Bacterial Diarrhea

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Bacterial Diarrhea

• Chris E. Forsmark, M.D.
• Division of Gastroenterology, Hepatology, and
  Nutrition

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Infectious Diarrhea

• 3-5 billion episodes yearly
• Major cause of worldwide morbidity and mortality
• 5 million deaths yearly, 80 lt 1 year of age
• Major cause of work/school absenteeism
• Major economic burden, especially in developing
  countries

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Organisms

• Bacteria
• E. Coli, Salmonella, Shigella, Campylobacter,
  Vibrio, Yersinia, Clostridium difficle
• Viruses
• Norwalk agent, Rotavirus
• Parasites
• Giardia, Amoeba

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How do these organisms cause diarrhea?

• Pathophysiology
• Osmotic
• Secretory
• Exudation
• Abnormal motility

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Osmotic Diarrhea
Definition Increased amounts of poorly absorbed,
osmotically active solutes in gut lumen

• Interferes with absorption of water
• Solutes are ingested
• Magnesium sulfate or citrate or magnesium
  containing antacids
• Sorbitol
• Malabsorption of food
• Lactase deficiency
• Celiac sprue
• Variety of infectious organisms (particularly
  viruses)

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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

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Secretory Diarrhea

• Bacterial or viral enterotoxins
• Cholera, enterotoxigenic E. coli, B. cereus, S.
  aureus, Rotavirus, Norwalk virus
• Hormonal secretagogues
• Certain laxatives (castor oil, senna)

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Exudative Diarrhea

• Intestinal or colonic mucosa inflamed and
  ulcerated
• Leakage of fluid, blood, pus
• Impairment of absorption
• Increased secretion (prostaglandins)
• The extent of bowel involved determines
• Severity of diarrhea
• Systemic signs and symptoms (abdominal pain,
  fever, etc)

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Exudative Diarrhea

• Infectious, invasive organisms
• Shigella, Campylobacter, Yersinia, E.
  histolytica, EHEC, C diff
• Idiopathic inflammatory bowel disease
• Crohns disease
• Ulcerative Colitis
• Ischemia

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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

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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

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Common syndromes of infectious diarrhea

• Food poisoning
• Acute watery diarrhea
• Travelers diarrhea
• Epidemics
• Acute bloody diarrhea
• Dysentery

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Special circumstances

• Outbreaks/food poisoning
• Overseas travel
• Immunocompromised host
• Raw seafood ingestion
• Antibiotic usage

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Host defense factors

• Gastric acidity
• Intestinal motility
• Intestinal microflora
• Mucus
• Systemic and local immune mechanisms
• Others (e.g. breast feeding)

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Bacterial virulence factors

• Adherence
• Enterotoxin production
• Cytotoxin production
• Mucosal invasion

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Mechanisms of infection

• Ingestion of preformed toxin (food poisoning)
• Fecal-oral contamination
• Food, flies, fingers, feces, and fomites
• Contaminated food
• Animal reservoir
• Fecal-oral contamination of food
• Infectious dose varies (100 to 109)

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History

• Onset and duration of diarrhea
• Timing of exposure to potential pathogens
• Travel, ingestion history, environment, recent
  medications, age
• Character of stool
• Volume, presence of blood, mucus, or pus
• Associated symptoms and signs
• Abdominal pain, fever, vomiting, dehydration

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Physical examination

• Vital signs Fever, tachycardia
• Abdominal tenderness or pain
• Signs of dehydration
• Blood in stool

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E. coli
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Nontyphoidal Salmonella

• Salmonella typhimurium and enteritidis
• Clinical syndromes
• Gastroenteritis and colitis
• Bacteremia and endocarditis
• Enteric fever (typhi and paratyphi)
• Localized tissue infection
• Carrier state (gt 1 year)
• Food-borne illness (poultry, meat, eggs)

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Shigella

• dysenteriae, flexneri, boydii, sonnei
• Watery or bloody diarrhea
• May be complicated by reactive arthritis and
  rarely HUS
• Very infectious ( 100 organisms cause disease)

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Campylobacter

• Mainly C. jejuni
• Transmission from infected animals or food
  products, fresh or salt water
• Watery diarrhea or dysentery
• May be complicated by Guillain-Barré and IPSID

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Vibrio

• Cholera
• Enterotoxin elaborated causes severe watery
  diarrhea
• Complications common due to dehydration

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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

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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

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Food-borne illness
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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

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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

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Is evaluation required in every patient?

• No
• Evaluate those with high fever, systemic illness,
  tenesmus, blood/pus in stool, dehydration,
  immunocompromised
• Remainder can often be managed without specific
  diagnosis with rehydration and antiperistaltic
  agents

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Evaluation of Infectious Diarrhea

• Stool studies
• fecal leukocytes and 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

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Fecal PMNs

• Common in Shigella, Campylobacter, EHEC, EIEC, C.
  diff
• Rare in Salmonella, Yersinia, ETEC, EAEC

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Treatment of Diarrhea

• Treatment of specific etiology
• Non-specific treatment
• hydration
• Absorptions (Kaopectate)
• Bismuth
• Antiperistaltics/opiate derivatives
• Fiber supplementation

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Oral rehydration solutions
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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)

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Who should be treated?
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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