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Enteric Infections 
Infectious Diarrhea/Gastroenteritis 
Dr. James C.L.Mwansa 
Consultant Microbiologist, 
University Teac...
Anatomy of Digestive Tract 
 Digestive tract is a “tube” (from mouth to anus); 
technically “outside” of the body 
 Lume...
Anatomy of Digestive Tract (cont.) 
 Mouth, pharynx, esophagus & esophageal sphincter 
 Stomach and pyloric valve (sphin...
Overview of Gastroenteritis 
• Gastroenteritis: Inflammation of the lining of the stomach and 
small and large intestines....
• Gastroenteritis is usually uncomfortable but self-limited. 
• Electrolyte and fluid loss is the main complication 
• Usu...
Infectious Diarrhea 
• 3-5 billion episodes of diarrhoea yearly 
worldwide 
• Major cause of worldwide morbidity and 
mort...
Organisms 
• Infectious gastroenteritis may be caused by 
viruses, bacteria, or parasites 
• Bacteria 
– E. Coli, Salmonel...
These organisms cause diarrhea through a 
wide variety of mechanisms 
Pathophysiology 
– Osmotic 
– Secretory 
– Exudation...
Osmotic Diarrhea 
Definition: Increased amounts of poorly absorbed, 
osmotically active solutes in gut lumen 
• Interferes...
Secretory Diarrhea 
• Excess secretion of electrolytes and water 
across mucosal surface 
• Usually coupled with inhibitio...
Secretory Diarrhea 
Bacterial or viral enterotoxins 
• Vibrio cholerae 
• Noncholeraic vibrios 
• Enterotoxigenic E. coli ...
Watery diarrhea: 
We wreck the GI: V, R, E, C, the Gi. 
These organisms wreck the GI and cause 
watery diarrhea. 
-V=VIBRI...
Exudative Diarrhea 
• Intestinal or colonic mucosa inflamed and 
ulcerated 
– Leakage of fluid, blood, pus 
– Impairment o...
Exudative Diarrhea 
• Infectious, invasive organisms 
– Shigella, Campylobacter, Yersinia, E. 
histolytica, EIEC, C diff 
...
Organisms that cause bloody diarrhea: 
SEECSY= BLOODY DIARRHEA DOESN'T SOUND 
SEXY 
S=SALMONELLA 
E=E COLI EHEC,ETEC 
E=EN...
Invasive organisms produce leukocytes 
and blood in stool 
A laboratory equivalent of this is the presence of 
lactoferrin...
Abnormal Motility 
• Increased colonic motility 
– Irritable bowel syndrome 
• Increased small bowel motility 
– Hyperthyr...
Diarrhea 
• Non-inflammatory 
– Watery diarrhea, no blood or mucus or pus in stool, no 
fever or systemic signs 
– Secreto...
Bloody Vs Watery diarrhoea 
• bloody diarrhoea - if there is necrosis of epithelium 
1. invasive organisms - like Salmonel...
Common syndromes of infectious diarrhea 
• Food poisoning 
• Acute watery diarrhea 
– Travelers diarrhea 
– Epidemics 
• A...
Viruses 
• Viruses the most common cause of gastroenteritis. 
• They infect enterocytes in the villous epithelium of 
the ...
Viruses 
• Four categories of viruses cause most gastroenteritis: 
• rotavirus and calicivirus (predominantly the noroviru...
Viruses 
• Norovirus most commonly infects older children and adults. Infections 
occur year-round. Norovirus is the princ...
Bacteria: 
• The bacteria most commonly implicated include: 
• Salmonella,Campylobacter,Shigella,Escherichia coli (especia...
Bacteria that invade mucosa 
• (eg, Shigella, Salmonella, Campylobacter, some E. coli subtypes) invade 
the mucosa of the ...
subtypes of E. coli causing diarrhea 
Epidemiology and clinical manifestations vary depending on the subtype: 
• (1) Enter...
Other bacteria causing 
gastroenteritis, 
• V. cholerae causes severe dehydrating diarrhea in approx 2% population 
• Yers...
Parasites: 
• The parasites most commonly implicated are Entamoeba 
histolytica Giardia,Cryptosporidium, Isospora belli 
•...
Parasites 
• Cryptosporidium parvum causes watery diarrhea sometimes accompanied 
by abdominal cramps, nausea, and vomitin...
Special circumstances 
• Outbreaks/food poisoning 
• Overseas travel 
• Immunocompromised host 
• Raw seafood ingestion 
•...
Gastroenteritis :Symptoms and Signs 
• The character and severity of symptoms vary. 
