NEET-PG 2012 Practice Questions

Q: What is the concentration of type 3 virus in the trivalent oral polio vaccine?

600,000 TCID 50. ***600,000 TCID 50*** - The **trivalent oral polio vaccine (tOPV)** traditionally contained specific concentrations of each serotype: **type 1 (1,000,000 TCID50/dose)**, **type 2 (100,000 TCID50/dose)**, and **type 3 (600,000 TCID50/dose)**. - Type 3 poliovirus requires a **higher concentration (600,000 TCID50)** compared to type 2 to achieve adequate immunogenicity and protection. - The **World Health Organization (WHO)** established these specific formulations for tOPV to ensure optimal efficacy and safety for each serotype. *100,000 TCID 50* - This is the concentration of **type 2 poliovirus** in tOPV, not type 3. - Due to the **global eradication of wild poliovirus type 2** by 2015, tOPV was replaced with bivalent OPV (bOPV) containing only types 1 and 3 in routine immunization programs. *400,000 TCID 50* - This concentration does not correspond to any standard poliovirus serotype in the traditional trivalent oral polio vaccine. - This value falls between type 2 (100,000) and type 3 (600,000) concentrations but is not used. *300,000 TCID 50* - This concentration is not the standard for any poliovirus serotype in the traditional trivalent oral polio vaccine. - Each serotype has a **distinct, empirically determined concentration** to achieve optimal immunity while minimizing adverse effects.

Q: Which of the following statements is false regarding yersiniosis?

Caused by Yersinia pestis. ***Caused by Yersinia pestis*** - **Yersinia pestis** is the causative agent of **plague**, not typical yersiniosis affecting the gastrointestinal tract. - Yersiniosis generally refers to infections caused by other *Yersinia* species like *Y. enterocolitica* and *Y. pseudotuberculosis*. *Gram-negative bacillus* - *Yersinia* species, including *Y. enterocolitica* and *Y. pseudotuberculosis*, are indeed **Gram-negative bacilli**. - This characteristic is fundamental to their classification and bacterial structure. *Caused by Yersinia pseudotuberculosis* - **Yersinia pseudotuberculosis** is a recognized cause of **yersiniosis**, particularly affecting children. - It can cause symptoms such as **abdominal pain** and **mesenteric lymphadenitis**, mimicking appendicitis. *Caused by Yersinia enterocolitica* - **Yersinia enterocolitica** is the **most common cause of yersiniosis** in humans. - It is responsible for a range of symptoms including **gastroenteritis**, **acute enteritis**, and **mesenteric lymphadenitis**.

Q: Schistosomiasis is transmitted by?

Snail. ***Snail*** - **Snails** act as the **intermediate host** for all species of Schistosoma, where the parasite undergoes asexual reproduction. - Humans become infected when they come into contact with water contaminated with **cercariae**, which are released from infected snails. *Cyclops* - **Cyclops** (a type of freshwater crustacean) are the intermediate hosts for parasites like **Dracunculus medinensis** (guinea worm) and **Diphyllobothrium latum** (fish tapeworm). - They are not involved in the life cycle or transmission of Schistosoma. *Fish* - Various fish can be intermediate hosts for parasites such as **Clonorchis sinensis** (Chinese liver fluke) or **Diphyllobothrium latum**. - Fish do not play a role in the transmission of schistosomiasis. *Cattle* - **Cattle** can serve as definitive hosts for certain parasites, such as **Taenia saginata** (beef tapeworm), where the larval stage (cysticerci) is found in their muscle tissue. - They are not involved in the life cycle or transmission of Schistosoma.

Q: Which of the following is the mechanism of action of tetanospasmin ?

