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Chapter 24. Microbial Diseases of the Respiratory System. Microbial Diseases of the Upper Respiratory System. Laryngitis: S. pneumoniae , S. pyogenes , viruses Tonsillitis: S. pneumoniae , S. pyogenes , viruses Sinusitis: Bacteria Epiglottitis: H. influenzae. Upper Respiratory System.

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Chapter 24 l.jpg

Chapter 24

Microbial Diseases of the Respiratory System

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Microbial Diseases of the Upper Respiratory System

  • Laryngitis: S. pneumoniae, S. pyogenes, viruses

  • Tonsillitis: S. pneumoniae, S. pyogenes, viruses

  • Sinusitis: Bacteria

  • Epiglottitis: H. influenzae

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Upper Respiratory System

  • Upper respiratory normal microbiota may include pathogens

Figure 24.1

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Streptococcal pharyngitis (Strep throat)

  • Streptococcus pyogenes

  • Resistant to phagocytosis

  • Streptokinases lyse clots

  • Streptolysins are cytotoxic

  • Diagnosis by indirect agglutination

Figure 24.3

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Scarlet Fever

  • Streptococcus pyogenes

  • Pharyngitis

  • Erythrogenic toxin produced by lysogenized S. pyogenes

Figure 24.4

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  • Corynebacterium diphtheriae: Gram-positive rod

  • Diphtheria membrane of fibrin, dead tissue, and bacteria

  • Diphtheria toxin produced by lysogenized C. diphtheriae

  • Prevented by DTaP and Td vaccine (Diphtheria toxoid)

  • Cutaneous diphtheria: Infected skin wound leads to slow healing ulcer

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Figure 24.6

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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

  • Incidence of S. pneumoniae reduced by vaccine

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Otitis Media

Figure 25.7

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Common cold

  • Rhinoviruses (50%)

  • Coronaviruses (15-20%)

  • Rhinoviruses attached to ICAN-1 on nasal mucosa

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Microbial Diseases of the Lower Respiratory System

  • Bacteria, viruses, & fungi cause:

    • Bronchitis

    • Bronchiolitis

    • Pneumonia

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Lower Respiratory System

  • The ciliary escalator keeps the lower respiratory system sterile.

Figure 24.2

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Pertussis (Whooping Cough)

  • Bordetella pertussis: Gram-negative coccobacillus

  • Capsule

  • Tracheal cytotoxin of cell wall damaged ciliated cells

  • Pertussis toxin

  • Prevented by DTaP vaccine (acellular Pertussis cell fragments)

Figure 24.8

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Pertussis (Whooping Cough)

  • Stage 1: Catarrhal stage, like common cold

  • Stage 2: Paroxysmal stage: Violent coughing sieges

  • Stage 3: Convalescence stage

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  • Mycobacterium tuberculosis: Acid-fast rod. Transmitted from human to human

  • M. bovis: <1% U.S. cases, not transmitted from human to human

  • M. avium-intracellulare complex infects people with late stage HIV infection

Figure 24.9

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Figure 24.10.1

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Figure 24.10.2

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Figure 24.10.3

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  • Treatment of Tuberculosis: Prolonged treatment with multiple antibiotics

  • Vaccines: BCG, live, avirulent M. bovis. Not widely used in U.S.

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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

Figure 24.11

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Figure 14.11c

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Figure 24.12

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Pneumomoccal Pneumonia

  • Streptococcus pneumoniae: Gram-positive encapsulated diplococci

  • Diagnosis by culturing bacteria

  • Penicillin is drug of choice

Figure 24.13

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Haemophilus influenzae Pneumonia

  • Gram-negative coccobacillus

  • Alcoholism, poor nutrition, cancer, or diabetes are predisposing factors

  • Second-generation cephalosporins

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Mycoplasmal Pneumonia

  • Mycoplasma pneumoniae: pleomorphic, wall-less bacteria

  • Also called primary atypical pneumonia and walking pneumonia

  • Common in children and young adults

  • Diagnosis by PCR or by IgM antibodies

Figure 24.14

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Mycoplasmal Pneumonia

Figure 11.19a, b

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  • Legionella pneumophila: Gram-negative rod

  • L. pneumophila is found in water

  • Transmitted by inhaling aerosols, not transmitted from human to human

  • Diagnosis: culturing bacteria

  • Treatment: Erythromycin

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Psittacosis (Ornithosis)

  • Chlamydia psittaci: gram-negative intracellular bacterium

  • Transmitted by elementary bodies from bird dropping to humans

  • Reorganizes into reticulate body after being phagocytized

  • Diagnosis: culturing bacteria in eggs or cell culture

  • Treatment: Tetracycline

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Chlamydial Pneumonia

  • Chlamydia pneumoniae

  • Transmitted from human to human

  • Diagnosis by FA test

  • Treatment: Tetracycline

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Q fever

  • Mycoplasma pneumoniae: pleomorphic, wall-less bacteria

  • 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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Q fever

Figure 24.15

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Viral Pneumonia

  • Viral pneumonia as a complication of influenza, measles, chickenpox

  • Viral etiology suspected if no 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

    • Treatment: Ribavirin

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  • Chills, fever, headache, muscle aches (no intestinal symptoms)

  • 1% mortality due to secondary bacterial infections

  • Treatment: Amantadine

  • Vaccine for high-risk individuals

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  • Hemagglutinin (H) spikes used for attachment to host cells

  • Neuraminidase (N) spikes used to release virus from cell

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Figure 24.16

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  • Antigenic shift

    • Changes in H and N spikes

    • Probably due to genetic recombination between different strains infecting the same cell

  • Antigenic drift

    • Mutations in genes encoding H or N spikes

    • May involve only 1 amino acid

    • Allows virus to avoid mucosal IgA antibodies

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Influenza serotypes

  • A: causes most epidemics, H3N2, H1N1, H2N2

  • B: moderate, local outbreaks

  • C: mild disease

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  • Histoplasma capsulatum, dimorphic fungus

(a) 37˚

(a) >35˚

Figure 24.17

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  • Transmitted by airborne conidia from soil

  • Diagnosis by culturing fungus

  • Treatment: amphotericin B

Figure 24.18

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  • Coccidioides immitis

Figure 24.19

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  • Transmitted by airborne arthrospores

  • Diagnosis by serological tests or DNA probe

  • Treatment: amphotericin B

Figure 24.20

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Pneumocystis Pneumonia

  • Pneumocystis jiroveci (P. carinii) found in healthy human lungs

  • Pneumonia occurs in newly infected infants & immunosuppressed individuals

  • Treatment: Timethoprim-sulfamethoxazole

Figure 24.22

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The mature cyst contains 8 intracystic bodies.



The cyst ruptures, releasing the bodies.

Intracystic bodies


Each trophozoite develops into a mature cyst.


The bodies develop into trophozoites.


The trophozoites divide.


Figure 24.21

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  • Blastomyces dermatitidis, dimorphic fungus

  • Found in soil

  • Can cause extensive tissue destruction

  • Treatment: amphotericin B

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Opportunistic fungi involved in respiratory disease:

  • Aspergillus

  • Rhizopus

  • Mucor

Mucor rouxii

Figure 12.2b, 12.4