A woman traveling from Bihar to Delhi is suspected to have Kala-azar. Suitable investigation is?
Heating a bacterial sample at 60°C for 30 minutes would isolate which of the following?
Which of the following viruses is a member of the Herpesviridae family?
HIV envelope is formed by:
Which HIV virus is associated with a higher transmission rate and virulence?
Which strain of the Influenza A virus, not of human origin, has the highest pandemic potential?
Which of the following can infect the ovary?
Which of the following is not a poxvirus?
What is a potential outcome of the integration of a viral genome into a host cell chromosome?
Which of the following statements about paramyxoviruses is false?
NEET-PG 2015 - Microbiology NEET-PG Practice Questions and MCQs
Question 51: A woman traveling from Bihar to Delhi is suspected to have Kala-azar. Suitable investigation is?
- A. P24 antigen
- B. Rk-39 test (Correct Answer)
- C. Combo RDT
- D. HRP-2 antigen
Explanation: ***Rk-39 test*** - The **Rk-39 test** is a rapid diagnostic test highly sensitive and specific for detecting antibodies against the **kinesin-related protein K39** of *Leishmania donovani*, the causative agent of **Kala-azar (visceral leishmaniasis)**. - It is particularly useful in **endemic regions** like Bihar for quick and accurate diagnosis, especially in patients with suspected Kala-azar presenting with fever, splenomegaly, and pancytopenia. *P24 antigen* - **P24 antigen** testing is primarily used for the diagnosis of **HIV infection**. - It detects the **core protein p24** of the HIV virus, which is not relevant for the diagnosis of Kala-azar. *Combo RDT* - A **Combo RDT** (Rapid Diagnostic Test), without further specification, typically refers to tests for **malaria**, which detect antigens like **HRP-2** and **aldolase**. - While RDTs are used for parasitic diseases, this general term does not specifically refer to a test for **Kala-azar**. *HRP-2 antigen* - **HRP-2 (Histidine-rich protein 2) antigen** is a specific marker for **Plasmodium falciparum**, used in the diagnosis of **malaria**. - It is not associated with the diagnosis of **Kala-azar**, which is caused by *Leishmania donovani*.
Question 52: Heating a bacterial sample at 60°C for 30 minutes would isolate which of the following?
- A. Staphylococci
- B. Micrococci
- C. Streptococci
- D. Enterococcus species (Correct Answer)
Explanation: ***Enterococcus species*** - **Enterococcus species** are known for their ability to survive harsh conditions, including temperatures of **60°C for at least 30 minutes**. - This characteristic is often used in laboratories for selective isolation and differentiation from other bacteria like streptococci and staphylococci. *Staphylococci* - While some staphylococci are quite hardy, most species, including *Staphylococcus aureus*, typically do not tolerate **60°C for 30 minutes** as well as enterococci. - Exposure to this temperature would likely significantly reduce the viability of most staphylococcal species, making their isolation difficult. *Micrococci* - **Micrococci** are generally less heat-tolerant than enterococci and would likely be killed or severely inhibited by exposure to **60°C for 30 minutes**. - They are generally susceptible to temperatures that would be survivable for thermoduric bacteria. *Streptococci* - Most **streptococcal species** are not highly resistant to heat and would be inactivated by prolonged exposure to **60°C**. - This heat treatment is often used in laboratory procedures to differentiate enterococci from other streptococci, as enterococci were historically classified as Group D streptococci.
Question 53: Which of the following viruses is a member of the Herpesviridae family?
- A. Variola
- B. Adenovirus
- C. HPV
- D. Herpes Simplex Virus (Correct Answer)
Explanation: ***Herpes Simplex Virus*** - **Herpes Simplex Virus (HSV)** is the type species of the *Herpesviridae* family, which includes other common human pathogens such as **cytomegalovirus** and **Epstein-Barr virus**. - Members of this family are characterized by a **double-stranded DNA genome**, an icosahedral capsid, and an envelope, and they typically cause **latent infections**. *Variola* - **Variola virus** is a member of the *Poxviridae* family, known for causing **smallpox**, a historically devastating disease. - Unlike herpesviruses, poxviruses are **large and complex DNA viruses** that replicate entirely in the cytoplasm of infected cells. *Adenovirus* - **Adenovirus** belongs to the *Adenoviridae* family and is a **non-enveloped DNA virus** known for causing a variety of conditions, including respiratory infections and conjunctivitis. - Its structure and replication cycle differ significantly from the enveloped *Herpesviridae*. *HPV* - **HPV (Human Papillomavirus)** is a member of the *Papillomaviridae* family, which are small **non-enveloped DNA viruses** associated with warts and certain cancers. - It is distinct from herpesviruses in its genomic organization, capsid structure, and disease manifestations.
