MCB 100 Exam 4 Questions and Correct Answers
sterilization definition
- kills ALL microbes (including spores)
- surgical tools, lab media
disinfection definition
kiss MOST (not spores)
- kills vegetative cells
disinfectant (sanitizers) examples
- chlorine, iodine (oxidizing, bleach)
- strong acids (HCl, H2SO4)
- heavy metal (binds -SH)
- alkylating agents (formaldehyde and ethylene oxide)
- strong detergents, phenols (triclosan)
- quats
disinfectants and antimicrobial agents
many natural or artificial agents that can be used to kill or slow-down the growth of microbes
sanitization definition
reduces microbes to safe public health levels
antiseptic definition
- safe for living tissue
- can kill many different microbes, but not as harsh
,antispectic (germicide) examples
- halides
- phenols
- alcohol (rubbing alcohol)
- hydrogen peroxide (oxidizing)
- weak acids
- milk detergents (hand soap)
aseptic definition
no contamination
pasteurization definition
- reduces pathogens in FOOD
- microbes still remain, just at safer levels
microbial death rate
death is exponential
D-value
time required to kill 90% of microbes
1,000,000 to 100,000 in 4 minutes
The d value is 4 minutes.
1,000,000 to 1
6 90% deductions: 6 x 4 = 24 minutes.
steeper slope
,faster killing
larger D-value
- more resistant microbes
- multiply D-values for length of sterlization
autoclave heating method
- steam (121 degrees C) and pressure for 15-60 min
- steam penetrates -> kills spores -> sterilization
dry heat method
- kills most common microbes
- Requires a long time (1-2 hrs at 160°C) to effectively sterilize.
- Effective on equipment or bedding materials
boiling heating method
- kills most, NOT spores
pasteurization heating method
- reduces microbes
- preserves food quality
heat method mechanism
denatures proteins and damages membranes
why is steam better than dry heat?
transfers heat more efficiently
filtration method
, - works based on SIZE
- removes bacteria, NOT viruses (too small)
UV radiation
- DNA damage
- causes thymine dimers -> blocks DNA replication
- doesn't penetrate well (surface only)
Ionizing radiation
- creates free radicals ->DNA breaks (stronger!)
- used for food irradiation and sterilizing some medical materials
- gamma, electron beams, x-rays
biosafety levels
1: harmless
2: moderate risk, PPE, biosafety cabinets
3: serious airborne, special containment
4: deadly (ebola-level)
Natural chemical method
antibiotics, acids, alcohol
Artificial chemical methods
bleach, chlorine, detergents, bromine, synthetic drugs
microbicidal (germicidal)
kill the microbe (germ)
microbiostatic
sterilization definition
- kills ALL microbes (including spores)
- surgical tools, lab media
disinfection definition
kiss MOST (not spores)
- kills vegetative cells
disinfectant (sanitizers) examples
- chlorine, iodine (oxidizing, bleach)
- strong acids (HCl, H2SO4)
- heavy metal (binds -SH)
- alkylating agents (formaldehyde and ethylene oxide)
- strong detergents, phenols (triclosan)
- quats
disinfectants and antimicrobial agents
many natural or artificial agents that can be used to kill or slow-down the growth of microbes
sanitization definition
reduces microbes to safe public health levels
antiseptic definition
- safe for living tissue
- can kill many different microbes, but not as harsh
,antispectic (germicide) examples
- halides
- phenols
- alcohol (rubbing alcohol)
- hydrogen peroxide (oxidizing)
- weak acids
- milk detergents (hand soap)
aseptic definition
no contamination
pasteurization definition
- reduces pathogens in FOOD
- microbes still remain, just at safer levels
microbial death rate
death is exponential
D-value
time required to kill 90% of microbes
1,000,000 to 100,000 in 4 minutes
The d value is 4 minutes.
1,000,000 to 1
6 90% deductions: 6 x 4 = 24 minutes.
steeper slope
,faster killing
larger D-value
- more resistant microbes
- multiply D-values for length of sterlization
autoclave heating method
- steam (121 degrees C) and pressure for 15-60 min
- steam penetrates -> kills spores -> sterilization
dry heat method
- kills most common microbes
- Requires a long time (1-2 hrs at 160°C) to effectively sterilize.
- Effective on equipment or bedding materials
boiling heating method
- kills most, NOT spores
pasteurization heating method
- reduces microbes
- preserves food quality
heat method mechanism
denatures proteins and damages membranes
why is steam better than dry heat?
transfers heat more efficiently
filtration method
, - works based on SIZE
- removes bacteria, NOT viruses (too small)
UV radiation
- DNA damage
- causes thymine dimers -> blocks DNA replication
- doesn't penetrate well (surface only)
Ionizing radiation
- creates free radicals ->DNA breaks (stronger!)
- used for food irradiation and sterilizing some medical materials
- gamma, electron beams, x-rays
biosafety levels
1: harmless
2: moderate risk, PPE, biosafety cabinets
3: serious airborne, special containment
4: deadly (ebola-level)
Natural chemical method
antibiotics, acids, alcohol
Artificial chemical methods
bleach, chlorine, detergents, bromine, synthetic drugs
microbicidal (germicidal)
kill the microbe (germ)
microbiostatic