• Generally, onset is sudden, with an...
Gastroenteritis :Symptoms and Signs 
• In viral infections, watery diarrhea is the most common symptom; 
• stools rarely c...
Gastroenteritis :Symptoms and Signs 
• Bacteria that cause invasive disease (eg, Shigella, Salmonella) are more 
likely to...
Diagnosis 
• Clinical evaluation 
• Stool testing in select cases 
• Other GI disorders that cause similar symptoms (eg, a...
History 
• Onset and duration of diarrhea 
• Timing of exposure to potential pathogens 
– Travel, ingestion history, envir...
Physical examination 
• Vital signs: Fever, tachycardia 
• Abdominal tenderness or pain 
• Signs of dehydration 
• Blood, ...
Stool testing: 
• If a rectal examination shows occult blood or if watery diarrhea 
persists > 48 h, 
• stool examination ...
Other Tests 
• All patients with grossly bloody diarrhea should be tested for E. 
coli O157:H7, as should patients with no...
General tests 
• Serum Urea, electrolytes, and creatinine 
should be obtained to evaluate hydration and 
acid-base status ...
Treatment 
• Oral or IV rehydration 
• Consideration of antidiarrheal agents if C. difficile or E. coli O157:H7 
infection...
Treatment 
• Children may become dehydrated more quickly and should be 
given an appropriate rehydration solution (several...
Treatment 
• When the patient can tolerate fluids without vomiting and the appetite 
has begun to return, food may be grad...
Treatment 
• If vomiting is severe and a surgical condition has been 
excluded, an antiemetic may be beneficial. 
• Agents...
Antimicrobials: 
• Empiric antibiotics are generally not recommended except for certain 
cases of traveler's diarrhea or w...
Antibiotics 
• Vibrio cholerae-Doxycycline,TMP-SMX, Ciprofloxacin 
Clostridium difficile-Metronidazole, Vancomycin 
(if fa...
Other antidiarrhoeal 
• The use of probiotics, such as lactobacillus, is 
generally safe and may have some benefit in reli...
Prevention 
• A new oral pentavalent rotavirus vaccine is available that is safe and 
effective against the majority of st...
Classic Syndromes: Acute food poisoning 
• Similar illness in 2 or more persons 
• Epidemiologic evidence of common food s...
Classic Syndromes: Travelers Diarrhea 
• Attack rates of as high 
as 25% 
• 90% brief and self-limited 
• Persistent diarr...
Food-borne illness 
Agent % 
Norovirus 45 
C. perfringens 12 
Salmonella 11 
S. aureus 4 
EHEC (0157) 4 
C. jejuni 4 
B. c...
Nosocomial diarrhea 
• Clostridium difficle 
• Increasing worldwide due 
to hypervirulent strain 
(North American 
Pulsefi...
Evaluation of diarrhea 
• How long has the diarrhea been present? 
• Was it acquired in a particular environment? 
– Hospi...
Is evaluation required in every patient? 
• No 
• Evaluate those with high fever, systemic 
illness, tenesmus, blood/pus i...
Evaluation of Infectious Diarrhea 
• Stool studies 
– fecal leukocytes or lactoferrin, RBC/blood 
– Bacterial culture 
• I...
Fecal PMNs 
• Common in Shigella, 
Campylobacter, EIEC, C. 
diff 
• Less common in 
Salmonella, Yersinia, 
ETEC, EAEC 
• N...
Treatment of Diarrhea 
• Treatment of specific etiology 
• Non-specific treatment 
– hydration 
– Absorptions (Kaopectate®...
Oral rehydration solutions 
Components WHO Ricelyte Pedialyte 
Na (mEq/L) 90 50 45 
K (mEq/L) 20 25 20 
Cl (mEq/L) 80 45...
Why not treat everyone with bacterial 
diarrhea? 
• Some have no effective specific treatment 
• Treatment may not change ...
Who should be treated? 
Antibiotics indicated Antibiotics indicated if 
•Severely ill 
•immunocompromised 
Antibiotics not...
Antibiotic choice 
• E. coli 
– Quinolone 
• Shigella 
– Quinolone or TMP-SMX 
• Vibrio cholera 
– Tetracycline or quinolo...
