INI-CET High Yield Questions for Microbiology

Mastering the INI-CET demands a strategic approach to preparation, with an emphasis on high-yield topics proving to be a successful tactic. This blog zeroes in on exactly that – a curated list of high-yield questions in Microbiology that are highly likely to appear on the INI-CET. By acquainting yourself with these questions and their detailed explanations, you'll deepen your understanding of Microbiology concepts, enhancing your confidence and readiness for exam day.

1. A 5-year-old presents with sudden fever and rash, following a recent sore throat. Examination reveals febrile state, tender anterior cervical lymph nodes, circumoral pallor, red lines in antecubital fossae, diffuse sandpaper-like rash on trunk and extremities, and a strawberry-like tongue. What is the most likely diagnosis?

A. Measles (Rubeola)

B. Kawasaki disease

C. Rocky Mountain spotted fever

D. Scarlet fever

Correct Option D - Scarlet fever:

• The clinical features described in this case are classic for scarlet fever, which is caused by Streptococcus pyogenes (Group A Streptococcus). 
• Clinical features of scarlet fever:
  • Sore throat
  • Circumoral pallor
  • Antecubital fossa: pastia lines
  • Sandpaper rash
  • Lymphadenopathy
  • Erythrogenic toxins (SPEs)
  • Strawberry Tongue

Incorrect Option:

Option A - Measles (Rubeola): Presents with a prodrome of high fever, cough, coryza, and conjunctivitis, followed by the characteristic erythematous maculopapular rash that starts on the face and spreads downward.

Option B - Kawasaki disease: Features prolonged fever, conjunctival injection, rash, erythema of the palms and soles, cervical lymphadenopathy, and changes in the lips and oral cavity.

Option C - Rocky Mountain spotted fever: Presents with fever, headache, myalgias, and a petechial rash that typically starts on the wrists and ankles and spreads centrally.

2. A 49-year-old diabetic patient presents with a cough for more than 3 weeks, a blood streak in sputum, fever, chills and night sweats. CXR revealed a nodular infiltrate in the apical area of the right upper lobe. Identify the media used as shown in the image?

A. Loeffler serum slope medium

B. Lowenstein-Jensen Medium

C. Dorset egg slope medium

D. Petragnani slope medium

Correct Option B - Lowenstein-Jensen medium:

• The scenario given in stem indicates that the patient has TB.
• The medium in the image is Lowenstein–Jensen medium.
• Used to culture acid-fast bacilli like Mycobacterium tuberculosis in which the colonies have seen are rough, buff, tough and eugenic (luxuriant growth).
• It takes around 6 – 8 weeks to grow, and the 'green' colour of the media is due to malachite green.

Colony characteristics on LJ Media:

M. Tuberculosis	M. Bovis
Rough, buff and tough colonies on LJ media	Flat, moist and smooth colonies on LJ media
Aerobic	Microaerophile
Shows glycerol and niacin enhancement	No such enhancement

• LJ medium contains
  • Potassium dihydrogen phosphate anhydrous, Magnesium sulphate anhydrous, Magnesium citrate
  • Asparagine
  • Glycerol
  • Malachite green, 2% solution [selective agent].
  • Eggs as solidifying agent (agar is not used).
• Sterilized by ‘Inspissation’: 80 to 85°C for 30 min (for 3 days) for media containing egg or serum – (LJ media, Dorset’s egg medium, Loeffler’s serum slope).

Incorrect Options:

Option A - Loeffler serum slope medium

• Loeffler's medium is a special substance used to grow diphtheria bacilli to confirm the diagnosis.
• It consists of media containing blood (fresh, heated, or lysed) and serum as a solidifying agent.
• The serum has created difficulties in immunodiffusion tests and biochemical tests.

Option C - Dorset egg slope medium

• They are used to grow more exacting bacteria in their nutritional needs.
• It is a creamy-coloured opaque slope kept in screw copped bottle
• Selective medium for isolation of Mycobacterium tuberculosis.
• Composition: Hen’s egg, Nutrient broth

Option D - Petragnani slope medium

• It is an alternative medium used for acid-fast bacilli
• Petragnani Medium is used in qualitative procedures to isolate and cultivate mycobacteria from clinical specimens.

3. A 55-year-old man with diabetes and recent severe COVID-19 presents with nasal discharge, bulging eyes, and headache. Black lesions on nasal mucosa are observed with rhizoids on microscopy culture. What is the most likely causative organism for his presentation?

A.Candida albicans

B. Aspergillus fumigatus

C. Rhizopus oryzae

D. Cryptococcus neoformans

Correct Option C - Rhizopus oryzae:

• The patient's history of diabetes, recent COVID-19 recovery with steroid use, along with the presentation of nasal discharge, headache, black-colored lesions on the nasal mucosa and presence of rhizoids from where the sporangiophores arising in groups, is highly suggestive of rhino-oculo-cerebral mucormycosis caused by the fungus Rhizopus oryzae.
• These infections are more concerning in individuals who have received steroids, especially in the context of diabetes and COVID-19 recovery, as immunosuppression can predispose to opportunistic fungal infections.

