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Acute Infectious Diarrheal Diseases and Bacterial Food Poisoning

Chapter 138 | Part 5: Infectious Diseases · Part 5 – Infectious Diseases: Bacterial · Chapter 138


Key Clinical Points

  1. Diarrhea is defined as the passage of loose or watery stools conforming to the shape of a container three or more times in a 24-h period.
  2. Symptoms of severe dehydration include lethargy, obtundation, feeble pulse, hypotension, and shock; these require IV fluids (e.g., Ringer's lactate).
  3. Bloody stools without fecal leukocytes should alert the laboratory to the possibility of infection with Shiga toxin–producing enterohemorrhagic Escherichia coli (EHEC).
  4. 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.
  5. Antibacterial agents should not be administered to individuals in whom enterohemorrhagic E. coli infection is suspected, as antibiotics may increase the risk of hemolytic-uremic syndrome (HUS) and renal failure.
  6. Traveler's diarrhea is most commonly caused by enterotoxigenic Escherichia coli (10–45%) and enteroaggregative E. coli (5–35%).
  7. Staphylococcal food poisoning has the shortest incubation period (1–6 h) and is associated with contaminated foods like ham, poultry, potato salad, and mayonnaise.
  8. Campylobacter jejuri is especially common in areas of Asia and is a major cause of reactive arthritis following infection with invasive organisms.
  9. Oral rehydration solution (ORS) is the mainstay of treatment for acute diarrheal diseases; WHO recommends reduced-osmolarity/reduced-salt ORS.
  10. Prophylactic antimicrobial agents are not generally recommended for the prevention of traveler's diarrhea except when travelers are immunocompromised or have underlying illness.

1. DEFINITION & OVERVIEW

Definition: Diarrhea is the passage of loose or watery stools that conform to the shape of a container three or more times in a 24-h period.

Global Impact: Acute diarrheal disease is a leading cause of illness globally, associated with an estimated 1.57 million deaths per year.

Pediatric Risk: In low- and middle-income countries, one in ten deaths among children <5 years of age is attributable to diarrhea.

Long-term Consequences: Recurrent intestinal infections are associated with physical and mental stunting, wasting, micronutrient deficiencies, and malnutrition.


2. EPIDEMIOLOGY

General Trends: Diarrhea mortality has decreased substantially in the past three decades.

Traveler's Diarrhea: Most common travel-related infectious illness, affecting 20–50% of people traveling from temperate industrialized countries to tropical regions of Asia, Africa, and Central and South America.

Timeline: Onset is usually 3 days to 2 weeks after arrival; most cases begin within the first 3–5 days. The illness is generally self-limited, lasting 1–5 days.

Outbreak Settings: Closed and semi-closed communities (day-care centers, schools, cruise ships) are important settings for outbreaks of enteric infections.

Key Pathogens by Setting: ◦ Norovirus: Most common etiologic agent associated with outbreaks in these settings. ◦ Clostridioides difficile: Predominant cause of nosocomial diarrhea among adults in the United States.

Table 138-3 Causes of Traveler's Diarrhea

ETIOLOGIC AGENT APPROXIMATE PERCENTAGE OF CASES COMMENTS
Bacteria 50–75
Enterotoxigenic Escherichia coli 10–45 Single most important agent
Enteroaggregative E. coli 5–35 Emerging enteric pathogen with worldwide distribution
Campylobacter jejuri 5–25 More common in Asia
Shigella 0–15 Major cause of dysentery
Salmonella 0–15
Others 0–5 Including Aeromonas, Plesiomonas, and Vibrio cholerae
Viruses 0–20
Norovirus 0–10 Associated with cruise ships
Rotavirus 0–5 Particularly common among children
Parasites 0–10
Giardia lamblia 0–5 Affects hikers and campers who drink from freshwater streams
Cryptosporidium 0–5 Resistant to chlorine treatment of water sources
Entamoeba histolytica <1
Cyclospora <1
Other 0–10
Acute food poisoning 0–5
No pathogen identified 10–50

2.1 Travel History

• 20–50% of travelers to tropical regions experience sudden onset of abdominal cramps, anorexia, and watery diarrhea.

• Enterotoxigenic and enteroaggregative E. coli are the most common pathogens in classic secretory traveler's diarrhea syndrome.

