Microbiology: A Systems Approach, 2nd ed'

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Microbiology A Systems Approach, 2nd ed.

• Chapter 22 The Gastrointestinal Tract and Its
  Defenses

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22.1 The Gastrointestinal Tract and Its Defenses

• GI tract is composed of eight main sections and
  augmented by four accessory organs
• Eight sections mouth, pharynx, esophagus,
  stomach, small intestine, large intestine,
  rectum, and anus
• Accessory organs salivary glands, liver,
  gallbladder, and pancreas
• Also known as the digestive tract or alimentary
  canal
• The GI tract is an internal tube (lumen) that
  passes through the body only chemicals absorbed
  through the GI tract actually gain entrance to
  the internal portions of the body

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Figure 22.1
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Defenses

• Mucus
• Secretory IgA
• Peristalsis
• Fluids with antimicrobial properties saliva,
  stomach fluid, bile
• GALT tissues tonsils, adenoids, lymphoid tissue
  in the esophagus, Peyers patches, appendix
• Microbial antagonism

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22.2 Normal Biota of the Gastrointestinal Tract

• Large variety of normal biota
• Oral cavity alone more than 550 known species
  of microorganisms
• Esophagus and stomach much more sparsely
  populated
• Large intestine billions of microorganisms

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22.3 Gastrointestinal Tract Diseases Caused by
Microorganisms

• Tooth and Gum Infections
• If left undisturbed, normal biota biofilm
  eventually contains anaerobic bacteria that can
  damage the soft tissues and bones (periodontium)
  surrounding the teeth
• Introduction of carbohydrates to the oral cavity
  can result in breakdown of dentition

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Dental Caries (Tooth Decay)

• Most common infectious disease of human beings
• Symptoms often not noticeable, but range from
  minor disruption in the enamel to complete
  destruction of the enamel and deeper layers
• Deeper lesions can result in infection to soft
  tissue inside the tooth leading to a toothache

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Figure 22.2
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Figure 22.3
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Figure 22.4
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Periodontal Disease

• 97 to 100 of the population has some
  manifestation of it by age 45
• Most are due to bacterial colonization and
  varying degrees of inflammation

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Periodontitis

• Initial stage gingivitis (swelling, loss of
  normal contour, patches of redness, and increased
  bleeding of the gingival)
• If persists, periodontitis develops
• Extension of gingivitis into the periodontal
  membrane and cementum
• Increases the size of pockets between the tooth
  and the gingival and can cause bone resorption
  enough to loosen and possible lose the tooth

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Figure 22.5
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Figure 22.6
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Necrotizing Ulcerative Gingivitis and
Periodontitis

• Syntergistic infections infolving Treponema
  vincentii, Prevotella intermedia, and
  Fusobacterium species
• Together they produce several invasive factors
  that cause rapid advancement into the periodontal
  tissues
• Severe pain, bleeding, pseudomembrane formation,
  and necrosis

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Mumps

• Incubation period 2o to 3 weeks
• Initial symptoms fever, nasal discharge, muscle
  pain, and malaise
• May be followed by inflammation of the salivary
  glands, producing gopherlike swelling of the
  cheekcs (parotitis)
• Multiplication in the salivary glands followed by
  invasion of other organs, especially testes,
  ovaries, thyroid gland, pancreas, meninges,
  heart, and kidneys

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Figure 22.7
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Figure 22.8
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Gastritis and Gastric Ulcers

• Heliobacter pylori thrives in the acidic
  environment of the stomach and has been linked to
  a variety of gastrointestinal ailments
• Gastritis sharp or burning pain emanating from
  the abdomen
• Gastric ulcers are actual lesions in the mucosa
  of the stomach
• Duodenal ulcer lesion in the uppermost portion
  of the small intestine
• Severe ulcers can be accompanied by bloody
  stools, vomiting, or both
• Long-term infection with H. pylori might be a
  contributing factor to stomach cancer

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Figure 22.9
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Acute Diarrhea

• In the U.S., up to a third of all cases
  transmitted by contaminated food
• Most cases are self-limiting and do not require
  treatment
• Some (E. coli O157H7) can be devastating

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Acute Diarrhea Caused by Salmonella

• Salmonellosis can be severe (elevated body
  temperature and septicemia) or mild (vomiting,
  diarrhea, and mucosal irritation) symptoms
  usually spontaneously subide after 2 to 5 days
• Typhoid fever fever, diarrhea, and abdominal
  pain the bacterium infiltrates the mesenteric
  lymph nodes and the phagocytes of the liver and
  spleen progressive and invasive that leads
  eventually to septicemia

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Figure 22.10
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Acute Diarrhea Caused by Shigella

• Causes the most severe form of dysentery
• Uncommon in the U.S.
• Frequent, watery stools, fever, and intense
  abdominal pain
• Nausea and vomiting are common
• Often bloody stools

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Figure 22.11