Chapter 22


Infectious Diseases Affecting the Gastrointestinal Tract



Dental Caries (Tooth Decay)

   Endogenous infection from normal flora

   Most common infectious disease of humans

   Young are more susceptible than old

   Caused by: Streptococcus mutans, Streptococcus sobrinus, and Lactobacillus

  Produce lactic acid when they ferment  sucrose and other refined carbohydrates

  Acid production results in decalcification and weakened enamel

  The organisms produce sticky polymers of glucose and adhere to the smooth surfaces of teeth to form a plaque biofilm

  Deeper lesions exposing the pulp result in tenderness and pain (toothache)




Periodontal Disease

   Chronic inflammation of the gums (gingivitis) spreads to the tissues around the roots of the teeth (periodontitis)

   Most cases are asymptomatic and its primarily a disease of persons 35+

   Symptoms include swollen and bleeding gums, bad breath, discoloration of teeth, receding gums

   Caused by the formation of biofilms by spirochetes and anaerobic bacteria, including Porphyromonas gingivalis

   Dental plaques near the gums become calcified forming dental calculus, or tartar

   Inflammatory responses and toxins cause swelling and redness; tooth may be lost




Acute Necrotizing Ulcerative Gingivitis (ANUG)

   The most destructive periodontal disease

   Caused by invasive Treponema, Prevotella, and Fusobacterium bacteria

   As diseased tissue necroses, the gums recede away from the teeth, causing fever, pain, bleeding gums, ulcers on gums

   All 3 diseases can be prevented with brushing, flossing, fluoride, and dental scaling





   Acute viral infection of the parotid gland caused by the Mumps virus

   Begins with fever, malaise, and aches, then painful swelling of the cheeks (parotitis)

   Infection causes cells to fuse together to form a syncytia

   The virus also targets the testes, ovaries, pancreas, meninges, heart, and kidneys

  most infections are self-limited

   Complications include pancreatitis, meningitis, and deafness

   Transmission is by inhaled salivary droplets

   Prevented with attenuated MMR vaccine




Cold Sores (Fever Blisters)

   Caused by Herpes Simplex Virus Type I (HSV-1)

   Begins with fever and painful blisters and ulcers in the mouth

   Virus particles enter sensory nerves and persist in a latent form for life

   Stress can reactivate infectious virus to form cold sores on lips

   Herpetic Whitlow a deep and extremely painful finger infection

  Common among nurses and dental hygienists

  Virus enters through small breaks in the skin when gloves arent used

  Can cause blindness if rubbed into the eye

   Anti-virals lessen severity and prevent recurrences





   Inflammation of the stomach associated with the production of gastric ulcers

   Caused by Helicobacter pylori

  It is acidophilic and urease positive

  It bores through the mucus lining and attaches to epithelial cells

   Bacteria cause inflammatory responses and lesions in the protective mucus layer

   Symptoms include abdominal pain, tenderness, and bleeding

   Treat with antibiotics and acid suppressors

   Associated with the development of stomach cancer




Acute Diarrhea: Salmonellosis

   Caused by variants of Salmonella enterica

  gram-negative rods

  normal flora of the GI tract of many animals especially poultry

   Symptoms include fever, abdominal cramps, nausea, vomiting, and diarrhea lasting 4-7 days and passing without treatment

   Transmission is primarily by eating raw or undercooked meat or unpasteurized dairy products

   Treat with fluid and electrolyte replacement or antibiotics, vaccine used for poultry



Typhoid Fever

   Caused by Salmonella typhi

  Humans are the only reservoir

   Diarrhea symptoms may be accompanied by intestinal rupture, internal bleeding, shock and death

   Attacks the small intestine and is carried throughout the body in phagocytes     

   Symptoms usually pass in about a month but patients may still spread the bacteria

   Often resides in the gallbladder of asymptomatic hosts

  ex. Typhoid Mary infected at least 53 people over 15 years

   Treat with antibiotics or gall bladder removal





   Caused by four species of Shigella

  Short Gram-negative rods

   Bacteria are not killed by stomach acid; small infectious dose required

   Humans are generally the only reservoir

  Commonly fatal in infants

   Shigella dysenteriae produces a potent exotoxin (Shiga toxin) which breaks down the intestinal lining

   Symptoms include fever, abdominal pain, vomiting, watery diarrhea containing blood & mucus (dysentery)

   Hemolytic uremic syndrome (HUS) severe anemia that can cause kidney failure

   Treat with antibiotics



Enterohemorrhagic E. coli (O157:H7)

   Gram-negative, lactose-fermenting rod

   Symptoms range from mild to severe, including bloody diarrhea, Hemolytic Uremic Syndrome (HUS), blindness, seizure, or stroke

   Shiga-like toxins lyse cells and destroy intestinal lining

   Acquired from ingestion of undercooked beef or contaminated food products or via fecal-oral route with a small infectious dose



Other species of E. coli

   Enterotoxigenic E. coli

  Cause most cases of Travelers diarrhea

  Produce enterotoxins that increase fluid secretion

  Can be life-threatening in infants

   Enteroinvasive E.coli

  Bacteria invade gut  mucosa and cause widespread destruction

  Causes an inflammatory disease and dysentery similar to Shigella

   Enteropathogenic E.coli

  Similar to enterohemorrhagic E.coli, but without systemic symptoms

  Profuse, watery diarrhea, fever, and vomiting

  Can be life-threatening in infants





   The leading bacterial form of diarrhea in the US

   Caused by Campylobacter jejuni

  Normal flora of the GI tract of many animals especially poultry

   Transmitted by ingestion of contaminated meat and beverages with a small infectious dose