• Campylobacter jejuni is especially common in Asia.

• Norovirus is highly contagious and associated with outbreaks on cruise ships.

• Rotavirus is rarely a cause of pediatric diarrheal outbreaks in the US since 2006 vaccination.

2.2 Location

• Closed communities (day-care centers, cruise ships) are key settings for enteric infections.

• C. difficile is the predominant cause of nosocomial diarrhea in adults.

• Norovirus outbreaks are common in healthcare settings.

• Klebsiella oxytoca causes antibiotic-associated hemorrhagic colitis.

• Enteropathogenic E. coli outbreaks occur in newborn nurseries.

• One-third of elderly patients in chronic-care institutions develop significant diarrheal illness annually.

2.3 Age

• Children <5 years account for most global morbidity/mortality from enteric pathogens.

• Breast-fed infants are protected until solid foods are introduced.

• Rotavirus infection is universal in unvaccinated children (first or second year of life).

• Norovirus infections are more common in older children and adults.

• Enterotoxigenic, enteropathogenic, and enterohemorrhagic E. coli; Shigella; C. jejuni; and Giardia lamblia have higher attack rates in children.

2.4 Host Immune Status

• Immunocompromised hosts are at elevated risk of acute/chronic infectious diarrhea.

• Cell-mediated immunity defects (AIDS) increase risk of invasive enteropathies (salmonellosis, listeriosis, cryptosporidiosis).

• Hypogammaglobulinemia increases risk of C. difficile colitis and giardiasis.

• Cancer patients are more likely to develop C. difficile due to antibiotic exposure/hospitalizations.

• Infectious diarrhea can be life-threatening in immunocompromised hosts with complications like persistent infection, bacteremia, and metastatic seeding.


3. ETIOLOGY & PATHOPHYSIOLOGY

• Enteric pathogens use multiple mechanisms to overcome host defenses: inoculum size, adherence, toxin production, invasion, intestinal motility, mucin disruption, immunity, and genetic determinants.

• Understanding virulence factors is critical for diagnosis/treatment.

Table 138-1 Gastrointestinal Pathogens Causing Acute Diarrhea

MECHANISM LOCATION ILLNESS STOOL FINDINGS EXAMPLES OF PATHOGENS INVOLVED
Noninflammatory (enterotoxin) Proximal small bowel Watery diarrhea No fecal leukocytes; mild or no increase in fecal lactoferrin Vibrio cholerae, enterotoxigenic Escherichia coli (LT and/or ST), enteroaggregative E. coli, Clostridium perfringens, Bacillus cereus, Staphylococcus aureus, Aeromonas hydrophila, Plesiomonas shigelloides, rotavirus, norovirus, enteric adenoviruses, Giardia lamblia, Cryptosporidium spp., Cyclospora spp., microsporidia
Inflammatory (invasion or cytotoxin) Colon or distal small bowel Dysentery or inflammatory diarrhea Fecal polymorphonuclear leukocytes; substantial increase in fecal lactoferrin Shigella spp., Salmonella spp., Campylobacter jejuri, enterohemorrhagic E. coli, enteroinvasive E. coli, Yersinia enterocolitica, Listeria monocytogenes, Vibrio parahaemolyticus, Clostridium difficile, A. hydrophila, P. shigelloides, Entamoeba histolytica, Klebsiella oxytoca
Penetrating Distal small bowel Enteric fever Fecal mononuclear leukocytes Salmonella Typhi, Y. enterocolitica

3.1 Inoculum Size

• Shigella, EHEC, Giardia, Entamoeba: 10–100 organisms needed to cause infection.

• Vibrio cholerae: 10^5–10^8 organisms required.

• Salmonella inoculum varies by species, host, and food vehicle.

• Shigella, EHEC, Giardia, Entamoeba can spread via person-to-person contact.

• Salmonella may require growth in food before reaching infectious dose.

3.2 Adherence

• Pathogens must adhere to gastrointestinal mucosa to initiate infection.

• V. cholerae uses toxin-coregulated pilus for adherence.

• Enterotoxigenic E. coli requires colonization factor antigen for upper small intestine colonization.

• EPEC and EHEC produce virulence determinants that allow attachment/effacement of intestinal epithelium.

