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: The function of an autoclave is to
A) Sterilize using dry heat
B) Sterilize using steam under pressure
C) Disinfect using alcohol
D) Kill viruses only
✅ Correct Answer: B
Explanation: Autoclaving uses moist heat under pressure to effectively sterilize equipment and media.
Q: Botulinum toxin acts by
A) Increasing neurotransmitter release
B) Damaging DNA
C) Inhibiting protein synthesis
D) Blocking acetylcholine release
✅ Correct Answer: D
Explanation: Botulinum toxin blocks acetylcholine release, causing flaccid paralysis.
Q: MacConkey agar is selective for
A) Fungi
B) Gram-negative bacteria
C) Gram-positive bacteria
D) Viruses
✅ Correct Answer: B
Explanation: MacConkey agar contains bile salts and crystal violet, which inhibit Gram-positive organisms and allow Gram-negative growth.
Q: A lytic bacteriophage
A) Kills the host cell
B) Converts bacteria into spores
C) Forms a symbiotic relationship
D) Integrates into the host genome
✅ Correct Answer: A
Explanation: Lytic phages infect bacteria and rapidly lyse the host cell after viral replication.
Q: The test used to detect syphilis antibodies is the
A) Widal test
B) Tuberculin test
C) ELISA for HIV
D) VDRL test
✅ Correct Answer: D
Explanation: The VDRL (Venereal Disease Research Laboratory) test screens for antibodies produced in response to syphilis infection.
Q: Leprosy is caused by
A) Mycobacterium tuberculosis
B) Clostridium botulinum
C) Treponema pallidum
D) Mycobacterium leprae
✅ Correct Answer: D
Explanation: Mycobacterium leprae infects peripheral nerves and skin, leading to chronic granulomatous disease known as leprosy.
Q: The acid produced by Lactobacillus during fermentation is
A) Butyric acid
B) Citric acid
C) Acetic acid
D) Lactic acid
✅ Correct Answer: D
Explanation: Lactobacillus ferments sugars into lactic acid, which is used in food preservation and digestion.
Q: The presence of bacterial endotoxins can be tested using the
A) VDRL test
B) Catalase test
C) Coagulase test
D) Limulus amoebocyte lysate test
✅ Correct Answer: D
Explanation: The LAL test detects endotoxins using the blood cells of horseshoe crabs, which clot in the presence of endotoxins.
Q: Transmission of rabies occurs primarily through
A) Airborne droplets
B) Fecal contamination
C) Infected animal bites
D) Insect vectors
✅ Correct Answer: C
Explanation: Rabies virus is transmitted through saliva via bites or scratches from infected animals.
Q: Staphylococcus aureus can be identified by a positive
A) Coagulase test
B) Oxidase test
C) Catalase test
D) Urease test
✅ Correct Answer: A
Explanation: The coagulase test differentiates Staphylococcus aureus from other staphylococci by its ability to clot plasma.