Bacterial diarrhea 2013 4th year unza medical,by DR MWANSA
Bacterial diarrhea 2013 4th year unza medical,by DR MWANSA
Bacterial diarrhea 2013 4th year unza medical,by DR MWANSA
Bacterial diarrhea 2013 4th year unza medical,by DR MWANSA
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Bacterial diarrhea 2013 4th year unza medical,by DR MWANSA

  1. 1. Enteric Infections Infectious Diarrhea/Gastroenteritis Dr. James C.L.Mwansa Consultant Microbiologist, University Teaching Hospital. Department of Pathology and Microbiology 22nd.October 2013
  2. 2. Anatomy of Digestive Tract  Digestive tract is a “tube” (from mouth to anus); technically “outside” of the body  Lumen = space within tubular or hollow organ such as an artery, vein, or intestine  Intestinal lumen = the inside of the intestine  Mesentery = membrane attaching organ (e.g., intestine) to body wall; often has lymphoid tissue  Food is moved down tract via peristalsis  Entire length of digestive tract epithelium is covered by mucosal membrane (mucosa) with mucus that is secreted from specialized glands  Surface area of intestine increased by presence of villi (finger-like projections) and microvilli that absorb nutrients and other products of digestion
  3. 3. Anatomy of Digestive Tract (cont.)  Mouth, pharynx, esophagus & esophageal sphincter  Stomach and pyloric valve (sphincter)  Small intestine (about 23 feet in length)  Duodenum (~10” in length) (bile & pancreatic ducts carry digestive juices secreted by gall bladder, liver & pancreas)  Jejunum (~8 feet in length)  Ileum (final 3/5 of length) and ileocecal valve  Absorbs bile salts & nutrients, including vitamin B12  Large intestine  Cecum(caecum) (blind pouch where appendix also enters)  Colon (ascending, transverse, descending, sigmoid)  Rectum and anus (with internal and external sphincters)
  4. 4. Overview of Gastroenteritis • Gastroenteritis: Inflammation of the lining of the stomach and small and large intestines. • Most cases are infectious, although gastroenteritis may occur after ingestion of drugs and chemical toxins (eg, metals, plant substances). • Symptoms include anorexia, nausea, vomiting, diarrhea, and abdominal discomfort. • Diagnosis is clinical or by stool culture, although immunoassays are increasingly used. • Treatment is symptomatic, although parasitic and some bacterial infections require specific anti-infective therapy.
  5. 5. • Gastroenteritis is usually uncomfortable but self-limited. • Electrolyte and fluid loss is the main complication • Usually little more than an inconvenience to an otherwise healthy adult but can be grave for people who are very young, elderly, or debilitated or who have serious concomitant illnesses or immunocompromised.
  6. 6. Infectious Diarrhea • 3-5 billion episodes of diarrhoea yearly worldwide • Major cause of worldwide morbidity and mortality • 3 to 6 million deaths yearly, 80% < 1 year of age • Major cause of work/school absenteeism • Major economic burden, especially in developing countries
  7. 7. Organisms • Infectious gastroenteritis may be caused by viruses, bacteria, or parasites • Bacteria – E. Coli, Salmonella, Shigella, Campylobacter, Vibrio, Yersinia, Clostridium difficle, S. aureus, B. cereus, C. botulinum • Viruses – Norovirus, Rotavirus, CMV • Parasites – Giardia, Amoeba, Ascaris, etc
  8. 8. These organisms cause diarrhea through a wide variety of mechanisms Pathophysiology – Osmotic – Secretory – Exudation – Abnormal motility
  9. 9. Osmotic Diarrhea Definition: Increased amounts of poorly absorbed, osmotically active solutes in gut lumen • Interferes with absorption of water • Solutes are ingested (fasting stops diarrhea) – Magnesium sulfate or citrate or magnesium containing antacids – Sorbitol – Malabsorption of food • Lactase deficiency • Celiac sprue • Variety of infectious organisms (particularly viruses)
  10. 10. Secretory Diarrhea • Excess secretion of electrolytes and water across mucosal surface • Usually coupled with inhibition of absorption • Clinical features – stools very watery – stool volume large – fasting does not stop diarrhea
  11. 11. Secretory Diarrhea Bacterial or viral enterotoxins • Vibrio cholerae • Noncholeraic vibrios • Enterotoxigenic E. coli • B. cereus • S. aureus • Others: Rotavirus, Norovirus Non-infectious causes
