Pyrogens: types and sources MCQs With Answer

Introduction
This quiz collection on “Pyrogens: types and sources” is designed for M.Pharm students studying Biological Evaluation of Drug Therapy. It focuses on the molecular nature, clinical significance, and pharmaceutical implications of pyrogens — including bacterial endotoxins, non-bacterial inducers, and endogenous mediators. Questions explore detection methods (LAL, rabbit pyrogen test, MAT), mechanisms of fever induction, risk points in manufacturing, and depyrogenation strategies used for parenteral products. The set aims to deepen your understanding of how pyrogens arise, how they provoke immune responses, and practical measures to detect and control them during drug development and production. Use these MCQs to test conceptual knowledge and apply it to pharmaceutical practice.

Q1. What is the most appropriate definition of a pyrogen?

• A substance that causes localized inflammation at the site of injection
• A substance that induces fever when introduced into the bloodstream or body tissues
• A toxin that specifically destroys white blood cells
• A molecule that enhances drug absorption across membranes

Correct Answer: A substance that induces fever when introduced into the bloodstream or body tissues

Q2. Which of the following is the classical bacterial pyrogen encountered in parenteral products?

• Lipopolysaccharide (endotoxin) from Gram-negative bacteria
• Teichoic acid from Gram-positive bacteria
• Mycolic acid from Mycobacteria
• Capsular polysaccharide from Streptococcus pneumoniae

Correct Answer: Lipopolysaccharide (endotoxin) from Gram-negative bacteria

Q3. What is the primary mechanism by which bacterial endotoxin (LPS) induces fever?

• Direct activation of hypothalamic neurons through membrane depolarization
• Interaction with Toll-like receptor 4 (TLR4) on immune cells leading to cytokine release and PGE2 synthesis in hypothalamus
• Enzymatic conversion to prostaglandins in the bloodstream
• Blocking of peripheral vasodilation resulting in increased core temperature

Correct Answer: Interaction with Toll-like receptor 4 (TLR4) on immune cells leading to cytokine release and PGE2 synthesis in hypothalamus

Q4. Which of the following are key endogenous pyrogens produced by immune cells?

• Interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6)
• Interferon-gamma (IFN-γ), interleukin-10 (IL-10) and transforming growth factor-beta (TGF-β)
• Histamine, bradykinin and serotonin
• Albumin, globulin and fibrinogen

Correct Answer: Interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6)

Q5. Which of the following represents non-bacterial pyrogens relevant to pharmaceutical products?

• β-glucans from fungal cell walls and viral proteins
• Only inorganic salts and sugars
• Pure water and oxygen
• Sterile polymer molecules that are chemically inert

Correct Answer: β-glucans from fungal cell walls and viral proteins

Q6. What is a major limitation of the Limulus Amebocyte Lysate (LAL) test?

• It detects all types of pyrogens equally well
• It requires live animals for each assay
• It detects bacterial endotoxin (LPS) from Gram-negative bacteria but not most non-endotoxin pyrogens
• It cannot be used for liquid samples

Correct Answer: It detects bacterial endotoxin (LPS) from Gram-negative bacteria but not most non-endotoxin pyrogens

Q7. Which statement correctly contrasts the rabbit pyrogen test and the Monocyte Activation Test (MAT)?

• Rabbit test is in vitro and MAT is an in vivo animal test
• Rabbit pyrogen test is in vivo whole-animal test; Monocyte Activation Test (MAT) is an in vitro human cell‑based alternative
• Both tests use Limulus amoebocyte lysate to measure endotoxin
• MAT measures clotting while rabbit test measures chromogenic change

Correct Answer: Rabbit pyrogen test is in vivo whole-animal test; Monocyte Activation Test (MAT) is an in vitro human cell‑based alternative

Q8. Which depyrogenation method is most appropriate for glassware used in parenteral production?

• High-temperature dry heat baking (e.g., 250°C for specified time) to destroy endotoxins on glassware
• Washing with distilled water at room temperature only
• Sterile filtration using 0.22 µm filters
• Gamma irradiation at low doses without heat

Correct Answer: High-temperature dry heat baking (e.g., 250°C for specified time) to destroy endotoxins on glassware

Q9. Which statement about endotoxin stability is correct?

• Endotoxins are easily destroyed by standard autoclaving at 121°C for 15 minutes
• Endotoxins (LPS) are relatively heat-stable and not reliably destroyed by standard autoclaving
• Endotoxins are volatile and evaporate during sterilization
• Endotoxins are only present in living bacteria and disappear after sterilization

Correct Answer: Endotoxins (LPS) are relatively heat-stable and not reliably destroyed by standard autoclaving

Q10. The Limulus Amoebocyte Lysate reagent is derived from which source and how does it indicate endotoxin?

• Derived from bacterial cultures and indicates endotoxin by color change
• Derived from synthetic peptides and indicates endotoxin by fluorescence
• Derived from horseshoe crab blood and produces a clotting or chromogenic reaction in presence of endotoxin
• Derived from human plasma and produces cytokine release in presence of endotoxin

Correct Answer: Derived from horseshoe crab blood and produces a clotting or chromogenic reaction in presence of endotoxin

Q11. How are endotoxin levels commonly reported and what is an approximate conversion for E. coli LPS?

