Chapter 22

Oral & Gastrointestinal Diseases

Overview of Digestive System

• Organs are separated into 2 groups– Alimentary canal (GI tract)

• Continuous muscular tube (30 ft); open to external environment at both ends

• Site of digestion and absorption• Includes mouth, pharynx, esophagus, stomach and

the intestines

– Accessory organs• Teeth, tongue, liver, gallbladder, pancreas and

salivary glands • Glands are outside GI tract; connected by ducts;

produce digestive enzymes and various other secretions

Digestive Processes • Six essential activities

1. Ingestion2. Propulsion

– Involves peristalsis – wave-like contractions

3. Mechanical digestion– Chewing of food in mouth stomach– Churning and segmentation in stomach

4. Chemical digestion– Series of catabolic steps facilitated by enzymes

5. Absorption– Passage of foodstuffs from GI tract into blood and lymph

6. Defecation – Elimination of indigestible substances

• Mouth – oral cavity – Common portal of entry for microbes; has normal flora – Lined with stratified squamous epithelium,slightly

keratinized to protect against abrasions, produces defensins

– Contains tongue, teeth and salivary glands– Primary functions; mastication and chemical digestion – Salvia has several functions

• cleans mouth, dissolves food chemicals for taste, contains enzymes like lysozymes to destroy microbes

– Each tooth has a crown covered with enamel above the gum and a root covered with cementum below the gum

– Under these coverings is a porous substance called dentin, a central pulp cavity and the root canals where blood vessels and nerves are located

A section through a typical tooth and gum

• Pharynx – throat; has three divisions– Oropharynx, laryngopharynx (common

passages for air and food) and the nasopharynx (plays no role in digestion)

– Has external muscle layer to propel food into esophagus below

• Esophagus – muscular tube that is collapsed when not involved in food propulsion– Pierces diaphragm and empties into the

stomach– Heartburn occurs when acidic stomach juice

(pH 4) is regurgitated into esophagus

• Stomach – site of protein digestion and more mechanical digestion– Food is converted into a creamy paste called

chyme– The epithelial lining has goblets cells which

produce a protective alkaline mucus coating– Lining is doted with millions of gastric glands

which produce hydrochloric acid & pepsin (protein digesting enzyme)

– Alcohol and aspirin and some lipid-soluble drugs pass across the mucous barrier to blood

• Small intestine is the body’s main digestive organ– Site of virtually all absorption

• Three subdivisions– Duodenum – beginning portion; drains stomach; curves

around pancreas; bile duct and main pancreatic duct converge here

– Jejunum – middle portion– Ileum – end portion; joins large intestine – Villi – finger-like projections

• Increase surface area form absorption, contain blood & lymph vessels

– Microvilli – tiny folds in plasma membranes of absorptive cells

• Secrete enzymes that complete the digestive process

• As food enters the duodenum it is mixed with secretions from the liver and pancreas – The liver secretes bile & cholesterols which help

digest fats– The pancreas produces a broad spectrum of

enzymes that help complete digestion of starches & proteins

• Sugars & amino acids are absorbed into the blood while fats are absorbed into the lymph

• The ileum contains special lymphoid tissues called Pyer’s patches to filter out microbes

• Large Intestine’s (colon) major function is to absorb water from indigestible foods and eliminate them from body as feces

• The beginning portion is a sac-like cecum, with a worm-like appendix extending off the back

• Most bacteria entering the large intestine are dead – the few that survive and those entering the anus make up the bacterial flora of the colon– Ferment indigestible carbohydrates releasing acids and

gasses – They also produce vitamin K needed for the liver to

produce clotting factors and complex B vitamins– In addition to absorbing water the colon absorbs these

vitamins

Normal Flora of the Digestive System

• Mouth has over 400 species of bacteria• Esophagus has no permanent flora • Stomach is usually too acidic for bacteria to

colonize• Some G- anaerobes colonize the lower small

intestine and into the colon – E. coli, Bacteroides, Clostridium

• Food may remain in the colon for over 60 hours allowing lots of time for colonization– About 50% of the weight of feces is bacteria

Bacterial Diseases of Mouth • Dental plaque

– continuously formed coating of the teeth with microbes and organic matter

– 1st step in tooth decay and gum disease – May become so firmly attached it requires professional

removal

– Plaque consists of over 30 different genera of bacteria and their metabolic products

• Plaque forming bacteria include Streptococcus mutans and Streptococcus sanguis

– May accumulate near the gum line and cause gingivitis• Actinomyces, Veillonella, Fusobacterium and Streptococci

