhinoviruses (50%, over 100 serotypes)
A single virus attached to mucosa might be
sufficient to cause a cold
Coronaviruses (15-20%)
Less frequent in older people
Possibly accumulated immunity
Duration ~1 week
With remedies ~ 7 days
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Bacteria, viruses, & fungi cause:
Bronchitis
Bronchiolitis
Pneumonia
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Bordetella pertussis
Gram-negative coccobacillus
Capsule
Numerous toxins and pathogenic factors
Tracheal cytotoxin
▪ Selective damages ciliated respiratory cells
▪ Local action
Pertussis toxin
▪ Overstimulates cells leading to dysfunction
▪ Locall + systemic action
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Stage 1: Catarrhal
stage, like
common cold
Stage 2:
Paroxysmal
stage: Violent
coughing sieges
Stage 3:
Convalescence
http://www.vaccineinformation.org/photos/pert_wi001.jpg
stage
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Major complications most common among infants
and young children
Include hypoxia, apnea, pneumonia, seizures,
encephalopathy, and malnutrition
Young children can die from pertussis
Most deaths occur among unvaccinated children
or children too young to be vaccinated
Prevented by DTaP vaccine (acellular Pertussis cell
fragments)
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Mycobacteria
Acid-fast rods
Lipid rich cell wall
M. tuberculosis
Primary cause
Transmitted from human to human
20 h generation time: slow growth
M. bovis
<1% U.S. cases
not transmitted from human to human
Attenuated strain used in BCG vaccine
M. avium-intracellulare complex
infects people with late stage HIV infection
Faster growing
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Bad cough over 3 weeks
Sputum production
Thick, viscous
Later on blood stained
Weight loss
Night sweat
Weakness or fatigue
Evening lower grade temperature or chills
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Airborne Infection
90 %
10 %
Latent TB
TB Disease
No symptoms
Not sick
Cannot spread disease
Chest X Ray and sputum
are normal
Symptoms
Can spread infection
Positive skin test
Possible abnormal chest X
ray
Positive sputum smear or
culture
Dissemination
AIDS increases
susceptibility
Reactivation
(secondary) TB
Untreated:
Severe illness,
Death
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Diagnosis: Tuberculin skin test screening
+ = current or previous infection
Followed by X-ray or CT, acid-fast staining of
sputum, culturing bacteria, PCR
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Prolonged treatment with multiple drugs
6 months at least
Combinantion
Pronounced side effects
Vaccines
BCG, live, avirulent M. bovis
Not widely used in U.S.
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Streptococcus pneumoniae
Gram-positive
encapsulated diplococci
Over 90 serotypes
Symptoms
High fever
Difficulty breathing
Chest pain
Diagnosis by culturing
bacteria
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Mycoplasma pneumoniae
Pleomorphic
Bacteria without a cell wall
Require cholesterol for growth
“Fried egg” appearance on agar
media
Also called primary atypical
pneumonia and walking
pneumonia
Common in children and
young adults
Diagnosis by PCR or by IgM
antibodies
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Coxiella burnetii
Obligate intracellular bacterium
Flulike pneumonia
High fever
Headache
Muscle ache
Coughing
Long recovery
2% may develop endocarditis
60% of all infections
asymptomatic
Reservoir: cattle
Infection via aerosol or ingestion
of unpasteurized milk
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Viral pneumonia as a complication of influenza,
measles, chickenpox
Viral etiology suspected if no other cause
determined
Respiratory Syncytial Virus (RSV)
Common in infants; 4500 deaths annually
Causes cell fusion (syncytium) in cell culture
Symptoms: coughing
Diagnosis by serologic test for viruses and antibodies
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Chills, fever, headache, muscle aches (no
intestinal symptoms)
1% mortality due to secondary bacterial
infections
Vaccine for high-risk individuals
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Segmented RNA virus
8 separate segments
Enveloped
Hemagglutinin (H)
spikes used for
attachment to host cells
Neuraminidase (N)
spikes used to release
virus from cell
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Antigenic drift
No proof reading of RNA polymerase
Mutations in genes encoding H or N spikes
May involve only 1 amino acid
Allows virus to avoid mucosal IgA antibodies
Antigenic shift
Changes in H and N spikes
Probably due to genetic recombination between different
strains infecting the same cell
Causes pandemic
1918/1919: over 20,000,000 deaths world wide
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Direct antigen detection with nasal swabs
Cell culture and PCR
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Histoplasmosis
Eastern US
Tb like symptoms but tuberculin negative
Can spread throughout the body
Coccidioidomycosis:
Southwestern US
Increased incidences after natural disasters,
e.g. earthquakes
Pneumocystis
Associated with immunodificiency e.g. AIDS
Pneumonia with dry strong and prolonged
cough
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Respiratory systems: structure and normal microbiota
Upper respiratory tract infections
General: pharyngitis, tonsillitis, laryngitis, sinusitis, epiglottitis, otitis
media
Bacterial diseases: strep throat, scarlet fever, dipheteria,
Viral diseases: Common cold
Lower respiratory tract infections
General: bronchitis, bronchiolitis, pneumonia
Bacterial diseases: pneumonia (lobar, atypical), tuberculosis
Viral diseases: influenza, RSV
Fungal diseases: histoplasmosis, coccidiomycosis, pneumocystis
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1) Which of the following does NOT confirm a diagnosis of strep throat?
A) Hemolytic reaction
B) Bacitracin inhibition
C) Symptoms
D) Serological tests
E) Gram stain
2) Which of the following pairs is mismatched?
A) Epiglottitis – Haemophilus
B) Q fever – Rickettsia
C) Diphteria - Corynebacterium
D) Whooping cough – Bordetella
E) All are correct
3) The recurrence of influenza epidemics is due to
A) Lack of antiviral drugs.
B) The Guillain-Barré syndrome.
C) Antigenic shift.
D) Lack of naturally acquired active immunity.
E) HA spikes.
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