MICROBIAL CONTROL AND ANTIMICROBIAL AGENTS Flashcards
Complete removal or destruction of all viable microbes including endospores
Sterilization
Use of physical or chemical agents (disinfectant) to kill vegetative bacteria and other microbes except endospores.
DISINFECTION
Use of physical or chemical agents to kill pathogens on living tissue
ANTISEPSIS
Reduction of microbial counts to acceptable levels of public health standards.
SANITATION
Physical removal or reduction of microbes from a limited area.
DEGERMING
reduce the surface tension thereby altering the membrane structure
Surfactants, such as soap or detergents
Lowest temperature at which all cells in a culture are killed in 10min.
Thermal death point (TDP)
Time needed to kill all cells in a culture
Thermal death time (TDT)
Minutes to kill 90% of a population at a given temperature
Decimal reduction time (DRT)
Types of Moist Heat
Boiling
Tyndallization
Pasteurization
Steam Under pressure
boiling hours needed by hepatitis B virus to be killed
at least one hour
boiling hours needed by hepatitis B virus to be killed
at least one hour
Fractional sterilization; Intermittent use of free-flowing steam for 30 to 60 minutes
Tyndallization
Example of Tyndallization
Used on heat-sensitive media, canned foods
Reduces spoilage caused by microbes and kills pathogens. Used in milk industry, wineries, breweries.
Pasteurization
Pasteurization method: Classic
63 C for 30 minutes
Pasteurization method: High Temp Short time
72 C for 15 secs
Pasteurization method: Ultra High Temp
140 C for <1 secs
Used in media preparation and glassware sterilization.
Steam under pressure
Autoclave settings effectively destroys spores
121 C, 15 psi pressure for at least
15 minutes
Types of Dry Heat
Hot Air
Incineration
Effects of Moist HEAT
Coagulation and denaturation of protein
Effects of DRY HEAT
dehydration, denaturation, oxidation
Useful for sterilization of glasswares and oils; Effective at 170oC for 2 hrs
Hot air
Destroys microbes to ashes or gas
Incineration
Incineration up to 1870 C
Bunsen Flame
Incineration 800 C- 6500 C
Furnance
exampe: Ionizing radiation
X-rays
Gamma rays
Electron Beams
Nonionizing radiation
Ultraviolet light
Microwave: kills by heat
UV light range
200nm to 400nm
200nm-300nm.
Bactericidal effect:
280nm-330nm
Tanning effect:
300nm-400nm
In sunlight:
Can cause damage to cells, whether barriers are present or not, by breaking their DNA.
Ionizing Radiation
If there are barriers, the UV does not penetrate and affect the cell. In the absence of barriers, the nonionizing radiation will form abnormal bonds in the DNA thus promoting stoppage of the proliferation of the cell.
Non-Ionizing Radiation
microbes capable of growth and reproduction in lower temperatures ranging from -20 C to 10oC.
Psychrophiles or cryophiles