Inhibition of release of GABA and glycine. ***Inhibition of release of GABA and glycine*** - **Tetanospasmin** is a potent neurotoxin produced by *Clostridium tetani* that acts by blocking the release of inhibitory neurotransmitters, specifically **GABA (gamma-aminobutyric acid)** and **glycine**, from presynaptic terminals in the spinal cord and brainstem. - This inhibition leads to **uncontrolled muscle spasms**, rigidity, and convulsions, characteristic of tetanus, due to the lack of inhibitory signals to motor neurons. *Inhibition of Ach release from synapse* - This mechanism is characteristic of **botulinum toxin** (produced by *Clostridium botulinum*), not tetanospasmin. - Botulinum toxin inhibits the release of **acetylcholine (ACh)** at the neuromuscular junction, leading to flaccid paralysis. *Inhibition of protein synthesis* - This mechanism is associated with toxins like **diphtheria toxin** and **exotoxin A** from *Pseudomonas aeruginosa*. - These toxins inactivate elongation factor-2 (EF-2), thereby blocking protein synthesis and causing cell death. *Activation of adenylyl cyclase* - Toxins such as **cholera toxin** and **pertussis toxin** act by activating adenylyl cyclase, leading to an increase in intracellular cAMP levels. - This mechanism causes effects like severe diarrhea in cholera and respiratory symptoms in whooping cough.

Q: Which of the following statements about trematodes is true?

Two hosts required. ***Two hosts required (Correct)*** - Trematodes typically require at least **two hosts** to complete their life cycle: an intermediate host (usually a **snail**) and a definitive host (a vertebrate). - This complex lifecycle involving multiple hosts is a characteristic feature of **flukes**. - This is a fundamental distinguishing feature that separates trematodes from some other helminths. *Segmented (Incorrect)* - Trematodes (flukes) have **unsegmented, leaf-shaped or cylindrical bodies**, unlike cestodes (tapeworms) which are segmented. - The absence of body segmentation is a key morphological distinction from other helminths. *Anus present (Incorrect)* - Trematodes have an **incomplete digestive system** with a mouth and an esophagus, but **no anus**. - Waste products are expelled back through the **mouth**. - This blind-ending gut is characteristic of the class Trematoda. *Body cavity present (Incorrect)* - Trematodes are **acoelomates**, meaning they lack a true fluid-filled body cavity (coelom). - Their internal organs are embedded in **parenchymatous tissue** filling the space between body wall and organs.

Q: Which of the following statements about corneal dystrophy is true?

It is typically bilateral.. ***It is typically bilateral.*** - **Corneal dystrophies** are inherited genetic disorders that usually affect both eyes symmetrically. - This bilateral presentation is a key characteristic distinguishing them from other corneal conditions. *It is caused by inflammation.* - **Corneal dystrophies** are primarily genetic and degenerative, not inflammatory. - While inflammation can cause corneal damage (e.g., keratitis), it is not the underlying cause of dystrophy. *It involves neovascularization.* - **Neovascularization** (growth of new blood vessels) is typically a response to chronic inflammation, hypoxia, or infection in the cornea. - It is generally not a feature of primary corneal dystrophies, which are characterized by abnormal deposits or structural changes within the corneal layers. *It is usually unilateral.* - As inherited genetic conditions, **corneal dystrophies** almost always affect both eyes. - Unilateral involvement would suggest a different etiology, such as trauma, infection, or a localized acquired condition.

Q: What is the most common complication of pars planitis?

Cataract (clouding of the lens). **Cataract (clouding of the lens)** - **Cataract formation** is the most common ocular complication in patients with pars planitis, often due to chronic inflammation or steroid use. - The inflammation can disrupt lens metabolism, leading to **opacification** over time. *Retinal detachment (separation of retina)* - While possible, **retinal detachment** is a less common complication of pars planitis compared to cataract formation. - It can occur in severe cases, often due to vitreous traction on fragile peripheral retina or tears associated with **snowbanking**. *Cystoid macular edema (swelling of central retina)* - **Cystoid macular edema (CME)** is a significant cause of vision loss in pars planitis but is not the most frequent complication overall. - It results from the inflammatory compromise of the blood-retinal barrier, leading to fluid accumulation in the **macula**. *Glaucoma (increased intraocular pressure)* - **Glaucoma** can occur in pars planitis, often secondary to chronic inflammation affecting the **trabecular meshwork** or prolonged steroid use. - However, it is less common than cataracts and CME as a primary complication.

Q: Jack in box scotoma is seen after correction of Aphakia by?