Incorrect Options:

Option A - Candida albicans: Candida albicans is a yeast species commonly associated with various fungal infections, such as oral thrush and vaginal yeast infections.

Option B - Aspergillus fumigatus: Aspergillus fumigatus is a mould species known for causing pulmonary and invasive aspergillosis. Rhizoids are not a characteristic of aspergillosis.

Option D - Cryptococcus neoformans: Cryptococcus neoformans is a yeast-like fungus known for causing cryptococcal infections, particularly in immunocompromised individuals. It commonly affects the central nervous system and may lead to symptoms like headache, fever, and altered mental status.

4. What parasite shown in the image can be isolated from both the sputum and stool of a 30-year-old woman with cough, blood-tinged sputum, right-sided abdominal pain, and diarrhea after consuming crabs and fish is?

A. Paragonimus westermani

B. Fasciola

C. Clonorchis Sinensis

D. Pneumocystis carinii

Correct Option A- Paragonimus westermani:

• Patient Symptoms of cough, blood-tinged sputum, right-sided abdominal pain, and diarrhea, after consumption of crabs and fish, are common sources of Paragonimus infection.
• Operculated eggs detected in both sputum and stool samples.
• Eosinophilia (an increased number of eosinophils) in the complete blood count (CBC) report, which is a common finding in parasitic infections.
• These findings collectively suggest an infection with Paragonimus westermani, a lung fluke known to cause pulmonary symptoms and produce operculated eggs.

Incorrect Options:

Option B- Fasciola:

• Fasciola hepatica is a sheep liver fluke that causes disease primarily in sheep, and humans are only affected by eating watercress contaminated by larvae of fasciola.
• It causes right upper quadrant pain, fever and hepatomegaly and the diagnosis is made by identification of eggs in a stool sample.

Option C- Clonorchis Sinensis:

• Clonorchis Sinensis causes clonorchiasis (Asian liver fluke infection). Humans are infected by eating undercooked or raw fish (second intermediate host) containing encysted larvae.
• Most patients are asymptomatic, but upper abdominal pain, anorexia, hepatomegaly and Eosinophilia can occur.

Option D - Pneumocystis carinii:

• Pneumocystis carinii is a blood & tissue protozoan that causes diffused pneumonia in immunocompromised hosts.
• It causes fever, tachypnea and respiratory distress. Diagnosis can be made by identifying P carinii in sputum, bronchoalveolar lavage or lung biopsy.

5. A 28-year-old woman with a recent travel history to Africa presents with fever, confusion and neurological deficits. Laboratory analysis reveals the following findings. This organism exhibits a specific property that facilitates sequestration in vascular beds to avoid splenic clearance. What is the phenomenon called?

A. Rosetting

B. Agglutination

C. Cytoadherence

D. Schizogony

Correct Option C - Cytoadherence:

• The phenomenon described, where infected red blood cells adhere to endothelial cells, is known as cytoadherence. This process is particularly associated with Plasmodium falciparum infection and is mediated by specialised proteins, such as PFEMP1 (Plasmodium falciparum Erythrocyte Membrane Protein 1), which are present on the surface of infected red blood cells. 
• At times, inflammatory cytokines, notably IFN-gamma, generated by the malaria parasite, enhance the expression of endothelial cytoadherence receptors such as thrombospondin, E-selectin, VCAM-1, and ICAM-1 in brain capillaries, chondroitin sulfate B in the placenta, and CD36 in various organs. This leads to the adherence of infected red blood cells within capillaries and venules, eventually causing blockage.

Incorrect Options:

Option A - Rosetting: Rosetting refers to the clustering of uninfected red blood cells around an infected red blood cell, often seen in Plasmodium falciparum infection. These results in clinical manifestation of cerebral malaria.

Option - B Agglutination: Agglutination involves the clumping together of particles or cells, often mediated by antibodies.

Option D - Schizogony: Schizogony is the process of asexual reproduction in Plasmodium parasites, leading to the release of merozoites.

Also Read: INI-CET Previous Year Question Papers

6. 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.

7. A 65-year-old man diagnosed with colorectal carcinoma presents with pallor, lethargy, blood pressure of 145/76 mmHg, and a pulse rate of 112 beats/min. He also has hypercholesterolemia and osteoarthritis and takes atorvastatin, celecoxib, and a multivitamin. Despite surgical tumor removal, it relapses, prompting consideration of gamma delta cell therapy. What is true about gamma delta cells?

