Gastroenteritis By Dr.Sadagoaban.Pharm.D

Introduction : The primary manifestation is diarrhea, but it may be accompanied by nausea, vomiting, and abdominal pain. Diarrhea associated with nausea and vomiting is referred to as gastroenteritis. Epidemiology Occurs worldwide Oral to fecal route of transmission Water common reservoir Overcrowding & poor sanitation are risk factors Animals may be source of infection Diarrheal illnesses may be classified as follows: 1.Osmotic, due to an increase in the osmotic load presented to the intestinal lumen, either through excessive intake or diminished absorption 2.Inflammatory (or mucosal), when the mucosal lining of the intestine is inflamed 3.Secretory, when increased secretory activity occurs 4.Motile, caused by intestinal motility disorders

Signs & Symptoms General features: diarrhea, loss of appetite, abdominal cramps, nausea, vomiting and possibly fever Dysentery Peristaltic abdominal pain are typical. Other findings include headache, myalgia, and hyperactive bowel sounds. Rotavirus gastroenteritis. This disorder commonly starts with a fever, nausea, and vomiting, followed by diarrhea. The illness can be mild to severe and last from 3 to 9 days. Diarrhea and vomiting may result in dehydration. Diarrhea secondary to gastroenteritis is the most common cause of dehydration in children, especially up to age 2 Enteric fevers Systemic with severe headache, high fever, abscesses, intestinal rupture, shock and death

Pathology The most common form of acute gastrointestinal infection is gastroenteritis, causing diarrhoea with or without vomiting. Bacteria can cause diarrhoea in three different ways. Mucosal adherence Most bacteria causing diarrhoea must first adhere to specific receptors on the gut mucosa. A number of different molecular adhesion mechanisms have been elaborated; for example, adhesions at the tip of the pili or fimbriae which protrude from the bacterial surface aid adhesion. For some pathogens this is merely the prelude to invasion or toxin production but others such as enteropathogenic. Escherichia coli (EPEC) cause attachment-effacement mucosal lesions on electron microscopy (EM) and produce a secretory diarrhoea directly as a result of adherence. Adhere in an aggregative pattern with the bacteria clumping on the cell surface and its toxin causes persistent diarrhoea. Diffusely adhering E. coli (DAEC) adheres in a uniform manner and may also cause diarrhoea seen in children.

Mucosal invasion: Invasive pathogens such as Shigella spp., enteroinvasive E. coli (EIEC) and Campylobacter spp. penetrate into the intes- tinal mucosa. Initial entry into the mucosal cells is facilitated by the production of ‘invasins’, which disrupt the host cell cytoskeleton. Subsequent destruction of the epithelial cells allows further bacterial entry, which also causes the typical symptoms of dysentery: low-volume bloody diarrhoea, with abdominal pain. Toxin production : Gastroenteritis can be caused by different types of bacterial toxins: Enterotoxins, produced by the bacteria adhering to the intestinal epithelium, induce excessive fluid secretion into the bowel lumen, leading to watery diarrhoea, without physically damaging the mucosa, e.g. cholera, enterotoxigenic E. coli (ETEC). Some enterotoxins preformed in the food primarily cause vomiting, e.g. Staph. aureus and Bacillus cereus. A typical example of this is ‘fried rice poisoning’, in which B. cereus toxin is present in cooked rice left standing overnight at room temperature. Cytotoxins damage the intestinal mucosa and, in some cases, vascular endothelium as well (e.g. E. coli)