Spectacles. ***Spectacles*** - **Jack-in-the-box scotoma** describes a visual phenomenon where objects appear to jump into and out of the field of vision. This occurs due to the **peripheral scotoma** and **ring scotoma** created by high-plus aphakic spectacle lenses. - Aphakic spectacles cause significant **magnification of the central visual field** (about 25-30%) and a corresponding minification/displacement of the peripheral field, leading to areas where objects are transiently obscured or reappear. *IOL* - An **intraocular lens (IOL)** replaces the natural lens within the eye, providing a much more stable and centered optical correction. - IOLs generally do not cause significant magnification changes or the peripheral scotoma associated with aphakic spectacles. *Contact lens* - **Contact lenses** sit directly on the cornea, offering a visual correction that is much closer to the nodal point of the eye than spectacles. - This placement results in less peripheral distortion and magnification compared to spectacles, making jack-in-the-box scotoma unlikely. *None of the options* - As **aphakic spectacles** are known to cause jack-in-the-box scotoma, this option is incorrect.

Q: Shaffer's sign is seen in ?

Retinal detachment. ***Retinal detachment*** - **Shaffer's sign** refers to the presence of **pigment cells** (tobacco dust) in the **anterior vitreous**, indicating a retinal break or detachment. - This sign is due to the release of retinal pigment epithelium cells into the vitreous following a tear in the retina. *Acute angle-closure glaucoma* - This condition is characterized by a **sudden increase in intraocular pressure** due to blocked fluid outflow, causing pain, redness, and blurred vision. - It does not involve pigment cells in the vitreous, but rather changes in the **anterior chamber angle**. *Diabetic retinopathy* - This is a microvascular complication of diabetes, leading to damage to the blood vessels in the retina, causing **hemorrhages**, **exudates**, and **neovascularization**. - It does not typically present with free pigment in the vitreous as a primary diagnostic sign. *Age-related macular degeneration* - This condition affects the **macula**, often causing distorted vision and central vision loss, and is characterized by drusen and atrophy. - While it can involve retinal changes, it does not classically present with pigment cells in the vitreous as a diagnostic indicator.

Question 1

What is the concentration of type 3 virus in the trivalent oral polio vaccine?

Accepted Answer

600,000 TCID 50

Answer

400,000 TCID 50

Answer

100,000 TCID 50

Answer

300,000 TCID 50

Question 2

Which of the following statements is false regarding yersiniosis?

Accepted Answer

Caused by Yersinia pestis

Answer

Gram-negative bacillus

Answer

Caused by Yersinia pseudotuberculosis

Answer

Caused by Yersinia enterocolitica

Question 3

Schistosomiasis is transmitted by?

Accepted Answer

Snail

Answer

Fish

Answer

Cattle

Answer

Cyclops

Question 4

Which of the following is the mechanism of action of tetanospasmin ?

Accepted Answer

Inhibition of release of GABA and glycine

Answer

Inhibition of Ach release from synapse

Answer

Inhibition of protein synthesis

Answer

Activation of adenylyl cyclase

Question 5

Which of the following statements about Haemophilus influenzae is true?

Accepted Answer

Encapsulated strains are the most common cause of severe H. influenzae diseases

Answer

It is not capsulated

Answer

Invasive strain causes severe diseases but is less common than non-invasive strains

Answer

Typically grown on chocolate agar in CO2-enriched environment but not clinically relevant to severe diseases

Question 6

Which of the following statements about trematodes is true?

Accepted Answer

Two hosts required

Answer

Segmented

Answer

Anus present

Answer

Body cavity present

Question 7

Which of the following statements about corneal dystrophy is true?

Accepted Answer

It is typically bilateral.

Answer

It involves neovascularization.

Answer

It is caused by inflammation.

Answer

It is usually unilateral.

Question 8

What is the most common complication of pars planitis?

Accepted Answer

Cataract (clouding of the lens)

Answer

Retinal detachment (separation of retina)

Answer

Cystoid macular edema (swelling of central retina)

Answer

Glaucoma (increased intraocular pressure)

Question 9

Jack in box scotoma is seen after correction of Aphakia by?

Accepted Answer

Spectacles

Answer

IOL

Answer

Contact lens

Answer

None of the options

Question 10

Shaffer's sign is seen in ?

Accepted Answer

Retinal detachment

Answer

Acute angle-closure glaucoma

Answer

Diabetic retinopathy

Answer

Age-related macular degeneration

NEET-PG 2012

Community Medicine

Microbiology

Ophthalmology