NEET PG High Yield Questions for Microbiology

To do well in the NEET PG exam, you need a smart study plan focusing on important topics. This blog provides a list of key questions in Microbiology that are likely to be on the exam. By studying these questions and their explanations, you'll improve your understanding of Microbiology concepts and feel more prepared and confident for the exam.

1. Which test, as shown in the image below, is being performed on the blood sample retrieved from a 3-week-old infant suffering from petechial rashes, fever, and irritability?

A. CAMP test

B. CAT

C. SAT

D. MAT

Correct Option A - CAMP test:

• The Christie, Atkins, and Munch-Peterson (CAMP) test is used to differentiate group B Streptococci (Streptococcus agalactiae–positive) from other streptococcal species. Listeria monocytogenes also produces a positive CAMP reaction.
• Blood agar shows two lines:
  • Longitudinal line represents Staphylococcus aureus haemolysis.
  • Perpendicular line due to Streptococcus agalactiae haemolysis.
• Arrowhead location - area of enhanced haemolysis at the meeting point of the two lines.

Incorrect Options:

Option B - CAT:

• CAT (cold agglutination test) is done for Mycoplasma.
• It is a blood test in which certain antibodies are checked that are made by immune system in response to infection.

Option C - SAT:

• SAT (standard agglutination test) is done for Brucella.
• It detects antibodies in the blood.
• Brucellosis diagnosis is made based on rising antibody titre.

Option D - MAT:

• MAT (micro agglutination test) is done for Leptospira.
• It is a gold standard test for the diagnosis of leptospirosis.

2. Which organism is likely involved in the formation of painless nodules that progressed to beefy red ulcers in the genital region of a 34-year-old, HIV-positive male with a history of unprotected intercourse?

A. Klebsiella granulomatis

B. Chlamydia trachomatis

C. Neisseria gonorrhea

D. Hemophilus ducreyi

Correct Option A - Klebsiella granulomatis:

• This is a case of donovanosis in which the patient presents with complaints of small painless nodules on his penis, which progressed to a beefy red ulcer in the genital region.
• The causative organism is Klebsiella granulomatis.
• Small, painless nodules appear after about 10–40 days of contact with the bacteria.
• Later, the nodules burst, creating open, fleshy, oozing lesions.
• The lesions occur at the region of contact typically found on the shaft of the penis, the labia, or the perineum.
• No other option above presents with a "beefy-red ulcer".

Incorrect Option:

Option B - Chlamydia trachomatis:

• Chlamydia trachomatis has serotypes of L1, L2 and L3.
• It usually causes lymphogranuloma venereum, characterized by suppurative inguinal adenitis. A small, painless papulovesicular lesion appears on the external genitalia after an incubation period of three days to five weeks. In later stages, the inguinal lymph nodes enlarge, suppurate, become adherent to the skin, and break down to form sinuses discharging pus.

Option C - Neisseria gonorrhoea:

• Neisseria gonorrhoea usually causes gonorrhoea.
• It usually presents as urethritis or cervicitis.

Option D - Hemophilus ducreyi:

• Hemophilus ducreyi causes chancroid.
• Chancroid is a painful genital ulcer.

3. A 32-year-old farmer presented with nodules on his leg. He walks barefoot and had a warty lesion on his foot a year ago, which grew in size and resulted in multiple nodular projections. Cauliflower-like ulcerated nodules are present on physical examination. What condition can be identified by this tissue specimen?

A. Chromoblastomycosis

B. Histoplasmosis

C. Sporotrichosis

D. Penicillium marneffi

Correct Option A – Chromoblastomycosis:

• The histological image above shows spherical or irregular, dark brown, yeast-like bodies with septae called sclerotic bodies/copper penny bodies/uniform bodies/medlar bodies which are seen in chromoblastomycosis.
• Chromoblastomycosis is a cutaneous infection affecting healthy individuals.
  • It is more common in tropical areas and among barefoot agricultural workers and woodcutters. Trauma, which often goes unnoticed, is the most frequent predisposing factor.
  • The disease is characterized by the appearance of warty, cutaneous nodules resembling cauliflower florets. Lesions may be verrucose (the most common type), crusted, ulcerative, or nodular/tumour-like, and usually grow slowly over time. It typically affects the subcutaneous tissue of the feet and lower legs. The fungi responsible for infection enter the skin through traumatic implantation, and the lesion slowly develops around the site of implantation.

Incorrect Options:

Option B - Histoplasmosis:

• Histoplasmosis is a pulmonary and hematogenous disease caused by Histoplasma capsulatum, found in soil and bird or bat droppings acquired by inhalation of spores.
• It presents as an asymptomatic or self-limiting disease in immunocompetent people. In immunocompromised state presents as fever, lymphadenopathy, hepatosplenomegaly and disseminated histoplasmosis.
• The infected tissue specimen shows large, thick-walled yeasts that appear oval and budding.