Toxin production

Lab analysis: Markers of fecal leukocytes (lactoferrin), or occult blood suggest inflammatory diarrhea caused by invasive pathogens. Pathogens commonly cultured in these patients include Shigella, Salmonella, Campylobacter, Aeromonas, Yersinia, noncholera Vibrio, and C. difficile. However, the absence of leukocytes in a stool specimen does not rule out inflammatory diarrhea. The mean sensitivity of fecal leukocytes for the prototypical inflammatory diarrhea disease agent Shigella averages 73% (range, 49% to 100%).14 The absence of fecal WBCs suggests a noninflammatory diarrhea. A definitive diagnosis of infectious diarrhea is often made by culture of the pathogen or isolation of the toxin (e.g., C. difficile) from a stool sample. severe diarrhea; oral temperature ≥101.3°F; bloody stools; or stools containing leukocytes, lactoferrin, or occult blood. More sensitive tests to diagnose parasitic infections include direct immunofluorescence staining (DFA) to detect G. lamblia and Cryptosporidium, and enzyme immunoassay (EIA) to detect G. lamblia and Cryptosporidium antigen.

Treatment -Rehydration. The treatment of cholera and other dehydrating diarrheal diseases was revolutionized by the promotion of oral rehydration solutions. The efficacy of which depends on the fact that glucose-facilitated absorption of sodium and water in the small intestine remains intact in the presence of cholera toxin. The World Health Organization recommends a solution containing 3.5 g sodium chloride, 2.5 g sodium bicarbonate, 1.5 g potassium chloride, and 20 g glucose (or 40 g sucrose) per liter of water. Oral rehydration solutions containing rice or cereal as the carbohydrate source may be even more effective than glucose-based solutions, and the addition of L-histidine may reduce the frequency and volume of stool output. Patients who are severely dehydrated or in whom vomiting precludes the use of oral therapy should receive IV solutions such as Ringer's lactate. Although most secretory forms of traveler's diarrhea—usually due to enterotoxigenic and enteroaggregative E. coli—can be treated effectively with rehydration, bismuth subsalicylate, or antiperistaltic agents, antimicrobial agents can shorten the duration of illness from 3–4 days to 24–36 h. Antibiotic treatment for children who present with bloody diarrhea raises special concerns. Laboratory studies of enterohemorrhagic E. coli strains have demonstrated that a number of antibiotics induce replication of Shiga toxin–producing lambdoid bacteriophages, significantly increasing toxin production by these strains. Clinical studies have supported these laboratory results, and antibiotics are not recommended for the treatment of enterohemorrhagic E. coli infections in children.

Loperamide should not be used by patients with fever or dysentery; its use may prolong diarrhea in patients with infection due to Shigella or other invasive organisms. The recommended antibacterial drugs are as follows: Adults: (1) A fluoroquinolone such as ciprofloxacin, 750 mg as a single dose or 500 mg bid for 3 days; levofloxacin, 500 mg as a single dose or 500 mg qd for 3 days; or norfloxacin, 800 mg as a single dose or 400 mg bid for 3 days. (2) Azithromycin, 1000 mg as a single dose or 500 mg qd for 3 days. (3) Rifaximin, 200 mg tid or 400 mg bid for 3 days (not recommended for use in dysentery). Children: Azithromycin, 10 mg/kg on day 1, 5 mg/kg on days 2 and 3 if diarrhea persists. Alternative agent: furazolidone, 7.5 mg/kg per day in four divided doses for 5 days. All patients should take oral fluids (Pedialyte, Lytren, or flavored mineral water) plus saltine crackers. If diarrhea becomes moderate or severe, if fever persists, or if bloody stools or dehydration develops, the patient should seek medical attention.

Patient education Patients should be educated on the importance and proper methods of oral rehydration and early appropriate feeding. All patients, especially the parents of infants and young children, must be extensively educated about the signs and symptoms of dehydration. Patients with food-borne exposures should be educated on deterrence. Immunocompromised patients and individuals with liver disease should be educated not to consume raw shellfish, especially oysters. Travelers to underdeveloped areas should be made aware of proper avoidance measures, appropriate treatment, and current endemic illnesses. Take enteric precautions to avoid spread to family members, especially by washing hands before eating and after each stool or diaper change. Avoid cross-contamination of foods during preparation (eg, cutting boards). Avoid raw or undercooked eggs or poultry. Consume acidic foods, such as citrus. Consume dry foods, such as bread and nuts. Drink carbonated beverages.

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