B.Pharm. Bachelor of Pharmacy Microbiology & Immunology 1 — Questions and Answers
Question 1: Which bacterial structure protects against phagocytosis and is a major virulence factor for Streptococcus pneumoniae?
- Flagella
- Pili
- Polysaccharide capsule (Correct answer)
- Endospore
Correct answer: Polysaccharide capsule
The polysaccharide capsule prevents opsonization and phagocytosis by macrophages, making encapsulated bacteria more virulent.
Question 2: The Gram stain differentiates bacteria based on differences in their:
- Cell membrane lipid content
- Cell wall peptidoglycan thickness (Correct answer)
- Capsule composition
- Flagella protein structure
Correct answer: Cell wall peptidoglycan thickness
Gram-positive bacteria have a thick peptidoglycan layer that retains crystal violet dye, while Gram-negative bacteria have a thinner layer and outer membrane causing them to appear pink after safranin counterstain.
Question 3: Which type of immunity is acquired naturally by the body's own immune response after exposure to an antigen?
- Passive artificial immunity
- Active natural immunity (Correct answer)
- Passive natural immunity
- Active artificial immunity
Correct answer: Active natural immunity
Active natural immunity develops when the body mounts its own immune response after natural infection, producing memory cells and antibodies.
Question 4: Bacteriostatic antibiotics differ from bactericidal antibiotics in that they:
- Kill bacteria directly
- Inhibit bacterial growth without killing (Correct answer)
- Are less effective against infections
- Cannot be used in immunocompromised patients
Correct answer: Inhibit bacterial growth without killing
Bacteriostatic agents inhibit bacterial reproduction, relying on the host immune system to eliminate the bacteria, while bactericidal agents directly kill bacteria.
Question 5: Which immunoglobulin class is the most abundant in human serum and provides the main antibody-based defense?
- IgA
- IgM
- IgG (Correct answer)
- IgE
Correct answer: IgG
IgG is the most abundant immunoglobulin in serum (~75%), providing long-term immunity, crossing the placenta, and activating complement.
Question 6: D-value (decimal reduction time) in microbiology sterilization refers to the time required to:
- Double the microbial population
- Reduce the microbial population by 90% (1 log) (Correct answer)
- Completely eliminate all microorganisms
- Inactivate 50% of spores
Correct answer: Reduce the microbial population by 90% (1 log)
The D-value is the time at a given temperature required to reduce the number of viable microorganisms by one decimal (10-fold or 90%) reduction.
