Microbiology: A Systems Approach, 2nd ed'

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Microbiology A Systems Approach, 2nd ed.

• Chapter 21 Infectious Diseases Affecting the
  Respiratory System

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21.4 Diseases Caused by Microorganisms Affecting
the Upper and Lower Respiratory Tract

• A number of infectious agents affect both the
  upper and lower respiratory tract regions
• Most well-known whopping cough, respiratory
  syncytial virus (RSV), and influenza

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Whooping Cough

• Also known as pertussis
• Two distinct symptom phases
• Catarrhal stage
• After incubation from 3 to 21 days
• Bacteria in the respiratory tract cause what
  appear to be cold symptoms (runny nose)
• Lasts 1 to 2 weeks
• Paroxysmal stage
• Severe and uncontrollable coughing
• Violent coughing spasms can result in burst blood
  vessels in the eyes or even vomiting
• Followed by a long recovery (convalescent) phase
• Complete recovery requires weeks or even months
• Other microorganisms can more easily cause
  secondary infection

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Respiratory Syncytial Virus Infection

• Produces giant multinucleated cells (syncytia) in
  the respiratory tract
• Most prevalent cause of respiratory infection in
  the newborn age group
• First symptoms fever that lasts approximately 3
  days, rhinitis, pharyngitis, and otitis
• More serious infections give rise to symptoms of
  croup coughing, wheezing, dyspnea, rales

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Influenza

• Begins in the upper respiratory tract serious
  cases may also affect the lower respiratory tract
• 1- to 4-day incubation period
• Symptoms begin very quickly headache, chills,
  dry cough, body aches, fever, stuffy nose, and
  sore throat
• Extreme fatigue can last a few days or a few weeks

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Figure 21.12
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Figure 21.13
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21.5 Lower Respiratory Tract Diseases Caused by
Microorganisms

• Diseases that affect the bronchi, bronchioles,
  and lungs
• Tuberculosis and pneumonia

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Tuberculosis

• Humans are easily infected with Mycobacterium
  tuberculosis but are resistant to the disease
• Only about 5 of infected people actually develop
  a clinical case of TB
• Untreated TB progresses slowly
• Clinical TB is divided into primary tuberculosis,
  secondary tuberculosis, and disseminated
  tuberculosis

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Primary Tuberculosis

• Period of hidden infection- asymptomatic or
  accompanied by mild fever
• After 3 to 4 weeks, immune system mounts a
  cell-mediated assault- large influx of
  mononuclear cells into lungs
• Tubercles form
• Frequently the centers of tubercles break down
  into necrotic caseous lesions that gradually heal
  by calcification
• Tuberculin reaction

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Secondary (Reactivation) Tuberculosis

• Live bacteria can remain dormant and become
  reactivated weeks, months, or years later
• Chronic tuberculosis tubercles filled with
  bacteria expand and drain into bronchial tubes
  and upper respiratory tract severe symptoms such
  as violent coughing, greenish or bloody sputum,
  low-grade fever, anorexia, weight loss, extreme
  fatigue, night sweats, chest pain

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Extrapulmonary Tuberculosis

• Outside of the lungs
• More common in immunosuppressed patients and
  young children
• Regional lymph nodes, kidneys, long bones,
  genital tract, brain, and meninges
• Complications are usually grave

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Figure 21.19
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Pneumonia

• Anatomical diagnosis
• Inflammatory condition of the lung in which fluid
  fills the alveoli
• Can be caused by a wide variety of different
  microorganisms
• Viral pneumonias are usually milder than
  bacterial
• Community-acquired vs. nosocomial pneumonias
• Begin with upper respiratory tract symptoms,
  including runny nose and congestion
• Headache common
• Fever is often present
• Onset of lung symptoms follows chest pain,
  fever, cough, discolored sputum

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Figure 21.20
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Figure 21.21
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Figure 21.22
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Figure 21.26