Diarrhea Causative Agents and Diagnosis

How will you define diarrhea?

1. When there are loose motions, at least three per day.
2. This may last for a few days and leads to:
   1. Dehydration.
   2. Decreased urination.
   3. Tachycardia.
3. A fresh stool sample is needed for the first culture, and then we can advise on additional tests.
4. Fresh stool is required for ova and parasite detection.

What microorganisms cause diarrhea?

1. Viruses.
2. Bacteria.
3. Parasites.

What are the types of Diarrhea?

1. Watery diarrhea.
2. Bloody diarrhea.
3. Another classification is:
   1. Acute diarrhea.
   2. Exudative diarrhea (There is inflammation of the intestinal mucosa).
   3. Chronic diarrhea.
      1. This diarrhea has been present for at least 4 weeks. This may be even longer, ranging from 6 to 8 weeks.
   4. Osmotic diarrhea (malabsorption).
   5. Secretory diarrhea (Due to abnormal electrolyte transport).
   6. Due to intestinal motility disturbances.

What are the causes of Acute infectious diarrhea?

Traveler’s diarrhea (community-acquired diarrhea)	Persistent diarrhea = >7 days	After hospitalization = >3 days	Immunocompromised patients due to HIV
Salmonella Shigella Yersinia E. Coli (O157:H7) toxin-producing E. Histolytica Vibrio Rotavirus (stool) Cytomegalovirus Adenovirus (stool) Bacillus cereus Staphylococcus aureus	Protozoa: Giardia Cyclospora Isospora belli Cryptosporidium	Salmonella Shigella E. Coli (toxin-producing) Campylobacter Clostridium group	Mycobacterium avium Microsporidia Can take a biopsy of the colon

What are the causes of Watery Diarrhoea?

1. Bacteria, such as Escherichia coli, and others produce enterotoxin.
   1. Usually seen in travelers.
2. Protozoa, Giardia lamblia, and others.
   1. This may be seen in travelers and contaminated water supply.
   2. In a child care center, this may be a chronic problem.
3. Pre-formed enterotoxin by Staphylococcus aureus, Bacillus cereus, and Clostridium perfringens.
   1. This is due to food poisoning.

What are the causes of Bloody Diarrhoea or dysentery?

1. Shigella and Salmonella.
2. Campylobacter.
3. Entamoeba histolytica.
   1. This may be common for travelers.

What are the common causes of diarrhea?

1. Shigella.
2. Salmonella.
3. Esch. Coli.
4. Staph. Aureus.
5. Campylobacter.
6. Cl.perfringens.
7. V.cholerae.

Shigella

1. Shigella causes bacillary dysentery.
2. This is a worldwide problem and fatal in young children, especially in the third world.
3. Shigella is a worldwide problem and an important cause of death in young children, especially in the third world.
4. Shigella is of four types:
   1. Sh. dysenteriae (also known as Shigella Shiga). It has 13 serotypes.
   2. Sh. boydii. It has 18 serotypes.
   3. Sh. sonnei. It has only one serotype.
   4. Sh. flexneri. It has six serotypes.
5. Epidemiology:
   1. The incubation period is 1 to 9 days.
   2. After an acute attack, the patient may continue to excrete the bacteria in their stool for several weeks or months.
   3. Patients during the acute stage are the primary source of spread because many bacteria are passed in the stool.
   4. The route of entry is the feco-oral, either direct spread or contaminated utensils, towels, and toilet seats.
   5. Shigella can remain viable for an extended period in a cool and moist environment.
   6. Contaminated water is a primary source of infection; other sources include flies, fomites, and contaminated food.
6. The stool has blood and mucus.
7. There may be pus in the stool.

How will you define Shigella dysentery?

1. It is due to Sh. dysenteriae is severe and life-threatening and is seen in tropical countries.
   1. There is a fever and abdominal pain.
   2. There is diarrhea.
   3. This produces a potent neurotoxin.
      1. It also produces enterotoxin and cytotoxin.
   4. This is an invasive disease.
   5. This is a severe, life-threatening disease and is found in tropical countries.
   6. Sometimes, this may produce septicemia.
   7. While dysentery from other species is mild.