  12. 12. Watery diarrhea: We wreck the GI: V, R, E, C, the Gi. These organisms wreck the GI and cause watery diarrhea. -V=VIBRIO CHOLERA -R=ROTAVIRUS -E=E COLI, ETEC -C=CRYPTOSPORIDIUM -GI=GIARDIA(PROTOZOA)
  13. 13. Exudative Diarrhea • Intestinal or colonic mucosa inflamed and ulcerated – Leakage of fluid, blood, pus – Impairment of absorption – Increased secretion (prostaglandins) • The extent and location of bowel involved determines – Severity of diarrhea – Systemic signs and symptoms (abdominal pain, fever, leukocytosis, etc) – Tenesmus, urgency
  14. 14. Exudative Diarrhea • Infectious, invasive organisms – Shigella, Campylobacter, Yersinia, E. histolytica, EIEC, C diff – CMV • Idiopathic inflammatory bowel disease – Crohns disease – Ulcerative Colitis • Ischemia
  15. 15. Organisms that cause bloody diarrhea: SEECSY= BLOODY DIARRHEA DOESN'T SOUND SEXY S=SALMONELLA E=E COLI EHEC,ETEC E=ENTAMOEBA (PROTOZOA) C=CAMPYLOBACTER S=SHIGELLA Y=YERSINIA ENTEROCOLITICA
  16. 16. Invasive organisms produce leukocytes and blood in stool A laboratory equivalent of this is the presence of lactoferrin in a sample of stool
  17. 17. Abnormal Motility • Increased colonic motility – Irritable bowel syndrome • Increased small bowel motility – Hyperthyroidism, post-operative dumping • Decreased small bowel motility – Scleroderma, with bacterial overgrowth • Anal sphincter dysfunction – Incontinence
  18. 18. Diarrhea • Non-inflammatory – Watery diarrhea, no blood or mucus or pus in stool, no fever or systemic signs – Secretory or osmotic mechanism – Dehydration may occur – Generally self-limited and more benign – Therapy generally supportive • Inflammatory – Frequent lower volume stool, mucoid, bloody, or purulent. Often with fever or systemic signs, tenesmus, urgency – Exudative mechanism – Dehydration rare – Less benign
  19. 19. Bloody Vs Watery diarrhoea • bloody diarrhoea - if there is necrosis of epithelium 1. invasive organisms - like Salmonella and Shigella which kill enterocytes 2. toxins which lead to necrosis • watery diarrhoea - without necrosis,if 1. bacteria cover absorptive surface or 2. decrease intestinal villi (due to toxins) so less can be absorbed from the intestines or 3. increase water and electrolytes secretion (due to toxins)
  20. 20. Common syndromes of infectious diarrhea • Food poisoning • Acute watery diarrhea – Travelers diarrhea – Epidemics • Acute bloody diarrhea – Dysentery
  21. 21. Viruses • Viruses the most common cause of gastroenteritis. • They infect enterocytes in the villous epithelium of the small bowel. • The result is transudation of fluid and salts into the intestinal lumen; • Sometimes, malabsorption of carbohydrates worsens symptoms by causing osmotic diarrhea. • Diarrhea is mostly watery.
  22. 22. Viruses • Four categories of viruses cause most gastroenteritis: • rotavirus and calicivirus (predominantly the norovirus [formerly Norwalk virus]) cause the majority of viral gastroenteritis, followed by astrovirus and enteric adenovirus. • Rotavirus is the most common cause of sporadic, severe, dehydrating diarrhea in young children (peak incidence, 3 to 15 mo). • Rotavirus is highly contagious; most infections occur by the fecal-oral route. • Adults may be infected after close contact with an infected infant. The illness in adults is generally mild. Incubation is 1 to 3 days.
  23. 23. Viruses • Norovirus most commonly infects older children and adults. Infections occur year-round. Norovirus is the principal cause of sporadic viral gastroenteritis in adults and of epidemic viral gastroenteritis in all age groups; large waterborne and food-borne outbreaks occur. Person-to-person transmission also occurs because the virus is highly contagious. Incubation is 24 to 48 h. • Astrovirus can infect people of all ages but usually infects infants and young children. Infection is most common in winter. Transmission is by the fecal-oral route. Incubation is 3 to 4 days. • Adenoviruses are the 4th most common cause of childhood viral gastroenteritis. Infections occur year-round, with a slight increase in summer. Children < 2 yr are primarily affected. Transmission is by the fecal-oral route. Incubation is 3 to 10 days. • In immunocompromised patients, additional viruses (eg, cytomegalovirus, enterovirus) can cause gastroenteritis.
