Diarrhea is an important cause of morbidity and mortality worldwide, particularly in children living in areas without adequate access to safe water and sanitation The 9th leading cause of death globally in 2015 and was responsible for 8.6% of deaths among children younger than 5 years Death rates from diarrhea have declined over the past decade with improvements in sanitation, more widespread use of oral rehydration solution, and the introduction of rotavirus vaccination programs.

1. Microbiological
causes of
Diarrhea
Dr. Muhammad Barkaat Hussain
MBBS, PhD
2021

3. Objectives
• Enlist the microbes causing diarrhea
• Understand the clinical syndromes associated with GI infections
including acute watery diarrhea and dysentery
• List the complications that may accompany or follow acute diarrheal
illness
• Approach the diagnostic tools and therapy for enteric infections

4. Definitions
• Gastroenteritis: is an inflammation of the stomach lining and the
intestine that is characterized by diarrhea and vomiting
• Diarrhea: three or more loose stools in a 24-hour period
(acute: the duration is 14 days or less; or persistent: longer than 14
days)
• GI infections may manifest with acute vomiting, acute watery
diarrhea, bloody diarrhea (dysentery), persistent diarrhea, or enteric
fever. Most pathogens may cause more than one syndrome.

5. Diarrhea
• Diarrhea is an important cause of morbidity and mortality
worldwide, particularly in children living in areas without
adequate access to safe water and sanitation
• The 9th leading cause of death globally in 2015 and was
responsible for 8.6% of deaths among children younger than 5
years
• Death rates from diarrhea have declined over the past decade
with improvements in sanitation, more widespread use of oral
rehydration solution, and the introduction of rotavirus
vaccination programs.

6. Causative agents Environmental and host risk factors
• Exposure to contaminated food and/or water
• Lower-income countries
• International travel (Traveller's diarrhea)
• Person-to-person contact
• Animal- contact (Zoonotic infections)
• Seasonal pattern
• Contaminate hospital environments
• Age
• Antibiotic use
• Breastfeeding
• Gastric acidity and physical barriers
• Intestinal microbiome
• Genetic, nutritional, and immune status

7. ORGANISM KEY EPIDEMIOLOGIC FEATURES
Viruses
Adenoviru
s
Serotypes 40/41 among the leading causes of infantile
gastroenteritis globally
Astrovirus Outbreaks in closed populations
Norovirus
Most common cause of medically attended gastroenteritis
in United States: winter vomiting illness; environmentally
hardy
Rotavirus
Most common global cause of gastroenteritis in young
children, particularly in settings without rotavirus
vaccination
Sapovirus Mainly affects infants and toddlers

8. Bacteria
Aeromonas spp.
Widely distributed in aquatic environments; may cause
diarrhea or extraintestinal infection
Bacillus cereus
Vomiting illness; rare fatal cases with hepatic necrosis;
testing for toxin available (preformed toxin)
Campylobacter jejuni
Associated with poultry; common cause of traveler’s
diarrhea in Asia; associated with postinfectious arthritis and
and Guillain-Barré syndrome
Clostridioides difficile
Leading cause of mortality from gastrointestinal infection in
United States (usually overuse of antibiotics)
Clostridium botulinum
Vomiting illness due to preformed toxin ingestion; infant
botulism due to germination of spores presents with
progressive weakness
Enteroaggregative Es
cherichia coli
Persistent diarrhea in young children, associated with
malnutrition
Enterohemorrhagic E.
coli (STEC)
Associated with hemolytic-uremic syndrome in children
Enteroinvasive E. coli Associated with dysentery

9. Listeria
Associated with raw dairy products; pregnancy
complications with systemic illness
Nontyphoidal Salmon
ella spp.
Intestinal carriage can be prolonged
Plesiomonas
shigelloides
May cause watery diarrhea, dysentery, or extraintestinal
infection
Shigella spp. Most common global cause of dysentery
Staphylococcus
aureus
Vomiting due to preformed staphylococcal enterotoxin
ingestion
Vibrio cholerae
Outbreaks of watery diarrhea associated with lack of
sanitation and humanitarian crises (rice water stool)
Vibrio
parahaemolyticus
Associated with shellfish consumption
Yersinia
enterocolitica
Zoonosis; able to grow in refrigerated food; associated
postinfectious polyarthritis
Yersinia
pseudotuberculosis
Appendicitis-like syndrome

