UPSC-CMS 2016 - Microbiology PYQs Practice Questions

Q: Consider the following statements: 1. The duration of immunity is longer when live vaccine is administered as compared to the administration of killed vaccine. 2. In the case of killed vaccine, single dose is sufficient whereas multiple doses are always required in the case of live vaccines. Which of these statements is/are correct?

1 only. ***1 only*** - **Live attenuated vaccines** stimulate a more robust, long-lasting immune response, often mimicking natural infection, leading to **longer duration of immunity** compared to killed vaccines. - This is because live vaccines can replicate in the host, providing a continuous antigenic stimulus that enhances the breadth and memory of the immune response. *2 only* - This statement is incorrect because **killed vaccines** typically require **multiple doses** (prime and booster shots) to achieve and maintain adequate protective immunity. - In contrast, **live vaccines** often achieve sufficient immunity with a **single dose** due to their ability to replicate and elicit a strong cellular and humoral response. *Both 1 and 2* - This option is incorrect as statement 2 is false. Live vaccines generally provide longer immunity, and killed vaccines usually require multiple doses, while live vaccines often need only one. *Neither 1 nor 2* - This option is incorrect because statement 1 is accurate regarding the longer duration of immunity provided by live vaccines. [Practice more Microbiology PYQs on OnCourse]

Q: Throat swab positive and Schick test negative indicate that the person is:

Immune to diphtheria. ***Immune to diphtheria*** - A **negative Schick test** indicates the presence of sufficient **antitoxin antibodies** in the individual's blood, conferring **immunity** against diphtheria toxin. - A positive throat swab combined with a negative Schick test indicates the person is a **healthy carrier** (or **immune carrier**) – harboring *Corynebacterium diphtheriae* but protected from developing disease due to existing immunity. - Such carriers pose a **public health concern** as they can transmit the organism to susceptible individuals, despite being personally protected. *Hypersensitive to diphtheria* - **Hypersensitivity** to diphtheria is not assessed by the Schick test; a negative result indicates protective immunity, not an allergic or hypersensitivity reaction. - The Schick test specifically measures the ability to neutralize diphtheria toxin through antitoxin antibodies, not immune hypersensitivity. *Susceptible to diphtheria* - **Susceptibility to diphtheria** would be indicated by a **positive Schick test**, meaning there is insufficient antitoxin to neutralize the injected toxin, resulting in a local inflammatory reaction at the test site. - The given scenario states a **negative Schick test**, which definitively rules out susceptibility. *Suffering from diphtheria* - While a **positive throat swab** indicates the presence of *Corynebacterium diphtheriae*, a **negative Schick test** means the individual has protective immunity and is **not suffering from clinical disease**. - Active diphtheria presents with characteristic symptoms (pseudomembrane, bull neck, etc.), which would not occur in an immune individual despite bacterial colonization. [Practice more Microbiology PYQs on OnCourse]

Q: Which of the following statements is true about hydatid disease?

It is a zoonosis. ***Correct: It is a zoonosis*** - Hydatid disease is caused by the larval stage of **Echinococcus granulosus**, a **tapeworm**, and is transmitted from animals to humans - **Zoonoses** are diseases that can be transmitted from animals to humans, making this the correct statement - The primary reservoir includes dogs (definitive hosts) and sheep (intermediate hosts), with transmission to humans occurring through contact with contaminated dog feces *Incorrect: It is a protozoal disease* - Hydatid disease is caused by a **tapeworm** (cestode), specifically *Echinococcus granulosus*, not by a protozoan - Protozoal diseases are caused by single-celled eukaryotic organisms such as *Plasmodium* (malaria) or *Giardia* (giardiasis) - This is a helminthic infection, not a protozoal one *Incorrect: Man is the definitive host* - In the life cycle of *Echinococcus granulosus*, **dogs and other canines** are the **definitive hosts**, harboring the adult tapeworm in their intestines - Humans are **accidental intermediate hosts**, getting infected by ingesting eggs and developing hydatid cysts in organs (especially liver and lungs) - The natural cycle involves dogs eating infected offal from sheep, not humans being part of the natural transmission cycle *Incorrect: It is rare in sheep rearing countries* - Hydatid disease is **endemic** and more common in **sheep-rearing countries** including Mediterranean regions, Middle East, South America, Australia, and parts of Africa - Sheep act as important intermediate hosts in the life cycle of *Echinococcus granulosus* - The dog-sheep-dog cycle maintains high endemicity in pastoral communities where dogs have access to infected sheep viscera [Practice more Microbiology PYQs on OnCourse]

Question 1

Consider the following statements:

1. The duration of immunity is longer when live vaccine is administered as compared to the administration of killed vaccine.

2. In the case of killed vaccine, single dose is sufficient whereas multiple doses are always required in the case of live vaccines. Which of these statements is/are correct?

Accepted Answer

1 only

Answer

2 only

Answer

Both 1 and 2

Answer

Neither 1 nor 2

Question 2

Throat swab positive and Schick test negative indicate that the person is:

Accepted Answer

Immune to diphtheria

Answer

Hypersensitive to diphtheria

Answer

Susceptible to diphtheria

Answer

Suffering from diphtheria

Question 3

Which of the following statements is true about hydatid disease?

Accepted Answer

It is a zoonosis

Answer

It is a protozoal disease

Answer

Man is the definitive host

Answer

It is rare in sheep rearing countries

UPSC-CMS 2016 — Microbiology