View
217
Download
1
Category
Tags:
Preview:
Citation preview
1
MICR 201 Microbiology for Health Related Sciences
Lecture 16: Microbial diseases of the respiratory systemEdith Porter, M.D.
2
Lecture outline
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
5
Normal microbiota of the respiratory system
Upper respiratory tract
Lower respiratory tract Mucociliary escalator Scarcely populated
Nasooropharynx
Gram+Gram- anaerobes
Neisseria spec.a-hemolytic streptococciHaemophilus spec.
6
Upper respiratory tract infections 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)
8
Otitis media
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%
9
Streptococcal pharyngitis (Strep throat)
Streptococcus pyogenes Group A streptococci
Resistant to phagocytosis
Streptokinases lyse clots Streptolysins are
cytotoxic Diagnosis
indirect agglutination ELISA
10
Scarlet fever
Streptococcus pyogenes Pharyngitis + exanthem
Erythrogenic toxin produced by lysogenized S. pyogenes
Tongue strawberry like
11
Diphtheria
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)
14
Common cold
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
15
Lower respiratory tract infections
Bacteria, viruses, & fungi cause: Bronchitis Bronchiolitis Pneumonia
18
Pertussis pathogenesis
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
19
Pertussis clinical course
Stage 1: Catarrhal stage, like common cold
Stage 2: Paroxysmal stage: Violent coughing sieges
Stage 3: Convalescence stage http://www.vaccineinformation.org/photos/
pert_wi001.jpg
20
Complications and prevention of pertussis
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)
23
Causes of tuberculosis
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
25
Tuberculosis symptoms
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
Development of disease depends on host resistance
26
Airborne Infection
No symptomsNot sick
Cannot spread diseaseChest X Ray and sputum
are normal
AIDS increases susceptibility
Reactivation(secondary) TB
Untreated:Severe illness,
Death
SymptomsCan spread infection
Positive skin testPossible abnormal chest
X rayPositive sputum smear
or cultureDissemination
Latent TB TB Disease
10 %90 %
27
Tuberculosis diagnosis
Diagnosis: Tuberculin skin test screening + = current or previous infection Followed by X-ray or CT, acid-fast staining
of sputum, culturing bacteria, PCR
28
Tuberculosis treatment and prophylaxis
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.
29
Pneumomoccal Pneumonia
Streptococcus pneumoniae Gram-positive
encapsulated diplococci Over 90 serotypes
Symptoms High fever Difficulty breathing Chest pain
Diagnosis by culturing bacteria
30
Mycoplasmal pneumonia
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
31
Q Fever
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
32
Viral pneumonia
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
33
Influenza
Chills, fever, headache, muscle aches (no intestinal symptoms)
1% mortality due to secondary bacterial infections
Vaccine for high-risk individuals
34
Influenza virus
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
35
High mutation rate of influenza viruses
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
39
Fungal respiatory tract infections
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
40
Important to Remember 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
41
Check your understanding1) Which of the following does NOT confirm a diagnosis of strep throat?
A) Hemolytic reactionB) Bacitracin inhibitionC) SymptomsD) Serological testsE) Gram stain
2) Which of the following pairs is mismatched?A) Epiglottitis – HaemophilusB) Q fever – RickettsiaC) Diphteria - CorynebacteriumD) Whooping cough – BordetellaE) All are correct
3) The recurrence of influenza epidemics is due toA) Lack of antiviral drugs.B) The Guillain-Barré syndrome.C) Antigenic shift.D) Lack of naturally acquired active immunity.E) HA spikes.
Recommended