Bacte Lec - Quiz 1 Control of Microbial Growth Flashcards
process of destroying all forms of microbial life (vegetative cells and spores)
Sterilization –
special structures resistant to chemical and physical changes
• Spores
substance that prevents growth of bacteria by destroying cells or inhibiting growth; applied on skin
• Antiseptic
chemical agent that destroys only vegetative cells but not spores; applied on inanimate objects
• Disinfectant
process of killing or inhibiting the growth of pathogens
• Disinfection
kills bacteria, even without chemical agent it will not grow again
• Bactericidal
agent that kills microbes
• Microbicidal
inhibits growth of bacteria, but without chemical agent bacteria will grow again
• Bacteriostatic
chemical agent that inhibits and kills/destroys pathogens without damaging body tissues
Antimicrobial agent or antimicrobial drug
agent that kills fungi
• Fungicidal
agent that kills spores
• Sporicidal
agent that kills viruses
• Virocidal
MoA of 70% alcohol
- Protein denaturation
2. Lipid dissolution
disinfectant, contains phenol, used in lab
Lysol
Mechanism of Action of Lysol
- Inactivation of enzymes
- Protein denaturation
- Cytoplasmic membrane destruction
– disrupts cell membrane
Soap
agent that limits the growth of bacteria to a safe level
Sanitizer
Methods to Control Microbial Growth (11)
Heat radiation filtration titration agitation osmotic pressure sonic vibration low temperature/ cold temperature lyophilization ethylene oxide dessication
2 physical methods of sterilization under heat
moist heat
dry heat
why is moist heat better than dry heat
has faster coagulation of proteins
methods of sterilization under moist heat
autoclaving boiling Fractional/ Tyndallization/Intermittent inspissation pasteurization
pressure
temp
duration/time of autoclaving
121 C
15 pounds per square inch
15-20 min
methods of sterilization under moist heat
makes use of steam under pressure
autoclaving
methods of sterilization under moist heat
no incubation in between
autoclaving
advantages of autoclaving (3)
> Abundant moisture
Penetrates rapidly
Temperature above boiling
methods of sterilization under moist heat
not effective because it only kills vegetative cells
boiling
temp and time for boiling
100C
either within 10 min or 2-3 min
added when boiling to increase killing effect
2% sodium carbonate
methods of sterilization under moist heat
-uses Arnold’s sterilizer
Fractional/ Tyndallization/Intermittent
is Fractional/ Tyndallization/Intermittent effective
yes
time and temp for Fractional/ Tyndallization/Intermittent
-100C for 30 min for 3 consecutive days with incubation period in between (to allow spores to germinate and be killed the next day)
Fractional/ Tyndallization/Intermittent uses what type of sterilizer
Arnold’s sterilizer
methods of sterilization under moist heat
-uses an inspissator
Inspissation
methods of sterilization under moist heat
-used for high protein culture media that cannot withstand high temperature of autoclave
Inspissation
time temp days for inspissation
-75 – 80C for 2 hours for 3 consecutive days
Materials Inspissated:
3
Dorset Egg Medium
Lowenstein-Jensten
Loeffler Serum
form of disinfection originally devised by Louis Pasteur to preserve wine
-but today it is more likely to associate with milk
Pasteurization
3 Ways by which Milk can be Pasteurized
a. High Temperature Short Time/ Flash Method
b. Low Temperature Cooling or Coding
c. Ultra-high Temperature (UHT)
3 Ways by which Milk can be Pasteurized
time and temp for High Temperature Short Time/ Flash Method
-milk heated at 72C for 15 sec
3 Ways by which Milk can be Pasteurized
time and temp for Low Temperature Cooling or Coding
-milk heated at 62C for 30 min
3 Ways by which Milk can be Pasteurized
time and temp for Ultra-high Temperature (UHT)
- dairy products stored without refrigeration
- milk heated at 72C to 140C and back to 72C for less than 5 sec
principle of dry heat
oxidation of cellular components
types of sterilization under dry heat
hot air
open flame
incinerator
time and temp for hot air
-160 – 180C for 1.5 hrs or 2 hrs
principle of open flame
burning to ashes
temp for incineration and for how long to incinerate
870 – 980C until burned into ashes
sterilizer of hot air
oven
equipment used in open flame
bunsen burner
equipment used in incineration
incinerator
method of dry heat sterilization
kills microbes rapidly
incineration
method to control microbial growth
-all types can be injurious, causing death or mutation
Radiation
2 types of radiation
ionizing and non-ionizing
MoA of dessication and lyophilization
removing water,
effect of dessication and lyophilization
dehydration
MoA of Low Temperature/Cold Temperature
changesin cellular proteins
MoA of osmotic pressure
plasmolysis
also called Sterilization/ Gas sterilization/ Gaseous-chemical sterilization
ethylene oxide
method of microbial growth control, uses a gas chamber
ethylene oxide
MoA of ethylene oxide
alkylation of nucleic acids of bacteria
how much chamber space
temp time
for ethylene oxide
450 – 750 mg/L of chamber space at 55 – 60C for 2 hours
– for inoculating microorganisms
- enclosed to protect from ____________ exposure
- with special filter paper: HEPA (High Efficiency Particulate Air) filter paper
Biological Safety Cabinet
special filter paper for biological safety cabinet
HEPA (High Efficiency Particulate Air) filter paper
MoA of titration and agitation
mechanical disruption of cell wall
MoA of sonic vibration
breaking of cell wall
removing microorganisms from solution or suspending fluid
-as fluid passes through filter, microbes are trapped in the pores of filtering material
Filtration –
effectivity of filtration depends on the ff
> Porosity
Electric charge of filter
Nature of fluid being filtered
Commonly Used Filters to Remove Microbes from a Suspending Fluid
- Berkefeld filter – made of diatomaceous earth
- Seitz – asbestos pad
- Chamberland – unglazed porcelain
- Membrane – cellulose ester/acetate
- Morton – sintered glass
– used to determine effectivity of chemical agent
Phenol coefficient test
types of ionizing radiation
x-rays
cathode rays
gamma rays
non-ionizing radiation is also ___
ultraviolet radiation
