ORAL AND GASTROINTESTINAL DISEASES CHAPTER 22 Copyright © 2012 John Wiley & Sons, Inc. All rights reserved.

Fig The structure of the digestive system. The digestive system has 5 major functions: 1) movement of food materials through the tract, 2) secretion of digestive juices and mucus to break down food materials, 3) digestion, the process of breaking large food molecules into small molecules, 4) absorption of digested food substances into the blood or lymph and 5) elimination of indigestible food materials and intestinal microflora. No questions about structure of digestive system will be on the exam. This figure is for your reference

Normal microflora of the mouth and digestive system- the mouth contains lots of different microorganisms, whereas the human esophagus does not appear to have a permanent normal microflora. The stomach and the first two-thirds of the small intestine contain very few microbes, mainly lactobacilli and streptococci that are merely passing through. The last third of the intestine is colonized by Gram- negative, facultatively anaerobes (e.g., E. coli) and obligately anaerobic organisms (e.g., Bacteroides and Clostridium). Feces are composed about 50 percent by weight and volume of bacterial Most of these are species of Bacteroides.

Diseases of the oral cavity-

Fig A section through a typical tooth and gum Root Canal No questions about structure of teeth and gum will be on the exam. It is for your reference

Following having the disease cholera about 1 in 5 will experience cardiovascular problems A.True B.False

Ebola vaccine worked in monkeys; potential drug target found A new Ebola vaccine may be trialled in humans after eight macaques immunized experimentally did not succumb to the deadly infection, whereas two unvaccinated monkeys did. And in a separate development, research into the biological mechanisms of the virus has produced results that could lead to a future drug treatment. The vaccine - which gave protection to the animals after a single dose - showed success in overcoming safety limitations that have been seen with the use of the vesicular stomatitis virus (VSV) as a vector. The use of this virus is designed to carry, as harmlessly as possible, the immunity-provoking proteins from the Makona strain of the Zaire Ebola virus. They say the vaccine-associated viremia that has been seen in the first- generation VSV-based vaccine, already in human trials, has now been "reduced tenfold" in their study.Ebola

Fig Dental plaque Dental plaque-Streptococcus mutans a gram ‑ positive coccus is probably the most important organism in the promotion of tooth decay. S. mutans produces a sticky polysaccharide of glucose called dextran which cements the bacteria to the teeth. The masses of bacterial cells and dextran adhering to the teeth are known as dental plaque. The acid produced by the organism localized in specific areas (plaque areas) as it ferments sucrose initiates decay. Periodontal disease is a term used to describe inflammation and degeneration of the gums, supporting bone, periodontal ligament and cementum.

Dental caries can be prevented or their incidence greatly reduced by limiting the intake of sugary and sticky foods, brushing regularly with plaque-removing tooth paste, and flossing between teeth. A vaccine against S. mutans is being developed to prevent tooth decay-and in fact is currently in trial. However, the development has been ongoing for a number of years with no product. The use of fluoride has been the most significant factor in reducing tooth decay. It works by hardening the surface enamel of teeth.

Fig The effect of fluoride on tooth decay

Periodontal disease- In its mildest form periodontal disease is called gingivitis, which affects the gums. The disease is caused by a number of virulent mostly Gram negative rods such as Porphyromonas gingivalis. Proper dental flossing is a major preventative against gum disease!

Fig Advanced periodontal disease Gram negative rods such as: Porphyromonas gingivalis a) Severe gum inflammation, which can lead to b) loss of bone (see arrows) surrounding roots of teeth, causing loosening and eentual loss of teeth.

Gastrointestinal Diseases Caused by Bacteria-

Bacterial food poisoning- ingestion of food contaminated with preformed toxins. Staphylococcus aureus- Staphylococcal food poisoning. This disease is an intoxication caused by an enterotoxin produced by Staphylococcus aureus. The toxin is heat stable, and can survive up to 30 minutes of boiling. The food poisoning is characterized by nausea, vomiting and diarrhea 1 to 6 hours after the contaminated food is ingested. Recovery is generally uneventful. Other kinds of food poisoning- Clostridium perfringens (gram positive spore ‑ forming anaerobic rod) gastroenteritis. Very common gastroenteritis that is caused by the ingestion of the vegetative cells of C. perfringens that sporulate in the GI tract and produce and enterotoxin during the germination period. Typical symptoms of diarrhea and abdominal pain result.