What are the signs and symptoms of Shigella groups?

1. There is diarrhea with blood and mucus.
2. Sometimes,  may find pus.
3. There may be a severe life-threatening disease or a mild or symptomless infection.

What do you know about Shigella sonnei?

1. It is a common cause of dysentery in the UK. It may be seen throughout the world.
2. It is common in young children.
3. Its outbreaks are common in the nursery school.
4. There are reports in the mental hospital that infection may be difficult to eradicate.
5. Mostly, the disease is mild, and in a few cases, dehydration may occur, requiring emergency treatment.

What do you know about Shigella flexneri?

1. It was also common in the UK.
2. It was the common cause of dysentery in Glasgow.
3. It is no longer seen in the UK.
4. It is also seen in tropical countries.

What do you know about Shigella boydii?

1. It is common in the Middle and Far East.

How will you diagnose Shigella dysentery?

1. It can be diagnosed with a stool or rectal culture.
2. Culture is performed on selective media, such as MacConkey, deoxycholate citrate agar, and XLD agar.
3. There are pale, non-lactose-fermenting colonies.
4. Shigella sonnei is a late fermenter of lactose.
5. Do biochemical tests for identification.
6. Serological identification can be made using specific antisera or polyvalent antisera.

How will you treat Shigella dysentery?

1. Antibiotics are usually not needed.
2. In a few cases, you may use  Trimethoprim (the first line of treatment).
3. Antibiotics may be needed for Shigella sonnei.
4. In severe cases, systemic antibiotics are used.

How will you prevent Shigella infection?

1. Shigella infection may be prevented by:
2. 1. This depends primarily on sanitation, access to safe water, and adequate sewage disposal.
   2. It isn’t easy to control in a nursery school.

Escherichia Coli

1. This is common normal commensal gut flora.
2. However, some of the strains lead to diarrhea.
   1. The E. coli 0157:H7 strain produces toxins that cause damage to the small intestinal lining.
3. How will E. Coli spread?
   1. Coughing.
   2. Kissing.
   3. Every day, engage in social interactions with friends and family.
   4. It can spread through contaminated water. Then it spreads through the feco-oral route.
   5. It spreads through raw or uncooked ground meat, raw milk, and cheese.
   6. It also spreads through contaminated vegetables.

What is the presentation of E. Coli diarrhea?

1. It starts with stomach pain and cramps.
2. There is a loss of appetite and nausea.
3. It is followed by vomiting.
4. The patient may have a low fever of <101 °F. But this is not a standard feature.
5. There may be watery diarrhea.
6. Watery diarrhea may last for one day and then change into bloody diarrhea.
7. This bloody diarrhea may last for 2 to 5 days.
8. There may be 10 or more bowel movements per day.
9. Most people recover without any treatment.

Hemorrhagic colitis and hemolytic uremic syndrome

How will you define hemorrhagic colitis and hemolytic syndrome?

1. There may be a life-threatening syndrome with a bleeding tendency.
2. This may be due to toxins that are cytopathic.
3. Hemorrhagic colitis has been observed in both children and adults as a sporadic infection.
   1. There may be death in older patients.
4. Hemolytic uremic syndrome is seen in children as an outbreak or sporadic case.
   1. This is usually seen with a serotype of 0157.
   2. There is diarrhea followed by uremia.
   3. There is thrombocytopenia.
   4. There is hemolytic anemia.

Traveler diarrhea (Turista)

How will you define traveler’s diarrhea?

1. This has different names, like:
   1. Montezuma’s revenge.
   2. Delhi belly.
   3. Tokyo two-step.
2. The serotype of traveler diarrhea:
   1. The strains of Escherichia cause this diarrhea, where E. coli produces enterotoxins, and the common ones are enterotoxigenic O6 and O78.
3. This can spread through contaminated foods and drinks.
4. There is diarrhea and abdominal pain.
5. There may be vomiting.
6. This is usually a self-limiting disease.
7. Damage is due to heat-labile or heat-resistant toxins.

