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metha 2010 chp 22
Infectious Diseases Affecting the Gastrointestinal Tract
| Question | Answer |
|---|---|
| 1. Gastrointestinal (GI) Tract or Alimentary Tract – | the mouth- pharynx (throat)- esophagus- stomach- small intestine- large intestine- rectum- and anus |
| 2. Accessory Organs | – the salivary glands- liver- gallbladder- and pancreas- which produce fluids and enzymes that aid in digestion |
| B. Normal Microbiota | 1. High populations of bacteria throughout 2. Stomach and small intestine have few microorganisms b/c of the hydrochloric acid produced by the stomach and rapid movement of food through the small intestine3. Large intestine has the highest amounts of bac |
| A. Dental Caries – Cavities | Most common infectious disease in developed countries where the diet contains relatively large amounts of refined sugar |
| 1. Plaque - | biofilm of bacteria- slime- and protein on tooth enamel a. Pellicle - (+) charged proteins in the saliva adhere to the (-) charged enamel to form a film over the tooth b. Streptococci and actinomycetes attach to the pellicle first and then secondary inva |
| 2. Sugars + bacteria account for much tooth decay- note: | starch has little effect; sugar alcohols- sorbitol and xylitol- not metabolized by bacteria |
| a. Fermentation of carbohydrates by the bacteria produces acid- | which in the denser regions of plaque accumulate in contact with the enamel |
| b. A pH below 5 will dissolve the | calcium phosphate of the enamel in that area resulting in cavities aka dental caries |
| c. Teeth are vulnerable to caries as soon as they appear (6 months); | Bottle mouth or nursing bottle caries occurs when babies are put down to sleep with a bottle of formula or fruit juice; only water should be given at nap time if bottle fed |
| 3. Treatment & prevention | removing decay and filling the cavity with amalgam- a mixture of Hg and other metals |
| b. Prevention | 1) Restricting intake of sucrose and refined carbohydrates;2) Regular brushing and flossing;3) Fluoride - works in two ways: inhibits bacterial enzymes that produce phosphates (ATP) and hardens surface enamel of teeth- which prevents acid penetration 4 |
| 4. Sugarless gum prevents tooth decay. | a. Xylitol and other sugar alcohols are not metabolized- so acids are not formed as with sucrose. b. Gum removes food particles and stimulates saliva which contains lysozyme. |
| B. Periodontal Disease | 1. Disease may come with age as the gums recede even in individuals without a history of dental caries; also predisposing factors such as genetics and diet and tooth placement |
| 2. Important to maintain good dental hygiene – if plaque becomes calcified with calcium and phosphate crystals | a calculus is formed above and below the gum line- which causes inflammation and damage to gum tissue and a portal of entry for bacteria |
| 3. Complex of | polymicrobial biofilms |
| a. Gingivitis – | infection is restricted to the gums (gingivae) Indicated by bleeding of the gums with brushing (occurs in almost everyone at some time) |
| b. Periodontitis | 1) Gums are inflamed; bleed easily- pus pockets can form around the teeth- infection progresses towards root tips; bone and tissue that support teeth are destroyed; not usually painful |
| Periodontitis 2) Responsible for almost | 10% tooth loss in older adults); research suggests links to heart disease- stroke and the risk of having a pre-term baby |
| 3) Treated either by surgical elimination of the periodontal pockets or by using specialized cleaning techniques on the tooth surfaces normally protected by the gums; coenzyme Q10 taken daily (70 mg) may decrease bleeding & inflammation | |
| c. Most destructive: necrotizing ulcerative gingivitis and necrotizing ulcerative peridontitis | |
| a) More serious with pain that accompanies chewing; halitosis | |
| b) Treatment with oxidizing agents- debridement and antibiotics may be helpful | |
| C. Mumps – | viral infection of the salivary glands- especially the parotid glands accompanied by swelling usually of both cheeks; vaccination with the MMR at 12 months has reduced incidence |
| A. Helicobacter Peptic Ulcer Disease | 1. Inflammation of the stomach and intestinal mucosa gastroenteritis 2. Microbe responsible for this disease- as well as stomach cancer- is Helicobacter pylori. 3. Incidence is higher in individuals with O blood type; thought to be a connected b/c one |
| B. Acute Infectious Diarrhea | 1. Caused by either infection or intoxication; If diarrhea is severe and accompanied by blood or mucus dysentery; usually abdominal cramps- nausea- and vomiting |
| a. Infection – | the pathogen enters the GI tract and multiplies with a delay: 12 hrs to 2 weeks in symptoms while pathogen increases and invades tissues; usually symptoms are accompanied by a fever |
| b. Intoxication – | ingestion of a preformed toxin producing a sudden appearance of symptoms (a few hours) with no fever |
| c. Diarrhea is a major factor in infant mortality worldwide with | 1 in 10 deaths before five years of age. Rehydration therapy plays a crucial role in treatment. US – food poisoning cases range from 6 to 80 million individuals/year- > 9000 deaths |
