NEET-PG 2018 - Microbiology Practice Questions

Q: Which is correct of the parasite shown below?

$A=$ Dipylidium caninum, $B=$ Hymenolepis nana. ***A = Dipylidium caninum, B = Hymenolepis nana*** - Image A displays a **scolex with four prominent suckers and a rostellum armed with hooks**, which is characteristic of *Dipylidium caninum*. - Image B shows a **scolex with four suckers and a distinct retractable rostellum armed with a single circlet of hooks**, a key morphological feature of *Hymenolepis nana*. *A = Taenia solium, B = Taenia saginata* - *Taenia solium* scolex (pork tapeworm) typically has **four suckers and a rostellum with a double crown of hooks**, not the single retractile coronet seen in B. - *Taenia saginata* scolex (beef tapeworm) is **unarmed (lacks hooks)** and only possesses four suckers, which contradicts both images. *A = Taenia saginata, B = Taenia solium* - This option is incorrect because *Taenia saginata* is an **unarmed tapeworm**, meaning it lacks hooks, which are clearly visible in Image A. - *Taenia solium* has a **scolex with hooks**, but Image B's scolex with a single circlet of hooks is more consistent with *Hymenolepis nana*. *A = Hymenolepis nana, B = Dipylidium caninum* - The scolex in Image A possesses a **double-crown rostellum with hooks clustered in rows**, which is characteristic of *Dipylidium caninum*, not *Hymenolepis nana*. - The scolex in Image B with four suckers and a retractile rostellum with a single circlet of hooks is indicative of *Hymenolepis nana*, not *Dipylidium caninum*.

Q: Which of the following life cycles is shown below?

Hymenolepis nana. ***Hymenolepis nana*** - The image clearly depicts the life cycle of *Hymenolepis nana*, showing direct human infection from ingesting **fertile eggs**, leading to the development of an **oncosphere** and then a **cercocyst** within the human host before maturing into an adult tapeworm in the intestine. - The presence of an "alternative rodent host (rat, mouse) of minor importance" is a characteristic feature of *Hymenolepis nana*, which can infect both humans and rodents. *Echinococcus granulosus* - This parasite's life cycle involves **dogs (definitive host)** and **sheep/humans (intermediate hosts)**, where humans develop **hydatid cysts**, which is not shown here. - The depiction of an adult tapeworm developing directly in humans after ingestion of eggs, with a rodent as an alternative host, is inconsistent with *Echinococcus granulosus*. *Ascaris lumbricoides* - This is a **roundworm (nematode)**, not a tapeworm, and its life cycle involves **lung migration** of larvae before returning to the intestines to mature, which is not illustrated. - The image shows development from an oncosphere to a cercocyst and then to an adult tapeworm, which is specific to certain **cestodes**. *Toxocara canis* - This is another **roundworm** primarily affecting **dogs**, and humans become **incidental hosts** by ingesting embryonated eggs, leading to visceral larva migrans, where larvae migrate through tissues but do not develop into adult worms in the human intestine. - The illustrated life cycle details, particularly the formation of an oncosphere and cercocyst within the human leading to an adult tapeworm, are not indicative of *Toxocara canis*.

Q: Which of the following CNS lesions is shown below?

Neurocysticercosis. ***Neurocysticercosis*** - The top image displays multiple **cystic lesions** within the brain parenchyma, consistent with various stages of **neurocysticercosis**. - The bottom image shows an **egg of *Taenia solium***, the causative agent of cysticercosis, confirming the parasitic origin. *Cerebral toxoplasmosis* - This typically presents as **multiple ring-enhancing lesions**, often with a predilection for the **basal ganglia** in immunocompromised patients. - The pathological image shown here does not primarily depict ring-enhancing lesions but rather macroscopic cysts. *Cryptococcal meningitis* - While Cryptococcus can cause CNS lesions, they are usually **gelatinous pseudocysts** or **meningitis**, not the distinct cystic structures seen in the image. - The causative organism is a **fungus**, not a parasitic worm, so the associated egg image would be incorrect. *Hydatid cyst* - Hydatid cysts (caused by *Echinococcus granulosus*) are typically **solitary, large, well-defined cysts** with a characteristic laminated membrane. - The image shows **multiple, smaller cysts** and the egg is characteristic of *T. solium*, not *Echinococcus*.

