NEET-PG 2013 Practice Questions

Q: Which of the following demographic characteristics can be GENERALLY assessed from the visual structure of a population pyramid without requiring precise statistical calculations?

Life expectancy. ***Life expectancy*** - A population pyramid visually represents the age and sex distribution of a population, which allows for a general inference of **life expectancy** based on the pyramid's shape. - A pyramid with a broad base and rapidly tapering top suggests **lower life expectancy**, while one with a more rectangular shape in older age cohorts indicates **higher life expectancy**. *Exact male-to-female population ratios* - While the pyramid shows the proportion of males and females in each age group, determining **exact numerical ratios** for the entire population from a visual glance is difficult. - Precise calculation would require **specific data values** for each bar. *Immigration and emigration rates* - Population pyramids can sometimes show **"bulges" or "indents"** in specific age groups that might hint at past large-scale migration. - However, **direct assessment of rates** (e.g., how many people per 1,000 immigrated or emigrated) from its visual structure alone is not possible. *Crude birth rate per 1,000 population* - The **width of the base** of the pyramid gives a general idea of the birth rate, with a wider base indicating higher births. - However, to determine the **exact crude birth rate per 1,000**, specific statistical data is required, not just a visual assessment of the pyramid's shape.

Q: Which of the following is a stomach poison?

Paris green. ***Paris green*** * **Paris green** (copper(II) acetoarsenite) is primarily used as a **stomach poison** for insects, meaning it needs to be ingested to be effective. * It is a **highly toxic inorganic compound** that disrupts cellular respiration. * *DDT* * **DDT (dichlorodiphenyltrichloroethane)** is a **contact poison** and neurotoxin, primarily absorbed through the insect's cuticle. * It primarily affects the insects' **nervous system**, causing uncontrolled firing of neurons. * *Malathion* * **Malathion** is an **organophosphate insecticide** that acts as a **contact and stomach poison**, but its primary mode of action is through contact and fumigant effects. * It inhibits **acetylcholinesterase**, leading to paralysis and death in insects. * *Pyrethrum* * **Pyrethrum** is a natural insecticide derived from **chrysanthemum flowers** that acts primarily as a **contact poison** and repellent. * It causes **rapid knockdown** of insects by affecting their nervous system, though many insects may recover if not exposed to high enough doses.

Q: What is the appropriate diluent for the BCG vaccine?

Sterile distilled water. ***Sterile distilled water*** - **Sterile distilled water** is the recommended diluent for the **BCG vaccine** to ensure proper reconstitution and antigen stability. - Using the correct diluent is critical for maintaining the **efficacy** and safety of the vaccine. *Sterile normal saline* - **Sterile normal saline** (0.9% NaCl) can be used as a diluent for some vaccines, but it is **not appropriate for BCG** as it can negatively impact vaccine viability. - The **salt concentration** in saline can affect the live attenuated organisms in the BCG vaccine. *Sterile dextrose solution* - **Dextrose solutions** are generally avoided as vaccine diluents due to their potential to support **bacterial growth** or alter vaccine stability. - They are primarily used for **intravenous fluid administration** and not for vaccine reconstitution. *Colloid solutions* - **Colloid solutions** like albumin or dextran are never used as vaccine diluents as they can interfere with the **vaccine antigens** and cause adverse reactions. - These solutions are typically used for **plasma volume expansion** and have no role in vaccine preparation.

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: In blood culture the ratio of blood to reagent is?

1:10. ***1:10*** - A 1:10 ratio of **blood to reagent (culture media)** is recommended for optimal growth of microorganisms in blood cultures. - This dilution minimizes the inhibitory effect of **human antimicrobial factors** present in the blood, while still providing sufficient blood volume for pathogen detection. *1:5* - A 1:5 ratio would mean a relatively **higher concentration of blood** in the culture. - This higher concentration could lead to increased inhibition of bacterial growth by **host defense mechanisms** or **antibiotics** present in the patient's blood, potentially causing false-negative results. *1:20* - A 1:20 ratio implies a **lower concentration of blood** relative to the culture media. - While it further dilutes inhibitory factors, it also reduces the total number of microorganisms sampled, possibly leading to **false-negative results** if the bacterial load is low. *1:100* - A 1:100 ratio would result in an **extremely low concentration of blood** in the culture. - This significantly reduces the likelihood of detecting microorganisms, especially when the **bacteremia is sparse**, due to insufficient bacterial inoculum, leading to a high rate of false negatives.

