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 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 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) 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 Treatment 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 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 Treatment Immunization Immunity not lifelong 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 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 Treatment 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