Question 54: HIV envelope is formed by:
- A. Host cell
- B. Virus
- C. Both (Correct Answer)
- D. None of the options
Explanation: ***Both (Correct Answer)*** - The HIV envelope is a **composite structure** derived from both host and viral components - The **lipid bilayer** is acquired from the **host cell membrane** during viral budding - **Viral glycoproteins (gp120 and gp41)** encoded by the viral genome are inserted into this host-derived membrane - This makes the envelope a true hybrid structure essential for viral infectivity *Host cell (Incomplete)* - While the **lipid bilayer** of the envelope comes from the host cell membrane during budding, this alone does not form a functional envelope - The host cell provides the membrane scaffold but lacks the viral glycoproteins necessary for receptor binding and cell entry - Without viral proteins, the envelope cannot mediate infection *Virus (Incomplete)* - The virus encodes essential **envelope glycoproteins** (gp120 for receptor binding, gp41 for membrane fusion) - However, the virus does **not synthesize the lipid bilayer** itself - The viral genome lacks genes for lipid synthesis; the membrane must be acquired from the host *None of the options* - This is incorrect as the HIV envelope clearly requires contributions from **both** the host cell (lipid membrane) and the virus (glycoproteins)
Question 55: Which HIV virus is associated with a higher transmission rate and virulence?
- A. Both have similar risks
- B. It depends on individual factors
- C. HIV-2
- D. HIV-1 (Correct Answer)
Explanation: ***HIV-1*** - **HIV-1** is responsible for the vast majority of HIV infections worldwide and is known for its **higher virulence** and more rapid progression to AIDS. - It also has a **higher transmission rate** compared to HIV-2, contributing to its global prevalence. *HIV-2* - **HIV-2** is less virulent and has a **slower progression** to AIDS compared to HIV-1. - Its transmission rate is **lower** than HIV-1, and it is primarily concentrated in West Africa. *Both have similar risks* - This statement is incorrect because **HIV-1 and HIV-2 differ significantly** in their transmission rates, virulence, and disease progression. - **HIV-1** poses a much greater global health burden due to its higher infectivity and pathology. *It depends on individual factors* - While individual factors can influence disease progression, the intrinsic characteristics of **HIV-1** and **HIV-2** (such as transmissibility and virulence) are distinct and not solely dependent on the host. - The inherent biological differences between the two viruses are the primary determinants of their differential impact.
Question 56: Which strain of the Influenza A virus, not of human origin, has the highest pandemic potential?
- A. H1N1
- B. H9N2
- C. H2N2
- D. H5N1 (Correct Answer)
Explanation: ***H5N1*** - The **H5N1 avian influenza virus** is widely considered to have high pandemic potential due to its ability to cause severe disease and high mortality in humans, despite limited human-to-human transmission. - It circulates extensively in **poultry populations**, providing ample opportunity for zoonotic spillover. *H1N1* - While H1N1 caused the **2009 swine flu pandemic**, the question specifies a strain "not of human origin" with high pandemic potential, and H1N1 is an avian-origin reassortant that adapted to humans. - Current circulating seasonal H1N1 strains already have some human immunity, reducing their pandemic potential. *H2N2* - The **H2N2 strain** caused the 1957 "Asian Flu" pandemic, and current human populations have some immunity due to previous exposure to related strains in circulation. - It is no longer circulating in humans and its pandemic potential is lower compared to novel highly pathogenic avian strains like H5N1. *H9N2* - **H9N2** is a low-pathogenic avian influenza virus that has caused sporadic human infections, primarily in agricultural workers. - While it has zoonotic potential, its infections in humans are typically mild and its capacity for sustained human-to-human transmission remains very limited, indicating lower pandemic potential than H5N1.
Question 57: Which of the following can infect the ovary?
