ACUTE DIARRHEAL DISEASES

INTRO

• leading cause of illness globally

• 4.6 billion episodes worldwide per year

• ranks second to LRI as the most common infectious cause of death worldwide

• contributes to malnutrition and thereby reduces resistance to other infectious agents - indirect factor in a far greater burden of disease

• wide variety of infectious agents involved, including viruses, bacteria, and parasitic pathogens

PATHOGENIC MECHANISMS

TOXIN PRODUCTION

• Enterotoxins - cause watery diarrhea by acting directly on secretory mechanisms in the intestinal mucosa. cholera toxin, heat-labile enterotoxin, heat-stable enterotoxin

• Cytotoxins - cause destruction of mucosal cells and associated inflammatory diarrhea

• Neurotoxins - act directly on the central or peripheral nervous system - produced by bacteria outside the host and therefore cause symptoms soon after ingestion - staphylococcal and Bacillus cereus toxins

INVASION

• Dysentery - from bacterial invasion and destruction of intestinal mucosal cells

• Shigella and enteroinvasive E. coli - invasion of mucosal epithelial cells, intraepithelial multiplication, and subsequent spread to adjacent cells

• Salmonella - inflammatory diarrhea by invasion of the bowel mucosa but generally is not associated with the destruction of enterocytes

• Salmonella typhi and Yersinia enterocolitica - penetrate intact intestinal mucosa, multiply intracellularly in peyer's patches and intestinal lymph nodes, and then disseminate through the bloodstream to cause enteric fever

GASTROINTESTINAL PATHOGENS CAUSING ACUTE DIARRHEA

NONINFLAMMATORY (ENTEROTOXIN)

• Vibrio Cholerae, ETE.Coli, EAE. Coli, Clostridium Perfringens, Bacillus Cereus, Staphylococcus Aureus

• Rotavirus, Norovirus, Enteric Adenoviruses

• Giardia Lamblia, Cryptosporidium Spp

• Proximal small bowel

• Watery diarrhea

• Stool - no fecal leukocytes; mild or no increase in fecal lactoferrin

INFLAMMATORY (INVASION OR CYTOTOXIN)

• Shigella Spp., Salmonella Spp., Campylobacter Jejuni, Enterohemorrhagic E. Coli, Enteroinvasive E. Coli, Yersinia Enterocolitica, Listeria Monocytogenes, Vibrio Parahaemolyticus, Clostridium Difficile

• Entamoeba Histolytica

• Colon or distal small bowel

• Dysentery or inflammatory diarrhea

• Stool - Fecal polymorphonuclear leukocytes; substantial increase in fecal lactoferrin

PENETRATING

• Salmonella Typhi, Y. Enterocolitica

• Enteric fever

• Stool - Fecal mononuclear leukocytes

TRAVELER'S DIARRHEA

• Most common travel-related infectious illness

• time of onset is usually 3 days to 2 weeks after the traveler's arrival in a resource-poor area

• most cases begin within the first 3–5 days

• generally self-limited, lasting 1–5 days

• related to the ingestion of contaminated food or water

• enterotoxigenic and enteroaggregative strains of E. coli are the most common

BACTERIAL FOOD POISONING

• Bacterial disease caused by an enterotoxin elaborated outside the host - staphylococcus aureus or b. cereus, has the shortest incubation period (1–6 h) and generally lasts <12h

• staphylococcal food poisoning - caused by contamination from infected human carriers

• B. cereus - syndrome with a short incubation period—the emetic form, mediated by a staphylococcal type of enterotoxin—or one with a longer incubation period (8–16 h)—the diarrheal form, caused by an enterotoxin resembling E. coli LT

• emetic form - contaminated fried rice

• Clostridium perfringens - slightly longer incubation period (8–14 h) , results from the survival of heat-resistant spores in inadequately cooked meat, poultry, or legumes

APPROACH TO THE PATIENT: INFECTIOUS DIARRHEA OR BACTERIAL

FOOD POISONING

PHYSICAL EXAMINATION

• Signs of dehydration - provides essential information about the severity of the diarrheal illness and the need for rapid therapy

• Mild dehydration - by thirst, dry mouth, decreased axillary sweat, decreased urine output, and slight weight loss

• Moderate dehydration - orthostatic fall in blood pressure, skin tenting, and sunken eyes

• Severe dehydration - lethargy, obtundation, feeble pulse, hypotension, and frank shock

LABORATORY EVALUATION

• Noninflammatory diarrhea - self-limited or can be treated empirically, no need to determine a specific etiology

• Cholera - stool should be cultured on selective media such as thiosulfate–citrate–bile salts–sucrose (TCBS) or tellurite-taurocholate-gelatin (TTG) agar

• rotavirus - latex agglutination test

• patients with fever and evidence of inflammatory disease - stool cultured for Salmonella, Shigella, and Campylobacter

DIAGNOSTIC APPROACH

TREATMENT

• Mainstay of treatment is adequate rehydration - oral rehydration solution

• glucose-facilitated absorption of sodium and water in the small intestine remains intact in the presence of toxin

• World Health Organization recommended a "reduced-osmolarity/reduced-salt" ORS that is better tolerated and more effective

• 2.6 g of sodium chloride, 2.9 g of trisodium citrate, 1.5 g of potassium chloride, and 13.5 g of glucose (or 27 g of sucrose) per liter of water

• severely dehydrated or in whom vomiting precludes the use of oral therapy - IV solutions such as Ringer's lactate

PROPHYLAXIS

• IMPROVEMENTS IN HYGIENE TO LIMIT FECAL-ORAL SPREAD OF ENTERIC PATHOGENS

• ROTAVIRUS VACCINE

• VACCINES AGAINST S. TYPHI AND V. CHOLERAE ARE ALSO AVAILABLE

TREATMENT OF TRAVELER'S DIARRHEA

• loperamide: 4 mg initially followed by 2 mg after passage of each unformed stool, not to exceed 8 tablets (16 mg) per day

• 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

• 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

• Azithromycin, 1000 mg as a single dose or 500 mg qd for 3 days

• Rifaximin, 200 mg tid or 400 mg bid for 3 days