– May mineralize causing the formation of tarter (calculus)

• Dental caries (tooth decay)– Chemical dissolution of enamel, dentin and pulp – The most common infectious disease in developing

countries because of refined sugar in diet– May form an abscess that damages the peridontal

ligaments and bone supporting the tooth • Periodontal disease

– Sugars diffuse through plaque then the acids produced by bacteria from fermentation of the sugars becomes trapped against tooth

– Preventable by reducing sugar, frequent brushing and fluoride treatment

• Hardens surface enamel• Water supply, toothpaste, mouthwash, gel treatments

Viral Diseases of the Mouth

• Mumps – caused by paramyxovirus – Transmitted in saliva & droplets – Swelling of parotid glands (salvia glands)– Common in children (6-10 yrs) – Preventable with MMR vaccine – May cause orchitis in post-pubertal males

• Inflammation of testes that predisposes them to testicular cancer

– Other complications include inflamation of ovaries and pancrease, eye and ear infections, and meningoencephalitis

paramyxovirus

• Other diseases of the mouth

• Herpes simplex – Primarily HHV type 1 – cause fever blisters or cold sores

• Thrush– Caused by the yeast Candida albicans– Characterized by milky patches of inflammation on oral

mucus membranes – Prevalent in infants, diabetics and immunosuppressed

individuals

Bacterial Gastrointestinal Diseases

• Bacterial food poisonings– Food poisoning is caused by ingesting food contaminated

with bacterial toxins, pesticides, heavy metals or other toxic substances

– Preventable by following proper food handling procedures

– If bacteria are consumed they can continue to produce toxins

• Tissue damage is a result of the action of the toxin not the growth

of the bacteria

– Bacteria producing such toxins include Staphylococcus aureus, Campylobacter jejune, Clostridium species and Bacillus cereus

– S. aureus causes enterotoxicosis by releasing enterotoxins A or D which are actually exotoxins

• damages intestinal wall and inhibits water reabsorbtion causing abdominal pain, vomiting and diarrhea usually within 1-6 hrs of ingestion

• Usually clears itself up in healthy adult; no immunity

– C. perfringens releases an enterotoxin only during sporulation under anaerobic conditions

• Main symptom is diarrhea usually 8-24 hrs after exposure• May also be transmitted by introducing spores to open wounds

causing gangrene

– C. botulinum produces the botulism neurotoxin which mainly affects the nervous system

– B. cereus secretes a toxin that induces vomiting• often associated with contaminated rice• Symptoms occur within 12 hrs of exposure and are short lived

S. aureus

C. perfringens

C. botulinum

B. cereus

• Peptic ulcers & gastritis – Etiological agent: Helicobacter pylori– Peptic ulcers are lesions in membrane lining GI tract– Require 46,000 surgeries & cause 14,000 deaths annually– Correlated to 89% of stomach cancers– Chronic gastritis is stomach inflammation; may lead to

ulceration – H. pylori generates ammonia from urea; ammonia

neutralizes acidic stomach juices– Unclear portal of exit or route of infection– Experimental antibiotic treatments and antacids

Knobs at end of flagella help it move through mucus that traps other normally flagellated bacteria

Helicobacter pylori

• Bacterial enteritis & enteric fevers – Enteritis is an inflammation of the intestine

• bacteria invade and damage the intestinal lining and deeper tissues

• Infection not intoxication like food poisoning – Mainly affects the small intestine causing diarrhea– If it affects the colon it is often called dysentery

• Severe diarrhea usually contains mucus, blood or pus – Some infections spread to the blood and cause systemic

infections called enteric fevers – Salmonellosis, Typhoid Fever, Shigellosis, Cholera,

Vibriosis, Traveler’s Diarrhea (Montezuma’s revenge) and Yersiniosis

• Salmonellosis– Etiological agent: Salmonella species

• S. typhi, S. choleraeusuis & S. enteritidis

– Various harmless animal hosts– Transmitted through contaminated food, water and

chicken eggs– Abdominal pain, fever and diarrhea with blood or mucus– No vaccine; antibiotics may induce a carrier state– Health adults usually recover within a week with no

treatment – Certain serovars have the ability to enter the blood and

cause enterocolitis – enteric fever– Chronic infections are not uncommon

Salmonella enteriditis

• Typhoid Fever– One of the most serious epidemic enteric infections– Etiological agent: Salmonella typhi– Common in areas with poor water & sewage treatment– Transmitted in contaminated food or water and invades

small intestine and lymphoid tissue– Survive and multiply in phagocytes – Headache, fever, malaise, enlargement of spleen,

abdominal distension & tenderness but no diarrhea – May result in internal hemorrhage, perforation of bowel

and pneumonia– Treatment: chloramphenicol (some strains are resistant)– Vaccine is available but requires booster every 3 yrs.