10. Protozoa
Cryptosporidium
hominis/parvum
Major cause of childhood diarrheal in children,
swimming pools outbreaks
Cyclospora
cayetanensis
Opportunistic infection; associated with
foodborne outbreaks
Cystoisospora belli
Tropical and subtropical areas; opportunistic
infection
Entamoeba histolytica May cause liver abscess
Giardia lamblia
Associated with drinking from contaminated
streams
Microsporidium
Ubiquitous in the environment; opportunistic
infection
Parasites
Anisakis simplex Vomiting illness after consuming raw fish

11. Causes of diarrhea
CLINICAL SYNDROME SIGNS AND SYMPTOMS PATHOGENIC MECHANISM EXAMPLE PATHOGENS
Acute watery diarrhea
(90%)
Loose stools, often with
mucus but not blood
Occasional vomiting and
anorexia
Low-grade fever, Malaise
Local infection in the gut
Norovirus genogroups I, II,
and IV, enteric adenovirus
types 40 and 41, rotavirus,
enterotoxigenic Escherichia
coli, enteropathogenic E.
coli, Cryptosporidium,
Clostridium perfringens,
Bacillus cereus
Dysentery (5 to 10%)
(acute bloody diarrhea)
Loose stools with gross
blood and mucus, Fever
Abdominal cramps and, in
some cases, tenesmus
May be clinically toxic
Local invasion of the gut
Shigella, enteroinvasive E.
coli, Campylobacter jejuni,
Entamoeba
histolytica, nontyphoidal Sa
lmonella, Yersinia
enterocolitica, Aeromonas,
Clostridioides difficile

12. Causes of Diarrhea
CLINICAL SYNDROME SIGNS AND SYMPTOMS PATHOGENIC MECHANISM EXAMPLE PATHOGENS
Profuse purging (abrupt or
violent removal) 1%
Copious watery stools
resembling “rice water”
Low-grade fever
Overt signs of dehydration
Toxin mediated
Vibrio cholerae O1 and O139,
enterotoxigenic E. coli
Persistent diarrhea (3-4%)
Similar to acute diarrhea, but
symptoms persist for at least
14 days or more
Local infection in the gut
and/or immune compromise
of host
Giardia lamblia,
Cryptosporidium
hominis/parvum,
Cystoisospora belli,
Cyclospora
cayetanensis, enteropathoge
nic E.
coli, enteroaggregative E. coli
Acute vomiting
Sudden onset of nausea and
vomiting
Little or no diarrhea
Local infection in the gut or
intoxication
Norovirus, food poisoning
due to Staphylococcus
aureus, Bacillus cereus
Enteric fever
Fever
Lymphadenopathy
Local invasion of the gut with
systemic spread
Salmonella enterica serovar
Typhi, S. enterica serovar
Paratyphi A, B, or C

13. Enteric
Bacterial Toxins
TOXIN
TYPE
TOXIN-PRODUCING
BACTERIA
TOXIN NAME, IF
RELEVANT
Neurotoxin
Staphylococcus aureus Enterotoxin B
Bacillus cereus Emetic toxin
Clostridium botulinum Botulinum toxin
Enterotoxin
Vibrio cholerae Cholera toxin
Enterotoxigenic Escherichia coli
Heat-labile toxin, heat-stable
toxin
Clostridium perfringens Enterotoxin
Cytotoxin
Shigella dysenteriae type I Shiga toxin
Enterohemorrhagic E. coli Shiga toxins 1 and 2
Vibrio parahaemolyticus Thermostable direct hemolysin
Campylobacter jejuni Cytolethal distending toxin
Clostridioides difficile Toxin A, toxin B
Bacteroides fragilis B. fragilis toxin
Clostridium perfringens Alpha toxin

14. Foodborne Syndromes
A-Nausea and Vomiting Lasting Less Than 24 Hours
1. Staphylococcus aureus (incubation period 1-8h)
2. Bacillus cereus (0.5-6h) (short-incubation emetic illness)
3. Noroviruses
B-Watery Diarrhea without Fever Lasting 1 to 2 Days
1. Enterotoxin-mediated syndrome: Clostridium perfringens type A (9-12h)
2. B. cereus (8-16h) (long-incubation diarrheal syndrome)
Highly heat resistant
Enterotoxins withstand
ordinary cooking

15. C- Watery Diarrhea and Abdominal Cramps Lasting More Than 2 Days:
1. Enterotoxigenic strains of E. coli (ETEC)
2. Vibrio parahaemolyticus
3. Vibrio cholerae strains O1 and O139
D- Dysentery, Abdominal Cramps, and Fever
Nontyphoidal Salmonella, Shigella, Campylobacter jejuni, enteroinvasive E.
coli, Entamoeba histolytica, and Yersinia enterocolitica
Foodborne Syndromes

