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CHAPTER 24- Microbial Diseases of the Respiratory System


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Anatomical defenses of Upper Respiratory System?
course hairs, mucus secreting cells, cilia, tonsils - lymphoid tissue
Laryngitis and tonsillitis caused by?
Streptococcus pneumoniae, Streptococcus pyogenes,viruses - can often work in combination - usually self-limiting (i.e., recovery will usually occur without medical intervention)
Epiglottitis caused by?
Haemophillus influenzae - most threatening disease of the URS, Hib vaccine has significantly reduced the number of cases
Strep throat caused by?
Streptococcus pyogenes - group A beta-hemolytic
Resistant to phagocytosis
Streptokinases lyse clots
Streptolysins are cytotoxic
Diagnosis by indirect agglutination - uses latex particles coated with antibodies against group A streptococci
Scarlet Fever caused by?
Streptococcus pyogenes
Erythrogenic toxin produced by lysogenized S. pyogenes - reddening toxin causes red skin rash and high fever
Diptheria caused by:
Corynebacterium diptheriae; gram postive rod
Diphtheria was the leading infectious killer of children until?
Leading infectious killer of children until 1935
What has a membrane that can block the air passage?
Diphtheria membrane of fibrin, dead tissue, and bacteria - can totally block air passage
Diphtheria toxin produced by? and the toxin does what?
Diphtheria toxin produced by lysogenized C. diphtheriae - toxin interferes in protein synthesis
Diptheria prevented by?
Prevented by DTaP and Td vaccine (Diphtheria toxoid, inactivated toxin that elicits an immune response)
Effective treatment requires antibiotics and antitoxin
Cutaneous diphtheria:
Infected skin wound leads to slow healing ulcer
Otitis Media:
Infections of the middle ear - account for nearly one half of office visits to pediatricians, affects 85% of children before the age of three
Causes and percentages of Otitis Media?
S. pneumoniae (35%)
H. influenzae (20-30%)
M. catarrhalis (10-15%)
S. pyogenes (8-10%)
S. aureus (1-2%)
Otitis Media is treated with?
Treated with broad-spectrum antibiotics
Incidence of S. pneumoniae reduced by vaccine
The Common Cold:
Viral disease of the URS; most prevalent disease of humans in the temperate zones (kids: 6-8 colds/year, and adults: 2-4 colds/yr)
What causes the common cold?
More than 200 agents cause the common cold

Rhinoviruses (50%) - at least 113 serotypes
A single virus particle can cause a cold
Almost all Rhinoviruses attached to ICAN-1 on nasal mucosa of host cells - possible mechanism for control

Coronaviruses (15-20%)
Lower respiratory system?
Larynx, trachea, bronchial tubes, alveoli
The ciliary escalator keeps the lower respiratory system sterile
Aveolar macrophages - destroy microorganisms that reach the lung
Bacteria, viruses, & fungi cause in the Lower Respiratory System:
Bacteria, viruses, & fungi cause:
Pertussis (whooping cough) caused by?
Bordatella pertussis: gram neg. coccobacillus, capsulated

Attach to ciliated cells in the trachea

Tracheal cytotoxin of cell wall damages ciliated cells

Pertussis toxin - enters bloodstream, causese symptoms of disease
Pertussis prevented by?
Prevented by DTaP vaccine (acellular Pertussis cell fragments)
Pertussis' 3 stages?
Stage 1: Catarrhal stage: like common cold
Stage 2: Paroxysmal stage: Violent coughing sieges
Stage 3: Convalescence stage: may last for months
Tuberculosis caused by:
Mycobacterium tuberculosis: acid-fast rod that is transmitted from human to human.
Mycobacterium Tuberculosis generation time?
>20 hours
M. bovis:
M. bovis: <1% U.S. cases, not transmitted from human to human
M. avium-intracellulare:
M. avium-intracellulare - infects people with late stage HIV infection
Stages of Tuberculosis:
1. bacilli is inhaled and reach the alveoli of the lung
2. ingested by a macrophage but survives
3. bacilli multiply in macrophages and cause a chemotactic response (start of tubercule)
4. after a few weeks, disease symptoms appear as many macrophages die, releaseing tubercule bacilli and forming a caseous center in the tubercule.
5. liquefication=caseous center enlarges and forms tuberculous cavity
6. tubercule ruptures and bacilli spill into bronchioles and diseminate throughout the lung, circulatory, and lymphatic systems.
Treatment of Tuberculosis:
Prolonged treatment with multiple antibiotics - bacilli are slow growing and may be hidden in macrophages or locations difficult to reach with antibiotics
Vaccines: BCG, live, avirulent M. bovis. Not widely used in U.S
Diagnosis of Tuberculosis
Diagnosis: Tuberculin skin test screening
+ = current or previous infection
Followed by X-ray, acid-fast staining of sputum, culturing bacteria
Pneumococcal Pneumonia caused by:
Streptococcus pneumoniae: Gram-positive encapsulated diplococci
Most common - typical pneumonia
Diagnosis and Treatment of Pneumococcal Pneumonia?
Diagnosis by culturing bacteria
Penicillin is drug of choice - antibiotic resistance is becoming a problem
Haemophilus influenzae Pneumonia? Predisposing factors?
Gram-negative coccobacillus

