Paper II
Question
Difference between amoebic dysentery and bacillary dysentery
Answer
| Feature | Amoebic dysentery (Entamoeba histolytica) | Bacillary dysentery (Shigella species) |
|---|---|---|
| Onset | Gradual | Sudden/acute |
| Fever | Usually absent or low-grade | Often present, can be high |
| Stool character | Large volume, foul-smelling, “anchovy sauce”-like, blood streaked through the stool | Small volume, frequent, with visible blood and mucus, less foul-smelling |
| Tenesmus | Less prominent | Prominent |
| Abdominal pain | Less severe, more colicky | More severe, cramping |
| Microscopy of stool | Trophozoites containing ingested (phagocytosed) RBCs — a diagnostic hallmark; few faecal leukocytes | Numerous faecal leukocytes (pus cells), predominantly neutrophils; no amoebae/RBC-laden trophozoites |
| Mucosal ulceration pattern | Flask-shaped ulcers (narrow neck, broad base) in the colon, from submucosal spread | Superficial mucosal ulceration, more diffuse |
| Extraintestinal spread | Can spread to liver (amoebic liver abscess) and other organs | Rare; systemic complications (e.g., HUS with S. dysenteriae type 1 Shiga toxin) differ in mechanism |
| Treatment | Metronidazole (tissue amoebicide) plus a luminal agent | Antibiotics (ciprofloxacin, azithromycin depending on resistance) |
| Causative organism type | Protozoan parasite | Bacterium |
Key distinguishing laboratory clue: the presence of trophozoites with ingested RBCs on fresh stool microscopy is the single most specific finding confirming invasive amoebic dysentery, while abundant faecal leukocytes without amoebae point toward a bacterial (e.g., shigellosis) cause.