Option C – Sporotrichosis:

• Sporotrichosis is a cutaneous infection caused by saprophytic mould sporothrix schenckii acquired by trauma, classically from a thorn.
• Presents as cutaneous nodules that spread via lymphatics and break down into abscesses and ulcers.
• KOH tissue mount shows a characteristic feature, the asteroid body, an oval yeast-like body with rays of an eosinophilic substance radiating from the yeast cell.

Option D - Penicillium marneffi:

• This causes opportunistic infections in diabetics and is a common airborne contaminant of culture media.
• Microscopy demonstrates septate hyphae.
• It is a dimorphic fungus and is reported to be an important opportunist pathogen in individuals infected with HIV.
• It causes dissemination through the bloodstream to multiple organs.

4. A 50-year-old man with history of chronic lung disease and recurrent respiratory infections presents to the hospital with hemoptysis, chest pain, and cough. Imaging reveals a cavitary lesion in the lung, and a sputum culture confirms the presence of Aspergillus species. Which of the following treatment approaches is most appropriate to manage his current presentation?

A. Oral itraconazole

B. Surgical resection

C. Intravenous liposomal amphotericin B (LAMB)

D. Topical clotrimazole

Correct Option B - Surgical resection:

• The patient's presentation of hemoptysis, chest pain, cough, and the presence of a cavitary lesion in the lung which allows colonisation of the aspergillus and chest x ray showing a ball colonizing a preexisting lung cavity is suggestive of aspergilloma. Surgical resection along with antifungal (amphotericin-B) is the primary treatment for aspergillomas, especially when they lead to significant clinical symptoms.

Incorrect Options:

Option A - Oral itraconazole: Itraconazole is an antifungal medication commonly used to treat various fungal infections, including Aspergillus infections. However, in the case of an aspergilloma, which is a fungal ball within a preexisting lung cavity, surgical resection is often the preferred treatment to alleviate symptoms and prevent complications.

Option C - Intravenous liposomal amphotericin B (LAMB): Intravenous liposomal amphotericin B is an antifungal medication used for severe fungal infections, particularly those with systemic involvement. While antifungal therapy may be used in some cases of aspergillomas, surgical resection is the mainstay of treatment, especially for symptomatic cases.

Option D - Topical clotrimazole: Clotrimazole is an antifungal agent used for superficial fungal infections, such as those involving the skin or mucous membranes.

5. A 32-year-old presents with fatigue, abdominal discomfort, and an itchy rash on the feet, often walking barefoot. Exam shows a linear, serpiginous, erythematous rash. They report early respiratory symptoms. Which clinical manifestation can be associated with this infection?

A. Perianal pruritus

B. Lymphatic filariasis

C. Iron deficiency anemia

D. Coconut cake rectum

Correct Option C – Iron deficiency anemia:

• The patient's symptoms, including persistent fatigue, abdominal discomfort, and an itchy rash on the feet, are indicative of a parasitic infection.
• The presence of a linear, serpiginous, erythematous rash on the feet suggests a condition known as "ground itch," which occurs when hookworm larvae penetrate the skin.
• During the early phase of the infection, respiratory symptoms may occur, referred to as "Loffler syndrome," due to the migration of hookworm larvae through the lungs.
• The most common and characteristic clinical manifestation of hookworm infection is iron deficiency anemia, which results from chronic blood loss in the intestines.

Incorrect Options:

Option A - Perianal pruritus: Perianal pruritus, or itching around the anus, is a common symptom associated with Enterobius vermicularis (pinworm) infection, a different parasitic infestation. While perianal pruritus can be distressing, it is unrelated to the patient's presentation of abdominal discomfort, skin rash on the feet, and anemia.

Option B - Lymphatic filariasis: Lymphatic filariasis is a parasitic infection caused by filarial worms transmitted through mosquito bites. It typically results in a condition known as elephantiasis, characterized by the swelling of limbs, especially the legs and scrotum. This condition is not related to the symptoms described in the scenario, which primarily involve abdominal discomfort, skin rash, and anemia.

Option D - Coconut cake rectum: "Coconut cake rectum" is usually seen in patients infected by Trichuris Trichuria infection. Endoscopy often shows adult worms attached to the bowel mucosa (coconut cake rectum).

Also Read: NEET PG Previous Year Question Papers of Last 6 Years

5. A 4-month-old infant diagnosed with severe respiratory infection, exhibiting fever, cough, dyspnea, and wheezing, possibly viral in origin. Which drug is recommended, particularly for cases involving the virus known for syncytial formation?

