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 is needed for the first culture, and then we can advise more tests.
4. Fresh stool is needed for ova and parasites.

What microorganisms cause diarrhea?

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

   Diarrhea causative agents and diagnosis

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 is present for at least 4 weeks. This may be an even longer duration, from 6 weeks to 8 weeks.
   4. Osmotic diarrhea (malabsorption).
   5. Secretory diarrhea (Due to abnormal electrolytes transport).
   6. Due to intestinal motility disturbances.

What are the causes of Acute infectious diarrhea?

What are the causes of Watery Diarrhoea?

1. Bacteria, 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 staphylococcal 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 bacteria causing 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 are of four types:
   1. Sh. dysenteriae (It is also called 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 the stool for some time; this may be weeks or months.
   3. Patients during the acute stage are the main source of spread because many bacteria pass in the stool.
   4. Route of entry is the feco-oral, either direct spread or contaminated utensils, towels, and toilet seats.
   5. Shigella can remain for a long period of time in a cool and moist atmosphere.
   6. Contaminated water is the source of infection; other sources are flies, fomites, and food.
6. The stool has blood and mucus.
7. There may be pus in the stool.

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 strong 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.
2. Signs and symptoms of other shigella groups:
   1. There is diarrhea with blood and mucus.
   2. Sometimes,  may find pus.
   3. There may be a severe life-threatening disease to a mild or symptomless infection.

Shigella sonnei

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

Shigella flexneri 

1. It was also common in the UK.
   1. It was the common cause of dysentery in Glasgow.
   2. Now it is not seen in the UK.
   3. It is also seen in tropical countries.

Shigella boydii

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

How will you diagnose Shigella dysentery?

1. It can be diagnosed with stool or rectal culture.
2. Culture is done on selective media like MacConkey, desoxycholate citrate agar, and XLD agar.
   1. There are pale, non-lactose fermenting colonies.
   2. Shigella sonnei is late lactose fermenter.
3. Do biochemical tests for identification.
4. Serological identification can be made. By specific antisera or use polyvalent anti-sera.

How will you treat Shigella dysentery?

1. Antibiotics usually are 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.

How will you Prevent Shigella infection?

1. Shigella infection may be prevented by:
2. 1. This depends mainly on sanitation, safe water, and adequate sewage disposal.
   2. It is difficult to control in 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. Everyday social interaction 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.
4. 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 common 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 bowels per day.
   9. Most people recover without any treatment.

Hemorrhagic colitis and hemolytic uremic 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 was seen in 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)

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 06, 078.
3. This can spread through contaminated foods and drinks.
4. There are 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

1. Serotypes:
   1. These are caused by Esch. Coli by the enteropathogenic strains, serogroup 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.
3. Epidemiology:
   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.
4. Pathogenesis:
   1. The number of strains that produce enterotoxins and others produces Vero cytotoxin.
   2. Some of these bacteria attach to the epithelium, which is an important pathogenic mechanism
5. Signs and symptoms:
   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.
6. Diagnosis:
   1. Take stool as a sample for culture.
   2. The stool is cultured on MacConkey media.
   3. There are pink-colored colonies (lactose-fermenting).
   4. Identify by the polyvalent sera.
7. Treatment:
   1. Rehydration is needed to correct the acid-base imbalance.
   2. In severe cases, antibiotics may work. Otherwise, their use is doubtful.
8. Prevention:
   1. Strict hygiene measures are important in neonatal units and nurseries.
   2. Exam all new cases for admission for these enteropathogenic strains.
   3. Isolate all positive cases.
   4. Check all the staff members for this infection.
   5. Can control by providing clean water and good hygiene.

Salmonella

1. Salmonella diarrhea is called food poisoning, but this term is misleading.
   1. S.enteritidis phage type 4 was common in the UK in 1980 and the commonest cause of incidents in poultry flocks.
   2. S.typhi, paratyphi A, B, and C mainly cause enteric fever, and in the late stage, these patients develop diarrhea.
   3. S.paratyphi causes enteric fever and diarrhea.
   4. The incubation period is short, 12 to 36 hours.
   5. Food derived from domestic animals and poultry are the main source.
      1. When these meats are not properly cooked and stored at room temperature.
      2. The eggs may also be the source.
      3. Another source may be contaminated milk and sometimes cheese.
      4. Human carriers may also play for the spread.
   6. Early symptoms are abdominal pain and diarrhea.
      1. There may be fever and vomiting.
      2. The patient may get dehydrated.
      3. In severe cases, septicemia may be seen.
   7. For diagnosis, do a culture of the feces on MacConkey and selective media.
      1. The biochemical test on culture material can confirm it.
   8. Treatment with antibiotics is contraindicated except in cases of septicemia.
      1. Rehydration is necessary.