Salmonella typhi--the cause of typhoid fever

• Typhoid Mary• Mary Mallon: an immigrant, Irish woman who made her

way as a cook • Well liked and respected ("good with the children") • Probably exposed to typhoid fever around 1900 • Between 1900 and 1907, she infected 22 people with

typhoid fever; one died • Quarantined on North Brother Island (age 37) for three

years • Released by the new health officer after promising never

to cook again • Traced to Sloan Maternity Hospital as cook!

– 25 more people infected – 2 died

• Returned to quarantine on North Brother Island • Died of a stroke 23 years later (in 1938)

• Shigellosis (bacillary dysentery)

– Etiological agent: several species of Shigella• S. dysenteriae, S. flexneri, S. sonnei, S. boydii

– Transmitted by contaminated food, fingers, water, flies, feces and fomites; only 10 organisms are enough to cause infection

– Cramps, fever & extreme diarrhea with blood – All strains produce fever inducing endotoxins but

S. dysenteriae produces a neurotoxin as well – Combination of antibiotics is used to treat

• Ampicillin, tetracycline and nalidixic acid (DNA synthesis inhibitor)

• Temporary immunity follows recovery & an oral vaccine is being developed

A colorized TEM ofShigella--the causeof shigellosis

• Asiatic Cholera– Etiological agent: Vibrio choleae– Problematic in areas with poor sewage & water treatment– Enterotoxin (choleragen) binds to cells of small intestine

making them highly permeable to water– Severe diarrhea, nausea and vomiting, death due to shock

from fluid loss– Treatment: fluid and electrolyte replacement – No effective vaccine & immunity is temporary

• Vibriosis– Caused mainly by Vibrio parahaemolyticus– Most common in Japan where raw fish is frequently

consumed– Can also infect skin wounds– Releases endotoxin causing nausea, vomiting, diarrhea – No vaccine & usually no treatment is given

A colorized SEM of Vibrio cholerae—the cause of Asiatic cholera

• Traveler’s Diarrhea (Montezuma's revenge)– Most commonly caused by E. coli (40-70%)– Different from the strains found in colon– Transmitted in contaminated food & water – Mild to severe diarrhea, vomiting, nausea, bloating and

malaise – May become irritable bowel syndrome & persist for years– Enter-hemorrhagic strains (E. coli O157:H7) cause deadly

outbreaks of bloody diarrhea (no more rare hamburger) – May lead to kidney failure (leading cause in children)

• Yersiniosis – Caused by Yersinia entercolitica – most common in

Western Europe– Transmitted in contaminated food (especially chitlins)– Releases endotoxin causing severe abdominal pain &

increase in WBCs

E. coli Yersinia enterocolitica

Viral Gastrointestinal Diseases

• Viral enteritis – major cause in children is the rotavirus

• Double stranded RNA virus

– Transmitted by the oral-fecal route, common in small children

– Damages GI lining, causes watery diarrhea – Major cause of infant mortality in under

developed countries – About ½ US cases caused by Norwalk virus

• Affects mostly older children and adults

rotavirus

• Hepatitis– Inflammation of liver usually caused by viruses but also by

an amoeba & various toxic chemicals– Most common viral form is Hepatitis A (infectious hepatitis)

caused by hepatitis A virus (HAV)• Single RNA transmitted by fecal-oral route; contaminated food

– Hepatitis B (serum hepatitis) caused by HBV• Double stranded DNA transmitted by blood; intravenous; direct

contact & contaminated body secretions

– Hepatitis C caused by more than 1 RNA virus (not HAV)• Transmitted parenterally by blood

– Hepatitis D (delta hepatitis) particularly severe caused by both HDV and HBV

– Hepatitis E caused by HEV • Transmitted by fecal-oral route; fecally contaminated water

– 3 more viruses have been identified as potential hepatitis viruses

Hepatitis B viruses

                                           

Protozoan Gastrointestinal Diseases• Giardiasis – caused by flagellated Giardia intestinalis

– Inflammation of bowel, frothy diarrhea due to decreased fat absorption, dehydration & weight loss

– Transmitted by contaminated food, water & hands – Giardia cysts are not killed by ordinary chlorination

• Amoebic dysentery – caused by Entamoeba histolytica

– Becomes chronic but can revert to acute – Transmitted through cyst infected water & food