Infantile gastroenteritis

How will you define infantile gastroenteritis?

1. Serotypes:
   1. These are caused by Esch. Coli by the enteropathogenic strains, serogroups 055 and 0111, and sometimes by enterotoxigenic strains, serogroups 06 and 078.
2. The incubation period is 1 to 3 days.
   1. It is usually seen in babies under the age of 2 years.

What is the epidemiology of infantile gastroenteritis?

1. There are sporadic cases in the community.
2. This infection is common in the third world due to poor sanitation and hygiene.
3. In the third world,  the major cause of mortality is due to this disease. Flies may be the main reason.
4. In nurseries and neonatal units, the infection spreads by direct contact, staff, or handling.

What is the pathogenesis of infantile gastroenteritis?

1. The number of strains that produce enterotoxins and others produce Vero cytotoxin.
2. Some of these bacteria attach to the epithelium, a crucial pathogenic mechanism.

What are the signs and symptoms of infantile gastroenteritis?

1. There is acute diarrhea, which may lead to dehydration.
2. There is an acid-base disturbance.
3. There is hypernatremia (increased sodium).
4. Culture from feces can be diagnosed.

How will you diagnose infantile gastroenteritis?

1. Take a stool as a sample for culture.
2. The stool is cultured on MacConkey media.
3. There are pink-colored colonies (lactose-fermenting).
4. Identified by the polyvalent sera.

How will you treat infantile gastroenteritis?

1. Rehydration is needed to correct the acid-base imbalance.
2. In severe cases, antibiotics may work. Otherwise, their use is doubtful.

How will you prevent infantile gastroenteritis?

1. Strict hygiene measures are essential in neonatal units and nurseries.
2. Examine all new cases for admission for these enteropathogenic strains.
3. Isolate all positive cases.
4. Check all the staff members for this infection.
5. It can be controlled by providing access to clean water and promoting good hygiene.

 Salmonella food poisoning

How will you define Salmonella food poisoning?

1. Salmonella diarrhea is often referred to as food poisoning, but this term is misleading.
2. S. enteritidis phage type 4 was common in the UK in 1980 and was the most common cause of incidents in poultry flocks.
3. S. typhi, paratyphi A, B, and C mainly cause enteric fever, and in the late stages, these patients develop diarrhea.
4. S.paratyphi causes enteric fever and diarrhea.
5. The incubation period is typically short, ranging from 12 to 36 hours.

What is the mode of spread of Salmonella food poisoning?

1. Food derived from domestic animals and poultry is the primary source.
2. When these meats are not properly cooked and stored at room temperature, they can cause foodborne illness.
3. The eggs may also be the source.
4. Another source may be contaminated milk and sometimes cheese.
5. Human carriers may also play a role in the spread.

What are the signs and symptoms of Salmonella food poisoning?

1. Early symptoms are abdominal pain and diarrhea.
2. There may be fever and vomiting.
3. The patient may get dehydrated.
4. In severe cases, septicemia may be seen.

How will you diagnose Salmonella food poisoning?

1. For diagnosis, do a culture of the feces on MacConkey and selective media.
2. The biochemical test on the culture material can confirm it.

How will you treat the Salmonella food poisoning?

1. Treatment with antibiotics is contraindicated except in cases of septicemia.
2. Rehydration is necessary.

Campylobacter

How will you define Campylobacter infection?

1. This is recognized as a major source of diarrhea.
2. Campylobacter is a small vibrio-like organism.
   1. These are curved gram-negative bacilli.
   2. These have characteristic darting motility.
   3. These are oxidase reactions positive.
3. The main cause of human infection is C. jejuni.
   1. Rarely caused by C. jejuni subspecies such as doylei, C. coli, and C.lari.
4. The incubation period is 3 to 10 days.

What are the sources of Campylobacter?

