Page 8 of 11
MI1.{1-2,10,12-13} | General Microbiology I: History, Morphology, Sterilisation & Staining — Practice Quiz
Practice
10 questions · Untimed · Unlimited attempts
Click any question card to reveal the correct answer.
Antony van Leeuwenhoek is credited as the first to observe living microorganisms. Which instrument did he use to make this landmark observation in the 1670s?
A
Compound microscope with two lenses
B
Simple single-lens microscope he crafted himself
✓
C
Camera lucida attached to a magnifying glass
D
Oil-immersion objective of a modern light microscope
Click to reveal answer
Robert Koch's postulates established the germ theory on a firm experimental basis. Which of the following is NOT one of Koch's original postulates?
A
The microorganism must be found in all cases of the disease
B
The microorganism must be isolated in pure culture from the diseased host
C
The disease must be preventable by vaccination with killed organisms
✓
D
The inoculated microorganism must reproduce the disease in a healthy host
Click to reveal answer
A first-year medical student examining a skin swab culture report reads: 'Gram-positive cocci in clusters'. Based on basic bacterial morphology and clinical correlation, which organism should be FIRST considered?
A
Streptococcus pyogenes
B
Staphylococcus aureus
✓
C
Neisseria meningitidis
D
Escherichia coli
Click to reveal answer
A laboratory technician needs to sterilise glass syringes with sharp metal plungers for reuse. Which physical method is MOST appropriate?
A
Autoclave at 121°C for 15 minutes
B
Hot air oven at 160°C for 60 minutes
✓
C
Boiling at 100°C for 20 minutes
D
UV radiation for 30 minutes
Click to reveal answer
In the Gram staining procedure, what is the role of Gram's iodine (mordant)?
A
It decolourises Gram-negative bacteria selectively
B
It forms an insoluble crystal violet–iodine complex that is trapped in the thick peptidoglycan
✓
C
It stains Gram-negative bacteria pink as a counterstain
D
It enhances the penetration of safranin into Gram-positive bacteria
Click to reveal answer
Viruses are described as obligate intracellular parasites. The PRIMARY reason they cannot replicate outside a host cell is that they:
A
Are too small to contain any genetic material
B
Lack ribosomes and metabolic machinery needed for protein synthesis
✓
C
Have a cell wall that prevents nutrient uptake from the environment
D
Cannot survive temperatures above 37°C outside a host
Click to reveal answer
A critical item (item that enters sterile tissue or the vascular system) must undergo which level of microbial reduction according to the Spaulding classification?
A
Low-level disinfection
B
High-level disinfection
C
Sterilisation
✓
D
Antisepsis only
Click to reveal answer
In the Ziehl-Neelsen (ZN) staining procedure, which property of mycobacteria allows them to retain carbol fuchsin even after treatment with 20% sulphuric acid?
A
Presence of a thick peptidoglycan layer similar to Gram-positive organisms
B
High mycolic acid content in the cell wall that is hydrophobic and resists decolourisation
✓
C
Possession of a polysaccharide capsule that retains the dye
D
Active efflux pumps that concentrate carbol fuchsin intracellularly
Click to reveal answer
Louis Pasteur's swan-neck flask experiments definitively disproved which theory about the origin of microorganisms?
A
Cell theory
B
Spontaneous generation
✓
C
Miasma theory of disease
D
Germ theory of fermentation
Click to reveal answer
A surgeon leaves an endoscope on an open shelf in the operating theatre for 3 hours after high-level disinfection with glutaraldehyde. She then uses it for a colonoscopy. What is the CHIEF infection control concern with this practice?
A
Glutaraldehyde degrades at room temperature, losing sporicidal activity
B
Re-contamination from environmental microorganisms after disinfection negates the process
✓
C
High-level disinfection is insufficient for endoscopes; sterilisation is required
D
Glutaraldehyde fumes denature proteins on the endoscope surface over time
Click to reveal answer