• Cryptosporidiosis – Cryptosporidium species transmitted from cyst infested feces of puppies & kittens – Opportunistic infection with no available treatment– Severe diarrhea and fluid loss

• Cyclosporiasis – Cyclospora cayentanenisis

– Transmitted by contaminated fruits and vegetables– Flu like symptoms, often with relapse

Giardia intestinalis

Cryptosporidium lining the intestinal tract

Effects of Fungal Toxins on GI Tract

• Fungi produce large numbers of toxins– Most come from species of Aspergillus & Penicillium – Various effects include loss of muscle coordination,

tremors, weight loss and cancers – Aflatoxins – produced by Aspergillus flavus

• Most potent carcinogen known • Transmitted from mold infected grain

– Ergot – produced by Claviceps purpurea • Transmitted on contaminated rye and wheat• Causes fever, hallucinations, gangrene and death

Claviceps purpurea

                                   

Helminth Gastrointestinal Diseases

• Helminthes that infect humans have complex life cycle with 1 or more intermediate hosts – Acquired mainly in tropical regions

• Fluke infections • Tapeworm infections• Trichinosis• Hookworm infections• Ascariasis• Pinworm infections

• Fluke infections– Affect 40 million people worldwide– Sheep liver fluke (Fasciola hepatica)

• Intermediate host is snail • Cercaria encyst on water vegetation forming

metacercaria• Diagnosed by eggs in stool• Treated with bithionol or other antihelminth• Prevented by avoiding uncooked water vegetation

– Chinese liver fluke (Clonorchis sinensis)• Has a second intermediate host – fish or crustacean• Diagnosed by eggs in stool• No effective treatment • Prevented by avoiding uncooked fish or crustaceans

• Tapeworm infections– Caused by several species- most found worldwide– Contracted by eating undercooked pork, beef or fish

and by contact with infected dogs– Pork tapeworm (Taenia solium) and Beef tapeworm

(Taenia saginata)• Enter as larvae in undercooked meat• Develop into adult in intestine stealing nutrients from host• May form masses that block intestines • Eggs may invade blood stream and spread to other body sites

– Echinococcus granulosus• Contracted through contact with infected dogs• Eggs produces cysts called hydatid cysts containing hundreds

of immature worms

– Diagnosed by eggs or proglottids in stool – Treated with niclosamide and other antihelminths

Liver Fluke

Pork Tapeworm

• Trichinosis– Caused by round worm Trichinella spiralis– Enters as encysted larvae in undercooked pork, horse

or game meat– Adults penetrate intestinal mucosa releasing toxins– Wandering larvae damage blood vessels an other

tissues – Hard to diagnose – muscle biopsy or immunological

tests may be effective– Treatment is restricted to alleviating symptoms– Prevented by thoroughly cooking meat – Average of 100 cases/yr in US

• Hookworm infections– Often caused by 1 of 2 species of roundworms

• Necator americanus or Ancylostoma duodenale

– Complex life cycle with a single host – Free-living larvae burrow through skin and travel to

heart or lungs– May be coughed up and swallowed where they reach

the intestines mature, lay eggs and start the cycle again

– 500 million cases worldwide– Diagnosed by worms or eggs in feces – Treatment: Tetrachloroethylene for Necator only;

Bephenium and mebendazole effective for both worms – Preventable through sanitary disposal of human waste

• Ascariasis– Caused by the large roundworm Acaris lumbricoides– Spread through water or food contaminated with eggs– Eggs hatch and larvae travel to lymph vessels and

results in systemic immune response– Mature in small intestine and begin laying eggs

• Single female lays 200,000 eggs/day and 26 million/ lifetime

– Worldwide 25% of population is infested– Ascaris worms cause three forms of damage

• Burrowing into lungs causes Ascaris pneumonitis• Malnutrition by stealing host nutrients• Wandering worms for abscess in liver and other organs

• Pinworm infections– Caused by small round worm Enterobius vermicularis– Humans are the only known host– Has the greatest geographical distribution of all human

worm parasites – 209 million infested worldwide (18 million in US and

Canada)– Adults attach to intestinal wall – Females carrying 15,000 eggs travel to anus and lay the

eggs on the exterior then travel back to intestines– Eggs are ealisly transmitted through contaminated

bedding, clothing and hands– Eggs may become airbourne– Usually not debilitating, but very uncomfortable– Diagnosed by eggs around anus– Treated with piperazine or other antihelminth– All personal items (bedding, clothing) should by cleaned

Adult Pin Worm

Hookworm

Round Worm

Hydatid cysts in brain

Ascaris lumbricoides

mass