Microbiology MCQs
Microbiology MCQs challenge students to identify pathogens, understand microbial physiology, and master infection control protocols. These questions span bacteriology, virology, mycology, parasitology, and immunology. Suitable for exams like MDCAT, FCPS, NTS, and USMLE, these quizzes improve both academic knowledge and clinical readiness.
Q: A pathogenic protozoan responsible for amoebic dysentery is
A) Trypanosoma brucei
B) Entamoeba histolytica
C) Giardia lamblia
D) Plasmodium vivax
✅ Correct Answer: B
Explanation: Entamoeba histolytica invades the intestinal lining, causing dysentery.
Q: Inactivation of microbes using high-frequency sound waves is known as
A) Radiation
B) Sonication
C) Desiccation
D) Filtration
✅ Correct Answer: B
Explanation: Sonication disrupts microbial cells by using ultrasonic vibrations.
Q: A selective medium allows growth of
A) Only specific microbes
B) All microorganisms
C) Only fungi
D) Only viruses
✅ Correct Answer: A
Explanation: Selective media contain agents that inhibit some organisms while allowing the growth of others.
Q: The causative agent of gas gangrene is
A) Clostridium perfringens
B) Staphylococcus aureus
C) Mycobacterium leprae
D) Pseudomonas aeruginosa
✅ Correct Answer: A
Explanation: Clostridium perfringens produces gas and toxins in necrotic tissue, leading to gas gangrene.
Q: Urease-producing bacteria can be detected using
A) Catalase test
B) Coagulase test
C) Urease test
D) TSI slant
✅ Correct Answer: C
Explanation: The urease test detects the production of ammonia by urease, leading to a color change in the medium.
Q: Microaerophilic bacteria require
A) Normal oxygen levels
B) No oxygen
C) Reduced oxygen levels
D) High carbon dioxide
✅ Correct Answer: C
Explanation: Microaerophiles grow best in environments with lower oxygen than atmospheric levels.
Q: A positive Mantoux test indicates
A) Hepatitis infection
B) HIV exposure
C) Malaria immunity
D) Tuberculosis exposure
✅ Correct Answer: D
Explanation: A positive tuberculin skin test suggests prior exposure or latent infection with Mycobacterium tuberculosis.
Q: An exotoxin is typically
A) Produced only during spore formation
B) Secreted by bacteria
C) Found only in viruses
D) A structural component of the cell wall
✅ Correct Answer: B
Explanation: Exotoxins are proteins secreted by bacteria that can cause damage to the host.
Q: The site of ATP generation in bacteria is the
A) Cell wall
B) Ribosomes
C) Nucleus
D) Cytoplasmic membrane
✅ Correct Answer: D
Explanation: Since bacteria lack mitochondria, energy production occurs at the cytoplasmic membrane.
Q: Haemophilus influenzae requires
A) Salt agar
B) No oxygen
C) EMB agar
D) Chocolate agar
✅ Correct Answer: D
Explanation: Haemophilus influenzae grows on chocolate agar due to its requirement for growth factors X (hemin) and V (NAD).