1. The main source of infection is poultry.
2. Other sources are milk and water.
3. Dogs and cats are also reported as the source.
4. The mode of spread is the fecal-oral route, which occurs when contaminated food is eaten.

What are the signs and symptoms of Campylobacter?

1. The main symptoms of Campylobacter are:
   1. Fever.
   2. A headache.
   3. A backache.
   4. Limb pain.
   5. Abdominal pain. This is a prominent feature of Campylobacter infection.
2. After 24 hours or later, the patient develops diarrhea.
3. Diarrhea sometimes is severe with mucus and blood.
4. There may be up to 20 stools per day.
5. In severe cases, you may see septicemia.
6. Typically, there is enterocolitis, which involves the small intestine, the ileum.
7. In some cases, there may be colitis.

How will you diagnose Campylobacter?

1. Advise the stool culture on the selective media containing antibiotics at 43 °C.

How will you treat Campylobacter?

1. Treatment: It is usually self-limiting.
2. Erythromycin can reduce the duration of the disease, but should be reserved for severe cases.
3. Another drug is ciprofloxacin.

Cholera

How will you define Cholera?

1. This is caused by Vibrio cholerae.
2. The causative agent is V.cholerae 01.
3. In Bengal, the epidemic was due to type 139.

What is the source and transmission of Cholera?

1. The incubation period ranges from 6 hours to 5 days, typically due to sewage water contamination.
2. Sometimes, this may occur due to food contamination.
3. Flies contaminate food.
4. It can exist freely in the water.
5. The spread is feco-oral. Human GIT is the reservoir.
6. Symptomless carriers are common in epidemics.

What are the signs and symptoms of Cholera?

1. The patient develops abdominal pain and diarrhea.
2. Watery diarrhea like rice water.
3. There may be mucous.
4. The patient may have vomiting and dehydration.
5. There is acidosis, and the patient may collapse.
6. Cholera is seen in two forms:
   1. Classical cholera (severe).
   2. A mild form of cholera is associated with the El Tor biotype.

What is the pathogenesis of Cholera?

1. Exotoxin: V. cholerae produces a potent protein exotoxin.
2. Endotoxin: This is a lipopolysaccharide.

How will you diagnose Cholera?

1. This can be diagnosed by:
2. The culture of feces on selective media.
3. There are typical colonies.
4. This can be identified by slide agglutination with polyvalent antisera.
5. Antigen capture test.
6. Latex agglutination test.

How will you treat Cholera?

1. This is treated by replacing the fluids.
2. When tetracycline is given, the disease course may be short.

Staphylococcus aureus

How will you define Streptococcus aureus diarrhea?

1. This is due to toxic food poisoning.
2. This is due to enterotoxin contamination of the foods by Staph. Aureus.
3. This is very rapid in onset due to the preformed toxin in the food.

What is the pathogenesis of Streptococcus aureus diarrhea?

1. Staphylococcus produces about 40% of the five antigenically different types of enterotoxins.
2.  These are named Enterotoxin A, B, C, D, and E.
3. The preformed toxins present in the contaminated foods have local action on the gut mucosa.
4. Toxins are resistant to high temperatures, which will kill the bacteria.
5. So, food contains toxins and no viable bacteria.

What are the signs and symptoms of Streptococcus aureus?

1. Symptoms due to Staphylococcus aureus are:
2. Acute onset of nausea and vomiting.
3. This may be followed by diarrhea.
4. This is a self-limiting disease.

How will you diagnose Streptococcus aureus diarrhea/dysentery?

1. Diagnosis of diarrhea due to Staphylococcus aureus:
2. Check the suspect’s food, vomit, or feces.
3. Culture on ordinary media or mannitol salt agar.
4. Perform a coagulase test.
5. Also, it can do phage typing.

Clostridium perfringens (Cl. perfringens)

How will you define Clostridium perfronges infection?

