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Questions and Answers
Which concentration method is used for detecting Ascaris lumbricoides?
Which concentration method is used for detecting Ascaris lumbricoides?
What is the normal pH range of stool?
What is the normal pH range of stool?
What reagent is used in the fecal occult blood test?
What reagent is used in the fecal occult blood test?
Which sugar level in stool indicates a disturbance in enzymes that digest sugar?
Which sugar level in stool indicates a disturbance in enzymes that digest sugar?
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Which agar medium is recommended for isolating Salmonella and Shigella from fecal samples?
Which agar medium is recommended for isolating Salmonella and Shigella from fecal samples?
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Which condition can cause an acidic pH in stools?
Which condition can cause an acidic pH in stools?
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What does the development of a green to blue color indicate in the fecal occult blood test?
What does the development of a green to blue color indicate in the fecal occult blood test?
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What is the use of Thiosulphate citrate bile salt sucrose (TCBS) agar in stool cultures?
What is the use of Thiosulphate citrate bile salt sucrose (TCBS) agar in stool cultures?
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What does the microscopic analysis of stool specimens include examining the sample for?
What does the microscopic analysis of stool specimens include examining the sample for?
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A large number of leukocyte clumps (> 50 cells per high power field) indicate which condition?
A large number of leukocyte clumps (> 50 cells per high power field) indicate which condition?
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What number of pus cells per high power field is typically found in salmonellosis?
What number of pus cells per high power field is typically found in salmonellosis?
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What does the presence of a large number of epithelial cells in feces indicate?
What does the presence of a large number of epithelial cells in feces indicate?
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Which staining method is used to detect the nuclei of some cyst forms of protozoans?
Which staining method is used to detect the nuclei of some cyst forms of protozoans?
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Which of the following is a disadvantage of the iodine staining method?
Which of the following is a disadvantage of the iodine staining method?
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What does a saline wet mount preparation help to detect?
What does a saline wet mount preparation help to detect?
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What type of solution is used in a saline wet mount?
What type of solution is used in a saline wet mount?
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Study Notes
Microscopic Examination
- Microscopic analysis of stool specimens includes examining the sample for: • Leukocytes • Epithelial cells • Blood • Qualitative fat • Parasites (eggs, larvae, cysts)
- Characteristic microscopic findings: • Shigellosis: large number of leukocytes (> 50 cells per high power field) with macrophages and erythrocytes • Salmonellosis and invasive E. coli: smaller number of pus cells (< 20 per high power field) • Cholera, EPEC, ETEC, and viral diarrhea: few leukocytes (< 5 cells per high power field)
- Abnormal epithelial cell presence indicates intestinal mucosa scratch
Laboratory Diagnosis of Parasitic Infections
- Methods for examining stool: • Saline wet mount examination • Iodine preparation • Buffered methylene blue stain • Concentration techniques
- Detection of parasites: • Live motile trophozoites (protozoa) • Cyst (inactive stage of protozoa) • Eggs and larvae (helminths)
- Saline wet mount: • Uses normal saline to maintain osmotic pressure • Examined under microscope with specific objectives (X4, X10, X40) • Detects trophozoites and cysts of protozoa, eggs and larvae of helminths • Useful for detecting live motile trophozoites of protozoa (e.g., E. histolytica) and helminths larvae (e.g., Strongyloides stercolaris)
- Iodine staining method: • Uses iodine to stain nuclei of some cyst forms of protozoa (e.g., Entamoeba histolytica) • Kills motile trophozoites, making it unsuitable for detecting live forms
Stool Testing
- Concentration methods: • Sedimentation: detects Ascaris lumbricoides, Schistosoma mansoni • Floatation: detects Enterobius vermicularis, Ancylostoma
- Chemical testing: • pH: normal range is 6-7.5, acidic in amoebic dysentery, and alkaline in bacillary dysentery • Occult blood (fecal occult blood test or stool occult blood test): • Uses benzidine powder and hydrogen peroxide • Detects occult blood in stool samples • Reducing factors: • Mono sugar and di sugar levels in stool (normal range: 6mg/g) • Elevated levels indicate disturbance in sugar-digesting enzymes (e.g., lactase, sucrase)
Stool Culturing
- Normal flora of the bowel includes certain bacteria
- Pathological bacteria can produce diarrhea and systemic infection
- Stool cultures evaluate diarrhea of unknown etiology to identify causative bacteria
- Bacteria produce diarrhea through: • Invasion of the intestinal wall • Production of toxins in the intestine • Ingestion of toxins produced by bacteria
- Culture media: • MacConkey's Agar: inhibits gram-positive organisms, differentiates lactose fermenters and non-lactose fermenters • Xylose Lysine Deoxycholate (XLD) agar: selective medium for Salmonella and Shigella isolation • Thiosulfate Citrate Bile Salt Sucrose (TCBS) agar: excellent selective medium for Cholerae isolation • Sorbitol MacConkey agar: useful for E. coli O157 screening
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Description
This quiz covers the microscopic examination of stool specimens, including the detection of leukocytes, epithelial cells, blood, fat, and parasites. It also explores the characteristics of shigellosis and salmonellosis.