Q: Which MRSA strain type is most commonly associated with hospital-acquired infections?

Phage type 80/81. ***Phage type 80/81*** - This **phage type**, particularly **epidemic methicillin-resistant *Staphylococcus aureus* (EMRSA) 15 and 16**, is historically and currently the most common cause of **hospital-acquired MRSA infections** worldwide. - It rapidly diversified and spread globally, becoming a significant nosocomial pathogen. *Phage type 83A* - While this phage type has been associated with **MRSA outbreaks**, it is not the most common strain type globally for hospital-acquired infections. - Its prevalence is more regional and sporadic compared to the widespread dominance of EMRSA 15/16. *Phage type 84* - **Phage type 84** is not widely recognized as a predominant strain associated with the majority of **hospital-acquired MRSA infections**. - Other, more virulent and successful clonal types have outcompeted it to become the most prevalent. *Phage type 85* - Similar to other less common types, **phage type 85** does not represent the major lineage responsible for the bulk of **hospital-acquired MRSA cases**. - The landscape of MRSA epidemiology is dominated by a few highly successful clonal complexes, of which 80/81 is a prime example.

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 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: All of the following are adverse effects of nicotinic acid except:

Pancreatitis. ***Pancreatitis*** - **Pancreatitis** is not a commonly reported adverse effect of nicotinic acid (niacin) therapy. - While other gastrointestinal side effects like nausea and vomiting can occur, pancreatic inflammation is not characteristic. *Vasodilation* - **Cutaneous flushing** and **vasodilation** are very common adverse effects of nicotinic acid, mediated by prostaglandin release. - This effect can cause a sensation of warmth, redness, and itching, especially at the start of therapy. *Liver dysfunction* - **Liver dysfunction**, including elevated liver enzymes and rare cases of **hepatotoxicity**, can occur with high doses of nicotinic acid. - Regular monitoring of liver function tests is recommended for patients on niacin therapy. *Hyperpigmentation* - **Hyperpigmentation**, particularly **acanthosis nigricans**, is a known cutaneous side effect of nicotinic acid. - This typically presents as dark, velvety patches on the skin, especially in skin fold areas.

Question 1

Which of the following demographic characteristics can be GENERALLY assessed from the visual structure of a population pyramid without requiring precise statistical calculations?

Accepted Answer

Life expectancy

Answer

Exact male-to-female population ratios

Answer

Immigration and emigration rates

Answer

Crude birth rate per 1,000 population

Question 2

Which of the following is a stomach poison?

Accepted Answer

Paris green

Answer

DDT

Answer

Malathion

Answer

Pyrethrum

Question 3

What is the appropriate diluent for the BCG vaccine?

Accepted Answer

Sterile distilled water

Answer

Sterile normal saline

Answer

Sterile dextrose solution

Answer

Colloid solutions

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

In blood culture the ratio of blood to reagent is?

Accepted Answer

1:10

Answer

1:5

Answer

1:20

Answer

1:100

Question 6

Which MRSA strain type is most commonly associated with hospital-acquired infections?

Accepted Answer

Phage type 80/81

Answer

Phage type 83A

Answer

Phage type 85

Answer

Phage type 84

Question 7

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

Accepted Answer

Salmonella

Answer

Streptococcus

Answer

Shigella

Answer

Pseudomonas

Question 8

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 9

Which of the following reduces the efficacy of oral contraceptives?

Accepted Answer

Griseofulvin

Answer

Disulfiram

Answer

Erythromycin

Answer

Cimetidine

Question 10

All of the following are adverse effects of nicotinic acid except:

Accepted Answer

Pancreatitis

Answer

Liver dysfunction

Answer

Vasodilation

Answer

Hyperpigmentation

NEET-PG 2013

Community Medicine

Microbiology

Pharmacology