Last 5 Year PYQs in Microbiology for INI-CET

Q1. Which of the following is the infective stage of the organism being transmitted through cat feces?

1. Tachyzoite
2. Bradyzoite
3. Oocyst
4. Gametocyte

Ans. 2) Oocyst Stage

• The cat, specifically the definitive host, is responsible for the sexual reproduction of Toxoplasma gondii. Inside the cat's intestine, the parasite produces oocysts. These oocytes are then shed in the cat's feces. After being shed in the environment, the oocysts require a period of time, usually 1 to 5 days, to undergo sporulation. Sporulation makes the oocysts infective and is transmitted by ingestion of the contaminated food and water.

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Q2. A man has undergone renal transplant and is taking immunosuppressant drugs. On biopsy, there was the presence of budding cells with pseudohyphae. Identify the organism.

1. Candida
2. Aspergillus
3. Pneumocystis jirovecii
4. Histoplasma capsulatam

Ans. 1) Candida

• Immunosuppressant drugs are commonly prescribed to prevent organ rejection after transplantation and treat autoimmune diseases like rheumatoid arthritis or lupus. These drugs can weaken the immune response, reducing the body's ability to fight off infections.
• Candidiasis can manifest as oral thrush (white patches in the mouth and throat), vaginal yeast infections, or invasive candidiasis affecting the bloodstream, organs, or other body sites.
• In Candida, the bud remains attached to the mother cell, elongates, and undergoes repeated budding to form chains of elongated cells known as pseudohyphae. An elderly male presented with meningitis, and the CSF sample was subjected to gram staining and microscopy as shown in the image given. Which of the following will be characteristics of the likely organism?

Q3. An elderly male presented with meningitis, and the CSF sample was subjected to gram staining and microscopy, as shown in the image given. Which of the following will be characteristics of the likely organism?

1. Motile at 22° C and non-motile at 37° C
2. No motility at 22° C and motile at 37° C
3. Motile at both 37° C and 22° C
4. Non motile at both 37° C and 22° C

Ans. 1) Motile at 22° C and non-motile at 37° C

• The most common cause of meningitis in an elderly patient more than 60 years are Streptococcus agalactiae and Listeria monocytogenes.
• The image shows gram-positive bacilli; therefore, Listeria monocytogenes is the causative agent of meningitis in this elderly patient.

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Q4. In which of the following disorders is vaccination not contraindicated?

1. Digeorge syndrome
2. Wiskott-Aldrich syndrome
3. Complement Deficiency
4. Ataxia telangiectasia

Ans. 3) Complement Deficiency

Immune deficiency		Diseases	Vaccine contraindication
Primary immune deficiencies	B lymphocyte (humoral)	Severe antibody deficiencies (X-linked agammaglobulinemia, variable immune deficiency)	OPV, live influenza (LAIV), live bacteria (BCG, typhoid fever), MMR, varicella and rotavirus
		Mild antibody deficiency (selective IgA deficiency, Ig subgroup deficiency)	OPV, BCG. All other live vaccines can be administered.
	T lymphocyte (cellular)	Complete deficiency (severe combined immune deficiency, complete DiGeorge syndrome)	All live vaccines
		Partial deficiencies (partial Di George syndrome, ataxia-telangiectasia, Wiskott-Aldrich syndrome)	All live vaccines
	Complement deficiency	Persistent complement deficiency, C5-C9, C3, properdin, factor B deficiency	None
	Phagocyte dysfunction	Chronic granulomatous disease, leukocyte adhesion defect, myeloperoxidase deficiency	Live bacterial vaccines (BCG, typhoid fever)
Secondary immune deficiencies		Asplenia/functional asplenia	None
		Chronic renal diseases	LAIV
		Cancer, organ transplantation, autoimmune disease, immunosuppressive treatment, radiotherapy	Depending on the individual’s immune status, all live viral/bacterial vaccines.
		HIV/AIDS	OPV, BCG, MMRV, LAIV; if severe immunosuppression is present, MMR and varicella vaccines are not administered
OPV: oral polio vaccine; LAIV: live attenuated influenza vaccine; HIV: human immunodeficiency virus; AIDS: acquired immunodeficiency syndrome; BCG: live bacterial vaccines; Hib: hemophilus influenza type B; MMR: measles-mumps-rubella;

Q5. Which statement about Rubella is incorrect?