3.3 Toxin Production

• Enterotoxins (cholera toxin, LT, ST) cause watery diarrhea via secretory mechanisms.

• Cytotoxins (Shigella dysenteriae type 1, V. parahaemolyticus, C. difficile) cause dysentery with bloody stools.

• Neurotoxins (staphylococcal, B. cereus) act on CNS to produce vomiting.

3.4 Invasion

• Shigella and EIEC invade mucosal epithelial cells, causing dysentery.

• Salmonella invades bowel mucosa but generally does not cause full dysentery syndrome.

• S. Typhi and Y. enterocolitica penetrate intestinal mucosa, multiply in Peyer patches, and disseminate via bloodstream to cause enteric fever.

3.5 Intestinal Motility

• Impaired motility (opioids, anatomic abnormalities) increases small bowel infection risk.

• Lomotil treatment for Shigella may prolong fever/organism shedding.

• Opioid use in Salmonella gastroenteritis increases bacteremia risk.

3.6 Intestinal Mucin

• Mucus barrier separates commensal microbiota from epithelium.

• Pathogens overcome mucus via enzyme secretion, flagella-mediated motility, or toxin diffusion.

• Shigella toxins disrupt mucus production to reach cell surface.

3.7 Immunity

• Humoral immunity (IgG, IgM, secretory IgA) and mucosal immune responses protect against enteric pathogens.

• M cells in distal small bowel bind bacterial antigens, leading to lymphocyte proliferation and IgA-secreting plasma cell formation.

3.8 Genetic Determinants

• Blood group O increases susceptibility to V. cholerae, Shigella, E. coli O157, norovirus.

• Polymorphisms in inflammatory mediator genes affect outcomes for EAggEC, STEC, Salmonella, C. difficile, and V. cholerae.

3.9 Host Defenses

• Intestinal microbiota provide colonization resistance via geographic/nutritional exclusion.

• Patients with fewer intestinal bacteria (infants, antibiotic users) are at higher infection risk.

• Acidic pH of stomach and volatile fatty acids from colonic microbiota inhibit pathogen colonization.

• Gastric surgery/achlorhydria increase infection risk with Salmonella, G. lamblia, helminths.

• Rotavirus and Shigella are resistant to gastric acidity.


4. CLINICAL MANIFESTATIONS

Definition: Diarrhea is the passage of loose or watery stools that conform to the shape of a container three or more times in a 24-h period.

Key Discriminators: ◦ Blood/mucus in stool → indicates ulceration. ◦ Rice-water stools → suggests cholera or similar toxigenic process. ◦ Tenesmus → feature of shigellosis or amebiasis. ◦ Abdominal pain severity → reflects inflammatory processes (e.g., Shigella, Campylobacter). ◦ Vomiting patterns → distinguish toxin-mediated vs. systemic illness.

Dehydration Assessment: ◦ Mild: thirst, dry mouth, decreased urine output. ◦ Moderate: orthostatic fall in BP, sunken eyes. ◦ Severe: lethery, obtundation, feeble pulse, hypotension, and shock.

Table 138-1 Gastrointestinal Pathogens Causing Acute Diarrhea

MECHANISM LOCATION ILLNESS STOOL FINDINGS EXAMPLES OF PATHOGENS INVOLVED
Noninflammatory (enterotoxin) Proximal small bowel Watery diarrhea No fecal leukocytes; mild or no increase in fecal lactoferrin Vibrio cholerae, enterotoxigenic Escherichia coli (LT and/or ST), enteroaggregative E. coli, Clostridium perfringens, Bacillus cereus, Staphylococcus aureus, Aeromonas hydrophila, Plesiomonas shigelloides, rotavirus, norovirus, enteric adenoviruses, Giardia lamblia, Cryptosporidium spp., Cyclospora spp., microsporidia
Inflammatory (invasion or cytotoxin) Colon or distal small bowel Dysentery or inflammatory diarrhea Fecal polymorphonuclear leukocytes; substantial increase in fecal lactoferrin Shigella spp., Salmonella spp., Campylobacter jejuri, enterohemorrhagic E. coli, enteroinvasive E. coli, Yersinia enterocolitica, Listeria monocytogenes, Vibrio parahaemolyticus, Clostridium difficile, A. hydrophila, P. shigelloides, Entamoeba histolytica, Klebsiella oxytoca
Penetrating Distal small bowel Enteric fever Fecal mononuclear leukocytes Salmonella Typhi, Y. enterocolitica

4.1 Physical Examination

Signs of dehydration: ◦ Mild: thirst, dry mouth, decreased urine output. ◦ Moderate: orthostatic fall in BP, sunken eyes. ◦ Severe: lethargy, obtundation, feeble pulse, hypotension.