A. Helper T cells

B. Kills directly

C. Dendritic cells

D. More common than αβ T cells

Correct Option B - Kills directly:

• The above given is a case of colorectal carcinoma.
• Gamma delta T cells therapy is used against malignancies
• Gamma delta T cells are T cells, that have a distinctive T-cell receptor (TCR) on their surface.
• Most T cells are alpha beta T cells with TCR composed of two glycoprotein chains called α (alpha) and β (beta) TCR chains.
• In contrast, gamma delta (γδ ) T cells have a TCR that is made up of one γ ( gamma ) chain and one δ (delta) chain
• Unlike some other immune cells that require the help of antibodies or other cells, γδ T cells can exert cytotoxic effects on target cells without the need for further assistance. This direct killing ability is one of the unique characteristics of γδ T cells and makes them attractive for certain immunotherapeutic approaches in conditions like colorectal carcinoma.

Incorrect Options:

Option A - Helper T cells:

• A type of CD4-positive T cell that functions in augmenting and coordinating the immune response.
• Releases cytokines in response to recognition of antigens presented on MHC-II receptors.
• Subtypes include Th1, Th2 and Th17 cells.
• The specific subtype determines which cytokines are released and the type of immune response.

Option C - Dendritic cells:

• A phagocytic antigen-presenting cell.
• Expresses MHC class II and Fc receptors.
• They are inhibited by interleukin-10.

Option D - More common than αβ T cells:

• A type of lymphocyte detects downregulation of MHC class I molecules (e.g., by tumour cells or virally infected cells).
• In response, they activate and release cytotoxic granules (perforin and granzyme) that induce the lysis of target cells

8. A 30-year-old woman presents to the clinic for a routine prenatal checkup. During the visit, the healthcare provider discusses the development of immune responses in the fetus and the properties of certain immunoglobulins. Which of the following characteristics is most consistent with the antibody shown below?

A.Valency of 10 antigens

B. 80% present in extravascular spaces

C. Maximum fetal transfer during the first trimester

D. Activation of the alternative complement system

Correct Option A - Valency of 10 antigens:

• IgM is the first immunoglobulin class to be produced during an immune response and is known for its pentameric structure. The pentameric form of IgM gives it a valency of 10 antigen-binding sites (10 antigens). However, in practice, due to steric hindrance, only about 5-6 antigens can bind effectively to IgM at one time.

Incorrect Options:

Option B - 80% present in extravascular spaces: IgM is primarily found in the blood, not extravascular spaces.

Option C - Maximum fetal transfer during the first trimester: IgM does not transfer efficiently across the placenta due to its large size.The maximum fetal transfer of IgG occurs during the third trimester, not the first trimester.

Option D - Activation of the alternative complement system: IgM and IgG primarily activate the classical complement system, not the alternative complement system.

9. Which of the following organisms is commonly used as a biological indicator to assess the effectiveness of ETO gas sterilization?

1. Clostridium difficile
2. Bacillus anthracis
3. Bacillus cereus
4. Bacillus globigii

Correct Option D - Bacillus globigii:

• Ethylene oxide is a colorless gas and a widely used gaseous chemical sterilant. It acts by alkylating the amino, carboxyl, and sulphydryl groups in protein molecules within the microbes and spores.
• The biological indicator commonly used to assess the effectiveness of ethylene oxide (ETO) gas sterilization is: Bacillus globigii (also known as Bacillus subtilis or Bacillus atrophaeus) is a non-pathogenic, spore-forming bacterium. Bacillus globigii spores are highly resistant to sterilization methods and serve as a challenging test organism for evaluating the efficacy of the sterilization process.

Incorrect Options:

Options A, B, and C are incorrect. For an explanation, refer to option D.

10. A 35-year-old laboratory technician presents with a high fever, headache, chest pain, shortness of breath, and recent history of coughing up blood. He mentions observing peculiar growth in the ghee broth from his blood culture test. Which organism displays this type of growth?

A. Yersinia pestis

B. Treponema pallidum

C. Haemophilus influenza

D. Corynebacterium diphtheria

Correct Option A - Yersinia pestis:

• In Ghee broth or Oil broth medium, the oil floats on top of the broth, so a characteristic growth of the organism occurs as it hangs down into the broth from the broth's surface, resembling the broth stalactites (a tapering structure hanging like an icicle from the roof of a cave, formed of calcium salts deposited by dripping water). The image shows characteristic stalactite growth.

Incorrect Options:

Option B - Treponema pallidum:

• Treponema pallidum cannot be cultured in the laboratory.
• A serological test is used to detect treponema pallidum for the diagnosis of syphilis.

Option C - Hemophilus influenzae:

• Haemophilus influenza grows on blood agar and shows Satellitism with Staphylococcus aureus.
• 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 a source of the factor V is also provided.

Option D - Corynebacterium diphtheriae:

• Corynebacterium diphtheriae can grow on blood agar, but tellurite agar is preferred.
• This agar inhibits other respiratory flora and allows only C. diphtheriae to grow.

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