1. It is one of the teratogenic TORCH infections
2. Causes maculopapular rash that starts on the face and spreads caudally to involve the trunk and extremities
3. It is a Flavivirus
4. Symptoms include “Blueberry muffin” appearance

Ans. 3) Flaviviruses

• This statement is incorrect as Rubella is a Togaviruses with a linear and single-stranded RNA.

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Q6. Identify the pathognomonic structure in the slide given below.

1. Sclerotic body
2. Budding yeast
3. Negri body
4. Asteroid body

Ans. 1) Sclerotic Body

• This is a micrograph of chromoblastomycosis caused by Phialophora verrucosa and Fonsecaea pedrosoi, showing the sclerotic bodies, aka copper penny bodies, or muriform bodies.
• The fungi produce thick-walled, single, or multicellular clusters called sclerotic or muriform bodies. There is remarkable pseudoepitheliomatous hyperplasia of the epidermis.

Q7. Antigen binding to MHC class I activates which of the following cells?

1. Cytotoxic T cells
2. B cells
3. NK cells
4. Helper cells

Ans. 1) Cytotoxic T Cells

• HLA genes 1 produce MHC class I molecules, which are present on the surface of all nucleated cells and platelets. The cytotoxic T cells (CD8) recognize MHC class I antigens.

Q8. Which of the following is true about anti-CMV IgG antibodies?

1. Denotes latent CMV infection
2. Denotes chronic CMV infection with immunity to other serotypes
3. Indicates acute CMV infection
4. IgG avidity assay helps in differentiating past and primary infection

Ans. 4) IgG avidity assay helps in differentiating past and primary infection

• Positive CMV IgG results indicate past or recent CMV infection. IgG avidity assays are the tests that show the binding strength between IgG antibodies and CMV. In primary CMV infection, IgG antibodies will show low binding strength (low avidity) initially (acute infection), then after 4 months, affinity increases, suggesting past infection.

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Q9. Which of the following statements regarding the given image is correct?

1. Albendazole is the drug of choice
2. Majority of infections are asymptomatic in humans
3. Infection is acquired by ingestion of aquatic plants
4. No scolex and suckers

Ans. 2) Majority of infections are asymptomatic in humans

• The given image is the Egg of Hymenolepis nana. The egg is round and slightly oval in shape. It has two membranes that surround an embryo with six hooklets. The space between the two membranes is filled by yolk granules. Both the poles of the embryophore are thickened.

Q10. Which of the organisms listed below are capable of being stained with acid-fast staining?

1. Nocardia
2. Mycobacterium leprae
3. Actinomyces
4. Cryptosporidium parvum
5. Isospora belli

1. 1, 2, 3, 4, 5
2. 1, 2, 4, 5
3. 1, 2, 3
4. 3, 4, 5

Ans. 2) 1, 2, 4, 5

• Among the given list, the acid-fast organisms are:

• Cryptosporidium.
• Mycobacterium leprae.
• Nocardia.
• Isospora belli.
• Actinomyces are gram-positive filamentous, non-acid, fast anaerobic to microaerophilic bacteria that typically colonize the human mouth, urogenital tract, and gastrointestinal tract but can cause an infection known as actinomycosis.

Q11. In a healthy adult, what is the proportion between T cells and B cells?

1. 1:1
2. 3:1
3. 1:2
4. 1:3

Ans. 2) 3 : 1

• The percentage of T cells in a normal individual is about 60 to 70% as compared to B cells, with a percentage of 20 to 30%. T cells outnumber the B cells at least 3 to 5 times. Hence, only option B shows more T cells than B cells, so the best option is 3:1.

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Q12. A patient presented with severe watery diarrhea resembling that of rice gruel stool. Damage of which structure is likely to have resulted in this diarrhea?

1. Zona occludens
2. Gap junction
3. Adherens junction
4. Hemidesmosomes

Ans. 1) Zona occludens

• Rice watery stool is a characteristic of cholera caused by vibrio cholerae. A toxin against the Zona occludens, or tight junctions, is produced in the cholerae disrupting the junction leading to increased permeability, leakage of fluid and electrolytes resulting in rice water stools.

Q13. A 55-year-old patient had a tooth extraction three days back. He now presents with a mass in the submandibular region, which is otherwise asymptomatic. There is no ulcer on the oral mucosa. On drainage of the discharge, it was foul-smelling with a lot of yellow granules. What is the most likely implicated pathogen?

