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?
HTLV-1 can be transmitted by -
Von Magnus phenomenon:
Trypanosoma cruzi is transmitted by which of the following?
Duodenal aspirate is used in diagnosis of:
What is required for precipitation in comparison to agglutination?
Which of the following statements about the VDRL test is LEAST accurate?
NEET-PG 2015 - Microbiology NEET-PG Practice Questions and MCQs
Question 61: 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 62: 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 63: 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 64: 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**.
Question 65: HTLV-1 can be transmitted by -
- A. Blood transfusion (Correct Answer)
- B. Droplet inhalation
- C. Contaminated water
- D. Animal bite
Explanation: ***Blood transfusion*** - **HTLV-1 (Human T-lymphotropic virus type 1)** can be effectively transmitted through **blood products** and is a significant concern for blood safety. - **Major transmission routes of HTLV-1 include**: blood transfusion, breastfeeding (mother-to-child, most common in endemic areas), sexual contact, and sharing contaminated needles. - Screening of blood donors for HTLV-1/2 antibodies is crucial in endemic areas (Japan, Caribbean, parts of Africa and South America) to prevent transfusion-associated transmission. - This mode of transmission has been significantly reduced in countries with mandatory donor screening programs. *Droplet inhalation* - **HTLV-1** is **not transmitted via respiratory droplets** or aerosols, unlike viruses such as influenza or SARS-CoV-2. - Transmission requires direct contact with **infected cells** (primarily CD4+ T lymphocytes) or bodily fluids containing infected cells. - HTLV-1 is a cell-associated virus, not present free in respiratory secretions. *Contaminated water* - **HTLV-1** is a **blood-borne and sexually transmitted retrovirus** and is not transmitted through contaminated water. - The virus cannot survive in water and requires cell-to-cell contact or cell-containing fluids for transmission. - Waterborne diseases are caused by pathogens that can survive in aquatic environments, which does not apply to HTLV-1. *Animal bite* - **HTLV-1** is a **human-specific retrovirus** with no animal reservoir; it is not transmitted through animal bites. - Unlike zoonotic viruses (rabies, certain arboviruses), HTLV-1 transmission is strictly human-to-human. - The virus specifically infects human CD4+ T cells and does not have vectors or animal hosts.
Question 66: Von Magnus phenomenon:
- A. Virus has high infectivity
- B. Is a normal replicative cycle
- C. Virus yields have high hemagglutination but low infectivity (Correct Answer)
- D. Virus yield has low hemagglutination
Explanation: ***Virus yields have high hemagglutination but low infectivity*** - The **von Magnus phenomenon** describes the serial passaging of influenza virus at high multiplicity of infection, leading to the production of **defective interfering particles (DIPs)**. - These DIPs retain their ability to **hemagglutinate** (due to intact hemagglutinin proteins) but have lost significant portions of their genome, resulting in **low infectivity**. *Is a normal replicative cycle* - The von Magnus phenomenon is characterized by an **abnormal replicative cycle** and the accumulation of defective viral particles. - A normal replicative cycle involves the production of **fully infectious** viral progeny. *Virus yield has low hemagglutination* - The abnormal particles produced during the von Magnus phenomenon, known as **defective interfering particles (DIPs)**, typically retain their **hemagglutinin protein**. - This allows them to still induce **hemagglutination**, despite their reduced infectivity. *Virus has high infectivity* - A hallmark of the von Magnus phenomenon is the production of virus particles with **significantly reduced infectivity**. - This is due to the deletion or mutation of essential genetic material necessary for a productive infection.
Question 67: Trypanosoma cruzi is transmitted by which of the following?
- A. Tse tse fly
- B. Reduviid bug (Correct Answer)
- C. Culex mosquito
- D. Sand fly
Explanation: ***Reduviid bug*** - *Trypanosoma cruzi*, the causative agent of **Chagas disease**, is primarily transmitted to humans through the feces of infected **reduviid bugs**, also known as **kissing bugs**. - The bug typically bites a person, often around the face, and then defecates near the bite wound, allowing the parasite to enter when the person scratches or rubs the area. *Tse tse fly* - The **tsetse fly** is the vector for **African trypanosomiasis** (sleeping sickness), caused by *Trypanosoma brucei*. - This fly is geographically restricted to sub-Saharan Africa, whereas *Trypanosoma cruzi* is prevalent in the Americas. *Culex mosquito* - **Culex mosquitoes** are known vectors for various diseases, including **West Nile virus**, **Japanese encephalitis**, and **filariasis**. - They are not involved in the transmission of *Trypanosoma cruzi*. *Sand fly* - **Sand flies** transmit **Leishmaniasis**, a parasitic disease caused by various species of *Leishmania*. - They are also responsible for transmitting **Bartonellosis** and some types of **Arboviruses**, but not Chagas disease.