4.2 Diagnostic Approach

• Distinguish inflammatory vs noninflammatory diarrhea using history/epidemiology.

• Fecal leukocytes/lactoferrin tests identify inflammatory disease.

• Stool culture/molecular testing for specific pathogens in severe cases/high-risk patients.

• Table 138-1 categorizes causes of acute infectious diarrhea.


5. DIFFERENTIAL DIAGNOSIS

Noninflammatory: Watery stools without fecal leukocytes (enterotoxins).

Inflammatory: Dysentery with fecal polymorphonuclear leukocytes (invasion/cytotoxins).

Penetrating: Enteric fever with fecal mononuclear leukocytes.

• Table 138-1 provides examples of pathogens in each category.


6. INVESTIGATIONS & DIAGNOSIS

• Noninflammatory diarrhea is often self-limited and may not require specific etiology determination.

• Fecal leukocyte/lactoferrin tests help distinguish inflammatory vs noninflammatory disease.

• Stool culture/molecular testing identifies causative organisms in severe cases/high-risk patients.

6.1 Laboratory Evaluation

• Fecal leukocytes: thin smear with methylene blue, examine wet mount.

• Fecal lactoferrin: more sensitive than fecal leukocyte tests (latex agglutination/ELISA formats).

• Stool culture/molecular testing for specific pathogens in severe cases/high-risk patients.


7. MANAGEMENT & TREATMENT

• Rehydration is the mainstay of treatment (WHO-recommended reduced-osmolarity ORS).

• Avoid loperamide in fever/dysentery; may prolong Shigella infection.

• Antibiotics contraindicated in suspected EHEC infection (risk of HUS).

7.1 Rehydration

• Oral rehydration solution (ORS) is the mainstay for acute diarrheal diseases.

• WHO recommends reduced-osmolarity/reduced-salt ORS.

• IV fluids (e.g., Ringer's lactate) required for severe dehydration.

7.2 Antimicrobial Therapy

• Avoid antibiotics in suspected EHEC infection (risk of hemolytic-uremic syndrome).

• Empirical antimicrobials may be used in inflammatory diarrhea (e.g., ciprofloxacin for Shigella, azithromycin for C. difficile).

7.3 Prophylaxis

• Not generally recommended for traveler's diarrhea except in immunocompromised patients.

• Bismuth subsalicylate may reduce risk in travelers.

7.4 Drug Therapy

• Loperamide contraindicated in fever/dysentery (may prolong Shigella infection).

• Racecadotril may be used for noninflammatory diarrhea.

• Antimicrobials: ciprofloxacin, azithromycin, metronidazole, etc., based on pathogen and severity.


8. PROGNOSIS & COMPLICATIONS

• Most cases are self-limited but can lead to dehydration, malnutrition, or complications like HUS.

• Postdiarrhea complications: reactive arthritis (C. jejuri), chronic carriage (Salmonella), C. difficile recurrence.

Table 138-2 Postdiarrhea Complications of Acute Infectious Diarrheal Illness

COMPLICATION DETAILS
Chronic diarrhea (diarrhea lasting >4 weeks) • Lactase deficiency
• Small-bowel bacterial overgrowth
• Malabsorption syndromes (tropical and celiac sprue)
(Occurs in ~1% of travelers with acute diarrhea; Protozoa account for approximately one-third of cases)
Irritable bowel syndrome Occurs in ~10% of travelers with traveler's diarrhea
Hemolytic-uremic syndrome (hemolytic anemia, thrombocytopynea, and renal failure) Follows infection with Shiga toxin–producing bacteria (Shigella dysenteriae type 1 and enterohemorrhagic Escherichia coli)

8.1 Postdiarrhea Complications

• Reactive arthritis following C. jejuri infection.

• Chronic intestinal carriage after Salmonella gastroenteritis.

• Recurrent C. difficile infections.


