INFECTIONS OF THE RESPIRATORY SYSTEM

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• INFECTIONS OF THE RESPIRATORY SYSTEM

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Anatomy of the Respiratory System
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Normal flora

• is diverse
• includes organisms that are potential pathogens
  (e.g., Streptococcus pnuemoniae and
  Staphylococcus aureus.
• Also includes diphtheroids, micrococci and
  viridians streptococci are part of the normal
  flora.

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• Diseases of the Upper Respiratory System

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Streptococcal Pharyngitis AKA Strep Throat

• Causative organism - Streptococcus pyogenes
  (Group A beta hemolytic streptococci)
• Strep throat is a common throat infection
  characterized by a red throat, pus pockets,
  enlarged lymph nodes, and fever. For most people
  the disease is self-limiting. The major problem
  associated with these infections involves the
  serious sequelae that sometimes follow Scarlet
  fever, Acute glomerulonephritis and Rheumatic
  fever
• Diagnosis - serology, culture and isolation
• Treatment antibiotics
• Prevention - avoiding overcrowded conditions,
  adequate ventilation

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Strep throat
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Scarlet fever
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Acute glomerulonephritis
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Rheumatic fever

• This is the heart of a 44 year old woman who had
  rheumatic fever and had been treated for
  congestive heart failure for about one year.
  There is extreme fibrosis of the mitral valve
  with fusion of commissures and rigidity of the
  leaflets, leading to both stenosis and
  insufficiency. Note that the cordae, which are
  normally like fine linen threads, look more like
  ropes here. Note the enormous

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Diphtheria.

• 1Causative organism- Corynebacterium diphtheriae
• Diphtheria begins (localized infection) with a
  mild sore throat, fever, fatigue, and swelling of
  the throat. A pseudomembrane forms in the
  throat that may cause asphyxiation. A systemic
  toxemia follows that is caused by the production
  of diphtherotoxin. Symptoms include
  cardiovascular complications, paralysis, and if
  untreated death. Mortality is about 10 (ranging
  from 3.5-22 depending on age, severity, and
  promptness of treatment). Humans are the primary
  reservoirs and the disease is spread by close
  contact with skin crusts shed by carriers or sick
  people, droplet nuclei or fomites.
• Diagnosis - Culture and isolation on special
  media
• Treatment Antitoxin and antibiotics
• Prevention - vaccination

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Pseudomembrane
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Skin lesion
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Bullneck symptom
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Other infections that arise from nasopharygneal
infections

• Sinusitis can be caused by bacteria (e.g.,
  Streptococcus pneumoniae, Hemophilus influenzae,
  or Bacteriodes) or by viruses.
• Otitis media (middle ear infections) are caused
  also by organisms such as Streptococcus
  pneumoniae and Hemophilus influenzae and can also
  lead to meningitis.
• Conjunctivitis (pinkeye) is caused by respiratory
  pathogens (most commonly Streptococcus pneumoniae
  and Hemophilus influenzae) but can also be
  viral. In addition, eye infections can be
  acquired during birth (Neisseria gonorrhoroae or
  Chlamydia trachomatis)

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Sinusitis
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Otitis media
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Conjunctivitis
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The Common cold (acute afebrile infectious
coryza).

• Causative agents include Orthomyxoviruses,
  paramyxoviruses, coronaviruses, adenoviruses,
  enteroviruses, but 30-50 are caused by the 100
  or more types of rhinoviruses. Overall, there
  are about 200 viruses and a few bacteria that
  cause colds.
• Colds are very common and are self-limited
  (leading cause of absences from school and the
  loss of about 150 million work days/year). A
  cold is characterized by a scratchy throat, nasal
  discharge, headache and cough. Humans are the
  only reservoirs and are most infective the first
  two or three days. Immunity to a particular
  viral strain lasts at best a few years.
• Diagnosis - not done, rule out bacterial
  infections sometimes
• Treatment - for symptoms
• Prevention - handwashing, avoidance of people
  with colds.

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Common cold
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Pneumonia (bacterial)

• Causative organisms - Streptococcus pneumoniae (gt
  60 of adult cases requiring hospitalization),
  also Klebsiella pneumoniae and Mycoplasma
  pneumoniae (walking pneumonia which is usually
  mild).
• These organisms are inhaled and cause symptoms
  such as chills, fever, cough, chest pain, and
  production of sputum (for Kp infections, also
  delirium). Alcoholism is a predisposing factor
  for Kp infections but other immunocompromised
  individuals are also at risk. With S.
  pneumoniae, complications are septicemia,
  endocarditis, and meningitis. However, most
  people recover. With K. pneumoniae, the
  mortality is 50-80 without treatment. Overall
  there are about 2 million cases of pneumonia/year
  in the US and 40,000-70,000 deaths.
• Diagnosis - Gram stain, culture and isolation
• Treatment antibiotics
• Prevention stay healthy, vaccination for some
  people, stop smoking

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Pneumonia
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Pertussis or whooping cough

