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MICROBIOLOGY
Chapter 24
Microbial Diseases of the Respiratory System
Dr. Abdelraouf A. Elmanama
Ph. D Microbiology
Medical Technology Department, Faculty of Science, Islamic University-Gaza
2008
Microbial Diseases of the Upper
Respiratory System
• Laryngitis: S. pneumoniae, S. pyogenes, viruses
• Tonsillitis: S. pneumoniae, S. pyogenes, viruses
• Sinusitis: Bacteria
• Epiglottitis: H. influenzae
2008
Upper Respiratory System
• Upper respiratory normal microbiota may include
pathogens
2008
Figure 24.1
Streptococcal pharyngitis (Strep throat)
• Streptococcus
pyogenes
• Resistant to
phagocytosis
• Streptokinases lyse
clots
• Streptolysins are
cytotoxic
• Diagnosis by indirect
agglutination
2008
Figure 24.3
Scarlet Fever
• Streptococcus
pyogenes
• Pharyngitis
• Erythrogenic toxin
produced by
lysogenized S.
pyogenes
2008
Figure 24.4
Diphtheria
• 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
2008
Diphtheria
2008
Figure 24.6
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
2008
Otitis Media
2008
Figure 25.7
Common cold
• Rhinoviruses (50%)
• Coronaviruses (15-20%)
• Rhinoviruses attached to ICAN-1 on nasal mucosa
2008
Microbial Diseases of the
Lower Respiratory System
• Bacteria, viruses, & fungi cause:
• Bronchitis
• Bronchiolitis
• Pneumonia
2008
Lower Respiratory System
• The ciliary escalator keeps the lower respiratory
system sterile.
2008
Figure 24.2
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)
2008
Figure 24.8
Pertussis (Whooping Cough)
• Stage 1: Catarrhal stage, like common cold
• Stage 2: Paroxysmal stage: Violent coughing sieges
• Stage 3: Convalescence stage
2008
Tuberculosis
• 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
2008
Figure 24.9
Tuberculosis
2008
Figure 24.10.1
Tuberculosis
2008
Figure 24.10.2
Tuberculosis
2008
Figure 24.10.3
Tuberculosis
• Treatment of Tuberculosis: Prolonged treatment with
multiple antibiotics
• Vaccines: BCG, live, avirulent M. bovis. Not widely
used in U.S.
2008
Tuberculosis
• Diagnosis: Tuberculin skin test screening
• + = current or previous infection
• Followed by X-ray or CT, acid-fast staining of
sputum, culturing bacteria
2008
Figure 24.11
Tuberculosis
2008
Figure 14.11c
Tuberculosis
2008
Figure 24.12
Pneumomoccal Pneumonia
• Streptococcus
pneumoniae:
Gram-positive
encapsulated
diplococci
• Diagnosis by
culturing
bacteria
• Penicillin is
drug of choice
2008
Figure 24.13
Pneumomoccal Pneumonia
2008
Haemophilus influenzae Pneumonia
• Gram-negative coccobacillus
• Alcoholism, poor nutrition, cancer, or diabetes are
predisposing factors
• Second-generation cephalosporins
2008
Mycoplasmal Pneumonia
• Mycoplasma
pneumoniae:
pleomorphic, wallless bacteria
• Also called primary
atypical pneumonia
and walking
pneumonia
• Common in children
and young adults
• Diagnosis by PCR or
by IgM antibodies
2008
Figure 24.14
Mycoplasmal Pneumonia
2008
Figure 11.19a, b
Legionellosis
• 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
2008
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
2008
Chlamydial Pneumonia
• Chlamydia pneumoniae
• Transmitted from human to human
• Diagnosis by FA test
• Treatment: Tetracycline
2008
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
2008
Q fever
2008
Figure 24.15
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
2008
Influenza
• Chills, fever, headache, muscle aches (no intestinal
symptoms)
• 1% mortality due to secondary bacterial infections
• Treatment: Amantadine
• Vaccine for high-risk individuals
2008
Influenza
• Hemagglutinin (H) spikes used for attachment to host
cells
• Neuraminidase (N) spikes used to release virus from
cell
2008
Influenza
2008
Figure 24.16
Influenza
• 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
2008
Influenza serotypes
• A: causes most epidemics, H3N2, H1N1, H2N2
• B: moderate, local outbreaks
• C: mild disease
2008
Histoplasmosis
• Histoplasma capsulatum, dimorphic fungus
(a) 37˚
2008
(a) >35˚
Figure 24.17
Histoplasmosis
• Transmitted by airborne conidia from soil
• Diagnosis by culturing fungus
• Treatment: amphotericin B
2008
Figure 24.18
Coccidioidomycosis
• Coccidioides immitis
2008
Figure 24.19
Coccidioidomycosis
• Transmitted by
airborne
arthrospores
• Diagnosis by
serological tests
or DNA probe
• Treatment:
amphotericin B
2008
Figure 24.20
Pneumocystis Pneumonia
• Pneumocystis jiroveci
(P. carinii) found in
healthy human lungs
• Pneumonia occurs in
newly infected infants
& immunosuppressed
individuals
• Treatment:
Timethoprimsulfamethoxazole
2008
Figure 24.22
Pneumocystis
1 The mature cyst contains
8 intracystic bodies.
Cyst
2 The cyst
ruptures,
releasing the
bodies.
Intracystic
bodies
5 Each trophozoite
develops into a
mature cyst.
4 The
trophozoites
divide.
3 The bodies
develop into
trophozoites.
Trophozoite
2008
Figure 24.21
Blastomycosis
• Blastomyces dermatitidis, dimorphic fungus
• Found in soil
• Can cause extensive tissue destruction
• Treatment: amphotericin B
2008
Opportunistic fungi involved in
respiratory disease:
• Aspergillus
• Rhizopus
• Mucor
Mucor rouxii
2008
Figure 12.2b, 12.4