9. SPECIAL POPULATIONS

Immunocompromised Hosts: - Higher risk of acute/chronic infectious diarrhea. - Increased risk of invasive enteropathies (salmonellosis, listeriosis, cryptosporidiosis). - Hypogammaglobulinemia increases risk of C. difficile colitis and giardiasis. - Risk of persistent infection, bacteremia, and metastatic seeding.

Travelers: - Prophylaxis not generally recommended unless immunocompromised. - Bismuth subsalicylate may be used to reduce risk.


10. CLINICAL DECISION PATHWAY (FIGURE 138-1)

  1. Initial Assessment: Presenting with diarrhea, nausea, or vomiting.
  2. Action: Initiate symptomatic/oral rehydration therapy.
  3. Evaluation of Severity & Duration:
  4. Is duration >1 day and is the illness severe?
  5. NO → Resolution.
  6. YES → Obtain history and stool for WBCs.
  7. Assessment of Inflammatory Status (based on WBC count):
  8. Noninflammatory (No WBCs present) → Continue symptomatic therapy; further evaluation if no resolution.
  9. Inflammatory (WBCs present) → Culture for Shigella, Salmonella, Campylobacter jejuri; Consider Clostridioides difficile toxin → Consider: Empirical antimicrobial therapy.
  10. Extended Duration Check:
  11. If duration >10 days → Examine stool for parasites → Specific antiparasitic therapy.

11. KEY PEARLS & HIGH-YIELD POINTS

EHEC Warning: Bloody stools without fecal leukocytes → Alert lab for EHEC. Antibiotics are contraindicated here due to HUS risk.

Loperamide Rule: Never use in patients with fever or dysentery (risk of prolongs Shigella infection).

Norovirus: Highly contagious and robust on surfaces; common in cruise ships/healthcare settings.

C. difficile: Leading cause of nosocomial diarrhea in adults.

Clinical Distinction: - Noninflammatory → Watery, no WBCs. - Inflammatory → Dysentery, WBCs present. - Penetrating → Enteric fever, mononuclear leukocytes.


12. ADDITIONAL TABLES

Table 138-4 Bacterial Food Poisoning: - 1–6 h: Staphylococcus aureus (Nausea, vomiting, diarrhea; Ham, poultry, potato/egg salad, mayonnaise) and Bacillus cereus (Fried rice). - 8–16 h: Abdominal cramps, diarrhea (vomiting rare). - >16 h: - E. coli: Watery diarrhea (Salads, cheese, meats, water). - EHEC: Bloody diarrhea (Ground beef, roast beef, salami, raw milk, raw vegetables, apple juice). - Salmonella spp.: Inflammatory diarrhea (Beef, poultry, eggs, dairy products). - Campylobacter jejuri: Inflammatory diarrhea (Poultry, raw milk). - Shigella spp.: Dysentery (Potato or egg salad, lettuce, raw vegetables). - Vibrio parahaemolyticus: Dysentery (Mollusks, crustaceans).

Table 138-5 Treatment of Traveler's Diarrhea: - Watery diarrhea (no blood, no fever), 1–2 unformed stools/day without distressing symptoms → ORS, Pedialyte, Lytren, or flavored mineral water + saltine crackers. - Dysentery (blood) or fever (>37.8°C) → Antibacterial drug. - Infants (<2 years old) → Fluids/electrolytes; continue feeding (especially breast milk); seek medical attention for moderate dehydration, fever >24 h, bloody stools, or diarrhea lasting several days.


Reference Tables

TABLE 138-1 Gastrointestinal Pathogens Causing Acute Diarrhea MECHANISM Noninflammatory (enterotoxin)

Harrison's 22e, p.1077

MECHANISM LOCATION ILLNESS STOOL FINDINGS EXAMPLES OF PATHOGENS INVOLVED
Noninflammatory
(enterotoxin)
Proximal
small bowel
Watery
diarrhea
No fecal leukocytes; mild
or no increase in fecal
lactoferrin
Vibrio cholerae, enterotoxigenic Escherichia coli (LT and/or ST), enteroaggregative
E. coli, Clostridium perfringens, Bacillus cereus, Staphylococcus aureus, Aeromonas
hydrophila, Plesiomonas shigelloides, rotavirus, norovirus, enteric adenoviruses,
Giardia lamblia, Cryptosporidium spp., Cyclospora spp., microsporidia
Colon or
distal small
bowel
Dysentery or
inflammatory
diarrhea
Fecal polymorphonuclear
leukocytes; substantial
increase in fecal
lactoferrin
Penetrating Distal small
bowel
Enteric fever Fecal mononuclear
leukocytes
Salmonella Typhi, Y. enterocolitica

