NEET-PG 2013 Practice Questions

Q: Which of the following statements about slow sand filters is true?

Requires a longer duration for filtration. ***Requires a longer duration for filtration*** - **Slow sand filters** operate at a much lower filtration rate (0.1–0.4 m/h) compared to rapid sand filters, thus requiring a **longer duration** to process the same volume of water. - This low filtration rate allows for the formation of a biological layer, the **schmutzdecke**, which is responsible for much of the purification. *Is more expensive than other filters* - **Slow sand filters** are generally **less expensive to construct and operate** than rapid sand filters because they do not require extensive chemical coagulation, flocculation, or backwashing equipment. - Their primary cost is often land acquisition due to the **larger footprint** required. *Uses sand size of 0.4 - 0.7 mm* - **Slow sand filters** use **finer (smaller) sand**, typically with an **effective size of 0.15-0.30 mm**, which is smaller than the sand used in rapid sand filters (0.4-0.7 mm). - The smaller sand particle size contributes to the slower filtration rate and enhanced biological treatment. *Occupies less space than other filters* - **Slow sand filters** require **significantly more land area** than rapid sand filters for a given output because of their low filtration rate and large basin size. - This larger footprint can be a limiting factor in areas with high land costs.

Q: Which of the following characteristics can be used to differentiate the rash of chickenpox from the rash of smallpox?

Pleomorphic. ***Pleomorphic*** - The rash of **chickenpox** is **pleomorphic**, meaning lesions at various stages of development (macules, papules, vesicles, scabs) are present simultaneously in the same body area. - In contrast, a **smallpox** rash is **monomorphic**, with all lesions in a given area appearing at the same stage of development. *Centrifugal* - A **centrifugal distribution** (lesions more concentrated on the face and extremities) is characteristic of **smallpox**. - **Chickenpox** typically has a **centripetal distribution**, with lesions more concentrated on the trunk. *Deep-seated* - **Smallpox** lesions are described as **deep-seated** and feel like "shot under the skin," often associated with significant scarring. - **Chickenpox** lesions are superficial and less likely to cause scarring unless secondarily infected. *Multilocular* - **Smallpox** vesicles and pustules are typically **multilocular**, meaning they have internal septations and do not collapse when punctured. - **Chickenpox** vesicles are unilocular, appearing as a single compartment, and collapse when punctured.

Q: What is the time limit for exhumation in India?

No specific time limit. ***No specific time limit*** - In India, there is **no specific legal time limit** for exhumation; it is subject to the discretion of a magistrate or judicial authority. - Exhumation is ordered if there is a **reasonable suspicion or compelling grounds** to believe that an examination of the remains will provide crucial evidence for a criminal investigation. *One month* - This is **incorrect** as there is no such restrictive time frame for exhumation in Indian law. - Exhumations are ordered based on the investigative needs, not arbitrary short deadlines. *One year* - This time limit is **not stipulated** in Indian legal provisions for exhumation. - The decision to exhume is made on a case-by-case basis, considering factors like the preservation status of the body and the potential evidentiary value. *Ten years* - There is **no fixed legal period** like ten years limiting exhumations in India. - The decaying state of a body over an extended period might reduce its forensic value, but technically, exhumation can still be ordered if deemed necessary for justice.

Q: Which of the following statements about Corynebacterium diphtheriae is NOT true?

Toxin mediated by chromosomal gene. ***Toxin mediated by chromosomal gene*** - The **diphtheria toxin** is encoded by the **tox gene**, which is a lysogenic bacteriophage (cornyphage) gene, not a chromosomal gene. - This **bacteriophage** integrates into the bacterial chromosome, making toxigenic *C. diphtheriae* strains lysogenized. *Has metachromatic granules* - *Corynebacterium diphtheriae* is known for possessing **metachromatic granules** (also called Babes-Ernst bodies), which are inclusions that stain differently from the rest of the cell. - These granules are composed of **polyphosphate reserves** and are important for identification. *Does not invade deeper tissues* - *Corynebacterium diphtheriae* remains **localized** to the mucosal surface of the upper respiratory tract or skin, forming a **pseudomembrane**. - Its pathogenicity is primarily due to the **exotoxin** it produces, which then disseminates systemically. *Toxigenicity demonstrated by elek's test* - The **Elek test** is a standard laboratory assay used to determine the **toxigenicity** of *Corynebacterium diphtheriae* strains by detecting the production of diphtheria toxin. - It works by identifying the **immunoprecipitation lines** formed between antitoxin and toxin in an agar medium.

Q: Which of the following bacteria can be identified using phage typing?

