NEET-PG 2017 - Microbiology Practice Questions

Q: Which of the following bacteria will have following appearance?

Alcaligenes faecalis. ***Alcaligenes faecalis*** - The image shown is a **rod-shaped bacterium** with a **tuft of flagella at each pole**, resulting in a **bipolar flagellation** pattern typical of *Alcaligenes faecalis*. - This arrangement of flagella (amphitrichous) is characteristic for motility in this specific bacterium. *Vibrio cholerae* - *Vibrio cholerae* is a **curved rod** (comma-shaped) and typically possesses a **single polar flagellum** (monotrichous), which is different from the structure shown. - Its unique shape and flagellar arrangement are key identifiers in microbiology. *Spirilla* - **Spirilla** are **spiral-shaped bacteria** with a rigid, wavy form, which is distinctly different from the rod shape depicted in the image. - They can have various flagellar arrangements, but their overall morphology is elongated and coiled, not straight. *Salmonella typhi* - *Salmonella typhi* is a **rod-shaped bacterium** but it is typically **peritrichous**, meaning it has flagella distributed all over its cell surface, not just at the poles. - The image clearly shows flagella only at the ends, ruling out *Salmonella typhi*.

Q: A 25-year-old abattoir worker presents with myoclonus and amnesia for recent and remote events for last 1 year. MRI head was performed. All statements are correct about the organisms leading to this disease except:

Sensitive to ethylene dioxide. ***Sensitive to ethylene dioxide*** - Prions, the causative agents of Creutzfeldt-Jakob Disease (CJD), are **resistant to conventional sterilization methods**, including ethylene oxide, radiation, and disinfectants like formaldehyde. This statement is incorrect. - They are primarily inactivated by methods that denature proteins, such as **autoclaving at high temperatures and pressures** or strong sodium hydroxide solutions. *Absence of nucleic acid* - **Prions are infectious proteinaceous particles** that lack nucleic acid (DNA or RNA), which distinguishes them from viruses, bacteria, and other conventional pathogens. - They propagate by inducing conformational changes in normal host proteins. *CSF examination of patient shows presence of protein 14.3.3* - The presence of **14-3-3 protein** in cerebrospinal fluid (CSF) is a significant and widely used diagnostic marker for **Creutzfeldt-Jakob Disease (CJD)**. - Elevated levels of this protein indicate neuronal damage and are often found in patients with rapidly progressive dementia caused by prions. *MRI shows cortical ribboning* - **Cortical ribboning**, characterized by hyperintense signal changes in the cerebral cortex on diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) sequences, is a **highly characteristic finding in MRI scans of patients with CJD**. - This MRI finding, along with involvement of the basal ganglia and thalamus, supports the diagnosis of CJD.

Q: The image shows:

Loeffler serum slope. ***Loeffler serum slope*** - This image shows a **Loeffler serum slope**, characterized by its **pale yellow, solidified appearance** in a test tube, often used for culturing *Corynebacterium diphtheriae*. - The medium provides various nutrients and typically encourages the rapid growth of diphtheria bacilli, producing **characteristic morphology**. *Lowenstein Jensen media* - **Lowenstein Jensen media** is typically **greenish** due to the presence of **malachite green**, which inhibits the growth of most contaminants. - It is primarily used for the cultivation of **mycobacteria**, particularly *Mycobacterium tuberculosis*. *Wilson-Blair medium* - **Wilson-Blair medium** is a classic selective medium used for the isolation of *Salmonella typhi* and other *Salmonella* species, appearing as **black colonies**. - This medium contains **bismuth sulfite**, which imparts a distinctive black color to the colonies due to hydrogen sulfide production. *Selenite F broth* - **Selenite F broth** is a **clear enrichment broth** used for the isolation of *Salmonella* and *Shigella* species from fecal samples. - It works by **inhibiting the growth of coliforms** while allowing *Salmonella* and *Shigella* to multiply.

Q: The image shows:

Selenite F broth. ***Selenite F broth*** - This image displays **Selenite F broth**, a **selective enrichment medium** typically used for the isolation of *Salmonella* and *Shigella* species. - The characteristic **pale blue-green color** is due to the oxidation of the selenite salt. *Lowenstein Jensen media* - **Lowenstein Jensen media** is a solid, egg-based medium that usually appears **green** and is used for the cultivation of **Mycobacterium tuberculosis**. - It would typically be a solid slant rather than a liquid broth, and the color is distinctly different. *Wilson-Blair medium* - **Wilson-Blair medium** (Bismuth Sulfite Agar) is a solid, opaque medium, generally appearing **black** due to the presence of bismuth sulfite, used for isolating *Salmonella typhi*. - It is a solid agar medium, not a liquid broth as shown in the image. *Loeffler serum slope* - **Loeffler serum slope** is a solid, yellowish-white medium containing inspissated serum, primarily used for the isolation and cultivation of **Corynebacterium diphtheriae**. - It would be a solid slanted surface, not a blue-green liquid broth.