  24. 24. Bacteria: • The bacteria most commonly implicated include: • Salmonella,Campylobacter,Shigella,Escherichia coli (especially serotype O157:H7) • Bacterial gastroenteritis is less common than viral. • Bacteria cause gastroenteritis by several mechanisms. • Certain species (eg, Vibrio cholerae, enterotoxigenic strains of E. coli) adhere to intestinal mucosa without invading and produce enterotoxins. These toxins impair intestinal absorption and cause secretion of electrolytes and water by stimulating adenylate cyclase, resulting in watery diarrhea. Clostridium difficile produces a similar toxin when overgrowth follows antibiotic use • Some bacteria (eg, Staphylococcus aureus, Bacillus cereus, Clostridium perfringens) produce an exotoxin that is ingested in contaminated food. The exotoxin can cause gastroenteritis without bacterial infection. These toxins generally cause acute nausea, vomiting, and diarrhea within 12 h of ingestion of contaminated food. Symptoms abate within 36 h.
  25. 25. Bacteria that invade mucosa • (eg, Shigella, Salmonella, Campylobacter, some E. coli subtypes) invade the mucosa of the small bowel or colon and cause microscopic ulceration, bleeding, exudation of protein-rich fluid, and secretion of electrolytes and water. • The invasive process and its results can occur whether or not the organism produces an enterotoxin. The resulting diarrhea contains WBCs and RBCs and sometimes gross blood. • Salmonella and Campylobacter are the most common bacterial causes of diarrheal illness . Both infections are most frequently acquired through undercooked poultry; unpasteurized milk is also a possible source. • Campylobacter is occasionally transmitted from dogs or cats with diarrhea. • Salmonella can be transmitted by undercooked eggs and poultry food. • Shigella are usually transmitted person to person, although food-borne epidemics occur. Shigella dysenteriae type 1 produces Shiga toxin, which can cause hemolytic-uremic syndrome (HUS)
  26. 26. subtypes of E. coli causing diarrhea Epidemiology and clinical manifestations vary depending on the subtype: • (1) Enterohemorrhagic E. coli (EHEC) is the most clinically significant subtype . • It produces Shiga toxin, which causes bloody diarrhea (hemorrhagic colitis). E. coli O157:H7 is the most common strain of this subtype . Undercooked ground beef, unpasteurized milk and juice, and contaminated water are possible sources. • Person-to-person transmission is common in the day care setting. Hemolytic-uremic syndrome is a serious complication that develops in 2 to 7% of cases, most commonly among the young and old. • (2) Enterotoxigenic E. coli (ETEC) produces two toxins (one similar to cholera toxin) that cause watery diarrhea. This subtype is the most common cause of traveler's diarrhea. • (3) Enteropathogenic E. coli (EPEC)causes watery diarrhea. A common cause of diarrhea outbreaks in nurseries. • (4) Enteroinvasive E. coli (EIEC)causes bloody or nonbloody diarrhea, primarily in the developing world.
  27. 27. Other bacteria causing gastroenteritis, • V. cholerae causes severe dehydrating diarrhea in approx 2% population • Yersinia enterocolitica can cause gastroenteritis or a syndrome that mimics appendicitis. • It is transmitted by undercooked pork, unpasteurized milk, or contaminated water. • Several other Vibrio species (eg, V. parahaemolyticus) cause diarrhea after ingestion of undercooked seafood. • Listeria causes food-borne gastroenteritis. • Aeromonas is acquired from swimming in or drinking contaminated fresh or sea water. • Plesiomonas shigelloides can cause diarrhea in patients who have eaten raw shellfish or traveled to tropical regions of the developing world.
  28. 28. Parasites: • The parasites most commonly implicated are Entamoeba histolytica Giardia,Cryptosporidium, Isospora belli • Adhere to or invade the intestinal mucosa, causing nausea, vomiting, diarrhea, and general malaise. • Entamoeba histolytica (amebiasis) is a common cause of subacute bloody diarrhea in the developing world • Giardiasis occurs throughout the world. The infection can become chronic and cause a malabsorption syndrome. It is usually acquired via person-to-person transmission (often in day care centers) or from contaminated water.
  29. 29. Parasites • Cryptosporidium parvum causes watery diarrhea sometimes accompanied by abdominal cramps, nausea, and vomiting. • In healthy people, the illness is self-limited, lasting about 2 wk. In immunocompromised patients(HIV), illness may be severe, causing substantial electrolyte and fluid loss. Cryptosporidium is usually acquired through contaminated water. • Other parasitesthat can cause symptoms similar to those of cryptosporidiosis include • Cyclospora cayetanensis and, in immunocompromised patients, Cystoisospora (Isospora) belli, • A collection of organisms referred to as microsporidia (eg, Enterocytozoon bieneusi,Encephalitozoon intestinalis).