Bacterial enteritis and enteric fevers. Salmonellosis (Salmonella gastroenteritis). Salmonellosis is a bacterial infection of the lower GI tract caused by species of the genus Salmonella, e.g., Salmonella enteritidis. Salmonella are gram ‑ negative organism that normally inhabits the GI tract of animals and man. Bacterial infections have a longer incubation period than do intoxications because the organism needs time to grow in the GI tract. Most of the GI infections caused by members of the genus Salmonella are relatively mild (although in infants they can be serious because of dehydration) and are known as salmonellosis, salmonella gastroenteritis, or salmonella food infection. There is nausea, abdominal pain and cramps, and diarrhea.

Typhoid fever. Unlike the mild disease described above Salmonella typhi causes the disease known as typhoid fever in which the organism crosses the intestinal barrier and becomes invasive. A live, attenuated oral typhoid vaccine is now available it stimulates both cell-mediated as well as humoral immunity including the production of IgA antibodies which aids in prevention of mucosal invasion Figure 22.8 Salmonella typhi the cause of typhoid fever

Shigellosis-Bacillary Dysentery (shigellosis) The disease is caused by members of the genus Shigella which includes 4 species: S. sonnei, S. dysenteriae, S. flexneri and S. boydii. The disease is characterized by open sores (ulceration) in the lower GI tract associated with great pain and some fever. The characteristic indication of shigellosis is the presence of "bloody stools".

Asiatic cholera (sometimes cholera is used as a generic term). The disease is caused by Vibrio cholerae which is a gram ‑ negative rod. The disease is spread via the fecal oral route frequently by contaminated water. The organism remains in the intestinal tract and are not invasive but they produce a potent exotoxin called enterotoxin. This toxin causes a marked elevation in the level of cyclic AMP in the cells that line the intestinal wall which in turn results in a striking increase in permeability of the intestinal wall and to a severe form of diarrhea which results in what are termed "rice water stools". Death from cholera is typically due to dehydration

Travelers diarrhea Escherichia coli gastroenteritis (traveler's or infant diarrhea). Most E. coli are harmless inhabitants of the GI tract. However some strains produce disease. Some strains of E. coli have attachment pili and produce an enterotoxin; these strains are known as enterotoxigenic E. coli. The mode of action of the enterotoxin is very similar to the toxin of V. cholerae. Therapy is by electrolyte replacement. Other strains, Enteropathogenic E.coli, contain a plasmid which codes for a particular surface antigen called K antigen which enables the strains to attach and to invade mucosal cells (similar to Shigella). These organisms are the primary agents of epidemic diarrhea in nurseries and a major cause of travelers diarrhea acquired in foreign countries. Enterpathogenic E. coil accounts for 50 ‑ 60% of the cases of traveler's diarrhea with the remaining caused by Shigella, Campylobacter and other organisms. Electrolyte replacement is the treatment of choice.

Other kinds of bacterial enteritis- Campylobacter. Causes diarrhea and may result in "blood stools". Take home: Campylobacter jejuni infections are now the leading cause of bacterial diarrhea reported in the United States

Bacterial infections of the stomach, esophagus and intestines

Peptic ulcer and chronic gastritis Today it is widely accepted that H. pylori is responsible for gastic (stomach) or duodenal (first few inches of small intestine) ulcers (Nobel Prize to Barry J. Marshall and J. Robin Warren for the discovery). Eradication of H.pylori with antimicrobial drugs usually leads to disappearance of peptic ulcers, and their recurrence rate is low. A number of antibiotics have proven effective, including metronidazole, bismuth subsalicylate (pepto-bismol) is also an effective antimicrobial for this application and is usually part of the drug regimen.

Helicobacter pylori

Bacterial Intestinal / Biliary Infections Pseudomembranous colitis –Clostridium difficile Biliary infections © 2012 John Wiley & Sons, Inc. All rights reserved.

Gastrointestinal Diseases caused by other Pathogens Viral gastrointestinal diseases viral enteritis -Rotavirus infection is a major cause of viral enteritis among infants and young children and is a major cause of infant morbidity and mortality in developing countries. Rotaviruses are reoviruses that replicate their double-stranded RNA is such great numbers that they can easily be found by electron microscopy in fecal suspensions. There are also ELISA tests that detect rotaviruses in stool specimens. Currently there is a vaccine available and recommended for all babies. The Norwalk virus is responsible for nearly one-half of all U.S. outbreaks of acute infectious nonbacterial enteritis.