1. Fonsecaea pedrosoi
2. Mucor
3. Actinomyces israelli
4. Histoplasma capsulatum

Ans. 3) Actinomyces Israelli

• The patient had a recent tooth extraction, and the subsequent mass in the submandibular region suggests an infection spreading from the oral cavity.
• Actinomyces israelii is a commensal bacterium in the oral flora, and it can cause infection when there is a breach in the mucosal barrier, such as after dental procedures or trauma.
• The presence of foul-smelling discharge and yellow granules is a characteristic finding in actinomycosis.
• Actinomyces form aggregates called sulfur granules, which are composed of bacterial colonies surrounded by host tissue reactions. These granules are typically yellowish and contain tangled filamentous structures seen on microscopy.

Q14. Which of the given statements accurately reflects the characteristics of trematodes?

1. Fasciola hepatica are seen in the intrahepatic biliary radicles
2. Schistosoma are monoecious
3. Fasciola hepatica is not acquired through contaminated water
4. Triclabendazole is the treatment of choice for all trematode infections

Ans. 3) Fasciola hepatica are seen in the Intrahepatic Biliary Radicles

• Fasciola hepatica is a species of trematode commonly known as the liver fluke.
• It is primarily found in the liver and bile ducts of infected animals and humans.
• The adult flukes reside in the intrahepatic biliary radicles, which are the smallest branches of the bile ducts within the liver. They cause inflammation and damage to the liver tissue.

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Q15. Galactomannan in serum is seen in :

1. Invasive aspergillosis
2. Systemic candidiasis
3. Mucormycosis
4. Histoplasma capsulatm

1. 1 & 2 only
2. 1 & 3 only
3. 1 only
4. 1, 2 & 3 only

Ans. 3) 1 only

• Galactomannan is a major polysaccharide constituent of Aspergillus cell walls. It is a useful diagnostic marker for detecting this fungal infection.
• It is commonly used for the diagnosis of Aspergillus.
• Other pathogens positive for galactomannan are Fusarium, Penicillium, Histoplasma, Blastomyces, and Paecilomyces.

Q16. What is the causative organism for the condition shown in the image below ?

1. Echinococcus granulosus
2. Schistsoma japonicum
3. Echinococcus multilocularis
4. Schistosoma mansoni

Ans. 1) Echinococcus granulosus

• The causative organism for the condition shown in the image of a hydatid cyst in the liver is Echinococcus granulosus.
• Hydatid cyst is characterized by multiple pearly white cysts filled with clear or pale yellow fluid, the pH of the fluid is acidic (6.5), and contains salts and proteins. It is antigenic in nature and can cause anaphylaxis.
• The cysts formed by Echinococcus granulosus can grow quite large and can lead to symptoms such as abdominal pain, hepatomegaly (enlarged liver), and cyst rupture.

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Q17. Which of the following methods can detect deoxynucleotide incorporation in a DNA?

1. Flow cytometry
2. Pyrosequencing
3. FISH
4. RFLP analysis

Ans. 2) Pyrosequencing

• Pyrosequencing is a DNA sequencing technique that uses light generation to detect nucleotide incorporation. The reaction mixture includes a single-stranded DNA template, sequencing primer, and several enzymes like DNA polymerase, ATP sulfurylase, luciferase, and apyrase. Two substrates, APS ( adenosine 5‘ phosphosulfate) and luciferin, are also added.
• DNA polymerase adds deoxynucleotides to the DNA strand, forming a phosphodiester bond and releasing pyrophosphate. The enzyme ATP sulfurylase turns PPi into ATP, which is then used by luciferase to convert luciferin into oxyluciferin, emitting light proportional to the amount of ATP used/ number of nucleotides incorporated.

Q18. CD 40 marker is absent in a person. Which of the following would be seen?

1. Absent T cells
2. Absent B cells
3. Absent NK cells
4. Absent Macrophages

Ans. 2) Absent B cells

• B cells cannot respond to T-dependent antigens without a co-stimulatory signal from T_H cells. These antigens bind to B cells and are presented to T cells.
• Once TH cells recognize these complexes, they secrete cytokines and start expressing the CD40 ligand, which interacts with the CD40 receptor on B cells, providing the stimulus for B cell activation.
• CD40 signaling is essential for B cell activation, maturation, and production of antibodies. In the absence of CD40, B cells would not receive the necessary signals for proper activation and differentiation. This would result in impaired B cell function and reduced production of antibodies.

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