Chapter 7 The Control of Microbial Growth

Aseptic Surgery

To prevent microbial contamination of surgical wounds

Sterilization

Is the removal or destruction of all forms of microbial life

Sterilant

A sterilizing agent

Commercial Sterilization

This limited heat treatment

Disinfection

Control directed at destroying harmful microorganisms

Antisepsis

Treatment is directed at living tissue and the chemical is an antiseptic

Degerming

The removal of microorganisms in an area called as degermination

Sanitization

Which is intended to lower microbial counts to safe public health levels and minimize the chances of disease transmission from one user to another

Sepsis

Refers to microbial contamination

Asepsis

The absence of significant contamination

Biocide/ germicide

Kills microbes

Bacteriostasis

Inhibiting, not killing microbes

Thermal death point (TDP)

Is the lowest temperature at which all the microorganisms in a particular liquid suspension will be killed in 10 minutes

Thermal Death Time (TDT)

The minimal length of time for all bacteria in a particular liquid culture to be killed at a given temperature

Decimal Reduction Time (DRT)

Is a third concept related to bacterial heat resistance

Autoclave

These high temperatures are most commonly achieved by steam under pressure

Nucleic acids

Damages to the lethal to the cell

Carbohydrates

Is the 4th cell wall with peptidoglycan

Boiling

kills within about 10 minutes (vegetative bacteria) not spores

Indicators

To shows sterilization

Pasteurization

The process of mild heating to kill particular spoilage microorganisms or pathogens

Thermoduric

Bacterial survive pasteurization, but these are unlikely to cause disease or cause refrigerated milk to spoil

High temperature short-time (HTST) pasteurization

Is applied as the milk flows continuously past a heat exchanger

Ultra-high-temperature (UHT)

sterilizes milk

Equivalent treatment

The temperature is increased, much less time is needed to kill the same number of microbes

Flaming

One of the simplest methods of dry heat sterilization is direct

Hot-air sterilization

Done in the oven. Longer than autoclave because heat is transferred better in water than in air

High-efficiency particular air (HEPA) filters

Remove almost all microorganisms larger than about 0.3 in dimeter

Membrane filters

Composed of such substances as cellulose esters or plastic poylmers, have become popular for industrial and laboratory use

Filtration

The passage of a liquid or gas through a screen like materials

High pressure

Denatures protein

Desiccation

Microorganisms cannot grow or reproduce but can remain viable for years

Ionizing radiation

Gamma rays, X-rays, or high-energy electron beams, has a wavelengths short than that of nonionizing radiation, less than about 1 nm.

Nonionizing radiation

Has a wavelength longer than that of ionizing radiations, usually greater than about 1nm

Microwaves

Do not have much direct effect on microorganisms, and better can readily be isolated from the interior of recently operated microwave oven

Osmotic Pressure

High concentration of salts and sugars create a hypertonic environment

Concentration

Of disinfectant

Organic matter

Can interfer with the action of a disinfectant

pH

Affects the activity of disinfectants

Time

Disinfection is usually a gradual process might take several hours

Use-dilution test

A method of determining the effectiveness of a disinfectant using serial dilutions

Disk-diffusion method

Is used in teaching laboratories to evaluate the efficacy of a chemical agent

Phenol

To control surgical infection in the operating room (carbolic acid)

Phenolics

Contain a molecule of phenol that has been chemically altered to reduce its irritating qualities or increase its antibacterial activity in combination with a soap or detergent

Bisphenols

Are derivatives of phenol that contains two phenolic groups connected by a bridge

Hexacholophene

Good against gram-poitive staphlyococci and streptococi

Triclosan

Widely used

Biguanides

Broad spectrum of activity

Chlorhexdine

Best known on the skin and mucus membrane

Halogens

Particularly iodine and chlorine, are effective antimicrobial agents, but alone and as contituents of inorganic or organic compounds

Tincture

That is in a solution in aqueous alcohol and as an iodophor

Iodophor

Is a combination of iodine and organic molecule, from which the iodine is released slowly

Alcohols

Effectively kill bacteria and fungi but not endospores and noneveloped viruses

Chlorine

Used for as a gas or in combination with others chemicals

Hypochlorous acid (HOCI)

Forms when chlorine is added to water

Bleach

Sodium hypocholrite (NaOCI)

Chloramine

Chlorine + Ammonia

Chlorine dioxide

Used in food processing industry

Ethanol

Optimum concentration is 70% denaturation requires water

Isopropanol

Rubbing alcohol

Oligodynamic action

The ability of very small amounts of heavy metals, especially silver and copper to exert antimicrobial activity

Surface-active agents (surfactants)

Can decrease surface tension among molecules of a liquid

Quaternary ammonium compounds (quats)

The most widely used surface-active agents are the cationic detergents most widely used surface-active agents

Copper

Copper sulfate is an algicide

Mercury

In inorganic compounds

Zinc

Used in building materials to deter growth of algae

Soaps and detergents

Little value as an antiseptic

Acid-anionic sanitizers

Contain anions that react with the plasma membrane

Sodium nitrate or nitrite

Added to meat products to prevent endospores germination

Nitrosamines

Result from reactions between nitrites and amino acids

Antibiotics

Ones used in food are not useful for treating disease

Nisin

A bacteriocin are produced by one bacterium to inhibit another

Natamycin

Antifungal antibiotic

Aldehydes

An organic molecules

Plasma

Is a state matter in which a gas is excited, in this case by an electromagnetic field, to make a mixture of nuclei with assorted electrical charges and free electrons

Peroxygens

Are a group of oxidizing agents that includes hydrogen peroxide and peracetic acid

Gram-negative bacterium

Less resistant than other microbes easier to kill

Mycobacterium

Also are more resistant to chemical biocides

Viruses

Ones with out an envelope are more resistant

Prions

Infectious proteins