Question 68: Duodenal aspirate is used in diagnosis of:
- A. E histolytica
- B. Giardia lamblia (Correct Answer)
- C. Taenia solium
- D. Leishmania
Explanation: ***Giardia lamblia*** - **Duodenal aspiration** is a highly sensitive method for detecting **Giardia lamblia trophozoites** or cysts, especially in cases where stool examination is inconclusive. - This parasite primarily inhabits the **duodenum** and **upper jejunum**, making aspirate from this region an ideal diagnostic sample. *E histolytica* - **Entamoeba histolytica** (causes amoebiasis) is typically diagnosed by identifying **trophozoites** or **cysts** in **stool samples**, or through serology for invasive disease. - While it can affect the gastrointestinal tract, its primary site of colonization and pathology is the **colon**, not the duodenum. *Taenia solium* - **Taenia solium** (pork tapeworm) is diagnosed by identifying **proglottids** or **eggs** in **stool samples**. - It resides in the **small intestine**, but **duodenal aspirate** is not a standard diagnostic method for its detection. *Leishmania* - **Leishmania species** cause **leishmaniasis**, a disease diagnosed by detecting **amastigotes** in tissue biopsies (e.g., bone marrow, spleen, skin lesions) or through serological tests. - These parasites are intracellular and do not inhabit the **duodenal lumen**, making duodenal aspirate irrelevant for diagnosis.
Question 69: What is required for precipitation in comparison to agglutination?
- A. Soluble antigen (Correct Answer)
- B. Increased temperature
- C. Specific cofactor
- D. Lower pH
Explanation: ***Soluble antigen*** - **Precipitation reactions** involve the interaction of antibodies with **soluble antigens** to form a detectable precipitate. - Unlike **agglutination**, which involves particulate antigens (e.g., cells), precipitation requires the antigen to be dissolved in a solution. *Increased temperature* - Most immunologic reactions, including precipitation and agglutination, are typically performed at **physiological temperatures** (e.g., 37°C) or room temperature. - An **increased temperature** is not a specific requirement that differentiates precipitation from agglutination. *Specific cofactor* - While some complex immunologic reactions might require **cofactors**, neither precipitation nor agglutination inherently requires a specific cofactor to occur. - The primary components are **antigen** and **antibody**. *Lower pH* - Both precipitation and agglutination reactions are sensitive to pH and typically occur within a **narrow pH range** close to neutral (e.g., pH 7.0-7.4). - A **lower pH** (acidic environment) could lead to antibody denaturation or non-specific aggregation, ultimately hindering the reaction rather than being a requirement.
Question 70: Which of the following statements about the VDRL test is LEAST accurate?
- A. VDRL is a treponemal-specific test with high specificity (Correct Answer)
- B. RPR is better than VDRL for monitoring drug therapy
- C. VDRL is a non-treponemal test and can give false positive results
- D. VDRL is a slide flocculation test for syphilis
Explanation: ***VDRL is a treponemal-specific test with high specificity*** - This statement is inaccurate because the **VDRL test** is a **non-treponemal** test, meaning it detects antibodies to cardiolipin, a lipid released from damaged host cells, rather than directly detecting antibodies to *Treponema pallidum*. - Non-treponemal tests like VDRL are known for their potential to produce **false-positive results** due to various conditions. *VDRL is a non-treponemal test and can give false positive results* - The **VDRL test** is indeed a **non-treponemal** test, detecting antibodies against cardiolipin, cholesterol, and lecithin. - Since it detects host-derived antibodies rather than specific *Treponema pallidum* antibodies, it is prone to **false-positive results** in conditions like autoimmune diseases, infections, and pregnancy. *RPR is better than VDRL for monitoring drug therapy* - Both **RPR (Rapid Plasma Reagin)** and VDRL are used to monitor response to therapy in syphilis, but **RPR is sometimes preferred** due to its ease of use (no need for a microscope), stability of reagents, and clearer macroscopic end-point. - The **titers of both VDRL and RPR typically decrease** after successful treatment, indicating a good response to therapy. *VDRL is a slide flocculation test for syphilis* - The **VDRL test** is a **flocculation test** where cardiolipin antigen mixed with a patient's serum (containing reagin antibodies) results in visible clumping or flocculation under a microscope. - It is used as a screening test for **syphilis**, caused by *Treponema pallidum*.