Microbial Control Methods: Physical, Chemical, and Resistance Factors

What are historical microbial control methods?

Salting, smoking, pickling, drying food, exposing items to sunlight, burning clothing and corpses, and storing water in copper and silver containers.

What is sterilization?

The destruction of all microbial life, also known as sporicidal.

What does disinfection do?

Destroys most microbial life, reducing contamination on inanimate surfaces.

Define antisepsis.

Destruction of microbial life on tissues using chemical agents.

What is degermation?

Mechanical removal of microbes from tissues, such as scrubbing or handwashing.

What is sepsis?

Bacterial contamination in tissues.

What is decontamination?

The mechanical removal of most microbes from surfaces, also called sanitization.

What is a bactericide?

A chemical that destroys bacteria but not endospores.

What is a fungicide?

A chemical that can kill fungal spores, hyphae, and yeasts.

What is a virucide?

A chemical that inactivates viruses.

What is a sporicide?

A chemical that can destroy bacterial endospores and achieve sterility.

What are critical medical devices?

Devices expected to come into contact with sterile tissues.

What are semicritical medical devices?

Devices that come into contact with mucosal membranes.

What are noncritical medical devices?

Devices that do not touch the patient or only touch intact skin.

What is thermal death time?

The shortest length of time required to kill all test microbes at a specified temperature.

What is thermal death point?

The lowest temperature required to kill all microbes in a sample in 10 minutes.

What is the effect of cold on microbes?

Cold treatment slows down the activities of most microbes; some may be killed, but most are not adversely affected.

What is desiccation?

Dehydration of vegetative cells directly exposed to normal room air, disrupting metabolism.

What is lyophilization?

A combination of freezing and drying used to preserve microorganisms and other cells in a viable state.

What types of radiation are suitable for microbial control?

Gamma rays, X-rays, and ultraviolet radiation.

What is the role of ionizing radiation?

It breaks DNA molecules and is used for medical supplies and food preservation.

What is the role of non-ionizing radiation?

It damages DNA molecules and causes abnormal bonds to form, such as pyrimidine dimers from ultraviolet light.

What is the advantage of food preservation by ionizing radiation?

It reduces foodborne illness and increases shelf-life.

What is the disadvantage of food preservation by ionizing radiation?

It slightly decreases the amount of thiamine (B1) and produces short-lived free radicals.

What is decontamination by filtration?

Passing liquid or gas through a filter with small pore size to remove microorganisms.

What are HEPA filters used for?

To filter air and are used in hospitals in combination with UV light to kill trapped bacteria and viruses.

What is the most widely used method of microbial control?

Heat

What are the other methods of microbial control besides heat?

Radiation, Filtration, Ultrasonic waves, Cold

What is the effect of dry heat on microbial cells?

Causes dehydration of cells and protein denaturation

What is incineration in the context of microbial control?

Flaming your loop to sterilize it

What temperature and time are required for baking as a dry heat method?

160°C for 2 hours or 171°C for 1 hour

What are the advantages of using dry heat for microbial control?

Cheap and easy

What is a disadvantage of dry heat sterilization?

Materials must withstand high temperatures

What is the effect of moist heat on microbial cells?

Causes protein denaturation

What is boiling and its limitation in microbial control?

Boiling at 100 °C will not kill endospores

What is pasteurization and its temperature/time requirements?

High temperature, short time (HTST) at 72°C for 15 seconds kills all pathogens and most nonpathogens

What is autoclaving?

A method using very high heat and pressure; 15 psi at 121 °C for 20 minutes

What is the effect of cold treatment on microbes?

Slows down the activities of most microbes; some are killed by cold temperatures

What is desiccation in microbial control?

Dehydration of vegetative cells exposed to normal room air, disrupting metabolism

What is the effect of ionizing radiation on DNA?

Breaks DNA molecules by ejecting electrons and forming ions

What is the effect of non-ionizing radiation on DNA?

Damages DNA molecules and forms abnormal bonds, such as pyrimidine dimers

What are the advantages of using ionizing radiation for food preservation?

Reduction in food borne illness and increased shelf-life

What is a disadvantage of ionizing radiation in food preservation?

Slightly decreases the amount of thiamine (B1) and produces short-lived free radicals

What is the method of decontamination by filtration?

Passing liquid or gas through a filter with small pore size to remove microorganisms

What is the role of UV light in hospital systems?

Used in combination with HEPA filters to kill trapped bacteria and viruses

What is the effect of cold on most microbes?

Cold merely retards the growth of most microbes

What are the three forms of antimicrobial chemicals?

Solid, Liquid, Gaseous

What is an aqueous solution?

A solution containing pure water as the solvent.

What are tinctures in the context of antimicrobial chemicals?

Antimicrobial chemicals dissolved in pure alcohol or water-alcohol mixtures.

List three desirable qualities of an antimicrobial chemical.

Rapid action in low concentrations, solubility in water or alcohol, broad-spectrum microbicidal action.

What is the effect of damaging the cell wall of a microorganism?

It makes the cell fragile and prone to lysis.

How do surfactants affect cell membranes?

They bind to the lipid layer and create leaky spots, allowing damaging chemicals in and vital ions out.

What are halogen antimicrobial chemicals?

Fluorine, bromine, chlorine, and iodine that are microbicidal and sporicidal.

What is the mode of action of chlorine as an antimicrobial?

Denatures enzymes permanently and suspends metabolic reactions.

What are the limitations of phenolics as antimicrobial agents?

Toxicity makes them dangerous to use as antiseptics; many phenols were banned in 2017.

What is the mode of action of chlorhexidine?

Disrupts the plasma membrane.

What is the effectiveness of alcohol as an antimicrobial agent?

Dissolves membrane lipids and denatures proteins at concentrations of 50% and higher.

What is the role of hydrogen peroxide as an antimicrobial?

It kills anaerobic bacteria and some viruses by forming free radicals.

What are cationic detergents?

Polar molecules that act as surfactants and are effective antimicrobials.

What is the primary action of detergents on microbial cells?

They disrupt the plasma membrane, causing cell death.

What is the significance of using a higher concentration of alcohol?

A higher concentration is more effective due to better protein coagulation.

What are two acids commonly used in food preservation?

Acetic acid and citric acid.

What is the primary use of hypochlorites in healthcare?

To treat wounds, disinfect bedding and instruments, and sanitize food equipment.

What is the action of phenolics at high concentrations?

They act as cellular poisons, disrupting cell walls, membranes, and proteins.

What is a major concern regarding the widespread use of triclosan?

It increases the risk of cancer and heart attack and suppresses the immune system.

What is the mode of action of oxidizing agents like hydrogen peroxide?

They form toxic free radicals that damage cell membranes.

What is the primary function of surfactants in antimicrobial action?

They create leaky spots in membranes, allowing harmful substances to enter.

What are the indications for using 3% hydrogen peroxide?

As an antiseptic for skin and wound cleansing, and mouthwashing.

What is the role of active ingredients in commercial antimicrobial products?

They target specific microbes and disrupt their cellular functions.

What is the significance of the term 'broad-spectrum' in antimicrobial action?

It refers to the ability to act against a wide range of microorganisms.