1. This is fairly common and is due to the contamination of foods by Cl. perferingens.
2. Clostridium perfringens is a spore-bearing, heat-resistant, and anaerobic organism.
3. These are non-hemolytic strains.
4. This bacterium can resist heat at 100 °C for 30 minutes.
5. During cooking, spores germinate into vegetative form.
6. If food is kept at room temperature, then these bacteria rapidly multiply.
7. After ingesting the vegetative form, sporulation occurs in the small intestine, resulting in the release of enterotoxins.
8. These toxins primarily affect the permeability of the small intestine’s membrane.
9. Cl. perfringens may be present as commensals in the intestines of humans and animals.
10. The incubation period is 8 to 24 hours after eating the contaminated food.

What are the signs and symptoms due to Clastridium perfronges infection? 

1. Abdominal pain.
2. Diarrhea.
3. Rarely, there may be vomiting.
4. This is a self-limiting disease.

How will you diagnose Clastridium perfronges infection?

1. Take a sample of the feces and suspected food.
2. Culture the sample on blood agar under anaerobic conditions.
3. Colonies are typically β-hemolytic or non-hemolytic.
4. The Nagler reaction can identify it.
5. Can do serotyping by slide agglutination.
6. Can detect enterotoxin in the stool by ELIZA.

How will you treat Clastridium perfronges infection?

1. Treatment is symptomatic by rehydration.
2. Antibiotic therapy is not needed.

What are the common Signs and Symptoms of various types of diarrhea?

1. Watery diarrhea may be seen in travelers due to contaminated water and food-related poisoning.
2. Bloody diarrhea may also be seen in travelers.
3. There may be fever and abdominal cramps.
4. Sometimes, there may be vomiting.

How will you diagnose Diarrhea?

1. Stool examination:
   1. Children and infants can get rectal swabs.
   2. Stool examination for the presence of WBCs and RBCs.
   3. Fresh stool for ova and parasites.
2. Suspected food sample:
   1. Try your best to get a suspected food sample. Because sometimes it is discarded or eaten.
   2. Vomitus can be used.
3. A blood culture:
4. This may be necessary in severe cases, especially in very young and elderly individuals.
5. Serology:
6. There is a Giardia lamblia rapid antigen detection test.
7. E. Histolytica can be seen by microscopy or antigen detection.
8. The serum antibody test for an amoebic liver abscess.
9. In outbreak areas;
   1. Take the sample from the kitchen area.
   2. Take the fecal samples from the food handlers (kitchen workers).

What is the Prevention of Diarrheal Disease?

1. It depends mainly upon sanitation.
2. Adequate disposal of sewage.
3. Supply clean foods.
4. Try your best to get a safe water supply.
5. Advise good personal hygiene.
6. Washing of the hands after defecation should be mandatory; wash hands at least three times.
7. The above measures will prevent the feco-oral spread of diarrheal diseases.

Diarrhea causes and diagnosis:

Causative agent	Source	A common source of infection	Diagnosis
Salmonella species	Animals and humans	Milk, eggs, meat, and poultry	The specimen is feces, cultured on selective media.
Shigella species	Humans	Food, fomites, and the feco-oral route	Stool and rectal swab on MacConkey and selective media
Escherichia coli	Humans	Food, water, fomites, and the feco-oral route	Feces culture on MacConkey medium
Bacillus species	Soil	Rice	Suspected food, vomitus, and stool culture on ordinary media
Staphylococcus aureus	Septic lesion on food handlers	Dairy products and cooked meat	Suspected food, vomitus, or feces are cultures on ordinary media
Campylobacter species	Animals	Meat, milk, and poultry	Feces culture on selective medium
Clostridium perfringens	Animal	Meat pies and stews	Feces and suspected food on aminoglycoside blood agar anaerobically
Clostridium difficle	Humans	Feco-oral and overgrowth of strains in the colon	Direct detection of toxins and isolation on selective media
Vibrio cholerae	Humans	Food and water	Feces on selective medium (TCBS agar).
Yersinia species	Animal	Food and water	Isolation from feces or blood or rising antibody titer

Questions and answers:

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