Respiratory System Infections

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Respiratory System Infections

• Chapter 22

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Respiratory System

• Most common entry point for infections
• Upper tract
• Mouth, nasal cavity, sinuses, pharynx
• Lower tract
• epiglottis, larynx, trachea, bronchi, bronchioles
  and lung tissue

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Protection

• Nasal hair
• Tonsils (adenoids)
• Mucus
• Ciliated mucus membrane
• Involuntary responses (coughing, etc.)
• Alveolar macrophages

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Normal flora

• Limited to the upper tract
• Mostly Gram positive
• S. aureus, alpha and non-hemolytic streptococci,
  diptheriods, Haemophilus influenzae and Moraxella
  catarrhalis

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Streptococcal Pharyngitis

• Strep throat
• Causative agent
• Streptococcus pyogenes
• ?-hemolytic group A streptococcus

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• Signs Symptoms
• Difficulty swallowing
• Fever, malaise, headache
• Red throat with pus patches
• Enlarged tender lymph nodes
• Localized to neck
• Most patients recover in a week or so

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• Complications of infection can occur during acute
  illness
• Laryngitis
• Bronchitis
• Scarlet fever (Scarlatina)

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Scarlet fever

• Strains infected with specific phage
• Erythrogenic toxin
• Sandpaper-like rash
• Spreads from chest across body
• Strawberry red tongue with white coating
• Skin peels away similar to scaled skin syndrome
• Children are at higher risk

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• Complications that can develop later
• Rheumatic fever
• Glomerulonephritis
• Necrotizing fasciitis

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Rheumatic fever

• M protein in cell wall allows pathogen to persist
• Autoimmune response
• Antibodies cross react with heart cell antigens
• Damage heart valves (endocarditis) and muscle
• Arthritis, nodules over bony surfaces under skin

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Glomerulonephritis

• Body fails to remove antigen-antibody complexes
• Accumulate in glomeruli of the kidneys
• Triggers inflammation obstructing blood flow
• High blood pressure and low urine output
• Irreversible kidney damage possible

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• Epidemiology (of Strep throat)
• Humans only host
• Spread by respiratory droplets
• Sore throats (with fever) should be cultured
• Beta hemolysis and serotype determination should
  be made for streptococci
• Peak incidence occurs in winter or spring
• Highest in grade school children

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• Prevention
• No vaccine available
• Adequate ventilation
• Avoid crowds
• Treatment
• Penicillin, erythromycin or cephalosporin

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Diphtheria

• Causative agent
• Corynebacterium diphtheria
• Gram variable
• Pleomorphic
• Non-spore forming
• Metachromatic granules

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• Signs Symptoms
• mild sore throat, slight fever, fatigue and
  malaise
• Dramatic neck swelling
• Pseudo-membrane forms in mouth, on tonsils or
  pharynx
• Phage infected strains release diphtheria toxin
• Toxin is produced in low iron environments

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• Not very invasive bacteria
• Exotoxin released into bloodstream
• Results in damage to heart, nerves and kidneys
• Very potent toxin
• Small amount inactivates large population of
  cells which explains potency
• Even with treatment 1 in 10 patents die

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• Epidemiology
• Humans primary reservoir
• Spread through direct/droplet contact
  transmission
• Reservoir of infection include
• Recovered and asymptomatic carriers
• People with active disease
• Diagnosed by immunoassay to detect circulating
  toxins

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• Prevention
• Immunization
• DTaP
• Immunity not lifelong
• Booster should be given every 10 years
• Treatment
• Open blocked airways
• Antitoxin must be given early
• No effect on absorbed toxin
• Penicillin and erythromycin to eliminate bacteria

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Sinusitis and Otitis Media

• Bacterial infection
• Streptococcus pneumoniae Haemophilus influenza
  Moraxella catarrhalis Staphylococcus aureus
• Viral infections
• Non-infectious allergies are the cause of many
  sinus infections

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• Signs Symptoms
• Mild fever
• Extreme ear pain (ear drum may rupture)
• Effusion
• Severe malaise
• Headache

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• Epidemiology
• Begins with infection of nasopharynx
• Spreads upward to sinuses or up Eustachian tubes
• Sinusitis occurs in more in adults
• Otitis Media occurs more often in children
• Predisposing factors
• damage to the ciliated mucus membrane

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• Prevention and treatment
• No proven prevention for sinusitis
• Prevention of otitis media involves influenza and
  pneumococcal vaccines
• Tubes installed to avoid recurrent infections
• Antibiotics for established bacterial cause
• Penicillin like Amoxicillin

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Common Cold

• Rhinitis
• Causative agent
• 30 to 50 caused by rhinovirus
• More than 100 types of rhinovirus
• Member of picornavirus family

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• Signs Symptoms
• Malaise, scratchy mild sore throat, runny nose
• Cough and hoarsness (laryngitis)
• Nasal secretion
• Initially profuse and watery
• Later, thick and purulent
• No fever

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• Injured cells produce inflammation which
  stimulates profuse nasal secretion, sneezing and
  tissue swelling
• Infection halted by inflammation, interferon
  release and immune response
• Increased risk for secondary bacterial infections!

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• Epidemiology
• Humans are only reservoir
• Aerosols, fomites, direct contact transmission
• Close contact with infected person or secretions
  necessary
• No proven relationship between exposure to cold
  temperature and disease

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• Prevention
• No vaccine
• Hand washing
• Keep hands away from face
• Avoid crowds during times when colds are
  prevalent
• Treatment
• Certain antiviral medications showing promise
• Pleconaril
• Must be taken at first onset of symptoms