Diseases of the Respiratory System

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Chapter 24

• Diseases of the Respiratory System

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Upper respiratory diseases-bacterial

• Streptococcal pharyngitis (strep throat)
• Caused by group A strep (GAS)
• Usually Streptococcus pyogenes
• Resist phagocytosis and produce streptokinase and
  streptolysins (destroy tissue cells, RBC, and
  Leukocytes)
• Rapid antigen tests for quick diagnosis
• Sore throat, fever, pus pockets, swollen lymph
  nodes

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Scarlet Fever

• S. pyogenes from strep throat may produce
  erthyrogenic toxin and cause rash
• Produce this toxin when infected by a
  bacteriophage!
• High fever, rash, tongue has a spotted strawberry
  appearance and swells, skin peels
• Once the most common cause of death in children
  world wide

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Diptheria

• Until 1935 was the leading infectious killer of
  children in the U.S.
• Sore throat, fever, followed by malaise and
  swelling of neck
• Cornyebacterium diptheriae infected by a phage
  produce an exotoxin that causes disease (first
  disease for which a toxic cause was identified!)
• Interesting characteristic is grey pseudomembrane
  in throat
• DPT or DTaP vaccine
• Fatal if diptheria toxin enters heart or kidneys

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Otitis Media

• Middle ear infection
• Buildup of pus puts pressure on eardrum causing
  pain
• Auditory tube in young children is small and
  horizontal, so fluids build easily
• S. pneumoniae very common, also H. influenzae,
  Moraxella catarrhalis, S. pyogenes, and S. aureus
• Affects 85 of children before age 3
• Vaccine for S. pneumoniae is reducing cases by
  6-7 (1 million a year)

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Upper respiratory diseases-viral

• The common cold-rhinoviruses are the most common
  cause and coronaviruses cause about 15-20
  (thrive at temperture slightly below body temp
  like in the nose when exposed to cold air!)
• Get fewer colds as we get older because we are
  usually immune to the virus after we get it!
  However, there are a bunch of viruses that cause
  colds (at least 200).
• Sneezing, coughing, running nose, congestion
• May spread and cause ear infection and laryngitis

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Lower respiratory diseases-bacterial

• Pertussis (whooping cough)-caused by Bordetella
  pertussis
• This is the P in the DPT shot
• This bacteria has a capsule when virulent
• Attaches to cilia in trachea and prevent their
  function (inhibits ciliary escalator)
• Toxins include tracheal cytotoxin which damages
  ciliated cells and pertussis toxin which enters
  the blood and causes systemic symptoms

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Pertussis continued

• Catarrhal stage resembles a cold
• Paroxysmal stage is characterized by excessive
  coughing which can occur several times a day for
  a week up to 6 weeks.
• Convalescence stage may last for months
• Immunity after disease is good, at least second
  attack is milder
• Almost all deaths occur in infants who havent
  been vaccinated with the acellular vaccine (DTaP)
  (effectiveness wanes after 12 years)
• More than 18,000 cases reported in 2004 (probably
  more, just not reported)
• Now recommend additional booster for ages 10-18
• Culture by inserting a swab into nose on a thin
  wire and obtaining a sample from the throat when
  the patient coughs

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Tuberculosis

• TB is caused by Mycobacterium tuberculosis
• Slow growing! Once called Consumption
• Synergy between HIV and TB (two most common
  causes of death from infectious diseases)
• Acquire by inhalation of bacteria, one to three
  bacteria enter lungs and are phagocytized by
  macrophages and are usually destroyed.

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TB continued

• In susceptible patients the host isolates the
  pathogen in a tubercle.
• If the disease is stopped at this point the
  tubercles heal and leave scars that show up on X
  ray and are called Ghons complexes
• If defenses fail the tubercle is ruptured and
  bacilli are released into airway of lung into
  cardiovascular and lymph systems
• Disseminated infection is called miliary TB, and
  patient loses weight, coughs, and deteriorates

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Treatment and diagnosis

• Once treated with streptomycin
• Now use combination drugs for at least 6 months
  (isoniazid and rifampin, and ethambutol are
  examples)
• Any patient who doesnt complete the long term
  therapy may increase the probability of
  resistance developing (see box page 453)
• Diagnosis by Tuberculin skin test (Mantoux test
  is most accurate)
• BCG vaccine is a live culture of M. bovis made a
  virulent by culturing on artificial media
  (effective in young children only)
• World Wide cases are increasing about 2 a year
  and many are resistant to multi drugs (MDR)

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Bacterial Pneumonias

• Pneumococcal pneumonia-S. pneumoniae is cause
• Forms capsule that helps it resist phagocytosis
• 90 serotypes (identification based on differences
  in capsules)
• May involve bronchi and alveoli inlungs
• Symptoms fever, breathing difficulty, chest
  pain, lungs look reddish because of dialated
  blood vessels
• Sputum is rust colored from blood coughed up from
  lungs
• Mortality 20 in the elderly
• Penicillins and fluoroquinolones are used, but
  seeing some resistance now to penicillins

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Pneumonias continued

• Haemophilus influenzae (H. flu) pneumonia-gram
  negative coccobacillus
• Found in patients with alcoholism, poor
  nutrition, cancer, diabetes, etc
• Use cephalosporins to treat
• Go here for a study table on diseases
• http//www.studystack.com/studytable-29480

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Legionellosis

• Legionnaires disease is caused by Legionella
  pneumophila
• First identified in 1976 at Legionnaires meeting
  in Philadelphia
• High fever, cough, pneumonia like symptoms
• Bacteria grows in water coolers, air
  conditioners, water lines in hospitals, etc
• Resists chlorine pretty well! Installation of
  copper-silver ionization systems to disinfect
  water in hospitals
• Pontiac Fever is similar to Legionnaires but has
  muscle aches too (usually milder)
• Grows on charcoal yeast extract and treat with
  Erythromycin

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Chlamydial pneumonia

• Chlamydophila pneumoniae common in college
  students
• Transmits by respiratory route person to person
• Resembles walking pneumonia
• Evidence of association with atherosclerosis
  (blocked arteries)

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Q fever

• Caused by Coxiella burnetti (intracellular
  parasite)
• Can multiply intracellularly and can survive
  airborne transmission
• Often asymptomatic (60)
• Acute Q fever-high fever, headache, muscle ache,
  cough, occasionally manifests as hepatitis, heart
  involved in 2 of cases
• Chronic Q fever-endocarditis occurs 5-10 years
  later!
• Cattle ticks spread infection among dairy herds,
  farmer gets it when he inhales the organism or by
  ingestion of raw milk
• Found a resistant body like a endospore that
  caused them to have to raise the temperature of
  pasteurization to kill it

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Viral diseases

• Viral pneumonia-complication of measles,
  chickenpox, or influenza
• RSV or respiratory syncytial virus-is most common
  viral respiratory disease in infants with 4500
  deaths per year
• Epidemics in early spring and winter
• Most children have been infected by age 2
• Symptoms are coughing, wheezing that lasts for
  more than a week, fever if secondary bacterial
  infection

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Influenza

• Chills, fever, headache, muscle aches
• Cold-like symptoms appear as fever disappears
• No nausea!
• Causes 50,000-70,000 deaths in U.S. per year
• Antigenic shifts occur that virtually guarantee
  youll get the flu more than once
• Pandemics in 1918, 1957, and 1968 (mostly type
  A)
• Treatments available now are Relenza and Tamiflu
  (watch for side effects in news)