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Gastrointestinal Tract

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  Gastrointestinal Tract. Most gastrointestinal pathogens are transmitted by food or drink contaminated with fecal material. Where hygiene fails, diarrheal disease becomes rampant.  Acidic gastric secretions are important defenses within the gastrointestinal tract and are lethal for many gastrointestinal pathogens. [14] Healthy volunteers do not become infected by Vibrio choleraeunless they are fed 10 11 organisms, whereas volunteers given V. choleraeand sodium bicarbonate have a 10,000-fold increase in susceptibility to cholera. In contrast, some ingested agents, such as Shigellaand Giardia cysts, are relatively resistant to gastric acid; hence, as few as 100 organisms of each are sufficient to cause illness. Other normal defenses within the gastrointestinal tract include (1) the layer of viscous mucuscovering the intestinal epithelium, (2) lytic pancreatic enzymes and bile detergents, (3) mucosalantimicrobial peptides called defensins, (4) normal flora, and (5) secreted IgA antibodies. IgAantibodies are made by plasma cells located in mucosa-associated lymphoid tissues (MALT).These lymphoid aggregates are covered by a single layer of specialized epithelial cells called Mcells. M cells are important for transport of antigens to mucosa-associated lymphoid tissues andfor binding and uptake of numerous gut pathogens, including poliovirus, enteropathicEscherichia coli, V. cholerae, Salmonella typhi, and Shigellaflexneri. [15] Infections via the gastrointestinal tract occur when local defenses are weakened or theorganisms develop strategies to overcome these defenses. Host defenses are weakened by lowgastric acidity, by antibiotics that alter the normal bacterial flora (e.g., in pseudomembranouscolitis), or when there is stalled peristalsis or mechanical obstruction (e.g., in blind-loop syndrome). Most enveloped viruses are inactivated by bile and digestive enzymes, butnonenveloped viruses may be resistant (e.g., the hepatitis A virus, rotaviruses, reoviruses, and norovirus).Enteropathogenic bacteria elicit gastrointestinal disease by a variety of mechanisms: ã While growing on contaminated food, certain staphylococcal strains release powerfulenterotoxins that cause food poisoning without any bacterial multiplication in the gut. ã V. choleraeand toxigenic E. coli multiply inside the mucous layer overlying the gutepithelium and release exotoxins that cause the gut epithelium to secrete large volumes of fluid, resulting in watery diarrhea. ã Shigella, Salmonella, and Campylobacter invade and damage the intestinal mucosa andlamina propria and so cause ulceration, inflammation, and hemorrhage that is clinically manifested as dysentery. ã Salmonella typhipasses from the damaged mucosa through Peyer patches andmesenteric lymph nodes and into the bloodstream, resulting in a systemic infection. Fungal infection of the gastrointestinal tract occurs mainly in immunologically compromisedpeople. Candida, part of the normal gastrointestinal flora, shows a predilection for stratified squamous epithelium, causing oral thrush or membranous esophagitis, but may also spread tothe stomach, lower gastrointestinal tract, and systemic organs. The cyst forms of intestinal protozoa are essential for their transmission, because cysts resiststomach acid. In the gut, cysts convert to motile trophozoites and attach to sugars on theintestinal epithelia through surface lectins. What happens next differs among pathogens. Giardia lambliaattaches to the epithelial brush border, whereas cryptosporidia are taken up byenterocytes, in which they form gametes and spores. E. histolyticacauses contact-mediatedcytolysis through a channel-forming pore protein and thereby ulcerates and invades the colonicmucosa. Intestinal helminths, as a rule, cause disease only when they are present in largenumbers or in ectopic sites, for example, by bstructing the gut or invading and damaging thebile ducts (Ascarislumbricoides). Hookworms may cause iron deficiency anemia by chronic lossof blood sucked from intestinal villi; the fish tapeworm Diphyllobothriumlatumcan deplete itshost of vitamin B12, giving rise to an illness resembling pernicious anemia. Finally, the larvae ofseveral helminths pass through the gut briefly on their way to another organ; for example,Trichinellaspiralislarvae preferentially encyst in muscle, Echinococcusspecies larvae in theliver or lung. Diarrheais defined as an increase in stool mass, frequency, or fluidity, typically greater than200 g per day. In severe cases stool volume can exceed 14 L per day and, without fluid resuscitation, result in death. Painful, bloody, small-volume diarrhea is known as dysentery. Diarrhea can be classified according to four major categories: ã Secretory diarrhea is characterized by isotonic stool and persists during fasting. ã Osmotic diarrhea, such as that which occurs with lactase deficiency, is due to the excessive osmotic forces exerted by unabsorbed luminal solutes. The diarrhea fluid is over 50 mOsm more concentrated than plasma and abates with fasting. ã Malabsorptive diarrhea follows generalized failures of nutrient absorption and is associated with steatorrhea and is relieved by fasting. ã Exudative diarrhea is due to inflammatorydisease and characterized by purulent, bloody stools that continue during fasting.  DRUG/PRODUCT: PROPOSED INDICATION: FORMULATION: DOSE: AVG. COST: UNICEF Low Osmolarity Oral Rehydration Salts (L-ORS) Diarrhea Sachets of powder for dilution in 200 ml, 500 mlm and 1 litre, appropriate flavor. Airtight packet preferably made of aluminum laminate.  At no signs of dehydration: 50-100 ml (or a quarter to half a large cup of fluid) for children under 2 years; 100-200 ml (one half to one large cup of fluid) for children ages 2-10 years until diarrhea stops. At some dehydration: dosing scheme as indicated in WHO diarrhea treatment guidelines or the amount of the child's weight (kg) multiplied by 75 ml.  Approximately US$ 0.08-0.11/ sachet 3  Drip Drop ORS Berry Flavor (24 Boxes of 4 Packets) Treats and prevents dehydration. Safe and effective for children, adults, and seniors. Enhances athletic performance. Replenishes vital fluids lost through diarrhea, vomiting, colds, or flu. Battles fatigue and improves alertness. Sucrose, sodium citrate, fructose, citric acid, natural flavors, potassium citrate, magnesium citrate, sea salt, ascorbic, sucralose, beta carotene for color, zinc aspartate. Each packet provides: Sodium, 665 mg; Potassium, 390 mg; Chloride, 140 mg; Citrate, 80 meq; Magnesium, 83 mg; Zinc, 3mg; CARBOHYDRATES, 16g; CALORIES, 65 Mix 1 pack into 16.9 oz or 500 ml (1/2 Liter) water $239.76  Adventure Medical Kits Oral Rehydration Salts Ideal for medicine cabinets and first-aid kits Contains: Sodium Chloride; Potassium Chloride; Trisodium Citrate, dihydrate; Glucose  Anhydrous Includes 3 packets; dissolve 1 packet in 1 liter of water $8.95
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