16. E- Bloody Diarrhea with Minimal Fever:
STEC, most often serogroup O157
F- Persistent Diarrhea Lasting 2 or More Weeks
Parasites including Cryptosporidium, Giardia, and Cyclospora.
Foodborne Syndromes

17. ETIOLOGY COMMONLY IMPLICATED FOODS
Bacterial
Salmonella Beef, poultry, eggs, dairy products, produce
Staphylococcus aureus
Ham, poultry, salads, sandwiches, unpasteurized dairy products in
some countries (e.g., France) (Birthday party food)
Campylobacter jejuni Poultry, produce, unpasteurized (raw) milk and dairy products
Clostridium botulinum Home-canned vegetables, preserved fish, honey (infants)
Clostridium perfringens Beef, poultry, gravy
Shigella Cold foods contaminated by food handler
Vibrio parahaemolyticus Shellfish
Bacillus cereus Fried rice, meats, vegetables
Yersinia enterocolitica Pork, chitterlings
Vibrio cholerae O1 Shellfish
Vibrio cholerae non-O1 Shellfish
STEC Ground beef, raw produce unpasteurized milk
Viral
Noroviruses Salads, shellfish
Parasitic
Toxoplasma gondii Undercooked meat, raw shellfish, produce
Trichinella Game meat, less commonly pork in United States
Cyclospora cayetanensis Imported fresh produce
Cryptosporidium Unpasteurized apple cider
Giardia Raw produce and a variety of other foods

18. Complications that may follow acute diarrhea
COMPLICATION
COMMONLY ASSOCIATED BACTERIAL
AGENT(S)
COMMENT
Bacteremia
Nontyphoidal Salmonella enterica,
Campylobacter fetus, Shigella spp.
Particular concern in HIV-infected
individuals
Seizure Shigella spp. Particularly in children
Chronic diarrhea
Enteropathogenic E. coli, Giardia,
Yersinia
Occurs in ≈1% of travelers with acute
diarrhea
Causes may include lactase deficiency,
small bowel bacterial overgrowth, and
malabsorption syndromes
Initial presentation or exacerbation of
inflammatory bowel disease
All bacterial pathogens,
including Clostridioides difficile
Irritable bowel syndrome
May follow infection with many
bacterial pathogens
Reactive arthritis (formerly Reiter
syndrome)
Shigella, Salmonella, Campylobacter,
Yersinia, STEC, C. difficile
Particularly likely after infection with
invasive organisms and in patients who
are HLA-B27 positive
Hemolytic-uremic syndrome
Shiga toxin–producing bacteria
(Shigella dysenteriae type I and STEC)
Characterized by hemolytic anemia,
thrombocytopenia, and renal failure
Guillain-Barré syndrome Campylobacter jejuni
Cross-reactive antibodies to GM1 or
GQ1b gangliosides

19. Investigations
• After an adequate medical history and physical examination, the clinician should
be able to classify the acute diarrheal illness and determine its severity and possible
complications.
• The clinician should also be able to determine whether any diagnostic tests are
needed. Because most episodes of acute diarrheal illness are self-limited,
diagnostic testing should be kept to a minimum.
• Investigations should be focused toward the diagnosis of specific pathogens as
suggested by the history. It is not appropriate to send the entire array of stool
cultures and stool examination for every patient. They should be performed only if
their results will influence management and outcome.
• Diagnostic testing should be reserved for patients with severe illness

20. Diagnostic tests for acute infectious diarrhoea
• Diagnostic tests for acute infectious diarrhoea in the normal host
include stool cultures for bacterial pathogens, stool examination for
ova and parasites, and stool testing for Clostridium difficile toxin and
for E. coli 0157:H7.
• In most microbiology laboratories, stool sent for culture of enteric
pathogens will be processed for Shigella, Salmonella, and
Campylobacter.
• Other enteric pathogens such as Yersinia, Vibrio, and E. coli 0157:H7
are not routinely sought.
• More invasive investigations, including flexible sigmoidoscopy with
biopsies and upper gastrointestinal endoscopy with duodenal
aspirate and biopsies, are reserved for special situations, such as an
immunocompromised patient in whom stool examination has not
yielded a diagnosis

