Transcript Respiratory System Infections

Respiratory System Infections
Chapter 22
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
Protection
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Nasal hair
Tonsils (adenoids)
Mucus
Ciliated mucus membrane
Involuntary responses (coughing, etc.)
• Alveolar macrophages
Normal flora
• Limited to the upper tract
• Mostly Gram positive
– S. aureus, alpha and non-hemolytic
streptococci, diptheriods, Haemophilus
influenzae and Moraxella catarrhalis
Streptococcal Pharyngitis
• Strep throat
• Causative agent
– Streptococcus pyogenes
• Β-hemolytic group A
streptococcus
• Signs & Symptoms
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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
• Complications of infection can occur during
acute illness
• Laryngitis
• Bronchitis
• Scarlet fever (Scarlatina)
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
• Complications that can develop later
• Rheumatic fever
• Glomerulonephritis
• Necrotizing fasciitis
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
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
• Epidemiology (of Strep throat)
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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
• Prevention
– No vaccine available
– Adequate ventilation
– Avoid crowds
• Treatment
– Penicillin, erythromycin or cephalosporin
Diphtheria
• Causative agent
– Corynebacterium
diphtheria
– Gram variable
– Pleomorphic
– Non-spore forming
– Metachromatic granules
• Signs & Symptoms
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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
• 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
• 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
• 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
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
• Signs & Symptoms
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Mild fever
Extreme ear pain (ear drum may rupture)
Effusion
Severe malaise
Headache
• 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
• 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
Common Cold
• Rhinitis
• Causative agent
– 30% to 50% caused by
rhinovirus
• More than 100 types of
rhinovirus
• Member of picornavirus
family
• 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
– 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!
• 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
• Prevention
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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