Microbiology week 3

Phenolics

-The phenolic compounds include phenol (carbolic acid), cresols(lysol), and hexachlorophene -control microbial growth by denaturing proteins anddisrupting cell membranes. -In most cases, phenolic compounds are not effective in killingbacterial endospores, so they do not make good sterilants.

chemically controlling microrganisms

Chemical antimicrobial agents fall into one of two broad categoriesbased on their suffix.• Those antimicrobial agents that end in the suffix -cide are agents thatwill kill a particular type of microorganism, while those that end in thesuffix -static will prevent the growth of a particular type ofmicroorganism

Several factors influence the effectiveness of anti microbial agents used to control microbial growth. Some of the most significant of those factors are:

Nature of the disinfectant • Concentration of the disinfectant • Nature of the material to be disinfected • Number of microorganisms present • Type of microorganism present • Length of exposure to disinfectant • Temperature of the disinfectant during exposure • Disinfectant's pH during exposure

Sporicides

agents that kill bacterial and mold spores, can also be used during theprocess of terminal disinfection of embalming instruments and equipment.

Aldehydes

are a group of organic compounds that controlmicrobial growth by reacting with the proteins inmicroorganisms and altering their chemical structure. • In the early days of the poliovirus vaccine, low concentrations offormaldehyde were used to prepare the vaccine causing manypeople to contract the disease because the concentration offormaldehyde was not sufficient to produce a safe vaccine.

Cresols

are phenolic compounds derived from a chemical known as toluene. -There are three slightly different forms of cresols known asortho-cresol, meta-cresol, and para-cresol. -These three forms of cresols can appear individually or in combination with each other. • Cresols are also used to produce the commercial product Lysol;additionally, cresols are used as deodorants and to produceinsecticides.

Alcohols, including ethyl alcohol and isopropyl alcohol

are used to control microbial growth.

Alcohols

are widely used disinfectants that control microbialgrowth by denaturing proteins and by dissolving lipids in thecell membrane of microorganisms. • They are most effective in aqueous solution because proteinsare not soluble in high concentrations of alcohol.

Halogens

are widely used disinfectants that work byoxidizing the components of microbial cells. Some halogensalso react with cellular proteins.

Viricides

inactive viruses

Ultraviolet (UV) light

is a form of nonionizing radiation that can effectively control the growth of microorganisms placed directly in its path .• It inhibits microbial growth by damaging the cell's genetic material .• When exposed directly to UV light, some microorganisms develop bonds between adjacent thymines in their DNA. • The sun contains UV light; however, much of it is filtered by the Earth's ozone and never reaches the surface in a form that kills microorganisms .• For UV light to be effective, the microorganism must be exposed to it directly .• Even paper prevents UV light from penetrating enough to kill microorganisms, and many microorganisms contain pigments resistant to the detrimental effects of UV light.

Scrubbing

is a manual process by which microorganisms are removedfrom a surface.• Even the best sterilizers, disinfectants, and antiseptics will noteffectively control the growth of microorganisms if the equipment,instruments, and deceased are covered in visible contaminants.

Hexachlorophene

is about 450 times more effective as a germicidethan phenol. • It is such an effective antibacterial agent that it was commonly usedin soaps, deodorants, toothpaste, talcum powder, mouthwash, andshaving cream .• Chlorhexidine is less toxic than hexachlorophene, and it is effective inthe control of a wider array of bacteria .• It has replaced hexachlorophene in many surgical scrubs, in thedisinfection of patient's skin prior to surgery, and as a woundcleanser .• Hexachlorophene is now only available with a prescription.

Temperature

is another physical method by which the growth ofmicroorganisms can be controlled. • Heat can be used to control the growth of microorganisms byincineration, dry heat, and moist heat, which are forms of boiling, free-flowing steam, and steam under pressure, respectively .• Heat kills microorganisms by denaturing the proteins they contain, andproteins are denatured more easily when they are wet. • The opposite extreme to heat, which is cold, can also be an effectivemeans of controlling microbial growth

Phenol

is slightly acidic and is also known as carbolic acid. -It has a sickeningly sweet and tarry odor and is available commercially as a liquid. -Phenol is flammable, and skin exposure to phenol has beenshown to cause chemical burns, liver damage, diarrhea, darkurine, and hemolytic anemia. Phenol is also breathed into the lungs when smoking tobacco. • Due to its toxic nature, phenolic derivatives have replacedphenol as a disinfectant and antiseptic.

Antisepsis

is the process by which microbial growth is inhibited on living tissue toprevent infection. Disinfectants are applied to inanimate objects, while antisepticsare applied to living tissue. Sanitization is the reduction of the microbialpopulation to a safe level as determined by public health standards. There are both physical and chemical methods of controlling microbial growth.

Disinfection

is the reduction of pathogenic agents by chemical or physical meansby applying the disinfectant to an inanimate object. Disinfection offers less controlof the growth of microorganisms. The process of disinfection does not inactivatemicrobial endospores; however, it does kill most vegetative microorganisms.During disinfection, the number of microorganisms is reduced to the point thatthey no longer present a serious health hazard.

Chlorine

is used to treat municipal drinking water and for themaintenance of swimming pools. Chlorine is actually a gas, so it isoften combined with water to form sodium hypochlorite.

Germicides

kill a variety of different types of microorganisms, but not necessarilytheir spores

Bactericides

kill bacteria but not necessarily their spores

Fungicides

kill both fungi and their spores

Insecticides

kill insects, and larvicides kill larvae, which are the wormlike formsof newly hatched insects.

Sterilization

offers the highest level of microbial growth control. It is the process of completely removing or destroying all life-forms, including bacterial endospores.

Quaternary ammonium compounds

which are also known asquats, are chemical disinfectants and antiseptics that damagecellular membranes and denature microbial proteins .• These surface-active agents, or surfactants, are capable ofaltering the surface tension of cell membranes causing theircellular contents to leak out, thus destroying the cell .• Quaternary ammonium compounds are deactivated in thepresence of soap and other organic matter found in items likegauze.

Iodine

which controls microbial growth by oxidizing certainmolecules within the microbial cell, can be used in the form of eithera tincture or aniodophore. A tincture is a solution of iodine andalcohol that is primarily used as an antiseptic.