Q: The image shows:

Robertson cooked meat broth. ***Robertson cooked meat broth*** - The image displays a glass jar containing a **meat-based medium** at the bottom, covered with a liquid, which is characteristic of Robertson cooked meat broth. - This medium is primarily used for the **cultivation of anaerobic bacteria**, as the meat particles create an anaerobic environment and provide nutrients. *Alkaline peptone water* - Alkaline peptone water is a **liquid enrichment medium** that appears as a clear, yellowish broth without any particulate matter like cooked meat. - It is specifically used for the enrichment of *Vibrio cholerae* due to its high pH. *Lowenstein Jensen media* - Lowenstein Jensen media is a **solid egg-based medium** that is typically green in color and typically slants in test tubes or petri dishes. - It is used for the isolation and culture of **mycobacteria**, and its appearance is distinctly different from the image. *Cary Blair medium* - Cary Blair medium is a **semisolid transport medium** used for the preservation of enteric bacteria in stool samples. - It appears as a clear or slightly opalescent gel in a tube and does not contain visible chunks of meat.

Q: Which of the following is correct about the media shown below?

Liquid paraffin layering over the broth prevents air entry. ***Liquid paraffin layering over the broth prevents air entry*** - The image depicts **Cooked Meat Medium (CMM)**, which is used primarily for cultivating **anaerobic bacteria**, particularly Clostridia species. - **Liquid paraffin layering** on top of the broth is a key feature of CMM that **creates anaerobic conditions** by preventing oxygen diffusion into the medium. - This technique, combined with the reducing substances from meat particles, ensures a truly anaerobic environment suitable for obligate anaerobes. *Saccharolytic bacteria turn meat black* - **Saccharolytic bacteria** primarily ferment carbohydrates and produce acid/gas, but do not typically cause blackening of meat. - Blackening in CMM is associated with **hydrogen sulfide (H2S) production** by proteolytic bacteria, not saccharolytic activity. *Proteolytic bacteria turn meat red* - This is incorrect. **Proteolytic bacteria** break down proteins and typically turn the meat particles **black** due to H2S production. - The digestion of meat proteins by proteolytic Clostridia results in darkening (blackening), not reddening of the medium. *Favor growth of microaerophilic bacteria* - CMM is designed for **anaerobic bacteria**, not microaerophiles. - **Microaerophilic bacteria** require low oxygen tension (5-10% O2) and are cultivated in specialized conditions like candle jars or microaerophilic atmosphere generators, not in CMM. - CMM provides an anaerobic environment through liquid paraffin seal and reducing agents from meat.

Q: The following diagram depicts blood smear of which species?

Plasmodium falciparum. ***Plasmodium falciparum*** - The image displays characteristic **crescent-shaped or banana-shaped gametocytes** (stages 16-20), which are **pathognomonic for *Plasmodium falciparum*** - The earlier stages (1-5) represent ring forms (multiple rings per RBC, delicate ring forms) - Subsequent stages (6-15) show maturation culminating in the distinct **crescentic gametocytes** - This morphology is the **key distinguishing feature** of P. falciparum *Plasmodium vivax* - Produces **oval-shaped gametocytes**, not crescent-shaped - Characterized by enlarged RBCs with **Schüffner's dots** - Shows amoeboid trophozoites, not seen in this smear *Plasmodium malariae* - Produces **oval to round gametocytes** - Characteristic **band forms** and **rosette-shaped schizonts** (8-12 merozoites) - Not crescent-shaped as shown in the image *Plasmodium ovale* - Produces **oval gametocytes** similar to P. vivax - RBCs show **fimbriated edges** and Schüffner's dots - Does not produce crescent-shaped gametocytes

Q: Which of the following is correct about the image shown?

