digestive infections

• Digestive System Structures


  • Gastrointestinal Tract (GI tract)
  • Accessory Digestive Organs
• Gastrointestinal Tract (GI tract)


  Muscular tube acts as a pathway from the mouth to the anus, most organs are protected by the peritoneum (serous membrane)
• Accessory Digestive Organs


  Organs involved in grinding food or providing digestive secretions (enzymes, bile, hormones) which aid in chemical breakdown of food
• Peritoneum


  Largest serous membrane in the body, lines the abdominal cavity (parietal peritoneum) and covers the abdominal organs (visceral peritoneum)
• Teeth


  • Physically fragment food
  • Enamel: hard calcified outer layer, contains no living cells, so cannot repair damage from decay or wear
  • Dentin: Layer beneath enamel
  • Pulp: soft tissue at the center of teeth, contains nerves, blood vessels and connective tissue
  • Gingiva (Gums): soft tissues that cover and protect tooth roots
• Tongue


  Mixes food with saliva, forms a bolus (moist ball of food) push to back of mouth, easily swallowed
• Salivary glands


  Secrete saliva into ducts which deliver saliva into the oral cavity, three pairs: Parotid, Submandibular, Sublingual
• Liver


  • Digestion functions: produce bile to break down fats, many metabolic and regulatory roles
• Gallbladder


  Stores bile when food digestion is not occurring, secretes it when fatty food enters the duodenum
• Pancreas


  • Produce digestive enzymes, and sodium bicarbonate (buffers stomach acid) also produces hormones (endocrine system)
• Microbiome of GI-tract


  300 to 500 bacterial species
• Regions of the digestive system with microbes

  • Saliva
  • Tongue, teeth, jejunum, ileum, colon, and rectum
  • Lower small intestine and colon
• Saliva


  Each milliliter of contains millions of bacteria
• Microbes in the tongue, teeth, jejunum, ileum, colon, and rectum

  • Viridans streptococci
  • Streptococcus mutans
• Esophagus, stomach, and duodenum

  These regions are almost free of microbes, peristalsis & rapid transport of food help prevent microbial colonization, very low pH
• Microbes in the lower small intestine and colon

  • Bacteroides
  • Lactobacillus
  • Escherichia
  • Enterobacter
  • Proteus
  • Klebsiella
  • Candida
  • Entamoeba
• Microbes in the lower small intestine and colon

  They are microbial antagonists (protective) and produce vitamins (e.g. B12, K) that we use as their wastes, mucous membrane prevents entry of microbes into the bloodstream (protective)
• Oral antimicrobials can inhibit intestinal microbiota, leading to transient or opportunistic infection (e.g. C. candida and C. diff.)
• Periodontal Disease: Dental Caries (cavities)
• Dental Caries


  Holes or pits in teeth, can result in tooth loss
• Pathogens causing dental caries

  • Streptococcus mutans
  • Lactobacillus spp.
• Pathogenesis of dental caries

  1. Streptococcus mutans produces dextran (an insoluble, sticky slime) from sucrose, dextran plus adhesion factors form plaques (a biofilm), leading to plaque formation in pits and crevices on enamel

  2. Lactobacillus spp. ferment sugars to acids (~pH5), dissolving enamel

  3. Allows them to invade dentin and pulp of tooth, eventually, blood vessels, nerves and may destroy tooth

  4. Decay continues into dentin and then into pulp of tooth, eventually, blood vessels, nerves and may destroy tooth
• Prevention of dental caries

  • Healthy eating, good oral hygiene, a dental pellicle (a protein film) forms on enamel seconds after a tooth is cleaned or after chewing, protects the tooth from the acids produced by oral microorganisms after consuming carbohydrates
• Periodontal Disease: Gingivitis
• Gingivitis


  Inflammation and infection of tissues surrounding and supporting the teeth (gums = gingiva)
• Signs and symptoms of gingivitis


  • Hard deposits of tartar (hard deposits of mineralized plaque)
  • Inflammation of gums
  • Anaerobic pockets (spaces) form at base of teeth
• Pathogen causing gingivitis


  Porphyromonas gingivalis
• Pathogenesis of gingivitis


  1. P. gingivalis, anaerobic, colonize pockets and release protein-digesting proteases

  2. These enzymes break down the gingival tissue

  3. Bacteria invade bone, causing osteomyelitis, teeth loosen and fall out
• Prevention of gingivitis


  • Healthy eating, good oral hygiene
• Periodontal Disease: Acute Necrotizing Ulcerative Gingivitis (ANUG)
• Acute Necrotizing Ulcerative Gingivitis (ANUG)


  Rare form of periodontal disease, also known as trench mouth
• Signs and symptoms of ANUG


  • Craterlike ulcers between teeth, extensive gum bleeding, foul taste in mouth, grayish biofilm on gums
• Pathogens causing ANUG


  Do not know exact cause, but suspect anaerobes and spirochetes e.g. Treponema
• Epidemiology of ANUG


  • Reversible if caught early, documented as early as the 4th century B.C., the term "trench mouth" came into use during World War I, soldiers in battlefield trenches experienced poor oral hygiene, intense psychological stress, poor diet, developed severe infections of the gums
• Peptic Ulcers
• Peptic Ulcers

  Erosions of the linings of the stomach (gastric ulcer) or small intestine (duodenal ulcers)
• Signs and symptoms of peptic ulcers

  • Abdominal pain is main symptom
  • Erosion of stomach or duodenum lining
  • Ulcers can lead to internal bleeding, bowel obstruction
• Pathogen causing peptic ulcers

  Helicobacter pylori
• Virulence factors of Helicobacter pylori

  • Flagella enable burrowing through stomach lining
  • Adhesins facilitate attachment to gastric cells
  • Urease neutralizes stomach acid
• Epidemiology and treatment of peptic ulcers

  • Fecal-oral transmission, stress may worsen ulcer symptoms, treated with antimicrobials and drugs that inhibit stomach acid, prevented by avoiding fecal-oral transmission