Chapter 22


Infectious Diseases Affecting the Gastrointestinal Tract



Dental Caries (Tooth Decay)

  Endogenous infection from normal flora

  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 various spirochetes and anaerobic bacteria

  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





  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

  Symptoms include fever, abdominal cramps, nausea, vomiting, and diarrhea lasting 4-7 days

  Severe cases may require fluid and electrolyte replacement




Acute Diarrhea: Salmonellosis

  Caused by variants of Salmonella enterica

  normal flora of the GI tract of many animals

  Usually a mild disease, but may cause septicemia

  Transmission is primarily by ingestion of undercooked meat, unpasteurized dairy, or contaminated animal products

  Severe cases treated with antibiotics

  vaccine used for poultry



Acute Diarrhea: 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         




Acute Diarrhea: Shigellosis

  Caused by four species of Shigella

  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 watery diarrhea containing blood & mucus (dysentery)

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

  Treat with antibiotics early



Shiga-Toxin-Producing E. coli  (STEC)

  Caused by E. coli  O157:H7

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

  Bacteriophage-encoded 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

  Treatment includes supportive therapy




Acute Diarrhea:  Campylobacteriosis

  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

  Diarrhea symptoms may last longer than a week and may recur

  enterotoxin increases fluid secretion

  Severe cases treated with antibiotics

  Guillain-Barre Syndrom (GBS) acute paralysis associated with previous Campylobacter  infection




Acute Diarrhea:  Clostridium difficile

  Normal intestinal flora that causes pseudomembraneous colitis following treatment with broad-spectrum antibiotics

  Produces enterotoxins that cause necrosis in the intestinal walls

  Treatment includes antibiotic withdrawal or fecal transplant




Acute Diarrhea: Cholera

  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




Acute Diarrhea: Cryptosporidiosis

  Caused by the protozoan Cryptosporidium parvum

  Zoonotic disease involving a variety of mammals, birds, and reptiles

  Transmitted by ingestion of oocysts in contaminated water or food

  resistant to chlorination

  Chronic in AIDS patients




Acute Diarrhea:  Rotavirus

  Cause most cases of viral gastroenteritis in infants and children

  Extreme dehydration can lead to shock and death

  Fecal-oral transmission via contaminated food, water, or fomites

  Prevented with oral attenuated vaccine




Acute Diarrhea:  Norovirus

  Often associated with outbreaks on cruise ships

  Causes profuse, watery diarrhea and severe vomiting

  Fecal-oral transmission via contaminated food, water, or fomites with a low infectious dose




Acute Diarrhea with Vomiting

  Commonly known as food poisoning and caused by bacterial exotoxins

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

  Staphylococcus aureus exotoxin - transmitted by ingestion of food contaminated by handling and then left unrefrigerated

Resistant to salt preservatives

  Produces a heat-stable enterotoxin

  Bacillus cereus exotoxin- transmitted by ingestion of vegetables and other foods in close contact with soil

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

  Clostridium perfringens exotoxin- transmitted by ingestion of undercooked meat, fish, or vegetables



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

  Fecal-oral transmission by ingestion of oocysts from contaminated water or imported fresh produce

  Treat with antibiotics




Chronic Diarrhea: Giardiasis

  Caused by the protozoan Giardia lamblia

  present in the GI tract in a variety of mammals

  Fecal-oral transmission by ingestion of cysts from contaminated ponds, lakes, and streams with a low infectious dose

  cysts survive stomach acid to emerge as trophozoites

  Treat with anti-protozoan medications




Chronic Diarrhea:  Amoebiasis

  Caused by the protozoan Entamoeba histolytica

  Severe cases can cause hemorrhage, appendicitis, and tumor-like growths called amoebomas

  Complications include amoebic hepatitis and pulmonary amoebiasis

  Transmitted by ingestion of cysts in fecally contaminated water or food

  dormant cysts 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)

  Spreads via fecal/oral route from contaminated water or food

  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)

  Transmitted via blood and semen with a small infectious dose

  Transmission has been traced to the sharing of razors, toothbrushes, needles, tattoos, piercings, 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)    

  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)

  Defective virus that can only infect individuals with HBV

  Magnifies the symptoms of HBV