- A. Mumps virus (Correct Answer)
- B. Epstein-Barr Virus (EBV)
- C. Cytomegalovirus (CMV)
- D. Measles virus
Explanation: ***Mumps virus*** - The mumps virus can cause **oophoritis** (inflammation of the ovary) in post-pubertal females, though it is less common than orchitis in males. - Oophoritis typically presents with **lower abdominal pain** and tenderness, often accompanied by fever and other mumps symptoms like parotitis. *Epstein-Barr Virus (EBV)* - While EBV causes **infectious mononucleosis** and is associated with various lymphomas and nasopharyngeal carcinoma, it is not a primary cause of direct ovarian infection. - EBV primarily targets **B lymphocytes** and epithelial cells, and ovarian involvement is not a typical manifestation. *Cytomegalovirus (CMV)* - CMV can cause a wide range of infections, particularly in **immunocompromised individuals** and neonates, leading to congenital abnormalities. - Although CMV can infect many organs, direct infection of the ovary leading to oophoritis is **extremely rare** and not a recognized clinical entity. *Measles virus* - The measles virus primarily causes a systemic infection characterized by a **maculopapular rash**, fever, cough, coryza, and conjunctivitis. - While it can lead to complications such as pneumonia or encephalitis, **ovarian involvement or oophoritis** is not a known or common complication of measles.
Question 58: Which of the following is not a poxvirus?
- A. Molluscum contagiosum
- B. Orf virus
- C. Vaccinia virus
- D. Coxsackie virus (Correct Answer)
Explanation: ***Coxsackie virus*** - The **Coxsackie virus** belongs to the family **Picornaviridae**, not Poxviridae. - It is known for causing diseases such as **hand, foot, and mouth disease**, herpangina, and myocarditis. *Vaccinia virus* - **Vaccinia virus** is a well-known member of the **Poxviridae** family, historically used in the smallpox vaccine. - It is a **large, complex DNA virus** that replicates in the cytoplasm of infected cells. *Molluscum contagiosum* - **Molluscum contagiosum virus (MCV)** is a **poxvirus** that causes a mild skin infection characterized by raised, pearly, umbilicated lesions. - It primarily infects **humans**, causing localized lesions that are spread through direct contact. *Orf virus* - **Orf virus**, also known as contagious pustular dermatitis virus, is a **poxvirus** that primarily affects sheep and goats. - It can be transmitted to humans, causing single papular or nodular lesions, usually on the fingers, hands, or forearms.
Question 59: What is a potential outcome of the integration of a viral genome into a host cell chromosome?
- A. Altered growth
- B. Malignancy
- C. Latency
- D. All of the options (Correct Answer)
Explanation: ***All of the options*** - The insertion of a viral genome, known as a **provirus**, into the host chromosome can lead to a variety of sustained and complex interactions. - This integration can cause **long-term changes** in cell behavior, including altered gene expression and cell cycle regulation, which may manifest as any of the specified outcomes. *Malignancy* - Viral integration can interrupt or activate host genes, such as **oncogenes** or **tumor suppressor genes**, leading to uncontrolled cell proliferation and potential tumor formation. - An example is **human papillomavirus (HPV)** integrating into host cells, increasing the risk of cervical cancer. *Altered growth* - Integration can change the cell's normal growth patterns, either by promoting excessive division or by causing cell cycle arrest, impacting tissue development and function. - This can be due to the insertion of viral promoters or enhancers near growth-regulating genes. *Latency* - The integrated viral genome can remain dormant within the host chromosome without producing new viral particles for extended periods, a state known as **latency**. - During latency, the virus can be reactivated later to cause a productive infection, as seen with **herpesviruses**.
Question 60: Which of the following statements about paramyxoviruses is false?
- A. Belong to the family Paramyxoviridae
- B. Are DNA viruses (Correct Answer)
- C. Are RNA viruses
- D. Have linear nucleic acid
Explanation: ***Are DNA viruses*** - Paramyxoviruses are characterized by their **single-stranded, negative-sense RNA genome**, not DNA. - Their replication and transcription processes occur in the cytoplasm, which is typical for RNA viruses. *Belong to the family Paramyxoviridae* - This statement is correct; paramyxoviruses are indeed classified under the **family Paramyxoviridae**. - This family includes important human pathogens like measles, mumps, and respiratory syncytial virus (RSV). *Have linear nucleic acid* - This statement is correct as paramyxoviruses possess a **linear, non-segmented RNA genome**. - The linear nature differentiates them from viruses with segmented genomes, such as influenza viruses. *Are RNA viruses* - This statement is correct; paramyxoviruses are characterized by their **RNA genome**. - Specifically, they are **negative-sense, single-stranded RNA viruses**.