• Causative agent - Bordetella pertussi
• Whooping cough is a severe life threatening
  infection in young children (milder in older
  children and adults). The initial phase
  (catarrhal) is characterized by nasal drainage,
  sneezing and occasional coughing. The later
  phase (paroxymsal) is characterized by recurrent,
  persistent cough followed by a whoop sound.
  The toxins produced by this organism kill the
  epithelial cells of the respiratory system.
  Pertussis is not a big problem in the US
  (isolated outbreaks do occur) but worldwide it
  causes 300,000-500,000 deaths per year and there
  are about 2,000-6,000 cases in the US each year.
  Whooping cough is transmitted by droplets
  (inhaled) and thus is easily acquired.
• Diagnosis - Fluorescent antibody techniques, and
  serology
• Treatment - early antibiotics
• Prevention - vaccination

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Tuberculosis

• Causative organism - Mycobacterium tuberculosis
• Healthy people are generally resistant. The
  stages are 1o that is subclinical and that is
  characterized by slight fever, chronic cough,
  weight loss, and night sweats. During this stage
  an inflammatory process resulting in the
  formation of tubercles (localized accumulations
  of bacteria and inflammatory cells). This stage
  may be followed by a latent period. The 2o stage
  (or reactivated TB) is characterized by violent
  coughing, greenish or bloody sputum, low-grade
  fever, anorexia, weight loss, fatigue, night
  sweats and chest pain. Finally a disseminated
  form may occur when the disease spreads to the
  other organs. This organism is spread by
  inhalation. World wide about 1/3 of the
  population is infected (maybe as many as 10
  million in the US) and there are about two
  million deaths annually. The incidence seems to
  be increasing partly due to the growing number of
  infected AIDS patients and partly because of
  antibiotic resistance world-wide, but it is again
  on the decline in the US. The WHO declared this
  pandemic a global emergency in 1993.
• Diagnosis - acid-fast staining, culture and
  isolation, skin test
• Treatment - cocktail of antibiotics (long term
  therapy required)
• 5.Prevention - a vaccine is available (not in the
  US) treatment of latent cases.

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Positive skin test
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Acid Fast Stain
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Legionnaires Disease

• 1. Causative organism - Legionella pneumophila
• 2. This disease is characterized by headache,
  malaise, fever, chills, cough and in 1/4 of the
  cases diarrhea, abdominal pain and vomiting. It
  is transmitted by breathing in the organisms from
  the environment (not from other people). The
  immunocompromised and smokers are more at risk
  (actually males over 50 years of age). There is
  a 15 mortality due to respiratory failure
• 3. Diagnosis - fluorescent antibody staining,
  culture and isolation (but the organism is
  fastidious)
• 4. Treatment - antibiotics
• 5. Prevention - avoiding water aerosols from
  contaminated sources and cleaning of these
  cooling systems etc.

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Influenza

• 1. Causative agent - orthomyxoviruses
• 2. This disease is characterized by headache,
  fever, muscle pain, and cough. It is spread by
  person to person aerosols. Pandemics occur and
  some have high mortality (1918). In the US there
  are 10,000-40,000 deaths annually, many due to
  secondary infections). Associated conditions
  Reyes syndrome occurs in children and seems to
  be related to taking aspirin for viral infections
  (30 mortality) and Guillain-Barre syndrome
  involving a spreading paralysis that occurs after
  vaccination for the flu or after a viral
  infection.
• 3. Diagnosis - symptoms, serology, and tissue
  culture
• 4. Treatment - symptoms
• 5. Prevention - vaccines and avoiding
  overcrowding or others with the flu

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• Respiratory Syncytial Virus Infections is one of
  the causes of croup. These are important
  infections in children causing 90,000
  hospitalizations and 4,500 deaths annually.
  There are no treatments except for symptoms and
  there is no prevention except isolation of
  patients. The naturally acquired active immunity
  that one gets by having the disease is short
  lived and thus repeated infections can occur
  yearly.

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Hantavirus Pulmonary Syndrome

• 1. Causative agent - a virus of the family
  Bunyaviridae
• 2. This starts as a flu-like illness but rapidly
  progresses to respiratory failure and death (more
  than 40 mortality). It is spread by the urine
  and feces of deer mice and other rodents.
• 3. Diagnosis - serology
• 4. Treatment - symptoms
• 5. Prevention - avoiding rodents and their
  droppings (do not create aerosols by sweeping)

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Coccidioidomycosis or Valley Fever

• 1. Causative agent - the fungus, Coccidioides
  immitis
• 2. This is a flu-like illness in those who
  develop symptoms. It is restricted in
  geographical area because people get it from
  breathing in the fungus from the environment (not
  from other people). The majority of people
  recover spontaneously within a month., but in
  some it becomes a TB like illness and in some it
  becomes systemic (with a 50 mortality with
  treatment). Morbidity is _at_ 100,000 cases/year
  but 60 are subclinical.
• 3. Diagnosis - microscopic exam for presence of
  fungi, skin tests, and serology
• 4. Treatment - anti-fungal drugs
• 5. Prevention - dust control (do not breath in
  fungal spores)

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Histoplasmosis

• 1. Causative organism - Histoplasma capsulatum
  (from soil associated with bird and bat
  droppings, also restricted geographically)
• 2. This disease is variable. The morbidity is
  500,000/ year with a low mortality. In general
  it is characterized by a flu-like illness that is
  self-limiting. In a few a serious systemic
  infection occurs which leads to
  hepatosplenomegaly, anemia, and circulatory
  collapse.
• 3. Diagnosis - microscopic exam, skin testing
  (limited value) and serology
• 4. Treatment - antifungal drugs
• 5. Prevention - avoiding aerosols in chicken
  coops and bat caves

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