TABLE 138-3 Causes of Traveler’s Diarrhea

Harrison's 22e, p.1079

ETIOLOGIC AGENT APPROXIMATE
PERCENTAGE OF
CASES
COMMENTS
Bacteria 50–75
Enterotoxigenic
Escherichia coli
10–45 Single most important agent
Enteroaggregative E. coli 5–35 Emerging enteric pathogen with
worldwide distribution
Campylobacter jejuni 5–25 More common in Asia
Shigella 0–15 Major cause of dysentery
Salmonella 0–15
Others 0–5 Including Aeromonas,
Plesiomonas, and Vibrio
cholerae
Viruses 0–20
0–10
0–5
Parasites 0–10
Giardia lamblia 0–5 Affects hikers and campers who
drink from freshwater streams
Cryptosporidium 0–5 Resistant to chlorine treatment
of water sources
Entamoeba histolytica <1
Cyclospora <1
Other 0–10
0–5
10–50

TABLE 138-2 Postdiarrhea Complications of Acute Infectious Diarrheal Illness COMPLICATION Chronic diarrhea (diarrhea…

Harrison's 22e, p.1079

COMPLICATION COMMENTS
Chronic diarrhea (diarrhea lasting
>4 weeks)
• Lactase deficiency
• Small-bowel bacterial overgrowth
• Malabsorption syndromes (tropical
and celiac sprue)
Occurs in ~1% of travelers with acute
diarrhea
Protozoa account for approximately
one-third of cases
Irritable bowel syndrome Occurs in ~10% of travelers with
traveler’s diarrhea
Hemolytic-uremic syndrome (hemolytic
anemia, thrombocytopenia, and renal
failure)
Follows infection with Shiga
toxin–producing bacteria
(Shigella dysenteriae type 1 and
enterohemorrhagic Escherichia coli)

TABLE 138-4 Bacterial Food Poisoning

Harrison's 22e, p.1080

INCUBATION PERIOD,
ORGANISM
SYMPTOMS COMMON FOOD
SOURCES
1–6 h
Staphylococcus aureus Nausea, vomiting,
diarrhea
Ham, poultry, potato or
egg salad, mayonnaise,
cream pastries
Bacillus cereus Nausea, vomiting,
diarrhea
Fried rice
8–16 h
Abdominal cramps,
diarrhea (vomiting rare)
Abdominal cramps,
diarrhea (vomiting rare)
>16 h
Watery diarrhea
Enterotoxigenic
Escherichia coli
Watery diarrhea Salads, cheese, meats,
water
Enterohemorrhagic
E. coli
Bloody diarrhea Ground beef, roast beef,
salami, raw milk, raw
vegetables, apple juice
Salmonella spp. Inflammatory diarrhea Beef, poultry, eggs, dairy
products
Campylobacter jejuni Inflammatory diarrhea Poultry, raw milk
Shigella spp. Dysentery Potato or egg salad,
lettuce, raw vegetables
Vibrio parahaemolyticus Dysentery Mollusks, crustaceans

TABLE 138-5 Treatment of Traveler’s Diarrhea on the Basis of Clinical Features a

Harrison's 22e, p.1081

CLINICAL SYNDROME SUGGESTED THERAPY
Watery diarrhea (no blood in stool,
no fever), 1 or 2 unformed stools
per day without distressing enteric
symptoms
Oral fluids (oral rehydration solution,
Pedialyte, Lytren, or flavored mineral
water) and saltine crackers
Dysentery (passage of bloody
stools) or fever (>37.8°C)
Antibacterial drugc
Diarrhea in infants (<2 years old) Fluids and electrolytes (oral rehydration
solution, Pedialyte, Lytren); continue
feeding, especially with breast milk; seek
medical attention for moderate dehydration,
fever lasting >24 h, bloody stools, or
diarrhea lasting more than several days