UPSC-CMS 2020 - Microbiology PYQs Practice Questions

Q: Which of the following represent the properties of an ideal disinfectant? 1. It is broad spectrum 2. It is fast acting 3. It is non-toxic Select the correct answer using the code given below:

1, 2 and 3. ***Correct Answer: 1, 2 and 3*** An **ideal disinfectant** should possess all three properties: - **Broad spectrum activity** - It should effectively kill or inactivate a wide range of microorganisms, including bacteria, viruses, fungi, and spores - **Fast-acting** - It should achieve rapid antimicrobial effect after application, which is crucial in clinical settings to prevent pathogen spread and minimize exposure time - **Non-toxic** - It should be safe for humans and animals when used as directed, minimizing adverse effects on users, patients, and the environment Additional desirable properties include stability, solubility in water, non-corrosive nature, pleasant odor, and cost-effectiveness. *Incorrect: 1 and 3 only* - While broad spectrum and non-toxic nature are crucial, **fast action** is also an essential property for an ideal disinfectant to ensure rapid microbial elimination - A disinfectant that is not fast-acting would be less practical in situations requiring quick decontamination *Incorrect: 2 and 3 only* - A disinfectant that is fast-acting and non-toxic is insufficient without **broad-spectrum activity** - Without broad-spectrum activity, it may fail to eliminate certain pathogens, limiting its overall utility in infection control *Incorrect: 1 and 2 only* - Although broad spectrum and fast-acting properties are important, an ideal disinfectant must also be **non-toxic** - Toxicity would severely limit its application, especially in healthcare settings where human contact is frequent [Practice more Microbiology PYQs on OnCourse]

Q: During the EARLY phase of a primary immune response, which of the following best describes the relationship between peak IgM and IgG antibody levels?

100 times more. ***100 times more*** - In the **early phase of a primary immune response**, **IgM** is the first antibody produced and reaches peak levels when **IgG** levels are still very low. - During this early period (approximately days 5-10), the **IgM concentration** can be significantly higher than IgG, with some references citing ratios up to 100-fold. - **Important note:** As the primary response matures, **IgG levels rise and eventually exceed IgM levels** through class switching. This question specifically addresses the early peak comparison. *50 times more* - While IgM does predominate early in the primary response, the 50-fold ratio underestimates the typical difference during the **early peak phase** when IgG production has just begun. - The most commonly cited ratio for early primary response is closer to 100-fold. *25 times more* - This ratio **underestimates** the relative abundance of **IgM** compared to **IgG** during the early peak of a primary immune response. - **IgG** levels are typically very low or just beginning to rise in the early stages, while IgM has reached peak levels. *10 times more* - This significantly **underestimates** the difference in antibody levels during the early primary immune response. - The rapid and robust initial production of **IgM** with delayed IgG production creates a much larger differential in the early phase. **Clinical Note:** In a **secondary immune response**, the pattern reverses dramatically—IgG is produced rapidly and in much higher quantities than IgM (often 100-1000 times more) due to memory B cell activation. [Practice more Microbiology PYQs on OnCourse]

Q: Which is the most specific causative agent of Rabies?

Rabies lyssavirus (RABV). ***Rabies lyssavirus (RABV)*** - **Rabies lyssavirus (RABV)**, also known as the **classical rabies virus** or **genotype 1**, is the primary and most specific causative agent of rabies in humans and animals worldwide. - While other lyssaviruses (Lagos bat, Mokola, Duvenhage, Australian bat lyssavirus, etc.) can cause rabies-like illnesses, **RABV is overwhelmingly responsible** for the vast majority of documented rabies cases globally. - It is transmitted primarily through dog bites in endemic regions and causes acute, progressive, fatal encephalomyelitis. *Lagos bat lyssavirus (LBV)* - **Lagos bat lyssavirus (genotype 2)** is a distinct species within the *Lyssavirus* genus that can cause rabies-like disease, primarily in bats in Africa. - It is **rarely associated with human rabies** and is not the most common or specific cause globally. *Mokola lyssavirus (MOKV)* - **Mokola lyssavirus (genotype 3)** is another lyssavirus found in Africa, isolated from shrews, rodents, and rarely humans. - Although it can cause a fatal encephalomyelitis similar to rabies, human cases are **extremely rare**, and it is not considered the typical rabies virus. *Duvenhage lyssavirus (DUVV)* - **Duvenhage lyssavirus (genotype 4)** is a bat-associated lyssavirus found in Africa, first isolated in 1970. - Human cases are **exceptionally rare** (only a few documented cases), and it is not the primary causative agent of classic rabies. [Practice more Microbiology PYQs on OnCourse]

Question 1

Which of the following represent the properties of an ideal disinfectant?

1. It is broad spectrum
2. It is fast acting
3. It is non-toxic

Select the correct answer using the code given below:

Accepted Answer

1, 2 and 3

Answer

1 and 3 only

Answer

2 and 3 only

Answer

1 and 2 only

Question 2

During the EARLY phase of a primary immune response, which of the following best describes the relationship between peak IgM and IgG antibody levels?

Accepted Answer

100 times more

Answer

50 times more

Answer

25 times more

Answer

10 times more

Question 3

Which is the most specific causative agent of Rabies?

Accepted Answer

Rabies lyssavirus (RABV)

Answer

Lagos bat lyssavirus (LBV)

Answer

Mokola lyssavirus (MOKV)

Answer

Duvenhage lyssavirus (DUVV)

UPSC-CMS 2020 — Microbiology