  30. 30. Special circumstances • Outbreaks/food poisoning • Overseas travel • Immunocompromised host • Raw seafood ingestion • Antibiotic usage
  31. 31. Gastroenteritis :Symptoms and Signs • The character and severity of symptoms vary. • Generally, onset is sudden, with anorexia, nausea, vomiting, borborygmi, abdominal cramps, and diarrhea (with or without blood and mucus). Malaise, myalgias, and prostration may occur. • The abdomen may be distended and mildly tender; in severe cases, muscle guarding may be present. • Gas-distended intestinal loops may be palpable. Borborygmi are present even without diarrhea (an important differential feature from paralytic ileus). • Persistent vomiting and diarrhea can result in intravascular fluid depletion with hypotension and tachycardia. In severe cases, shock, with vascular collapse and oliguric renal failure, occurs. • If vomiting is the main cause of fluid loss, metabolic alkalosis with hypochloremia can occur. • If diarrhea is more prominent, acidosis is more likely. Both vomiting and diarrhea can cause hypokalemia. • Hyponatremia may develop, particularly if hypotonic fluids are used in replacement therapy.
  32. 32. Gastroenteritis :Symptoms and Signs • In viral infections, watery diarrhea is the most common symptom; • stools rarely contain mucus or blood. • Rotavirus gastroenteritis in infants and young children may last 5 to 7 days. • Vomiting occurs in 90% of patients, and fever > 39° occurs in about 30%. • Norovirus typically causes acute onset of vomiting, abdominal cramps, and diarrhea, with symptoms lasting only 1 to 2 days. • In children, vomiting is more prominent than diarrhea, whereas in adults, diarrhea usually predominates. • Patients may also experience fever, headache, and myalgias. • The hallmark of adenovirus gastroenteritis is diarrhea lasting 1 to 2 wk. • Affected infants and children may have mild vomiting that typically starts 1 to 2 days after the onset of diarrhea. • Low-grade fever occurs in about 50% of patients. Astrovirus causes a syndrome similar to mild rotavirus infection.
  33. 33. Gastroenteritis :Symptoms and Signs • Bacteria that cause invasive disease (eg, Shigella, Salmonella) are more likely to result in fever, prostration, and bloody diarrhea. • Bacteria that produce an enterotoxin (eg, S. aureus, B. cereus, C. perfringens) usually cause watery diarrhea. • Parasitic infections typically cause subacute or chronic diarrhea. • Most cause nonbloody diarrhea; • an exception is E. histolytica, which causes amebic dysentery. • Fatigue and weight loss are common when diarrhea is persistent.
  34. 34. Diagnosis • Clinical evaluation • Stool testing in select cases • Other GI disorders that cause similar symptoms (eg, appendicitis, cholecystitis, ulcerative colitis) must be excluded. • Findings suggestive of gastroenteritis include copious, watery diarrhea; • Ingestion of potentially contaminated food (particularly during a known outbreak), untreated surface water, or a known GI irritant; • Recent travel; or contact with similarly ill people. • E. coli O157:H7–induced diarrhea is notorious for appearing to be a hemorrhagic rather than an infectious process, manifesting as GI bleeding with little or no stool. • Hemolytic-uremic syndrome may follow as evidenced by renal failure and hemolytic anemia • Recent oral antibiotic use (within 3 mo) must raise suspicion for C. difficile infection
  35. 35. History • Onset and duration of diarrhea • Timing of exposure to potential pathogens – Travel, ingestion history, environment, recent medications (antibiotics), age • Character of stool – Volume, presence of blood, mucus, or pus • Associated symptoms and signs – Abdominal pain, fever, vomiting, dehydration
  36. 36. Physical examination • Vital signs: Fever, tachycardia • Abdominal tenderness or pain • Signs of dehydration • Blood, mucus, or pus in stool
  37. 37. Stool testing: • If a rectal examination shows occult blood or if watery diarrhea persists > 48 h, • stool examination (fecal WBCs, ova, parasites) and culture are indicated. • However, for the diagnosis of giardiasis or cryptosporidiosis, stool antigen detection using an enzyme immunoassay has a higher sensitivity. • Rotavirus and enteric adenovirus infections can be diagnosed using commercially available rapid assays that detect viral antigen in the stool, but these are usually done only to document an outbreak.
  38. 38. Other Tests • All patients with grossly bloody diarrhea should be tested for E. coli O157:H7, as should patients with nonbloody diarrhea during a known outbreak. • Specific cultures must be requested because this organism is not detected on standard stool culture media. • Alternatively, a rapid enzyme assay for the detection of Shiga toxin in stool can be done; a positive test indicates infection with E. coli O157:H7 or one of the other serotypes of enterohemorrhagic E. coli. • Adults with grossly bloody diarrhea should have sigmoidoscopy with cultures and biopsy. • Appearance of the colonic mucosa may help diagnose amebic dysentery, shigellosis, and E. coli O157:H7 infection, although ulcerative colitis may cause similar lesions. • Patients with recent antibiotic use should have a stool assay for C. difficile toxin.
