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Normal microbiota of respiratory system

answer

Suppress pathogens by competitive inhibition in upper respiratory system
Lower respiratory system is sterile

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Streptococcal Pharyngitis

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Also called strep throat
Streptococcus pyogenes
Resistant to phagocytosis

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Scarlet Fever

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Streptococcus pyogenes
Pharyngitis
Erythrogenic toxin produced
Rash- fine, rough, blanches with pressure; worse in skin folds; spares face
Followed by peeling

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Diphtheria

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Corynebacterium diphtheriae: Gram-positive rod
Diphtheria toxin
Diphtheria membrane: Fibrin, tissue, bacterial cells
Prevented by DTaP vaccine
Diphtheria toxoid

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Otitis Media

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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 vaccine

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Common Cold

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Rhinoviruses (50%)
Coronaviruses (15–20%)
Over 200 agents cause
Sneezing, nasal secretions, congestion
Fever suggests complications
Ear infection
Sinus infection

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Pertussis (whooping cough)

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Bordetella pertussis
Gram-negative coccobacillus
Capsule
Tracheal cytotoxin of cell wall damages ciliated cells
Pertussis toxin
Prevented by DTaP vaccine (acellular Pertussis cell fragments)
Increase in cases in last 20 years because of waning immunity from vaccine

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Turberculosis

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Mycobacterium tuberculosis
Acid-fast rod; transmitted from human to human; aerosol
M. bovis: <1% U.S. cases; not transmitted from human to human
M. avium-intracellulare complex infects people with late-stage HIV infection

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Treatment of tuberculosis

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Treatment: Prolonged treatment with multiple antibiotics
Rifampin, Isoniazid
MDR- multidrug resistance rising concern
Vaccines: BCG, live, avirulent M. bovis; not widely used in United States
ineffective in adolescents and adults
Gives positive PPD
Deadly in HIV positive individuals

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Tuberculin skin test

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Tuberculin skin test screening
PPD- purified protein derivative of M. tuberculosis injected subcutaneously
Cell-mediated immune response against organisms occurs within 48 hours
Indurated and red
Positive reaction means current or previous infection
Followed by X-ray or CT exam, acid-fast staining of sputum, culturing of bacteria

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Pneumococcal pneumonia

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Streptococcus pneumoniae
Gram-positive encapsulated diplococci
Most common cause of bacterial pneumonia; 2/3 of cases; “typical pneumonia”
Symptoms: Infected alveoli of lung fill with fluids; interferes with oxygen uptake
Treatment: antibiotics
Prevention: Pneumococcal vaccine

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Mycoplasmal pneumonia

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Primary atypical pneumonia; “walking pneumonia”
Mycoplasma pneumoniae
wall-less bacteria
Fried-egg colonies
Common in children and young adults
low fever, cough, headache
Treatment: antibiotics

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Legionellosis

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Legionella pneumophila
Gram-negative rod
Found in water
Cooling tanks; air conditioning
Transmitted by inhaling aerosols; not transmitted from human to human
Potentially fatal pneumonia that tends to affect older men who drink or smoke heavily
Treatment: antibiotics

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Psittacosis (Ornithosis)

answer

Chlamydophila psittaci
Gram-negative intracellular bacterium
Transmitted to humans from bird droppings
Reorganizes into reticulate body after being phagocytized
fever, headache, chills
Treatment: antibiotics

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Chlamydial pneumonia

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Chlamydophila pneumoniae
Transmitted from human to human
Mild respiratory illness common in young people; resembles mycoplasmal pneumonia
Treatment: antibiotics

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Viral pneumonia

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occurs as a complication of influenza, measles, or chickenpox
Viral etiology suspected if no other cause is determined

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Respiratory Syncytial Virus (RSV)

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Common in infants; 4500 deaths annually
Causes cell fusion (syncytium) in cell culture
Epidemics in winter and spring
Life-threatening pneumonia in infants (2-6 months)
Treatment: antivirals

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Influenza (flu)

answer

Symptoms: Chills, fever, headache, and muscle aches
No intestinal symptoms
1% mortality, very young and very old
Treatment: Zanamivir (Relenza) and oseltamivir (Tamiflu) inhibit neuraminidase
Prophylaxis: vaccine

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Influenza Virus

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Hemagglutinin (HA) spikes used for attachment to host cells
Neuraminidase (NA) spikes used to release virus from cell

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Antigenic shift

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Changes in HA and NA spikes
Probably due to genetic recombination between different strains infecting the same cell

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Antigenic drift

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Point mutations in genes encoding HA or NA spikes
May involve only 1 amino aci
Allows virus to avoid immune response

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Pneumocystis pneumonia

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Causative agent: Pneumocystis jirovecii; formerly Pneumocystis carinii
Unknown; possibly humans or soil
Mild disease in healthy; severe, deadly pneumonia in immunocompromised (HIV)

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