21. Diagnosis

22. Treatment
• Rehydration – oral vs. IV
• Antiemetics and antimotility agents: in adults, not
recommended for children
• Bismuth subsalicylate (Pepto-Bismol) is safe and efficacious in
the treatment of infectious bacterial diarrhea. It stimulates
intestinal sodium and water reabsorption, binds enterotoxins,
and has a direct antibacterial effect.
• Antibiotics: Depends on pathogen (in severe illness , patients
older than 50, infants, immunocompromised patients):
Fluoroquinolone in adults
Third-generation cephalosporin in children

23. Treatment- Recent recommendations
NICE guidelines make a stronger recommendation for the use of
1. Probiotics (beneficial bacteria)
2. Prebiotics (undigested oligosaccharides)
3. Combination of probiotic and prebiotic is called symbiotic
4. Zinc supplementation
5. Antibiotics in case of some bacterial diarrhea

24. Natural source of antibiotic, probiotics, prebiotics
and zinc
1. Probiotics (youghrut, honey)
2. Prebiotics (rice, bannana, honey)
3. Zinc supplementation (honey)
4. Natural, potent, broad spectrum and safe antimicrobial
substances (honey).
5. Amazingly, so for, antibacterial resistance to honey has been
reported.
6. Not only effective in GIT disorders, rather numerous human
illnesses like, infected wounds, burns, allergic disorders, cancer
etc.

25. About fourteen hundred years ago when scientific
knowledge regarding gastrointestinal diseases like
diarrhea did not exist, a person came to Prophet
Muhammad ‫ﷺ‬ and asked about his brother’s
abdominal illness. The Honorable Prophet ‫ﷺ‬
prescribed honey for his brother illness for four
consecutive days and his brother got cured (al
Bukhari).
History?

27. A historical apiary with traditional hives of Saudi Apis mellifera jemenitica maintained over
500 years by the same family in Taif

28. Prevention

29. Summary
• Acute infectious diarrhoea is the leading cause of morbidity leading to
dehydration, hospital admission and death in children.
• Viral causes (rotavirus) predominate as the pathogen.
• Initial management rely on assessment of severity of dehydration and fluid
replacement.
• Early refeeding
• Antibiotic are needed only in some bacterial and parasitic infections.
• Probiotics, prebiotics and zinc reduce the duration and severity of
symptoms.
• Honey, amazingly contain all these substances.
• Yogurt, banana and boiled rice are also best natural therapy to treat acute
gastroenteritis.
• Hand washing has pivotal role in preventing gastroenteritis.
• Practicing golden teaching of Islam related to personal hygiene (Wudu) and
food (halal) can save us not only from gastroenteritis rather numerous
other diseases.

30. References
Mandell, Douglas, and Bennett’s. Principles and practice of infectious
diseases. Ninth edition.
Thank you!

31. Match each pathogen with its related illness
Pathogens
• Adenovirus
• Norovirus
• Rotavirus
• Campylobacter jejuni
• Enterohemorrhagic E. coli (STEC)
• Shigella spp.
• Vibrio cholerae
illness
a) Traveller's diarrhea
b) Haemolytic-uremic syndrome in
children
c) Infantile gastroenteritis
d) gastroenteritis without vaccination
e) Dysentery
f) Outbreaks of watery diarrhea
g) Winter vomiting illness

32. Question 1
Two hours after a delicious dinner of barley soup, roast turkey, stuffing, sweet
potato, green beans, cranberry sauce, and pumpkin pie topped with whipped
cream, the Ahmed family of four, experience vomiting and diarrhea. Which one of
the following organisms is MOST likely to cause these symptoms?
A. Staphylococcus aureus
B. Salmonella enteritidis
C. Campylobacter jejuni
D. Shigella flexneri

33. Question 2
Five hours after eating reheated rice at a restaurant, a 24-year-old woman and her
husband both developed nausea, vomiting, and diarrhea. Which one of the
following organisms is the MOST likely to be involved?
A. Salmonella typhi
B. Enterotoxigenic Escherichia coli
C. Bacillus cereus
D. Clostridium perfringens

34. Assessment Question 3
Microbiology laboratory reports the presence of 0157:H7 strains of E. coli in the bloody stools of 6
children ages 3-5 who attended a local petting zoo. These young children would be at an increased
risk for developing
A.Renal stones
B.Rice water stools
C.Haemolytic uremic syndrome
D.Meningitis

35. Nice quiz for refreshing
https://blog.microbiologics.com/foodborne-pathogens-quiz/