  39. 39. General tests • Serum Urea, electrolytes, and creatinine should be obtained to evaluate hydration and acid-base status in patients who appear seriously ill. Full blood count is nonspecific, although eosinophilia may indicate parasitic infection.
  40. 40. Treatment • Oral or IV rehydration • Consideration of antidiarrheal agents if C. difficile or E. coli O157:H7 infection is not suspected • Antibiotics only in select cases • Supportive treatment is all that is needed for most patients. Bed rest with convenient access to a toilet or bedpan is desirable. Oral glucose-electrolyte solutions, broth, or bouillon may prevent dehydration or treat mild dehydration. Even if vomiting, the patient should take frequent small sips of such fluids: vomiting may abate with volume replacement. For patients with E. coli O157:H7 infection, rehydration with isotonic IV fluids may attenuate the severity of any renal injury should hemolytic-uremic syndrome develop.
  41. 41. Treatment • Children may become dehydrated more quickly and should be given an appropriate rehydration solution (several are available commercially. • Carbonated beverages and sports drinks lack the correct ratio of glucose to Na and thus are not appropriate for children < 5 yr. • If the child is breastfed, breastfeeding should continue. • If vomiting is protracted or if severe dehydration is prominent, IV replacement of volume and electrolytes is necessary
  42. 42. Treatment • When the patient can tolerate fluids without vomiting and the appetite has begun to return, food may be gradually restarted. • There is no demonstrated benefit from restriction to bland food (eg, cereal, gelatin, bananas, toast). • Some patients have temporary lactose intolerance. • Antidiarrheal agents are safe for patients > 5 yr with watery diarrhea (as shown by heme-negative stool). • However, antidiarrheals may cause deterioration of patients with C. difficile or E. coli O157:H7 infection and thus should not be given to any patient with recent antibiotic use or heme-positive stool, pending specific diagnosis. • Effective antidiarrheals include loperamide initially, followed by 2 mg po for each subsequent episode of diarrhea (maximum of 6 doses/day or 16 mg/day), or diphenoxylate 2.5 to 5 mg tid or qid in tablet or liquid form. 4 mg po
  43. 43. Treatment • If vomiting is severe and a surgical condition has been excluded, an antiemetic may be beneficial. • Agents useful in adults include prochlorperazine 5 to 10 mg IV tid or qid, or 25 mg per rectum bid; • and promethazine 12.5 to 25 mg IM tid or qid, or 25 to 50 mg per rectum qid. • These drugs are usually avoided in children because of lack of demonstrated efficacy and the high incidence of dystonic reactions.
  44. 44. Antimicrobials: • Empiric antibiotics are generally not recommended except for certain cases of traveler's diarrhea or when suspicion of Shigella or Campylobacter infection is high • antibiotics should not be given until stool culture results are known, particularly in children, who have a higher rate of infection with E. coliO157:H7 (antibiotics increase the risk of hemolytic-uremic syndrome in patients infected withE. coli O157:H7). • In proven bacterial gastroenteritis, antibiotics are not always required. • They do not help withSalmonella and prolong the duration of shedding in the stool. • Exceptions include immunocompromised patients, neonates, and patients with Salmonella bacteremia. • Antibiotics are also ineffective against toxic gastroenteritis (eg, S. aureus, B. cereus, C. perfringens). • Indiscriminate use of antibiotics fosters the emergence of drug-resistant organisms. However, certain infections do require antibiotics
  45. 45. Antibiotics • Vibrio cholerae-Doxycycline,TMP-SMX, Ciprofloxacin Clostridium difficile-Metronidazole, Vancomycin (if fails,metronidazole Shigella Nalidixic acid • Ciprofloxacin,TMP-SMX • Giardia intestinalis (lamblia) • Metronidazole,Nitazoxanide Entamoeba histolytica, Metronidazole Campylobacterjejuni-Ciprofloxacin,Azithromycin
  46. 46. Other antidiarrhoeal • The use of probiotics, such as lactobacillus, is generally safe and may have some benefit in relieving symptoms. • They can be given in the form of yogurt with active cultures. • For cryptosporidiosis, nitazoxanide may be helpful in immuno competent patients.