Salmonella. ***Salmonella*** - **Phage typing** is the most classical and widely used method for subtyping *Salmonella* species based on their susceptibility to specific bacteriophages. - This technique is extensively used in **epidemiological tracking** of outbreaks, particularly for *Salmonella typhi* and *S. enteritidis*, allowing differentiation of strains within the same species. - **Most commonly associated organism** with phage typing in clinical microbiology and medical education. *Streptococcus* - While phage typing was historically used for *Streptococcus pyogenes* (Group A Streptococcus), it has largely been replaced by **molecular typing methods** and is not the primary association when phage typing is mentioned. - *Streptococcus* species are typically identified through **Gram staining**, **catalase tests**, **hemolysis patterns** on blood agar, and **serological methods** (Lancefield grouping). *Shigella* - **Phage typing** is not routinely used for *Shigella* identification or subtyping in clinical practice. - **Serotyping** and **molecular methods** like pulse-field gel electrophoresis (PFGE) or whole genome sequencing are the standard approaches for *Shigella* differentiation. *Pseudomonas* - While **phage typing** has been used for *Pseudomonas aeruginosa* in research and outbreak investigations, it is not the primary or most commonly cited example of phage typing in medical education. - Routine identification relies on **culture characteristics** (pigment production, oxidase positive), **biochemical tests**, and **molecular methods**.

Q: Inclusion body containing glycogen is seen in which of the following organisms?

Chlamydia trachomatis. ***Chlamydia trachomatis*** - This species is known to form **intracytoplasmic inclusion bodies** that contain **glycogen**. - The presence of this glycogen allows these inclusions to be stained by **iodine**, aiding in laboratory identification. *Chlamydia pneumoniae* - Inclusion bodies of *Chlamydia pneumoniae* are typically **round or pear-shaped** and **do not contain glycogen**. - They are often **vacuolated** and stain poorly with iodine, unlike those of *C. trachomatis*. *Chlamydia psittaci* - The inclusion bodies of *Chlamydia psittaci* are usually **dense and pleiomorphic**, but they **do not contain glycogen**. - They tend to be **larger** and are often found near the host cell nucleus. *None of the options* - This option is incorrect because *Chlamydia trachomatis* specifically forms **glycogen-containing inclusion bodies**. - The presence of glycogen within inclusions is a key distinguishing feature of this species.

Q: Which is a GABA transaminase inhibitor?

Valproate. ***Valproate*** - Valproate is known to inhibit **GABA transaminase**, an enzyme responsible for the breakdown of **gamma-aminobutyric acid (GABA)**. - By inhibiting this enzyme, valproate increases the concentration of **GABA** in the brain, enhancing its inhibitory effects and contributing to its anticonvulsant properties. *TCA* - **Tricyclic antidepressants (TCAs)** primarily work by inhibiting the reuptake of **norepinephrine** and **serotonin** in the brain. - They do not directly inhibit GABA transaminase but rather modulate monoamine neurotransmission. *Sertraline* - **Sertraline** is a **selective serotonin reuptake inhibitor (SSRI)** that works by blocking the reabsorption of **serotonin** into presynaptic neurons. - Its primary mechanism of action is focused on serotonin pathways, not on GABA metabolism. *Gabapentin* - **Gabapentin** is an anticonvulsant that is thought to exert its effects by modulating **calcium channels** and increasing **GABA synthesis**, but it is not a direct inhibitor of GABA transaminase. - Its mechanism of action is distinct from directly preventing GABA breakdown.

Q: Drug of choice for familial hypercholesterolemia?

Lovastatin. ***Lovastatin*** - **Statins** (HMG-CoA reductase inhibitors) are the **first-line therapy** for familial hypercholesterolemia as they effectively lower **LDL cholesterol** levels by inhibiting cholesterol synthesis [1]. - While other agents can be used adjunctively, statins like lovastatin are the cornerstone for managing this genetic condition [2]. *Nicotinic acid* - **Nicotinic acid** (niacin) primarily lowers **triglycerides** and increases **HDL cholesterol**, but it is less potent than statins for reducing LDL-C, especially in familial hypercholesterolemia [1]. - Its use is often limited by significant **side effects** like flushing. *Cholestyramine* - **Cholestyramine** is a **bile acid sequestrant** that binds to bile acids in the intestine, preventing their reabsorption and mildly lowering LDL cholesterol. - It is less effective than statins and often causes **gastrointestinal side effects** such as constipation and bloating. *Gemfibrozil* - **Gemfibrozil** is a **fibrate**, primarily used to lower **triglyceride levels** and increase HDL cholesterol. - It has minimal impact on LDL cholesterol compared to statins and is not the primary treatment for familial hypercholesterolemia [2].

