Diarrhoea can range from mild to severe and life-threatening. It is defined medically as stool weight over 250g/24h. Diarrhoea can be acute (<2 weeks), prolonged (2 weeks to 2 months), or chronic (>2 months). The causes include bacteria, viruses, parasites, and fungi. Common infectious agents are C. jejuni, Shigella, Salmonella, C. difficile, Giardia lamblia, and Entamoeba histolytica. Chronic diarrhoea in immunocompromised patients like those with AIDS can be caused by microsporidia, cryptosporidium, and mycobacterium avium complex.

2. Diarrhoea is a common symptom that can range
in severity from an acute, self-limited annoyance
to a severe, life-threatening illness.
Patients may use the term “Diarrhoea" to refer to
increased frequency of bowel movements,
increased stool liquidity, a sense of fecal urgency,
or fecal incontinence.
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3. In the normal state, approximately 10 L of fluid
enter the duodenum daily, of which all but 1.5 L is
absorbed by the small intestine. The colon
absorbs most of the remaining fluid, with only 100
mL lost in the stool. From a medical standpoint,
diarrhea is defined as a stool weight of more than
250 g/24 h
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4. Classified by course
Acute diarrhea: <2 weeks
Prolonged diarrhea: 2 weeks ~ 2 months
Chronic diarrhea: >2 months
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5. The causes of diarrhoea are myriad.
In clinical practice, it is helpful to distinguish
acute from chronic diarrhoea, as the
evaluation and treatment are entirely
different.
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8. Bacteria Virus Parasite Fungus
C. jejunii CMV Cryptosporidium C. albicans
Shigella sp Enteric adeno Isospora belli
Salmonella Calici virus Cyclospora
C. difficle HIV Microsporidium
EAEC Giardia lamblia
M. avium complex Entamoeba histolytica
Int. Schistosoma
Ancylostoma duodenale
Ascaris lumbriciodes
Strongyloidiosis
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9. Chronic parasitic infections may cause diarrhea
through a number of mechanisms.
Although the list of parasitic organisms is a long one,
agents most commonly associated with diarrhea
include the protozoans Giardia, E histolytica,
Cyclospora, and the intestinal nematodes
Immunocompromised patients, especially those with
AIDS, are susceptible to a number of infectious
agents that can cause acute or chronic diarrhea
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10. Chronic diarrhea in AIDS.
It is commonly caused by Microsporida,
Cryptosporidium, cytomegalovirus, Isospora
belli, Cyclospora, and Mycobacterium avium
complex.
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13. Cultural Characteristics :
Plating Media – Blood Agar, MacConkey Agar, SS Agar,
DCA, XLD, HE Agar, WB medium etc;
Biochemical Reactions :
Sugar Fermentation (G, L, M & S), Indole, MR, VP, Citrate,
Urease, H2S production, Catalase, Oxidase, Nitrate
Reduction, Motility
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Biochemical Reactions Triple Sugar Iron (TSI) Agar

16. Serotyping :
Important for epidemiological purpose
Antibiotic sensitivity :
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Macroscopy : Gross appearance
Colour, consistency, Blood, Mucus, pH,
Parasites
Microscopy :
Wet mount & Iodine Preparations :
Ova / Cyst, Parasites (Adult / Larvae);
Modified ZN Stain :
for Cryptosporidium, Isospora etc.

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Microscopy :
Electron Microscopy, Immunofluorescence
Microscopy, Immunoelectron Microscopy,
Serology :
NT, CFT, IF, RIA, ELISA,
PCR
Detection of IgG – indication of chronic infection.

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Adenovirus CMV_colitis
CMV_ulcers_cecum

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Microscopy :
KOH preparation – to observe fungal elements;
Gram stain – to observe Yeast-like cells and / or
Clamydospores;
Germ tube test – for Candida albicans.

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23. Clostridium difficile - ¼ of antibiotic-associated
diarrhea.
Antibiotics :clindamycin, ampicillin, amoxicillin, and
cephalosporins
Treatment :
Oral Metronidazole (500mg tid for 7-10 days) or oral
Vancomycin hydrochloride for 10 to 14 days
oral metronidazole is preferred
Approximately 15% of patients experience relapse…

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