Q: The life cycle shown in the image below is characteristic of which organism?

Schistosomiasis. ***Schistosomiasis*** - The image clearly depicts the characteristic **cercariae** penetrating human skin, with subsequent migration to the portal blood and maturation into adult worms in specific venous plexuses (e.g., rectum, liver, bladder). - The presence of **miracidia** hatching from eggs and infecting snails, followed by the release of cercariae from snails, is the hallmark life cycle of *Schistosoma* species. The eggs are shown in feces and urine, indicating different species of Schistosoma. *Paragonimus* - The life cycle of *Paragonimus* (lung flukes) involves ingestion of **undercooked crustaceans** (crabs or crayfish) containing metacercariae, not skin penetration by cercariae. - Adult worms typically reside in the **lungs**, and eggs are coughed up and swallowed or passed in feces, which is different from the venous system involvement shown. *Fasciolopsis buski* - *Fasciolopsis buski* (intestinal fluke) infection occurs through ingestion of **aquatic plants** contaminated with metacercariae. - The adult worms reside in the **small intestine**, and while eggs are passed in feces, the characteristic skin penetration by cercariae is absent in its life cycle. *Fasciola hepatica* - *Fasciola hepatica* (liver fluke) is acquired by ingesting **metacercariae** on aquatic vegetation, similar to *Fasciolopsis buski*. - Adult worms inhabit the **bile ducts** of the liver, and the life cycle does not involve skin penetration by cercariae as the mode of human infection.

Q: Which of the following Schistosoma egg is shown below?

Schistosoma hematobium. ***Schistosoma hematobium*** - The image clearly displays an **elongated, oval-shaped egg** with a characteristic **terminal spine**. - This morphology is pathognomonic for **Schistosoma hematobium**, distinguishing it from other Schistosoma species. *Schistosoma mansoni* - Eggs of *Schistosoma mansoni* are typically **oval-shaped** with a distinct **lateral spine**. - The spine is located on the side of the egg, not at one of its poles as seen in the image. *Schistosoma japonicum* - *Schistosoma japonicum* eggs are more **rounded or oval** and possess a very small, **rudimentary spine** that is often difficult to visualize or absent. - The clearly visible, prominent terminal spine in the image rules out *S. japonicum*. *Cannot be differentiated on wet mount* - The distinct morphological features (shape and spine location) of Schistosoma eggs allow for reliable differentiation on a **wet mount** microscopic examination. - These features are crucial for accurate species identification in laboratory diagnostics.

Question 1

Which is correct of the parasite shown below?

Accepted Answer

$A=$ Dipylidium caninum, $B=$ Hymenolepis nana

Answer

A = Taenia saginata, B = Taenia solium

Answer

$A=$ Hymenolepis nana, $B=$ Dipylidium caninum

Answer

A = Taenia solium, B = Taenia saginata

Question 2

Which of the following life cycles is shown below?

Accepted Answer

Hymenolepis nana

Answer

Echinococcus granulosus

Answer

Ascaris lumbricoides

Answer

Toxocara canis

Question 3

Which of the following CNS lesions is shown below?

Accepted Answer

Neurocysticercosis

Answer

Cerebral toxoplasmosis

Answer

Cryptococcal meningitis

Answer

Hydatid cyst

Question 4

The life cycle shown in the image below is characteristic of which organism?

Accepted Answer

Schistosomiasis

Answer

Paragonimus

Answer

Fasciolopsis buski

Answer

Fasciola hepatica

Question 5

Which of the following Schistosoma egg is shown below?

Accepted Answer

Schistosoma hematobium

Answer

Schistosoma mansoni

Answer

Schistosoma japonicum

Answer

Cannot be differentiated on wet mount

NEET-PG 2018 — Microbiology