Alcoholism, poor nutrition, cancer, or diabetes are predisposing factors
Haemophilus influenzae Pneumonia treatment?
Second-generation cephalosporins = drugs of choice
Mycoplasmal Pneumonia caused by?
Mycoplasma pneumoniae: pleomorphic, wall-less bacteria
Mycoplasmal Pneumonia also called?
Also called primary atypical pneumonia and walking pneumonia
Mycoplasmal Pneumonia common in what age group? and how do you diagnose?
Common in children and young adults
Diagnosis by PCR or by IgM antibodies
Legionellosis caused by?
Legionella pneumophila: Gram-negative rod
L. pneumophila found where? and how is it trasmitted?
L. pneumophila is found in water
Transmitted by inhaling aerosols, not transmitted from human to human
Diagnosis and Treatment of Legionellosis?
Diagnosis: culturing bacteria
Treatment: Erythromycin
Psittacosis (Ornithosis) caused by?
Chlamydia psittaci: gram-negative intracellular bacterium associated with birds such as parakeets and parrots
Psittacosis (Ornithosis) transmitted by?
Transmitted by elementary bodies from bird dropping to humans
What reorganizes into reticulate body after being phagocytized?
Psittacosis (Ornithosis)
Diagnosis and Treatment of Psittacosis (Ornithosis)?
Diagnosis: culturing bacteria in eggs or cell culture
Treatment: Tetracycline
Chlamydial Pneumonia caused by?
Chlamydia pneumoniae
Resembles mycoplasmal pneumonia
Transmitted from human to human
Chlamydial Pneumonia transmitted by?
Transmitted from human to human
Diagnosis and Treatment of Chlamydial Pneumonia?
Diagnosis by FA test
Treatment: Tetracycline
Q fever caused by? transmitted by? Who is most at risk?
Coxiella burnetti: obligate, intracellular bacterium
Can survive airbourne transmission(has an endospore like body)
Inhaling a single pathogen can cause infection
Workers in dairy and meat processing plants are most at risk
Viral Pneumonia (LRS)?
can occur as a complication of influenza, measles, chickenpox

Viral etiology suspected if no cause determined
Respiratory Synctial Virus (RSV)?
Common in infants; 4500 deaths annually
Causes cell fusion (syncytium) in cell culture
Symptoms: coughing and wheezing
Diagnosis by serologic test for viruses and antibodies
Influenza symptoms and mortality?
Chills, fever, headache, muscle aches (no intestinal symptoms)
1% mortality due to secondary bacterial infections
Treatment of Influenza?
Treatment: Amantadine
Vaccine for high-risk individuals
Structure of Influenza Virus:
8 separate RNA segments of different lengths
enclosed by inner layer of protein (capsid)
outer lipid bilayer-which contains H and N spikes
H spikes:
Hemagglutinin (H) spikes used for attachment to host cells
N spikes:
Neuraminidase (N) spikes used to release virus from cell
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
Influenza serotypes:
A: causes most epidemics, Antigenic subtypes = H3N2, H1N1, H2N2
B: moderate, local outbreaks
C: mild disease
Histoplasmosis caused by? transmitted by?
Histoplasma capsulatum; dimorphic fungus
Transmitted by airborne conidia from soil - >75% of population in affected areas have antibodies
Diagnosis and Treatment of Histoplasmosis?
Diagnosis by culturing fungus
Treatment: amphotericin B
Coccidioidomycosis caused by? and Life cycle?
Cocciodioides immitis
arthrospore grows into tubular hypha --> hypha segments into arthrospores-->arthrospores inhaled -->inhaled arthrospore (how they are transmitted) grows into spherule-->endopores grown inside spherule-->spherule releases endospores
Diagnosis and Treatment of Coccidioidomycosis?
Diagnosis by serological tests or DNA probe
Treatment: amphotericin B
Pneumocystis Pneumonia caused by?
Pneumocystis jiroveci (P. carinii) found in healthy human lungs (once thought to be a protozoan but now identified as a fungus)
Pneumocystis Pneumonia occurs in?
Pneumonia occurs in newly infected infants & immunosuppressed individuals (had become a primary indicator of AIDS)
Pneumocystis Pneumonia treated by?
Treatment: Timethoprim-sulfamethoxazole
Pneumocystis life cycle:
Mature cyst contains intracystic bodies-->cyst ruptures releasing bodies-->bodies develop into trophozites-->trophozites divide-->trophozites develop into a cyst.
Blastomycosis caused by?
Blastomyces dermatitidis, dimorphic fungus
Found in soil
Blastomycosis causes? treatment?
Can cause extensive tissue destruction
Treatment: amphotericin B
Opportunistic fungi involved in respiratory disease:
What requires both antibiotics and an antitoxin?

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