INI-CET 2019 — Microbiology

Question 1: Slow growing alveolar like tumor in liver is caused by:

• A. Amoebic liver abscess
• B. E. granulosus
• C. Cysticercus cellulosae
• D. E. multilocularis (Correct Answer)

Explanation: **Correct: E. multilocularis** - *Echinococcus multilocularis* causes **alveolar echinococcosis**, characterized by a slow-growing, infiltrative, and destructive lesion in the liver with a sponge-like, alveolar appearance - This parasite's larval stage forms multiple small cysts that are not encapsulated, leading to a tumor-like mass, often described as having an "alveolar" structure - The growth pattern mimics a malignant tumor, with irregular borders and infiltration into surrounding liver tissue *Incorrect: Amoebic liver abscess* - An amoebic liver abscess is caused by **Entamoeba histolytica** and typically presents as a single or multiple well-defined, encapsulated lesions filled with "anchovy paste-like" pus, which is distinct from an alveolar tumor - These abscesses usually develop relatively quickly (acute to subacute) and are often associated with fever and right upper quadrant pain, unlike the slow, asymptomatic growth of alveolar echinococcosis *Incorrect: E. granulosus* - *Echinococcus granulosus* causes **cystic echinococcosis** (hydatid disease), which typically presents as a single, large, unilocular cyst with a clear, laminated membrane, often surrounded by a fibrous capsule - Unlike *E. multilocularis*, *E. granulosus* cysts tend to be well-defined, spherical, and expansile rather than infiltrative and alveolar - The key distinguishing feature is the **cystic** (unilocular or with daughter cysts) versus **alveolar** (multiple small vesicles) morphology *Incorrect: Cysticercus cellulosae* - *Cysticercus cellulosae* is the larval form of **Taenia solium** and causes cysticercosis, which primarily affects muscles, subcutaneous tissue, brain, and eyes - While it forms cysts, these are typically small, solitary, and calcify in various tissues, not forming a large, infiltrative, alveolar tumor-like mass in the liver - Hepatic cysticercosis is extremely rare