Microbial Growth Control Flashcards
• Process of destroying unwanted microbes
Has improved throughout human history and today, many countries have clean drinking water, sterilized food and medical equipment
MICROBIAL CONTROL
Millennia before animalcules were viewed by Sir Anton van Leeuwenhoek and before the Germ Theory of Disease in Koch’s Postulates had been accepted, references to germicidal agents had been made in the ancient writings of_______
• Their_______ applied spices, vegetable oils, and gums to their dead
• Using techniques that have kept them in a superior state of preservation even today
Egyptians
embalmers
Persians, Greeks and Romans had legal documents requesting the use of _____ and_____ vessels for the storage of public drinking water
• Early civilizations practiced salting, smoking, pickling, drying, use of spices in cooking and exposure of food and clothing to sunlight to control microbial growth.
bright copper and silver
in the year 1847 at the Maternity Clinic of Vienna’s General Hospital requested that interns who had performed autopsies, washed their hands with chlorinated lime before examining expectant mothers
IGNAZ SEMMELWEIS
• In mid 1800s,______ and______ helped developed aseptic techniques to prevent contamination of surgical wounds by the use of ______on surgeon’s hands - and in the operating field, the surgical instruments used, the hospital environment in general
Ignaz Semmelweis and Joseph Lister
carbolic acid
• Before then:
Nosocomial infections caused death in
______of surgeries.
Up to_____ mothers delivering in hospitals died due to infection.
10%
25%
• is the most common method used to kill microorganisms, unfortunately, for the food industry, temperatures used to kill all living microbes will also result in degrading the quality of food during the cunning process
Instead, commercial sterilization is used
EXTREME HEAT
• Can be achieved by applications of heat, pressure, chemicals, radiation/ filtration
STERILIZATION
• Items to be_____ can be surfaces, equipment, food, medication, as well as biological culture media.
Sterilized
• Killing or removing all forms of microbial life (including endospores and prions-the most resistant forms)in a material or an object.
STERILIZATION
• Heat treatment that kills endospores of Clostridium botulinum, the causative agent of botulism, in canned food.
COMMERCIAL STERILIZATION
• Does not kill endospores of thermophiles, (not pathogens that may grow at temperatures above 45 degrees Celsius.)
COMMERCIAL STERILIZATION
• May use physical or chemical methods.
• Destruction of vegetative microorganisms by chemical or physical methods
DISINFECTION
• Reducing the number of pathogenic microorganisms to the point where they no longer cause diseases.
• Usually involves the removal of vegetative or non-endospore-forming pathogens.
DISINFECTION
Does not destory bacterial endospores and can be achieved by chemicals
Ultraviolet radiation, boiling water, or steam
Disinfection
Applied to the use of a chemical to treat an inert surface or substance
DISINFECTANT
Applied to living tissue (antisepsis)
ANTISEPTIC
• Medical instruments require sterilization, but in other areas of life, microbes do not have to be completely eliminated-just reduced to insufficient numbers to prevent infection, disease, and the transmission of infection and disease
DEGERMING
Mechanical removal of most microbes in a limited area
• Example: when someone is about to receive an injection, the skin is swabbed with alcohol
DEGERMING
• reduction of the number of microorganisms to safe public health levels
SANITIZATION
• Minimizes the chances of disease transmission between users
• E.g.: Hot soup and water
• Glassware and other tableware in restaurants, institutions as well as the home environment
SANITIZATION
Indicates bacterial contamination, as in septic tanks for sewage treatment.
SEPSIS
Comes from Greek for decay or putrid.
SEPSIS
Absence of significant contamination.
Technique that prevents the entry of microorganisms into sterile tissues
ASEPSIS
• prevent contamination of surgical instruments, medical personnel, and the patient during surgery; prevent bacterial contamination in food industry.
ASEPTIC TECHNIQUES
Microbial growth is at a standstill.
• Suffix stasis: To stop or steady.
BACTERIOSTATIC AGENT/MICROBIOSTATIC
• An agent that inhibits the growth of bacteria, but does not necessarily kill them.
BACTERIOSTATIC AGENT/MICROBIOSTATIC
• Inhibit fungal growth
FUNGISTATIC AGENTS
-> an agent that kills certain microorganisms
Germicide
• -> an agent that kills bacteria. Most do not kill endospores.
Bactericide
-> an agent that inactivates viruses
Virucide
-> an agent that kills fungi
• Fungicide
•-> an agent that kills bacterial endospores or fungal spores
Sporicide
When bacterial populations are heated or treated antimicrobial chemicals, they usually die at a..
constant rate
_______ is the PERMANENT LOSS of reproductive ability of microbes
• Permanent loss of all other vital activities
• Lethal agents do not always alter the appearance of a microbial cell even if the motility of the organism is gone.
• Therefore, the term ____can be used
ONLY if the reproduction cannot occur even if the organism is given the optimal growth conditions
Microbial death
• Destructive forces of chemical / physical agents act on the individual cells; and if exposed intensively and long enough, the cell structures become DYSFUNCTIONAL and the cells show irreversible damage
• In general, cells in a given culture or in a given environment vary in their susceptibility to antimicrobial agents
Microbial death
They die at some fractional rate per unit time
If 50% of microorganisms in a population die every minute, after 2 minutes, ___% will still be alive; after 3 minutes, ___% are still alive; and so on
If 50% of microorganisms in a population die every minute, after 2 minutes, 25% will still be alive; after 3 minutes, 12.5% are still alive; and so on
It is therefore safe to say that the total number of organisms present, when the disinfection process begun, determines the time required to eliminate all microbes
RATE OF MICROBIAL DEATH
SEVERAL FACTORS THAT INFLUENCE THE EFFECTIVENESS OF ANTIMICROBIAL TREATMENT
- Number of Microbes
- Type of Microbes
- Environmental influences
- Time of Exposure
a. Dictates the time required for the destruction of all contaminants
Number of Microbes
a. Nature of organisms to be destroyed - biofilms include a number of organisms and species-
b. other contaminants can include vegetative organisms such as spores, and any target population that contains more than 1 organism can present a broad spectrum of resistance
Type of Microbes
a. Presence of organic material (blood, feces, saliva) tends to inhibit antimicrobials, pH etc.
Environmental influences
a. Chemical antimicrobials and radiation treatments are more effective at longer times.
b. In heat treatments, longer exposure compensates for lower temperatures.
Time of Exposure
Order of resistance against biocidal process
Prions
Bacterials spores
Protozoal oocysts
Helminth eggs
Mycobacteria
Small non-enveloped viruses
Protozoal cysts
Fungal spores
Gram-negative bacteria
Vegetative fungi and algae
Vegetative helminths and protozoa
Large non-enveloped viruses
Gram-positive bacteria
Enveloped viruses
HIGHLY RESISTANT:
prions (Creutzfeldt-Jakob disease)
Kills microorganisms by denaturing their enzymes and other proteins.
Heat resistance varies widely among microbes.
Heat
Lowest temperature at which all of the microbes in a liquid suspension will be killed in ten minutes.
Thermal death point
Minimal length of time in which all bacteria will be killed at a given temperature.
Thermal death time