INI-CET 2021 - Microbiology PYQs Practice Questions

Q: Identify the correct 'organism-drug to which it is intrinsically resistant' pair.

Candida krusei - Fluconazole. ***Candida krusei - Fluconazole*** - **Candida krusei** is intrinsically resistant to **fluconazole** due to reduced affinity of its target enzyme, **lanosterol 14-alpha demethylase**, for the drug. - This resistance is a natural characteristic of the species, meaning it is inherent and not acquired through exposure. *Aspergillus fumigatus - Micafungin* - **Aspergillus fumigatus** is generally susceptible to **micafungin**, an **echinocandin drug** that targets fungal cell wall synthesis. - While resistance can develop, it is not an intrinsic characteristic of *A. fumigatus* to micafungin. *Candida albicans - Amphotericin B* - **Candida albicans** is typically susceptible to **amphotericin B**, a polyene antifungal that binds to ergosterol in the fungal cell membrane. - Intrinsic resistance to amphotericin B in *C. albicans* is rare, though acquired resistance can occur. *Aspergillus niger - Voriconazole* - **Aspergillus niger** is usually susceptible to **voriconazole**, a broad-spectrum triazole antifungal. - There is no known intrinsic resistance of *A. niger* to voriconazole. [Practice more Microbiology PYQs on OnCourse]

Q: Hepatitis B subunit vaccine contains which of the following antigens?

HbsAg. ***HbsAg*** - The Hepatitis B vaccine is a **subunit vaccine** that contains recombinant **hepatitis B surface antigen (HBsAg)**. - This antigen is highly immunogenic and elicits a protective antibody response (anti-HBs) that neutralizes the virus. *HbeAg* - **HBeAg** indicates active viral replication and high infectivity, but it is not the antigen used in the vaccine. - While important for diagnostic purposes, antibodies to HBeAg (anti-HBe) indicate reduced viral replication. *HbcAg* - **HBcAg (hepatitis B core antigen)** is an internal component of the virion and is not found in the subunit vaccine. - Antibodies to HBcAg (anti-HBc) indicate past or current infection but do not confer protective immunity. *HBV DNA* - **HBV DNA** represents the viral genetic material and is a marker of active viral replication and infectivity. - It is not an antigen and therefore not included in a subunit vaccine designed to induce an immune response to viral proteins. [Practice more Microbiology PYQs on OnCourse]

Q: A patient presented with meningitis, and the CSF sample was subjected to gram staining and microscopy and appears as shown in the microscopic image given below. Which of the following features / tests will be characteristic of the organism?

Catalase negative, optochin sensitive.. ***Catalase negative, optochin sensitive*** - The image shows **Gram-positive diplococci** (lancet-shaped, occurring in pairs), indicative of *Streptococcus pneumoniae*. - *S. pneumoniae* is known for being **catalase-negative** and **optochin-sensitive**, which are key diagnostic features that distinguish it from other α-hemolytic streptococci. - Additional characteristic: *S. pneumoniae* **ferments inulin** (bile soluble, quellung positive). *Ferments glucose and maltose but not inulin* - The phrase "does not ferment inulin" would suggest a streptococcus species OTHER than *S. pneumoniae*. - *S. pneumoniae* characteristically **DOES ferment inulin**, which is an important diagnostic feature. - This option is incorrect because it describes sugar fermentation that contradicts *S. pneumoniae* characteristics. *Oxidase and catalase negative, does not ferment inulin* - While *S. pneumoniae* is catalase-negative and oxidase-negative (oxidase test not routinely used for Gram-positive cocci), the statement "does not ferment inulin" is **incorrect** for *S. pneumoniae*. - *S. pneumoniae* **ferments inulin**, which is a key differentiating feature from other streptococci. - This combination of features does not match the organism shown in the microscopy. *Oxidase and catalase positive and does not ferment maltose or glucose* - This biochemical profile is typical for non-fermenting Gram-negative bacteria like *Pseudomonas aeruginosa*. - Such organisms would appear as **Gram-negative rods**, not the **Gram-positive diplococci** seen in the image. - This option is clearly incorrect based on the Gram stain morphology alone. [Practice more Microbiology PYQs on OnCourse]

Q: A 32 year old laborer working at a construction site presented with fever and hemoptysis. The sputum sample collected for examination showed the following. The smear will be stained by which of the following sequences?