A.Oseltamivir

B. Acyclovir

C. Amantadine

D. Ribavirin

Correct Option D - Ribavirin:

• Ribavirin is an antiviral medication that has been used in the treatment of severe viral infections, particularly those caused by the respiratory syncytial virus (RSV). It is often considered for severe cases, especially in immunocompromised individuals or those at high risk of complications. Ribavirin's mode of action involves interfering with viral RNA synthesis and replication.

Incorrect Options:

Option A - Oseltamivir: Oseltamivir is an antiviral medication used primarily to treat influenza infections. It inhibits the neuraminidase enzyme and is effective against influenza A and B viruses. It is not commonly used for treating respiratory syncytial virus (RSV) infections.

Option B - Acyclovir: Acyclovir is an antiviral drug used to treat infections caused by the herpes simplex virus (HSV) and varicella-zoster virus (VZV), including herpes labialis, genital herpes, and shingles. It is not indicated for RSV infections.

Option C - Amantadine: Amantadine is an antiviral drug that was historically used to treat influenza A virus infections. However, due to the development of resistance, its use has declined, and it is not typically recommended for treating respiratory infections caused by RSV.

6. A 4-year-old boy is brought to the physician complaining of itching, redness, and watery discharge from both eyes. A sample streaked with Staphylococcus aureus and left overnight shows the following findings. What is the probable organism responsible for this finding?

A. Haemophilus

B. StreptococcusC. Klebsiella

D. Proteus

Correct Option A- Haemophilus:

• Haemophilus spp. requires either or both of the X-factor (hemin or protoporphyrin IX) and V-factor (nicotinamide adenine dinucleotide (NAD)) for their growth and survival. Haemophilus spp. can be distinguished down to the level of the species based on whether they require either one or both of these growth factors.
• The finding shown in the image is known as Satellitism.
• The patient is suspected of having conjunctivitis due to Haemophilus influenza.

Satellitism

• The growth of Haemophilus influenzae is scanty on blood agar, as factor V is not freely available, being imprisoned inside the red blood cells. Growth is, therefore, better if the source of the V factor is also provided.
• When Staph aureus is streaked across a plate of blood agar on which a specimen containing H. influenzae has been inoculated, after overnight incubation, the colonies of H. influenzae will be large and well developed alongside the streak of staphylococcus and smaller further away. This phenomenon is called satellitism.
• Satellitism is due to the release of a high concentration of factor 'V' present in red blood cells by staphylococcus aureus, which is released into the medium and is used by H. influenzae.

Incorrect Options:

Option B - Streptococcus:

• Very occasionally, Satellitism is done by streptococcus species, Neisseria, and Diphtheroid.
• Streptococcus rarely can show satellitism but is unlikely to cause conjunctivitis. 

Option C- Klebsiella:

• Satellitism is not done by Klebsiella.
• Klebsiella grows on blood agar, but its colonies are non-hemolytic.

Option D- Proteus:

• Proteus grows in a successive waveform pattern on the blood agar plate to make concentric circles. This is called a swarming pattern. A bacteria showing a swarming pattern does not form discrete colonies on blood agar.

7. A 40-year-old woman presents with greenish discoloration of the nail bed. She is afebrile with normal vitals, and a mild elevation of WBCs is noted in lab results. Culture reveals pigmented colonies of gram-negative bacilli. What is the likely cause of this manifestation?

A. Candida

B. Pseudomonas

C. Staphylococcus aureus

D. Fusarium

Correct Option B - Pseudomonas:

• Pseudomonas is the likely cause of this manifestation.
• The diagnosis of this image is green nail syndrome.
  • Discolouration of the infected nail as it turns a dark green color due to Pseudomonas secreting the greenish pigments pyoverdin and Pyocyanin.
  • Paronychial infection can develop in individuals whose hands are frequently submerged in water.

Incorrect Options:

Option A - Candida:

• Candida can also infect the nail bed but does not produce pigments or green nail syndrome. It causes onychomycosis, seen in occupations that leads to frequent immersion of the hands in water.

Option C - Staphylococcus aureus:

• Bacterial nail infections can be caused by microorganisms such as staphylococcus aureus (S. aureus).
• It is a nail fold infection, which may involve the nail plate.
• Staphylococcus does not produce the characteristic finding of green nail syndrome.

Option D - Fusarium:

• Fusarium does cause nail infection but does not cause green nail syndrome.
• Symptoms include white or yellow nail discolouration, thickening, and separation from the nail bed.

8. Which specific type of pulmonary cells in the lungs is maximally equipped with ACE2 receptors for the attachment of a novel virus with a non-segmented positive-sense single-stranded RNA genome, facilitated by its spike protein?

