Chapter 24: Microbial Diseases of the Respiratory System

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Chapter 24 Microbial Diseases of the Respiratory
System

• Anatomy and physiology
• Normal flora
• Upper respiratory infections
• Bacterial
• Viral
• Lower respiratory infections
• Bacterial
• Viral
• Fungal

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Anatomy and Physiology
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Characteristics of normal flora
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Upper respiratory infections

• Bacterial
• Strep throat
• Diphtheria
• Otis media
• Viral
• Common cold

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Strep throat

• Streptococcal pharyngitis
• Caused by Streptococcus pyrogenes
• Cell envelope components causes virulence
• Severe infections lead to
• Scarlet fever
• Rheumatic fever
• Toxic shock
• Glomerulonephritis

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Features of strep throat
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Diphtheria

• Corynebacterium diphtheriae
• Gram-positive rod
• Exotoxin
• produced by lysogenized C. diphtheriae
• Vaccination is available
• DTaP and Td vaccine (Diphtheria toxoid)

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Features of diphtheria
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Otitis Media

• S. pneumoniae (35)
• H. influenzae (20-30)
• M. catarrhalis (10-15)
• S. pyogenes (8-10)
• S. aureus (1-2)
• Treated with broad-spectrum antibiotics
• S. pneumoniae infections reduced by vaccine

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Common cold

• Caused by many different viruses
• Rhinoviruses are the most common
• Can lead to more serious bacterial diseases

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Features of the common cold
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Lower respiratory infections

• Bacterial
• Whooping cough
• Tuberculosis
• Pneumonia
• Viral
• Influenza
• Fungal
• Spelunkers disease (histoplasmosis)
• Valley fever (coccidioidomycosis)

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Whooping cough

• Bordetella pertussis Gram-negative
  coccobacillus, encapsulated
• Tracheal cytotoxin,
• A B endotoxin
• Stage 1 Catarrhal stage
• Stage 2 Paroxysmal stage
• Stage 3 Convalescence stage
• Prevented by DTaP vaccine

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Features of pertussis
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Tuberculosis

• Mycobacterium tuberculosis Acid-fast rod.
  Transmitted from human to human
• M. bovis lt1 U.S. cases, not transmitted from
  human to human
• M. avium-intracellulare complex infects people
  with late stage HIV infection
• Chronic illness
• Remains latent and can be reactivated
• Multi drug resistant

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Tuberculosis lesion
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Features of tuberculosis
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Pneumococcal Pneumonia

• Streptococcus pneumoniae Gram-positive
  encapsulated diplococci
• Diagnosis by culturing bacteria
• Penicillin is drug of choice

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Klebsiella pneumonia

• Causes permanent damage to the lung
• Complications lung abscesses, bacteremia
• Plasmids contain resistant genes
• Capsule mucoid colonies

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Mycoplasmal pneumonia

• Mycoplasma pneumoniae pleomorphic, no cell wall
• Also called walking pneumonia
• Common in children and young adults
• Diagnosis by PCR or by IgM antibodies

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Bacterial pneumonia
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Legionnaires disease

• Caused by Legionella pneumophila Gram-negative
  rod
• Bacterium commonly found in the environment
• Disease due to high infecting dose

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Features of Legionnaires disease
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Influenza

• Caused by influenza A virus
• Orthomyxovirus family
• Wide spread epidemics due to antigenic shifts
• Hemagglutinin (H) spikes used for attachment to
  host cells
• Neuraminidase (N) spikes used to release virus
  from cell

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Antigenic shift
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Features of influenza
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Spelunkers disease

• Caused by Histoplasma capsulatum (dimorphic
  fungus)
• Found in soils contaminated by bat and bird feces
• Occurs in tropical and temperate zones

(b) gt35
(a) 37
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Features of Histoplasmosis
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Valley fever

• Caused by Coccidioides immitis
• Initiated by airborne fungal spores
• Tissue injury due to immune response

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Features of coccidioidomycosis