• Endotoxin is expressed as mg/mL; 1 mg = 1,000,000 EU for E. coli
• Endotoxin is expressed in Endotoxin Units (EU); 1 EU is approximately 0.1–0.2 ng of E. coli LPS (source-dependent)
• Endotoxin is expressed in colony-forming units (CFU)
• Endotoxin is expressed in International Units (IU) where 1 IU = 100 EU

Correct Answer: Endotoxin is expressed in Endotoxin Units (EU); 1 EU is approximately 0.1–0.2 ng of E. coli LPS (source-dependent)

Q12. Which manufacturing source commonly contributes pyrogen contamination in parenteral products?

• Leachables and residues from rubber stoppers, seals or inadequate cleaning of container closures
• Sterile single-use polyethylene containers always free from pyrogens
• Pure analytical grade ethanol used in formulation
• Active ingredients always prevent pyrogen formation

Correct Answer: Leachables and residues from rubber stoppers, seals or inadequate cleaning of container closures

Q13. Regarding sterile filtration and endotoxins, which statement is true?

• Sterile filtration (0.22 µm) reliably removes soluble endotoxins
• Sterile filtration removes bacteria but does not reliably remove soluble endotoxins
• Sterile filtration converts endotoxin to non-pyrogenic fragments
• Sterile filtration is unnecessary if LAL test passes

Correct Answer: Sterile filtration removes bacteria but does not reliably remove soluble endotoxins

Q14. At which stage of pharmaceutical production is the risk of pyrogen contamination typically highest?

• Initial compound synthesis in an organic solvent isolated from water
• Aseptic processing and handling of Water for Injection (WFI) and final parenteral filling operations
• Final lyophilization when in a closed sterile vial
• Packaging in cardboard outer boxes

Correct Answer: Aseptic processing and handling of Water for Injection (WFI) and final parenteral filling operations

Q15. How do Gram-positive bacterial components differ from Gram-negative endotoxin in pyrogenicity?

• Gram-positive bacteria produce lipid A that acts exactly like LPS
• Gram-negative bacteria are never pyrogenic
• Gram-negative bacteria produce endotoxin (LPS); Gram-positive bacteria produce lipoteichoic acid and peptidoglycan which can also be pyrogenic via TLR2
• Only fungal components can be pyrogenic, not bacterial

Correct Answer: Gram-negative bacteria produce endotoxin (LPS); Gram-positive bacteria produce lipoteichoic acid and peptidoglycan which can also be pyrogenic via TLR2

Q16. What is the basic principle of the Monocyte Activation Test (MAT) used for pyrogen detection?

• Measurement of clotting time of amoebocyte lysate
• Detection of bacterial growth after incubation with sample
• Measures cytokine release (e.g., IL-6) from human monocytes exposed to sample in vitro as indicator of pyrogenicity
• Assessment of thermal stability of the sample

Correct Answer: Measures cytokine release (e.g., IL-6) from human monocytes exposed to sample in vitro as indicator of pyrogenicity

Q17. How are acceptable endotoxin limits for a parenteral product defined?

• They are fixed global values of 0.25 EU/mL for all products
• They are calculated based on the maximum human dose (EU per kg body weight) and product route
• Endotoxin limits are only based on product color and viscosity
• Regulators do not require endotoxin limits for parenterals

Correct Answer: They are calculated based on the maximum human dose (EU per kg body weight) and product route

Q18. Which mediator produced in the hypothalamus directly elevates the thermoregulatory set point during fever?

• Corticotropin-releasing hormone (CRH)
• Prostaglandin E2 (PGE2) produced via COX-2 in the hypothalamus mediates fever response
• Serotonin released from platelets
• Bradykinin acting on peripheral nociceptors

Correct Answer: Prostaglandin E2 (PGE2) produced via COX-2 in the hypothalamus mediates fever response

Q19. Which of the following methods is effective for removing soluble endotoxin from a protein solution?

• Simple 0.22 µm sterile filtration
• Polymyxin B adsorption, ion‑exchange chromatography, or specific affinity resins; ultrafiltration has limited effect on soluble endotoxin
• Adding antimicrobial preservatives to neutralize LPS
• Storing the solution at 4°C for extended periods

Correct Answer: Polymyxin B adsorption, ion‑exchange chromatography, or specific affinity resins; ultrafiltration has limited effect on soluble endotoxin

Q20. Why is pyrogen testing particularly critical for biological products and parenteral formulations?

• Biological products are always sterile and do not need pyrogen testing
• Biological products may contain endogenous pyrogens or be produced by living organisms; testing ensures safety for parenteral administration
• Pyrogen testing is only required for oral tablets
• Parenteral products never contact water during manufacture

Correct Answer: Biological products may contain endogenous pyrogens or be produced by living organisms; testing ensures safety for parenteral administration

Download