Q: Which of the following reduces the efficacy of oral contraceptives?

Griseofulvin. ***Griseofulvin*** - **Griseofulvin** is an antifungal agent known to induce liver enzymes, specifically the **cytochrome P450 system**. - Enzyme induction accelerates the metabolism and clearance of **oral contraceptives**, leading to lower plasma concentrations and reduced efficacy. *Erythromycin* - **Erythromycin** is a macrolide antibiotic that typically inhibits liver enzymes rather than inducing them. - While it can interfere with the metabolism of some drugs, it usually **increases** rather than decreases the plasma levels of co-administered medications, and is not known to reduce oral contraceptive efficacy. *Disulfiram* - **Disulfiram** is used to treat chronic alcoholism and inhibits aldehyde dehydrogenase. - It does not significantly interact with the metabolism of **oral contraceptives** via the cytochrome P450 system or other mechanisms that would reduce their efficacy. *Cimetidine* - **Cimetidine** is an H2 receptor antagonist that is known to inhibit cytochrome P450 enzymes. - This inhibition would likely **increase** the plasma concentration of drugs metabolized by these enzymes, such as oral contraceptives, rather than reducing their efficacy.

Q: Which second generation antihistaminic does not produce an active metabolite?

Cetirizine. ***Cetirizine*** - Cetirizine is unique among second-generation antihistamines as it is an **active metabolite** of hydroxyzine and **does not undergo further significant metabolism** to an active compound. - This characteristic contributes to its relatively **predictable pharmacokinetics** and reduced potential for drug interactions related to metabolism. *Loratadine* - Loratadine is a **prodrug** that is extensively metabolized in the liver by **CYP3A4 and CYP2D6** to its active metabolite, **desloratadine**. - Desloratadine is responsible for most of the **antihistaminic effects** of loratadine. *Terfenadine* - Terfenadine is a **prodrug** that is extensively metabolized by **CYP3A4** to its active metabolite, **fexofenadine**. - Due to its **cardiotoxicity** (QT prolongation) when its metabolism was inhibited, terfenadine was withdrawn from the market, and fexofenadine was developed as a safer alternative. *None of the options* - This option is incorrect because **cetirizine** does not produce an active metabolite, making it a valid answer for the question.

Question 1

Which of the following statements about slow sand filters is true?

Accepted Answer

Requires a longer duration for filtration

Answer

Is more expensive than other filters

Answer

Uses sand size of 0.4 - 0.7 mm

Answer

Occupies less space than other filters

Question 2

Which of the following characteristics can be used to differentiate the rash of chickenpox from the rash of smallpox?

Accepted Answer

Pleomorphic

Answer

Deep-seated

Answer

Centrifugal

Answer

Multilocular

Question 3

What is the time limit for exhumation in India?

Accepted Answer

No specific time limit

Answer

One year

Answer

Ten years

Answer

One month

Question 4

Which of the following statements about Corynebacterium diphtheriae is NOT true?

Accepted Answer

Toxin mediated by chromosomal gene

Answer

Has metachromatic granules

Answer

Toxigenicity demonstrated by elek's test

Answer

Does not invade deeper tissues

Question 5

Which of the following bacteria can be identified using phage typing?

Accepted Answer

Salmonella

Answer

Streptococcus

Answer

Shigella

Answer

Pseudomonas

Question 6

Inclusion body containing glycogen is seen in which of the following organisms?

Accepted Answer

Chlamydia trachomatis

Answer

Chlamydia pneumoniae

Answer

Chlamydia psittaci

Answer

None of the options

Question 7

Which is a GABA transaminase inhibitor?

Accepted Answer

Valproate

Answer

TCA

Answer

Gabapentin

Answer

Sertraline

Question 8

Drug of choice for familial hypercholesterolemia?

Accepted Answer

Lovastatin

Answer

Nicotinic acid

Answer

Cholestyramine

Answer

Gemfibrozil

Question 9

Which of the following reduces the efficacy of oral contraceptives?

Accepted Answer

Griseofulvin

Answer

Disulfiram

Answer

Erythromycin

Answer

Cimetidine

Question 10

Which second generation antihistaminic does not produce an active metabolite?

Accepted Answer

Cetirizine

Answer

Loratadine

Answer

Terfenadine

Answer

None of the options

NEET-PG 2013

Community Medicine

Forensic Medicine

Microbiology

Pharmacology