A. Type 1 pneumocytes

B. Type 2 pneumocytes

C. Alveolar macrophages

D. Clara cells

Correct Option B- Type 2 pneumocytes:

• In this scenario, the virus in question has a non-segmented positive-sense single-stranded RNA genome and uses its spike protein to attach to host cells via ACE2 receptors, suggests the diagnosis of SARS-COV2.
• ACE2 receptors are present in various tissues, including the lungs. The expression of these receptors is particularly high in type 2 pneumocytes, which are specialised cells responsible for surfactant production and repair of the alveolar epithelium. These cells are also known to express high levels of TMPRSS2 (Transmembrane serine protease 2), an enzyme that facilitates viral entry into cells.

Incorrect Options:

Option A- Type 1 pneumocytes: Type 1 pneumocytes are the main cells responsible for gas exchange in the lungs. While they are an essential component of the alveolar epithelium, they do not express high levels of ACE2 receptors.

Option C- Alveolar macrophages: Alveolar macrophages are immune cells that reside in the alveoli of the lungs. Their primary function is to engulf and remove foreign particles, pathogens, and cellular debris. While they play an essential role in lung defence, they are not the primary cells targeted by the virus for attachment and entry via ACE2 receptors.

Option D- Clara cells: Clara cells also known as club cells, are found in the bronchioles of the lungs. They secrete a variety of substances that help protect the bronchioles and maintain lung homeostasis. Clara cells are not known to express high levels of ACE2 receptors, and they are not the primary cell type for viral attachment in the lungs.

9. What are the primary modes of transmission and the timing of maximum viral shedding for the virus responsible for the sudden-onset fever, cough, and fatigue in a 32-year-old healthcare worker with close contact to an infected colleague?

A. Infected fomites; maximum shedding occurs during the initial onset of symptoms

B. Blood transfusion; maximum shedding occurs 2 weeks after symptom onset

C. Sexual contact; maximum shedding occurs during the first week after symptom onset

D. Infected droplets and aerosol; maximum shedding occurs 5 to 8 hours before symptom onset

Correct Option D- Infected droplets and aerosol; maximum shedding occurs 5 to 8 hours before symptom onset:

• The sudden-onset fever, cough, and fatigue described in the patient are indicative of a respiratory viral infection, likely caused by a virus such as influenza. The most common modes of transmission for respiratory viruses are infected droplets and aerosol. Healthcare workers, due to their close interactions with patients, can be at higher risk of exposure.
• The key piece of information in this scenario is the timing of maximum viral shedding, which occurs 5 to 8 hours before symptom onset. This is a characteristic feature of many respiratory viruses, including influenza. Individuals shedding the virus just before symptoms become apparent can contribute significantly to its spread, as they may be unaware that they are contagious.

Incorrect Options:

Option A- Infected fomites; maximum shedding occurs during the initial onset of symptoms: Infected fomites refer to objects or surfaces that can become contaminated with pathogens. While some viruses can be transmitted through contact with contaminated surfaces (fomites), the symptoms described in the patient (fever, cough, fatigue) are more characteristic of a respiratory viral infection. Additionally, the timing of maximum viral shedding just before symptom onset doesn't align with maximum shedding occurring during the initial onset of symptoms.

Option B- Blood transfusion; maximum shedding occurs 2 weeks after symptom onset: Blood transfusion is not a common mode of transmission for respiratory viruses. The timing of maximum shedding (2 weeks after symptom onset) is not consistent with the rapid onset of symptoms described in the patient.

Option C - Sexual contact; maximum shedding occurs during the first week after symptom onset: Respiratory viruses are not typically transmitted through sexual contact. The symptoms (fever, cough, fatigue) and timing of maximum shedding (5 to 8 hours before symptom onset) do not match the pattern of a sexually transmitted infection.

10. A 49-year-old woman presents with generalized weakness, fatigue hindering dinner preparation, and double vision after prolonged reading, all alleviated by rest. Physical exam reveals drooping upper eyelids. Sensation and deep tendon reflexes are normal. Laboratory evaluation shows the prozone phenomenon. What is true about this phenomenon in this case?

A. It is a false negative result, implying excess antigen

B. It is a false negative result, implying excess Ab

C. False positive reaction

D. None of the above

Correct Option B - It is a false negative result, implying excess Ab:

• This is a case of myasthenia gravis.
• For a given antibody system, the optimal or equivalent ratio will be constant, irrespective of the quantity of the reactants.
• If the amounts of precipitate in the different tubes are plotted on a graph, the resulting curve will have three phases:
  • An ascending part (Prozone or zone of antibody excess)
  • A peak (zone of equivalence)
  • A descending part (Postzone or zone of antigen excess)
• The Prozone is important in clinical serology, as sera rich in antibodies may sometimes give false negative precipitation or agglutination results unless several dilutions are tested.

Incorrect Options:

Options A, C, and D are incorrect. Refer to Option B for an explanation.

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