  47. 47. Prevention • A new oral pentavalent rotavirus vaccine is available that is safe and effective against the majority of strains responsible for disease. This vaccine is now part of the recommended infant vaccination schedule and is given at 2, 4, and 6 mo of • Prevention of infection is complicated by the frequency of asymptomatic infection and the ease with which many agents, particularly viruses, are transmitted from person to person. • In general, proper procedures for handling and preparing food must be followed. • Travelers must avoid potentially contaminated food and drink. • Breastfeeding affords some protection to neonates and infants. • Caregivers should wash their hands thoroughly with soap and water after changing diapers, and diaper-changing areas should be disinfected • Children with diarrhea should be excluded from child care facilities for the duration of symptoms. • Children infected with enterohemorrhagic E. coli or Shigella should also
  48. 48. Classic Syndromes: Acute food poisoning • Similar illness in 2 or more persons • Epidemiologic evidence of common food source • Onset of symptoms typically within 6 hours of ingestion • Nausea and vomiting prominent • Preformed toxin of S. aureus or B. cereus • Longer incubation periods for C. perfringens
  49. 49. Classic Syndromes: Travelers Diarrhea • Attack rates of as high as 25% • 90% brief and self-limited • Persistent diarrhea in 1-2% • Depends on destination, eating habits, length of stay Pathogen % ETEC 40 EAEC 15 C. jejuni 10 Shigella 10 EHEC or EIEC <5 Salmonella < 5 Vibrio < 5
  50. 50. Food-borne illness Agent % Norovirus 45 C. perfringens 12 Salmonella 11 S. aureus 4 EHEC (0157) 4 C. jejuni 4 B. cereus 2 Shellfish-borne % Norovirus 52 Vibrio 37 Salmonella <1 Other 10
  51. 51. Nosocomial diarrhea • Clostridium difficle • Increasing worldwide due to hypervirulent strain (North American Pulsefield type 1) • High fluoroquinolone resistance • Less responsive to usual therapy (metronidazole) • Higher complication rate
  52. 52. Evaluation of diarrhea • How long has the diarrhea been present? • Was it acquired in a particular environment? – Hospital – Recent antibiotic use – While traveling – Day care, cruise ship, picnic, etc – Exposure to sick persons • What are the characteristics of the diarrhea – Is there blood, mucus, or pus in the stool – Is it high volume or low volume – Is there associated tenesmus or urgency • What are the associated symptoms? – Fever, abdominal pain, vomiting, dehydration
  53. 53. Is evaluation required in every patient? • No • Evaluate those with high fever, systemic illness, tenesmus, blood/pus in stool, dehydration, immunocompromised, prolonged course • Remainder can often be managed without specific diagnosis with rehydration and anti-peristaltic agents
  54. 54. Evaluation of Infectious Diarrhea • Stool studies – fecal leukocytes or lactoferrin, RBC/blood – Bacterial culture • Include C. difficle toxin assay • May need to request EHEC screen • Endoscopic evaluation may be useful in some – especially for bloody diarrhea or chronic diarrhea
  55. 55. Fecal PMNs • Common in Shigella, Campylobacter, EIEC, C. diff • Less common in Salmonella, Yersinia, ETEC, EAEC • Now largely replaced with fecal lactoferrin
  56. 56. Treatment of Diarrhea • Treatment of specific etiology • Non-specific treatment – hydration – Absorptions (Kaopectate®) – Bismuth – Antiperistaltics/opiate derivatives – Fiber supplementation
  57. 57. Oral rehydration solutions Components WHO Ricelyte Pedialyte Na (mEq/L) 90 50 45 K (mEq/L) 20 25 20 Cl (mEq/L) 80 45 35 Citrate (mEq/L) 30 34 30 Glucose (g/L) 20 30 25
  58. 58. Why not treat everyone with bacterial diarrhea? • Some have no effective specific treatment • Treatment may not change disease duration or severity • Treatment may predispose to carrier state • Treatment may produce complications (HUS, antibiotic resistance, C. difficle, toxic megacolon)
  59. 59. Who should be treated? Antibiotics indicated Antibiotics indicated if •Severely ill •immunocompromised Antibiotics not indicated Shigella Campylobacter EHEC ETEC Yersinia viruses V. cholera EAEC Food poisoning C. diff Salmonella
  60. 60. Antibiotic choice • E. coli – Quinolone • Shigella – Quinolone or TMP-SMX • Vibrio cholera – Tetracycline or quinolone • Salmonella – Quinolone or TMP-SMX • Campylobacter – Erythromycin or quinolone • Yersinia – tetracycline, TMP-SMX, or quinolone
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AN OUTLINE OF BACTERIAL DIARRHEA

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