| 2. Salmonellosis or Salmonella Gastroenteritis | a. An infection caused by many different serotypes of Salmonella enteriditis b. Found in the intestinal tracts of animals so mainly a food-borne illness; poultry- eggs and egg products are a major source- as well as pet reptiles (90% carry the bacteria)c |
| e. Serovar S. enteriditis serovar typhi causes | typhoid fever where the infection proceeds to the blood causing septicemia; not common in the US |
| 3. Shigellosis or Bacillary Dysentery | a. Closely related to Salmonella and Escherichia coli and cause similar symptoms b. Unlike many other intestinal pathogens that grow in the large intestine- Shigella grows in the small intestine |
| Shigella - Similar to but not as invasive as | Salmonella and does not perforate the intestine and spread to the bloodstream |
| Shigella - Enterotoxin and shiga toxin producing species cause | greater intestinal damage |
| Shigella - Spread is | typically associated with human to human spread under unsanitary conditions |
| 4. Escherichia coli Gastroenteritis | a. Normally a harmless bacterium that inhabits the lower intestinal tract b. Pathogenic strains have specialized fimbriae that allow binding to specific intestinal cells |
| Escherichia coli Gastroenteritis enterohemorrhagic strains | 1) E. coli O157:H7; newly emerging disease in the early 1980s; ID50 < 10 bacteria 2) Occasional inhabitant in the intestinal tract of animals but does not cause disease to the animal |
| 3) Shiga toxin produces | hemorrhagic colitis; and in serious cases hemolytic uremic syndrome – blood in the urine leading to kidney failure |
| Escherichia coli Gastroenteritis 4) Most cases linked to | rare or raw ground hamburger; the toxin is destroyed with cooking |
| 5. Campylobacter Gastroenteritis | a. Leading food-borne illness in the US b. Found in the animal intestinal tract; most cases are associated with raw or undercooked poultry – “Cutting board” principle; ID50 < 500 bacteria c. Illness begins within 2-5 days; fever- cramping abdominal pain- |
| d. Unusual complication – Guillain-Barré syndrome (GBS)- | a temporary paralysis; 20-40% of the cases linked to Campylobacter |
| 6. Clostridium difficile | a. Major cause of diarrhea in hospitals; usually following broad-spectrum antibiotic therapy b. Causes pseudomembranous colitis or antibiotic-associated colitis which usually is resolved upon withdrawal of antibiotics and fluid replacement c. Restoration |
| 7. Cryptosporidium | a. Intestinal protozoan that infects animals; humans accidentally ingest oocyst contaminated water or food |
| b. Oocysts are highly | infectious and resistant to chlorine – Cryptosporidiosis occurs in areas with unreliable water and food sanitation |
| c. AIDs patients | may have chronic infections |
| 8. Viral Gastroenteritis – | many different viruses including rotaviruses- adenoviruses- caliciviruses- astroviruses- Norwalk virus- and a group of Noroviruses |
| Viral Gastroenteritis –Symptoms – | watery diarrhea and vomiting- and sometimes headache- fever- and abdominal cramps beginning 1 to 2 days following infection and may last for 1 to 10 days- depending on which virus causes the illness. |
| Viral Gastroenteritis –Spread | – fecal-oral route |
| Viral Gastroenteritis –Treatment | – Rehydration therapy |
| 1. Staphylococcal Food Poisoning | a. Caused by the ingestion of an enterotoxin produced by coagulase (+) S. aureusb. Pathogen is resistant to environmental stresses – cells can tolerate 60C for 30 min.- resistant to drying and radiation and high osmotic pressures c. When competition is r |
| 2. Bacillus cereus Food Poisoning | Two types associated with two different toxins: Emetic (ee-met-ik) or vomiting disease – reheated fried rice; Diarrheal disease – cooked meats or vegetables held at a warm temperature for long periods of time encourages production of the toxin- which cau |
| Chronic diarrhea 1. Cyclospora cayetanensis – | emerging protozoan pathogen associated with consumption of fresh produce and water; fecal-oral transmission |
| Chronic diarrhea Giardiasis caused by Giardia lamblia | a. Protozoan - most common flagellate isolated clinically b. Cysts are very hardy – survive chlorination- survive 2 months outside the host; ingested in water or food contaminated by those afflicted or from fomites; water used in camping must be treated |
| 3. Amoebic dysentery caused by Entamoeba histolytica: | a. Worldwide- but occurrence highest in the tropics and subtropics; b. No alternate hosts or vectors; passed to humans from water or food contaminated with human feces or by oral/anal sexual practices c. Symptoms - abdominal pain- diarrhea- dysentery (bl |
| E. Hepatitis – | Inflammation of the liver that has many causes- viral infection is one Necrosis of hepatocytes + swelling and disruption of excretion of bile pigments such as bilirubin- accumulate in the blood & tissues causing jaundice- a yellow tinge in the skin and e |
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