Microbial Control Flashcards
the process of destroying all forms of microbial life.
Sterilization
An agent, usually a chemical that kills the grow forms but not necessarily the resistant spore forms of disease – producing microorganisms.
Disinfectant
is the process of destroying infectious.
Disinfection
A substance that opposes sepsis, to prevent the growth or action of microorganism or action microorganisms either by destroying or by inhibiting their growth and metabolism.
Antiseptics
An agent that reduces the microbial population to safe levels as judged by public health requirements.
Sanitizer
An agent that kills the growing forms but not necessarily the resistant spore forms of germs
Germicide (Microbicide)
An agent that kills bacteria, similarly the terms fungicide, virucide and sporicidal refers to agents that kill fungi, viruses and spores respectively.
Bactericide
A condition in which the growth of bacteria is prevented. Similarly, fungistatic describes an agent that stops the growth of fungi.
Bacteriostasis
One that interferes with the growth and metabolism of microbes.
Antimicrobial agent
Some antimicrobial agents are used to treat infections, and they called
chemotherapeutic agents
Methods of Microbial Control:
- Nature of the material to be treated
- Types of microorganisms
- Environmental conditions
To cite an extreme example ( a chemical agent used in disinfectant contaminated utensils might be quite unsatisfactory for application to the skin; It might do serious injury to the tissue cells.
Nature of the material to be treated
Chemical agents are not all equally effective against bacteria, fungi, viruses and other microorganisms.
Types of microorganisms
The factors temperature, pH, time, concentrations and presence of extraneous organic material, may all have a bearing on the rate and efficiency of antimicrobial action.
Environmental conditions
Temperatures below the minimum usually have a ____ action on microorganisms.
static
An agent that is static in action will inhibit the growth of microorganisms.
static
An agent that is cidal in action will kill microorganisms and viruses.
cidal
Temperatures above the maximum usually have a ____ action on microorganisms.
cidal
Keep in mind that when evaluating or choosing a method of controlling microorganisms, you
must consider the following factors which may influence antimicrobial activity:
- the concentration and kind of a chemical agent used;
- the intensity and nature of a physical agent used;
- the length of exposure to the agent;
- the temperature at which the agent is used;
- the number of microorganisms present;
- the organism itself; and
- the nature of the material bearing the microorganism
Vegetative microorganisms can generally be killed at temperatures from 50°C to 70°C with moist heat.
High Temperature
are very resistant to heat and extended exposure to much higher temperature is necessary for their destruction
Bacterial endospores
is generally more effective than dry heat for killing microorganisms because of its
ability to penetrate microbial cells.
Moist heat
Moist heat kills microorganisms by
denaturing their
proteins
employs steam under pressure.
Autoclaving
Examples of dry heat include:
- Hot air sterilization
- Incineration
will generally kill vegetative cells after about 10 minutes of exposure.
Boiling water
kills microorganisms through a process of protein oxidation rather than protein
coagulation.
Dry heat
is the mild heating of milk and other materials to kill particular spoilage
organisms or pathogens. It does not, however, kill all organisms.
Pasteurization
inhibits microbial growth by slowing down microbial metabolism.
Low temperature
generally has a static effect on microorganisms. Lack of water inhibits the action of microbial enzymes. Dehydrated and freeze-dried foods
Desiccation, or drying
in their natural environments, are constantly faced with alterations in osmotic pressure. Water tends to flow through semipermeable membranes, such as the cytoplasmic membrane of microorganisms, towards the side with a higher concentration of dissolved materials (solute).
microorganisms
the cell is said to be in a _______ environment and water will flow into the cell.
hypotonic
CHARACTERISTICS OF GOOD ANTIMICROBIAL AGENT
- Antimicrobial activity
- Solubility
- Stability
- Nontoxicity to human and other animals
- Homogeneity
- Noncombination with extraneous organic material
- Toxicity to microorganisms at room or body temperatures
- Capacity to penetrate
- Noncorroding and non - staining
- Deodorizing ability
- Detergent capacities
- Availability
The capacity of the substance to kill or inhibit microorganisms is the first requirement.
Antimicrobial activity
The substance must be soluble in water or other solvents to the extent necessary for effective use.
Solubility
Changes in the substance upon standing should be minimal and should not result in significant loss of germicidal action.
Stability
Ideally, the compound should be lethal to microorganisms and non injurious to humans and other animals.
Nontoxicity to human and other animals
The preparation must be inform in composition so that active ingredients are present in each application.
Homogeneity
Many disinfectants have an affinity for proteins or other organic material
Noncombination with extraneous organic material
In using the compound, it should not be necessary to raise the temperature beyond that normally found in the environment where it is to be use.
Toxicity to microorganisms at room or body temperatures
Unless the substance can penetrate through the surfaces, its germicidal action is limited solely to the site of application.
Capacity to penetrate
It should not rusts or otherwise disfigure metals nor stain or damage fabrics.
Noncorroding and non - staining
Deodorizing while disinfecting is a desirable attribute. Ideally the disinfectant itself should either be odorless or have a pleasant smell.
Deodorizing ability
A disinfectant which also a detergent (cleaning agent) accomplish two objectives and the cleansing action improves the effectiveness of the disinfectant.
Detergent capacities
The compound must be available in large quantities at a reasonable price.
Availability
Commonly used Chemical agents
- Phenol and Phenolic compounds
- Alcohols
- Halogens (Iodine)
- Heavy Metals and Their Compounds
- Dyes
- Synthetic Detergent
- Quaternary Ammonium
- Aldehydes
- Formaldehyde
is a unique and powerful sterilizing agent. It is use for sterilizing heat or moisture sensitive materials in hospitals, industry and laboratories has become universal.
Ethylene oxide
Heavy metal
Mercury, Silver, Copper
has the distinction of being used successfully in the 1880s by Joseph Lister, a surgeon, to reduce infection of surgical incisions and surgical wounds.
Phenol
measures the disinfecting power or effectiveness of a disinfectant or antiseptic (the test disinfectant) compared to phenol: a well-established antiseptic agent.
the phenol – coefficient technique.
are inactive and dormant structures.
Spores
are actively growing cells that form the endospore.
Vegetative cells
CH3CH2OH in concentrations between 50 and 90s, is effective against vegetative or non – spore forming cells.
ethyl alcohol
is less bactericidal than ethyl alcohol; furthermore it is highly poisonous.
methyl alcohol
is one of the oldest and most effective germicidal agents. It has been in use for more than a century, having been recognized by the US Pharmacopoeia in 1830.
halogens (iodine)
are mixtures of iodine with surface – active agents which act as carriers and solubilizers for the iodine.
iodophores
Two classes of dye compounds
triphenylmethane and acridine dyes.
These compounds exhibit selective inhabitation against bacteria, particularly staphylococci and Gonococci.
Acridine Dyes
Most compounds of the germicidal cationic – detergent class are
quaternary ammonium salts.
is the simplest compound in the aldehyde series. It is a gas that is stable only in high concentrations and at elevated temperatures.
Formaldehyde
is a unique and powerful sterilizing agent. It is use for sterilizing heat or moisture sensitive materials in hospitals, industry and laboratories has become universal.
Ethylene oxide
