NEET-PG 2015 Practice Questions

Q: What is the most common mode of transmission of HIV?

Sexual contact. ***Sexual contact*** - **Unprotected sexual intercourse**, both heterosexual and homosexual, is overwhelmingly the most common way HIV is transmitted globally. - The virus can be exchanged through **bodily fluids** such as semen, vaginal fluids, and rectal fluids during sexual activity. - Accounts for approximately **80% of new HIV infections** worldwide. *Occupational exposure (needle stick injury)* - While a recognised mode of transmission, **needle stick injuries** account for a very small percentage of total HIV infections, primarily affecting healthcare workers. - The risk of transmission per exposure is relatively low (approximately **0.3%**), especially compared to sexual contact. *Perinatal transmission (mother to child)* - **Mother-to-child transmission** can occur during pregnancy, childbirth, or breastfeeding. - Although significant, especially in resource-limited settings, global efforts and **PMTCT programs** have resulted in a significant reduction in this type of transmission. *Transmission via blood and blood products* - This mode was once a major concern but is now extremely rare in countries with robust **blood screening programs**. - While sharing contaminated needles among **intravenous drug users** remains a risk, transfusion-related HIV is largely controlled.

Q: Which of the following statements about Corynebacterium diphtheriae is true?

Toxin production is dependent on iron concentration. ***Toxin production is dependent on iron concentration*** - The production of **diphtheria toxin** by *Corynebacterium diphtheriae* is directly regulated by the iron concentration in the environment. - When **iron levels are low**, the diphtheria toxin repressor (DTxR) is inactivated, leading to increased toxin production. *All strains produce toxin* - Not all strains of *Corynebacterium diphtheriae* produce the diphtheria toxin; only those strains that are **lysogenized by a bacteriophage carrying the tox gene** are toxigenic. - Non-toxigenic strains can cause other infections but do not produce the classic diphtheria disease. *The toxin is heat stable* - The **diphtheria toxin** is a **heat-labile** protein, meaning its activity can be destroyed by heat. - Heating diphtheria toxin to 60°C for 30 minutes can inactivate its pathogenic effects. *It inhibits cAMP* - The diphtheria toxin does not inhibit **cAMP**; instead, it acts by **ADP-ribosylating and inactivating elongation factor-2 (EF-2)**, thereby inhibiting protein synthesis in eukaryotic cells. - Inhibition of EF-2 ultimately leads to cell death.

Q: Heating a bacterial sample at 60°C for 30 minutes would isolate which of the following?

Enterococcus species. ***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.

Q: Which of the following viruses is a member of the Herpesviridae family?

Herpes Simplex Virus. ***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.

Q: HIV envelope is formed by:

Both. ***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)

Q: Which HIV virus is associated with a higher transmission rate and virulence?

HIV-1. ***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.

Q: Which strain of the Influenza A virus, not of human origin, has the highest pandemic potential?

H5N1. ***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.

Q: Which statement is true regarding the influenza vaccine?

All statements are correct.. ***All statements are correct.*** - Each of the preceding statements is factually accurate regarding influenza vaccines. - The **inactivated vaccine** is widely used, the **live attenuated vaccine** is administered via nasal spray, and the **inactivated vaccine** is given intramuscularly [1]. *The inactivated vaccine is used most commonly.* - The **inactivated influenza vaccine (IIV)**, given by injection, is the most frequently administered type of influenza vaccine. - It is recommended for most age groups and is safe for individuals with chronic medical conditions, pregnant women, and the elderly. *The live attenuated vaccine is given by nasal spray.* - The **live attenuated influenza vaccine (LAIV)**, also known as FluMist, is administered as a **nasal spray** [1]. - This vaccine is suitable for healthy individuals aged 2-49 years and is not recommended for pregnant women or individuals with certain immune compromising conditions. *The inactivated vaccine is given intramuscularly in the deltoid.* - The standard route of administration for the **inactivated influenza vaccine (IIV)** is via **intramuscular injection**, most commonly into the **deltoid muscle** in adults and older children [1]. - This method ensures proper absorption and an effective immune response, a common practice for many vaccines.

Q: Which of the following can infect the ovary?

Mumps virus. ***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.

Q: Which viral proteins are known to act as carcinogens in causing carcinoma cervix?

E - gene. ***E - gene*** - The **E - gene** in human papillomavirus (HPV) is known to play a crucial role in the **transformation of cervical cells**, leading to cancer development [1]. - Specifically, the **E6 and E7 proteins** encoded by this gene interfere with tumor suppressor functions, contributing to cervical carcinoma [1,2]. *L - gene* - The **L - gene** is associated with the virus's structural proteins, primarily aiding in the formation of the viral capsid. - It does not have a direct role in the oncogenic process leading to cervical cancer. *H - gene* - The **H - gene** is not specifically linked to the oncogenic effects of HPV; it is not recognized for contributing to cancer development. - It is often confused in discussions but doesn't directly influence the carcinogenic pathway like the E gene does. *P 24 - gene* - The **P 24 - gene** is not related to HPV; instead, it is associated with **HIV** and its structural components. - This gene does not play any role in the development of cervical carcinoma or transformation of cervical cells. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Female Genital Tract, pp. 1006-1007. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Neoplasia, pp. 334-335.

Question 1

What is the most common mode of transmission of HIV?

Accepted Answer

Sexual contact

Answer

Occupational exposure (needle stick injury)

Answer

Perinatal transmission (mother to child)

Answer

Transmission via blood and blood products

Question 2

Which of the following statements about Corynebacterium diphtheriae is true?

Accepted Answer

Toxin production is dependent on iron concentration

Answer

All strains produce toxin

Answer

The toxin is heat stable

Answer

It inhibits cAMP

Question 3

Heating a bacterial sample at 60°C for 30 minutes would isolate which of the following?

Accepted Answer

Enterococcus species

Answer

Staphylococci

Answer

Micrococci

Answer

Streptococci

Question 4

Which of the following viruses is a member of the Herpesviridae family?

Accepted Answer

Herpes Simplex Virus

Answer

Variola

Answer

Adenovirus

Answer

HPV

Question 5

HIV envelope is formed by:

Accepted Answer

Both

Answer

Host cell

Answer

Virus

Answer

None of the options

Question 6

Which HIV virus is associated with a higher transmission rate and virulence?

Accepted Answer

HIV-1

Answer

Both have similar risks

Answer

It depends on individual factors

Answer

HIV-2

Question 7

Which strain of the Influenza A virus, not of human origin, has the highest pandemic potential?

Accepted Answer

H5N1

Answer

H1N1

Answer

H9N2

Answer

H2N2

Question 8

Which statement is true regarding the influenza vaccine?

Accepted Answer

All statements are correct.

Answer

The live attenuated vaccine is given by nasal spray.

Answer

The inactivated vaccine is used most commonly.

Answer

The inactivated vaccine is given intramuscularly in the deltoid.

Question 9

Which of the following can infect the ovary?

Accepted Answer

Mumps virus

Answer

Epstein-Barr Virus (EBV)

Answer

Cytomegalovirus (CMV)

Answer

Measles virus

Question 10

Which viral proteins are known to act as carcinogens in causing carcinoma cervix?

Accepted Answer

E - gene

Answer

P 24 - gene

Answer

L - gene

Answer

H - gene

NEET-PG 2015

Community Medicine

Microbiology

Pathology