Dracunculus. ***Dracunculus*** - The image shows a procedure for extracting a **guinea worm (Dracunculus medinensis)** by gradually winding it around a stick. - This characteristic method of removal is pathognomonic for **dracunculiasis**. *Cutaneous Larva migrans* - This condition presents as **serpiginous, erythematous, pruritic tracks** on the skin, caused by hookworm larvae. - It does not involve a visible worm being extracted with a stick. *Visceral larva migrans* - This is caused by the migration of nematode larvae (typically *Toxocara canis* or *cati*) through internal organs, with systemic symptoms. - It does not manifest as a worm emerging from a skin lesion. *Tenia solium* - *Taenia solium* (pork tapeworm) infection can manifest as taeniasis (intestinal infection) or **cysticercosis** (larval cysts in tissues). - Neither of these presentations involves a worm being manually extracted from a skin lesion in this manner.

Q: A diplomat from Peru was posted to India last week. Today he has brought his 10-year-old daughter to your clinic since the child has developed this swelling in the eye and feels feverish. Comment on the clinical sign and the insect bite responsible for the same:

Romana sign, Triatomine bug. ***Romana sign, Triatomine bug*** - The image depicts **Romana sign**, characterized by **unilateral periorbital edema**, which is a classic early clinical manifestation of **Chagas disease** (American trypanosomiasis). - This sign is caused by the bite of a **Triatomine bug** (also known as a **kissing bug**) near the eye or by rubbing its feces containing *Trypanosoma cruzi* into the eye. The diplomat's origin from Peru suggests a potential exposure in an endemic region. *Faget sign, Reduvid bug* - **Faget's sign** is a clinical finding where the **pulse rate remains normal or decreases** despite a fever, which is typically found in diseases like **typhoid fever** or **yellow fever**, not associated with a specific insect bite causing periorbital edema. - While Triatomine bugs belong to the **Reduviidae family**, "Reduvid bug" is a broad term, and Faget's sign is unrelated to the described swelling. *Chigger allergy, Trombiculid mites* - **Chigger bites** (from Trombiculid mites) typically cause intensely **itchy, reddish welts or papules**, often in clusters, commonly on ankles, wrists, or waistbands. - They do not typically present as a significant unilateral periorbital edema like Romana sign and are not a cause of Chagas disease. *Eschar, Cimex Lectularis* - An **eschar** is a dark, scab-like lesion that occurs due to necrosis of skin tissue, often seen in conditions like **rickettsial diseases** (e.g., scrub typhus) following a tick or mite bite. - **Cimex Lectularis** refers to **bed bugs**, which cause itchy, erythematous wheals or papules, often in a linear pattern, but do not produce an eschar or Romana sign.

Question 1

Which of the following bacteria will have following appearance?

Accepted Answer

Alcaligenes faecalis

Answer

Vibrio cholerae

Answer

Spirilla

Answer

Salmonella typhi

Question 2

A 25-year-old abattoir worker presents with myoclonus and amnesia for recent and remote events for last 1 year. MRI head was performed. All statements are correct about the organisms leading to this disease except:

Accepted Answer

Sensitive to ethylene dioxide

Answer

Absence of nucleic acid

Answer

CSF examination of patient shows presence of protein 14.3.3

Answer

MRI shows cortical ribboning

Question 3

The image shows:

Accepted Answer

Loeffler serum slope

Answer

Lowenstein Jensen media

Answer

Wilson-Blair medium

Answer

Selenite F broth

Question 4

The image shows:

Accepted Answer

Selenite F broth

Answer

Lowenstein Jensen media

Answer

Wilson-Blair medium

Answer

Loeffler serum slope

Question 5

The image shows:

Accepted Answer

Robertson cooked meat broth

Answer

Alkaline peptone water

Answer

Lowenstein Jensen media

Answer

Cary Blair medium

Question 6

Which of the following is correct about the media shown below?

Accepted Answer

Liquid paraffin layering over the broth prevents air entry

Answer

Saccharolytic bacteria turn meat black

Answer

Proteolytic bacteria turn meat red

Answer

Favor growth of microaerophilic bacteria

Question 7

The following diagram depicts blood smear of which species?

Accepted Answer

Plasmodium falciparum

Answer

Plasmodium malariae

Answer

Plasmodium ovale

Answer

Plasmodium vivax

Question 8

Which of the following is correct about the image shown?

Accepted Answer

Dracunculus

Answer

Cutaneous Larva migrans

Answer

Visceral larva migrans

Answer

Tenia solium

Question 9

A diplomat from Peru was posted to India last week. Today he has brought his 10-year-old daughter to your clinic since the child has developed this swelling in the eye and feels feverish. Comment on the clinical sign and the insect bite responsible for the same:

Accepted Answer

Romana sign, Triatomine bug

Answer

Faget sign, Reduvid bug

Answer

Chigger allergy, Trombiculid mites

Answer

Eschar, Cimex Lectularis

NEET-PG 2017 — Microbiology