Campylobacter

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.
   2. The incubation period is 3 to 10 days.
4. The main source of infection is poultry.
   1. Other sources are milk and water.
   2. Dogs and cats are also reported as the source.
   3. The mode of spread is the fecal-oral route by eating contaminated food.
5. 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.
   6. After 24 hours or later, the patient develops diarrhea.
      1. Diarrhea sometimes is severe with mucus and blood.
      2. There may be up to 20 stools per day.
   7. In severe cases, you may see septicemia.
   8. Typically, there is enterocolitis, which involves the small intestine, the ileum.
      1. In some cases, there may be colitis.
   9. Diagnosis:
      1. Advise the stool culture on the selective media containing antibiotics at 43 °C.
   10. Treatment: usually, it is self-limiting.
       1. Erythromycin can reduce the duration of the disease but should be reserved for severe cases.
       2. Another drug is ciprofloxacin.

Cholera

1. This is caused by Vibrio cholerae.
   1. The causative agent is V.cholerae 01.
   2. In Bengal, the epidemic was due to type 139.
2. Source and transmission:
   1. The incubation period is 6 hours to 5 days, usually by sewage water contamination.
   2. Sometimes, this may occur by contamination of the foods.
   3. Flies contaminate foods.
      1. It can exist freely in the water.
   4. The spread is feco-oral. Human GIT is the reservoir.
   5. Symptomless carriers are common in epidemics.
3. Signs and symptoms:
   1. The patient develops pain abdomen 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.
4. Cholera is seen in two forms:
   1. Classical cholera (severe).
   2. A mild form of cholera is associated with the El Tor biotype.
5. Pathogenesis:
   1. Exotoxin: V. cholerae produces potent protein exotoxin.
   2. Endotoxin: This is a lipopolysaccharide.
6. This can be diagnosed by:
   1. The culture of feces on selective media.
      1. There are typical colonies.
      2. This can be identified by slide agglutination with polyvalent antisera.
   2. Antigen capture test.
   3. Latex agglutination test.
7. This is treated by replacing the fluids.
   1. When tetracycline is given, the disease course may be short.

Staphylococcus aureus

1. This is due to toxic food poisoning.
   1. This is due to enterotoxin contamination of the foods by Staph. Aureus.
   2. This is very rapid in onset due to the preformed toxin in the food.
   3. Staphylococcus about 40% produces five antigenically different types of enterotoxins.
      1.  These are named Enterotoxin A, B, C, D, and E.
2. The preformed toxins present in the contaminated foods have local action on the gut mucosa.
   1. Toxins are resistant to high temperatures, which will kill the bacteria.
   2. So, food contains toxins and no viable bacteria.
3. Symptoms due to staphylococcus aureus are:
   1. Acute onset of nausea and vomiting.
   2. This may be followed by diarrhea.
   3. This is a self-limiting disease.
4. Diagnosis of diarrhea due to staphylococcus aureus:
   1. Check the suspect’s food, vomit, or feces.
   2. Culture on ordinary media or mannitol salt agar.
   3. Perform a coagulase test.
   4. Also, can do phage typing.

Clostridium perfringens (Cl. perfringens)

1. This is fairly common and is due to the contamination of foods by Cl. perferingens.
   1. The Cl. perfringens are spores-bearing, heat-resistant, and anaerobic organisms.
   2. These are non-hemolytic strains.
   3. This bacteria can resist heat at 100 °C for 30 minutes.
   4. During cooking, spores germinate into vegetative form.
   5. If food is kept at room temperature, then these bacteria rapidly multiply.
   6. After ingesting the vegetative form, sporulation occurs in the small intestine with the release of enterotoxins.
      1. These toxins mainly act on the membrane permeability of the small intestine.
2. Cl. perfringens may be present as commensals in the human and animal intestines.
3. The incubation period is 8 to 24 hours after eating the contaminated food.
4. Symptoms are:
   1. Abdominal pain.
   2. Diarrhea.
   3. Rarely, there may be vomiting.
   4. This is a self-limiting disease.
5. Diagnosis: Take a sample of the feces and suspected food.
   1. Culture the sample on blood agar anaerobically.
      1. Colonies are typical, β-hemolytic or non-hemolytic.
      2. The Nagler reaction can identify it.
      3. Can do serotyping by slide agglutination.
      4. Can detect enterotoxin in the stool by ELIZA.
6. Treatment is symptomatic by rehydration.
   1. 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 parasite.
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:
   1. This may be taken in severe cases, especially very young and old people.
4. There is Giardia lamblia’s rapid antigen detection test.
5. E. Histolytica can be seen by microscopy or antigen detection.
6. The serum antibody test for an amoebic liver abscess.
7. In outbreak areas;
   1. Take the sample from the kitchen area.
   2. Take the fecal samples from the food handlers (kitchen workers).

Diarrhea causative agents and diagnosis

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:

Questions and answers: