Last 5 year PYQs in Microbiology for NEET PG

Q1. A 35-year-old HIV-positive patient presents with mucosal lesions in the mouth as shown in the image below. On microscopy, budding yeasts and pseudohyphae are seen. What is the likely diagnosis?

1. Oral candidiasis
2. Hairy leukoplakia
3. Lichen planus
4. Diphtheria

Answer A) - Oral Candidiasis

Explanation

• The likely diagnosis for a 35-year-old HIV-positive patient with mucosal lesions in the mouth and the presence of budding yeasts and pseudohyphae on microscopy is oral candidiasis.
• Oral candidiasis, also known as oral thrush, is a fungal infection caused by the overgrowth of Candida species, particularly Candida albicans, in the oral cavity.
• It is common in individuals with compromised immune systems, such as those with HIV/AIDS.
• Microscopic examination of a sample from the mucosal lesions would reveal the presence of budding yeasts (small circular structures) and pseudohyphae (elongated structures with constrictions or constrictions between the budding cells). This characteristic appearance confirms the diagnosis of oral candidiasis.

Q2. Zika virus is transmitted by:

1. Aedes aegypti
2. Culex
3. Anopheles
4. Phlebotomus

Answer A) - Aedes Aegypti

Explanation

• Aedes aegypti mosquitoes are known as the primary vector for Zika virus transmission.
• These mosquitoes are also responsible for transmitting other diseases such as Eastern equine encephalitis, California encephalitis, Chikungunya, Rift valley fever, Yellow fever, and dengue..

Q3. Which of the subsequent microorganisms leads to illness after being introduced into the skin through trauma?

1. Sporothrix schenckii
2. Blastomyces dermatitidis
3. Coccidioides immitis
4. Paracoccidioides brasiliensis

Answer  A) - Sporothrix Schenckii:

• The organism that commonly causes disease following traumatic inoculation into the skin is Sporothrix schenckii.
• Sporothrix schenckii is a dimorphic fungus that causes a condition known as sporotrichosis or rose gardener's disease.
• It is found in soil and vegetation, particularly in environments associated with decaying plant matter.
• Traumatic inoculation occurs when the fungus enters the skin through thorns, splinters, or other puncture wounds, leading to localized infections.

Q4. Identify the class of immunoglobulin shown in the image below.

1. Ig A
2. Ig G
3. Ig M
4. Ig E

Correct Options A - IgA:

• The image given is of dimeric IgA aka secretory IgA.
• IgA (Immunoglobulin A) is a class of antibodies that plays a critical role in mucosal immunity, protecting the mucous membranes in various parts of the body. It exists in two main forms:
  • Monomeric IgAr/Serum IgA
  • Dimeric IgA/Secretory IgA.
• Monomeric IgA:
  • Each subunit of IgA monomer consists of two heavy chains (alpha chains) and two light chains (kappa or lambda chains) connected by disulfide bonds.
• Dimeric IgA:
  • IgA monomers can further polymerize to form IgA dimers.
  • The joining of two IgA monomers occurs through the J chain, a polypeptide that links the monomers together.
  • Additionally, a secretory component (also known as the polymeric immunoglobulin receptor or pIgR) is associated with the IgA dimer.

Q5. Which organism is the most probable cause of the symptoms described in a 14-year-old boy who experienced vomiting within 3 hours after eating at a party?

1. Staphylococcus aureus
2. Clostridium botulinum
3. Clostridium perfringes
4. Salmonella typhi

Answer  A) - Staphylococcus Aureus:

• Staphylococcus aureus is a bacterium known to produce toxins that can cause food poisoning. 
• Staphylococcus aureus can produce enterotoxins in dairy items and meat that cause rapid-onset symptoms of nausea and vomiting, typically occurring within a few hours (within 6 hours) of ingesting contaminated food.

Q6. Which of the subsequent organisms is responsible for the production of superantigens?

Staphylococcus epidermidis

Streptococcus pyogenes

Clostridium perfringens

Vibrio cholera

Answer B) - Streptococcus Pyogenes:

• Streptococcus pyogenes produces a group of superantigens known as streptococcal pyrogenic exotoxins (SPEs).
• Superantigens are a class of antigens that binds to the lateral Vβ part of toll-like receptors inducing activation of a large number of T-cells.
• Other examples of superantigens are:
  • Staphylococcal antigen/ Toxic Shock Syndrome Toxin (TSST)/ Enterotoxin F.
  • Streptococcal toxin (SPE- A&C).
  • Yersinia enterocolitica.
  • Yersinia pseudotuberculosis.
  • M.tuberculosis
  • EBV
  • CMV
  • Rabies
  • Malassezia furfu

Q7. A female patient from the north-eastern region of the country presented to the hospital with symptoms of gradually increasing swelling in her upper limb. She has a previous medical history of coronary artery disease and had a procedure called percutaneous coronary intervention. Upon examination, it was observed that the swelling is more pronounced closer to the body than towards the extremities. What would be the most appropriate course of action to manage this patient?

1. Echocardiography
2. Night blood test for worms
3. Duplex venous scan of limbs
4. ECG

Answer B) - Night blood test for worms

• The next best step in the management of this patient would be a night blood test for worms.

• Night blood testing, specifically for certain parasitic infections, can help identify the presence of filarial worms.
• Filarial infections, such as lymphatic filariasis, can cause lymphedema, which is characterized by progressive swelling of the limbs.
• The distribution of swelling, with more swelling proximally than distally, is suggestive of a possible filarial infection.
• During the night, certain species of filarial worms release microfilariae (larval forms) into the bloodstream.
• Collecting a blood sample during the night allows for the detection of these microfilariae, aiding in the diagnosis of a filarial infection.

Q8. Which of the following causative agents is commonly transmitted by soil and is characterized by the egg in stool, as shown in the image below?

1. Trichuris trichiura
2. Ancyclostoma duodenale
3. Necator americanus
4. Ascaris lumbricoides

Answer A) - Trichuris Trichiura:

• The helminthic infection commonly transmitted by soil and characterized by the egg in stool, as shown in the image, is Trichuris trichiura (whipworm) infection.
• Transmission: Trichuris trichiura is primarily transmitted through ingestion of food or water contaminated with soil containing infective eggs.
• Microscopic examination of the stool sample is used to identify the presence of Trichuris trichiura eggs. The eggs are characterized by
  • Bomb barrel-shaped.
  • Brown colored spots: Bile stained.
  • Mucous plugs at both ends are non-bile stained.

Q9. A 30-year-old female from a tribal area presented with fever for the last 3 days. On examination of the peripheral smear, a diagnosis of malaria was made. Which of the following is most likely to be the causative agent?

1. P. falciparum
2. P. malariae
3. P. ovale
4. P. vivax

Answer A) - P. Falciparum:

• The image shows multiple ring forms/headphone-shaped late trophozoites in erythrocytes, the most likely causative agent of malaria in this case is Plasmodium falciparum.
• Plasmodium falciparum is one of the species of Plasmodium that causes cerebral malaria in humans characterized by high fever, headache, anorexia, nausea, anemia, hypotension, tachycardia, hepatosplenomegaly, thrombocytopenia, confusion, increased muscle tone, seizures, paralysis, and coma.

Q10. The test kit shown in the image below works on the principle of

1. ELISA
2. Immunochromatography
3. Immunofluroscence
4. Chemiluminiscence

Answer B) - Immunochromatography:

The image showing HbsAg rapid card test, the test kit works on the principle of immunochromatography.

• Principle: Immunochromatography uses a liquid sample to carry the target substance through the components of a test strip. The test strip contains a capture antibody that is immobilized on the nitrocellulose membrane, as well as a labeled antibody that typically contains colored particles. This labeled antibody specifically binds to the target substance, and when it interacts with it, produces a visible line or color change that indicates a positive result.

Q11. What is the likely vector for the disease in a patient from Uttar Pradesh who presented with symptoms of fever, pallor, hepatosplenomegaly, pancytopenia, peripheral smear examination showing macrophages laden with organisms containing a kinetoplast?

1. Sandfly
2. Tse-Tse fly
3. Triatomine bug
4. Female anopheles mosquito

Answer A) - Sandfly:

• The clinical presentation of fever and hepatosplenomegaly with a peripheral smear showing pancytopenia and organism-laden macrophages with kinetoplast is highly suggestive of visceral leishmaniasis, aka kala-azar caused by Leishmania donovani.
• It is transmitted by a sandfly that releases promastigote in the blood, leading to leishmaniasis.

Q12. An unimmunized 2-year-old child presented with cough, coryza, conjunctivitis, and bluish-white spots in his buccal mucosa near the lower molar teeth. A day later, he developed a maculopapular rash on the face and neck. What is the nature of the causative virus?

1. Enveloped ssRNA
2. Naked ssRNA
3. Naked dsRNA
4. Enveloped ds RNA

Answer A) - Enveloped ssRNA:

• The characters stated in question point towards measles infection.
• Measles is caused by a single-stranded, enveloped RNA virus with 1 serotype. It is classified as a member of the genus Morbillivirus in the Paramyxoviridae family. Humans are the only natural hosts of the measles virus.
• Measles presents with
  • Fever - 1st manifestation around 10th day.
  • 3 C's - Cough, coryza, and conjunctivitis.
  • Pathognomonic feature - Kopliks spot near molar, white color dots on erythematous base.
  • Rash - Appears on the 14th day; the maculopapular rash starts from the ear to the face & follows the rest of the body.

Q13. What is the probable causative agent involved in the case of two individuals from a group of 20 friends who experienced nausea and vomiting in the early morning after consuming pastries from an external source during a late-night party?

1. Enterotoxin of staphylococcus
2. Emetic toxin of B. cereus
3. Verocytotoxin from E. coli
4. Shiga toxin from shigella

Answer A) - Staphylococcus aureus:

• The history of taking pastry and presentation of nausea and vomiting early in the morning is suggestive of food poisoning caused by enterotoxin of the Staphylococcus aureus. 
• Staphylococcus aureus can produce enterotoxins in dairy items and meat that cause rapid-onset symptoms of nausea and vomiting, typically occurring within a few hours (within 6 hours) of ingesting contaminated food.

Q14. A 3-year-old child presents with fever, loose stools, and blood in the stool. Which enrichment medium is used to isolate the organism from the stool sample?

1. Robertson cooked meat broth
2. Alkaline peptone water
3. Selenite F broth
4. Brain heart infusion broth

Answer C) - Selenite F broth:

• The clinical presentation of the patient suggests the diagnosis of dysentery most commonly caused by salmonella, shigella species, or enteroinvasive coli.
• Among the options, Selenite F broth is an enrichment media for detecting Salmonella and Shigella species.

Q15. Which type of microscope can be used to detect the motility of the probable causative organism in a truck driver presenting with painless indurated genital ulcer following unprotected sexual activity?

Dark-field microscope

Electron microscope

Light microscope

Fluorescent microscope

Answer A) - Dark-field microscope:

• The clinical presentation of painless indurated genital ulcer and occupation of the patient is suggestive of syphilis caused by treponema pallidum. 
• Treponema can be visualized under dark field microscope, it appears as slender, flexible, spirally coiled bacilli with tapering ends and slow movements.
• Spiral-shaped bacteria with axial filaments, includes leptospira, treponema, and borrelia. Only borrelia can be visualized using aniline dyes (Wright or Giemsa stain) in light microscopy due to size. Treponema is visualized by dark-field microscopy or direct fluorescent antibody (DFA) microscopy.

Q16. Microfilariae with sheathed tail and two nuclei at the tail is suggestive of?

1. Wuchereria bancrofti
2. Brugia malayi
3. Loa loa
4. Onchocerca volvulus

Answer B) - Brugia malayi

• Sheathed microfilariae with 2 nuclei at the tip of the tail is suggestive of Brugia malayi.

Q17. Which of the following is not used for induction of anesthesia in pediatric patients?

1. Halothane
2. Sevoflurane
3. Desflurane
4. Nitrous oxide

Answer C) - Desflurane:

• Desflurane is not commonly used for the induction of anesthesia in pediatric patients.
• It is mainly used for the maintenance of anesthesia due to its pungent odor and potential airway irritation during induction.

Q18. A central line infection is noted in an ICU patient, and staining shows a gram-positive oval-shaped organism that reproduces by budding. Identify the organism:

1. Staphylococcus aureus
2. Candida
3. Staphylococcus epidermidis
4. Escherichia coli

Answer B) - Candida:

• Candida species are yeast-like fungi that reproduce by budding and can cause central line infections, especially in immunocompromised patients.

Q19. A patient has a history of infection by Enterohemorrhagic Escherichia coli (EHEC) 0157, H7. What does the "H" represent?

1. Capsule
2. Flagella
3. Fimbriae
4. Lipopolysacharides

Answer B) - Flagella:

• The "H" in EHEC 0157, H7, refers to the flagella of Enterohemorrhagic Escherichia coli.

Q 20. A farmer suffered a wound on the dorsum of his foot. It later involved the subcutaneous tissue and became a discharging ulcer. Microscopy reveals gram-positive branching filaments. Identify the organism.

1. Nocardia
2. Sporothrix
3. Histoplasma
4. Candida

Answer A) - Nocardia

• Nocardia is a gram-positive bacterium that forms branching filaments and is often associated with causing cutaneous infections in immunocompetent individuals.

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