   Symptoms include frequent watery stools, fever, vomiting, headaches, and severe abdominal pain

  enterotoxin increases fluid secretion




Clostridium difficile

   A gram positive, endospore forming rod found as normal intestinal flora

   Causes pseudomembraneous colitis resulting from treatment with broad-spectrum antibiotics

   Produces enterotoxins that cause necrosis in the intestinal walls

   Symptoms include diarrhea, abdominal cramps, and fever





   Caused by Vibrio cholerae

  Produces a powerful enterotoxin (cholera toxin) that results in the loss of 20L of fluid daily

   Severe watery diarrhea, vomiting, muscle cramps, dehydration, coma, convulsions, and even death if left untreated

  Commonly referred to as rice-water stool

   Transmitted through fecally contaminated water with a large infectious dose

  also foods such as shellfish or crab harvested from contaminated waters and vegetables fertilized with human feces

   Treat with antibiotics and oral rehydration therapy (ORT)

  Vaccines available for travelers to endemic areas





   Caused by the protozoan Cryptosporidium parvum

   Zoonotic disease involving a variety of mammals

   Characterized by headache, sweating, vomiting, abdominal pain, and profuse watery diarrhea

   Transmitted via contaminated food or water

  resistant to chlorination




   Cause most cases of viral gastroenteritis in infants and children

   Symptoms include vomiting, fever, and watery diarrhea for about a week; extreme dehydration can lead to death

   Fecal-oral transmission

   Prevented with oral attenuated vaccine




Acute Diarrhea with Vomiting

   Staphylococcus aureus Exotoxin

  Caused by ingestion of contaminated food left unrefrigerated

  Resistant to salt preservatives

  Produces a heat-stable enterotoxin

  Symptoms include cramping, nausea, vomiting, and diarrhea for 24 hours

   Bacillus cereus Exotoxin

  Gram-positive, spore-forming bacterium found in the soil

  Transmitted by ingestion of vegetables and other foods in close contact with soil

  Produces two possible exotoxins, one causes diarrhea and one causes vomiting




Chronic Diarrhea

   Diarrhea that lasts longer than 14 days

   Common in AIDS patients

   Most infections are caused by protozoans and transmitted via fecally contaminated water and food




Chronic Diarrhea: Cyclosporiasis

   Caused by the protozoan Cyclospora cayetanensis

  Responsible for widely scattered outbreaks in US and Canada traced to imported foods from tropics

   Characterized by stomach cramps, muscle aches, vomiting, and watery diarrhea

   Treat with antibiotics





   Caused by the protozoan Giardia lamblia

  present in the GI tract in a variety of mammals, including beavers, cattle, coyotes, cats, and muskrats

   Symptoms are generally mild including indigestion, nausea, diarrhea, flatulence, and abdominal cramps

   Transmitted via fecal-oral route from contaminated  ponds, lakes, and streams with a low infectious dose

  ingested as dormant cysts that survive stomach acid to emerge as trophozoites

   Symptomatic & asymptomatic patients become long-term carriers

   Treat with anti-protozoan medications





   Caused by the protozoan Entamoeba histolytica

   Symptoms include dysentery, abdominal pain, fever, diarrhea, and weight loss

   Can cause hemorrhage, appendicitis, and tumor-like growths called amoebomas

   Complications include amoebic hepatitis and pulmonary amoebiasis

   Transmitted by ingestion of fecally contaminated water or food

  ingested as dormant cysts that survive stomach acid to emerge as trophozoites

   Humans are primary host

   Treat with anti-protozoan medications





   Inflammation of the liver

   Viruses that infect the liver cause necrosis of hepatocytes and an immune response that disrupts liver function

   Most often characterized by jaundice a yellow tinge in the skin and eyes



Hepatitis A Virus (HAV)

   Formerly called infectious hepatitis

   Spreads via fecal/oral route

   Most infections are asymptomatic or show only mild symptoms of fatigue, fever, nausea, jaundice, or swollen liver

   Inactivated vaccine is available or immune globulin




Hepatitis B Virus (HBV)

   Formerly called serum hepatitis

   Transmitted via blood and semen with a small infectious dose

  Transmission has been traced to the sharing of razors, toothbrushes, needles, semen and vaginal secretions

   Symptoms include fever, chills, diarrhea, nausea, anorexia, and jaundice

  Complications include glomerulonephritis and arterial inflammation

   Virus has been linked with liver cancer and chronic liver disease (cirrhosis)

   Subunit vaccine is available or immune globulin if exposed (HBIG)

  can treat with interferon or antivirals




Hepatitis C Virus (HCV)

   Formerly called non-A non-B hepatitis             

   Causes few or no symptoms but can lead to chronic liver disease and cancer

   Transmission via blood or body fluids

   There is no vaccine; treat with interferon or antivirals




Hepatitis D Virus (HDV)

   Can only infect individuals with HBV

   Magnifies the symptoms of HBV