Carbol fuchsin - acid - alcohol- methylene blue. ***Carbol fuchsin - acid - alcohol- methylene blue*** - The image displays thin, red, rod-shaped bacteria against a blue background, characteristic of **acid-fast bacilli** stained using the **Ziehl-Neelsen (ZN) method**. This staining sequence identifies *Mycobacterium tuberculosis*. - The ZN stain involves **carbol fuchsin** as the primary stain, followed by **acid-alcohol** as a decolorizer, and then **methylene blue** as a counterstain. *Methylene blue- malachite green-acetic acid - water* - This sequence is not a standard microbiological staining procedure for identifying common pathogens or acid-fast bacteria. - It does not contain the necessary components to achieve **acid-fast staining**, which is crucial for identifying mycobacteria. *Gentian violet - iodine - alcohol saffranin* - This sequence describes the reagents used in a **Gram stain**, which differentiates bacteria based on their cell wall composition. - Gram staining would show either purple (Gram-positive) or pink (Gram-negative) bacteria, not the red acid-fast bacilli seen in the image. *Methanol - methylene blue-acid - water* - While methylene blue is a counterstain in ZN, this sequence is incomplete and incorrect for standard acid-fast staining or other common bacterial stains. - It lacks **carbol fuchsin** as the primary stain, which is essential for acid-fast bacteria to retain the stain after destaining. [Practice more Microbiology PYQs on OnCourse]

Question 1

Identify the correct 'organism-drug to which it is intrinsically resistant' pair.

Accepted Answer

Candida krusei - Fluconazole

Answer

Candida albicans - Amphotericin B

Answer

Aspergillus fumigatus - Micafungin

Answer

Aspergillus niger - Voriconazole

Question 2

Hepatitis B subunit vaccine contains which of the following antigens?

Accepted Answer

HbsAg

Answer

HbeAg

Answer

HbcAg

Answer

HBV DNA

Question 3

A patient presented with meningitis, and the CSF sample shows Gram-negative diplococci on Gram staining and microscopy. Which of the following features/tests will be characteristic of the organism?

Accepted Answer

Oxidase positive, catalase positive, ferments glucose and maltose

Answer

Catalase negative, optochin sensitive, alpha-hemolytic

Answer

Oxidase negative, catalase positive, coagulase positive

Answer

Catalase positive, urease positive, does not ferment glucose

Question 4

A patient presented with meningitis, and the CSF sample was subjected to gram staining and microscopy and appears as shown in the microscopic image given below. Which of the following features / tests will be characteristic of the organism?

Accepted Answer

Catalase negative, optochin sensitive.

Answer

Ferments glucose and maltose but not inulin

Answer

Oxidase and catalase negative, does not ferment inulin

Answer

Oxidase and catalase positive and does not ferment maltose or glucose

Question 5

A 32 year old laborer working at a construction site presented with fever and hemoptysis. The sputum sample collected for examination showed the following. The smear will be stained by which of the following sequences?

Accepted Answer

Carbol fuchsin - acid - alcohol- methylene blue

Answer

Methylene blue- malachite green-acetic acid - water

Answer

Gentian violet - iodine - alcohol saffranin

Answer

Methanol - methylene blue-acid - water

Question 6

Identify the organism from the life cycle shown in the image given below

Accepted Answer

Cryptosporidium

Answer

Cystoisospora

Answer

Plasmodium knowlesi

Answer

Toxoplasma gondii

Question 7

Which pathogen causes attachment - effacement lesion in the intestinal mucosa as shown in the image?

Accepted Answer

Enteropathogenic Escherichia coli

Answer

Enterotoxigenic Escherichia coli

Answer

Diffusely adherent Escherichia coli

Answer

Enteroinvasive Escherichia coli

INI-CET 2021 — Microbiology