Mircobiology - Lecture 3

Which of the following best describes "decontamination"?
A. Complete elimination of all forms of microbial life
B. Process of removing all pathogens from a liquid
C. Treatment to make an object safe to handle
D. Killing only endospores

Treatment to make an object safe to handle.

Which process directly targets pathogens but may not eliminate all microorganisms?

A. Sterilization
B. Disinfection
C. Pasteurization
D. Sanitization

Disinfection.

What is the decimal reduction time (D value)?

A. Time to sterilize a sample
B. Energy needed to denature proteins
C. Time required at a given temperature to reduce microbial viability by 90%
D. Time to kill all cells in a population

Time required at a given temperature to reduce microbial viability by 90%.

What effect does increasing temperature have on heat killing of microbes?

A. Slows the rate of killing
B. No effect
C. Decreases decimal reduction time
D. Increases thermal death time

Decreases decimal reduction time.

Why is moist heat more effective than dry heat?

A. Higher temperature
B. Lower humidity
C. Better penetration of microbial cells
D. Kills endospores

Better penetration of microbial cells.

What is the primary factor responsible for microbial killing in an autoclave?

A. Pressure
B. High temperature
C. Steam volume
D. Time

High temperature.

Which method is intended to reduce microbial load in heat-sensitive liquids without sterilizing?

A. Autoclaving
B. Pasteurization
C. Filtration
D. UV radiation

Pasteurization.

Why can endospores survive typical heat sterilization conditions?

A. They lack DNA
B. They are not affected by moisture
C. They have a tough, protective structure
D. They metabolize quickly

They have a tough, protective structure.

Which type of radiation has poor penetration and is primarily used on surfaces?

A. Gamma radiation
B. X-rays
C. UV radiation
D. Alpha particles

UV radiation.

What is the D10 value?

A. Amount of time to sterilize a surface
B. Radiation dose to reduce viability 10-fold
C. Radiation frequency for maximum damage
D. Autoclave temperature threshold

Radiation dose to reduce viability 10-fold.

Which type of filtration is most commonly used for sterilizing liquids?

A. Depth filter
B. HEPA filter
C. Membrane filter
D. Carbon filter

Membrane filter.

Which filter type is best suited for scanning electron microscopy due to observable etched pores?

A. HEPA
B. Depth filter
C. Membrane filter
D. Nucleopore filter

Nucleopore filter.

HEPA filters are designed to remove particles of what size from air?

A. ≥0.2 μm
B. ≥0.3 μm
C. ≥1.0 μm
D. ≥10 μm

≥0.3 μm.

What distinguishes a bacteriostatic agent?

A. Kills cells by lysis
B. Inhibits growth without killing
C. Kills by binding irreversibly
D. Effective only on fungi

Inhibits growth without killing.

Which agent binds tightly and kills cells without causing lysis?

A. Bacteriostatic
B. Bactericidal
C. Bacteriolytic
D. Antiseptic

Bactericidal.

Which antimicrobial agent type causes cell lysis?

A. Bacteriostatic
B. Bactericidal
C. Bacteriolytic
D. Fungistatic

Bacteriolytic.

The minimum inhibitory concentration (MIC) is defined as:

A. Maximum tolerated agent dose
B. Minimum dose that kills all cells
C. Smallest concentration that inhibits visible growth
D. Concentration needed for complete lysis

Smallest concentration that inhibits visible growth.

What assay involves placing an antimicrobial disk on agar to evaluate inhibition zones?

A. MIC assay
B. Broth dilution assay
C. Disk diffusion assay
D. LAL test

Disk diffusion assay.

Which of the following would NOT be trapped by a 0.2 μm membrane filter?

A. E. coli
B. Bacillus subtilis
C. Bacteriophage
D. Influenza virus

Influenza virus.

Which radiation method generates ions and reactive molecules to kill microbes?

A. UV radiation
B. Infrared radiation
C. Ionizing radiation
D. Microwave radiation

Ionizing radiation.

Which term best describes a chemical that kills fungi?

A. Fungistatic
B. Bacteriostatic
C. Fungicidal
D. Viricidal

Fungicidal.

Which agent category is non-toxic enough for application to living tissue?

A. Disinfectant
B. Antiseptic
C. Sterilant
D. Sanitizer

Antiseptic.

What term is used for a chemical that kills all microorganisms, including endospores?

A. Disinfectant
B. Sanitizer
C. Sterilant
D. Antiseptic

Sterilant.

Which of the following reduces microbial numbers but does not sterilize?

A. Sterilant
B. Disinfectant
C. Sanitizer
D. Antiseptic

Sanitizer.

Which of the following can act as antiseptic, disinfectant, or sterilant depending on context?

A. Ethylene oxide
B. Hydrogen peroxide
C. Sodium hypochlorite
D. Formaldehyde

Hydrogen peroxide.

Which process does NOT achieve sterilization?

A. Autoclaving
B. Pasteurization
C. Ionizing radiation
D. Filtration through 0.2 μm pores

Pasteurization.

What best describes the function of a depth filter?

A. Physically adsorbs toxins
B. Traps particles in a fibrous network
C. Sterilizes via heat
D. Chemically modifies pathogens

Traps particles in a fibrous network.

The primary killing mechanism of UV radiation is:

A. Protein denaturation
B. RNA cleavage
C. DNA damage
D. Cell membrane lysis

DNA damage.

Which process uses steam at 121°C to sterilize materials?

A. Filtration
B. UV treatment
C. Pasteurization
D. Autoclaving

Autoclaving.

Which is the most effective chemical for sterilizing medical instruments?

A. Ethanol
B. Phenol
C. Sterilant
D. Detergent

Sterilant.