Chapter 7 Controlling microbial growth chemical and physical methods.

Types of Action of antimicrobial control agents? 3

- Alteration of membrane permeability Example: shrivle or burst microbe. -Denature proteins Example: unfold proteins (can't function), effects enzymes (blocks metabolism) -Damage nucleic acids (DNA/RNA) Example: affects DNA replication, translation, transcription.

Physical methods of microbial control: Heat Examples:

-bacti-cinerator = sterilant -Autoclave = sterilization, penetrates and used for liquids, uses high temp and steam (messes with osmotic pressure) -Dry heat = can be sterilant, not for liquids. doesn't penetrate. -Boiling water = not reliable sterilization method, she says disinfection. -pasteurization = ONLY disinfection. uses heat to kill pathogens and reduce the number of spoilage organisms.

Sterilization and disinfection, things to consider?

-number of microbes -duration of exposure -type of microbes -temperature, (cold effects duration of exposure.) -concentration of chemical agent. -pH, they like basic less than acidic. -endospore formation, clostridium, bacillus will produce unless done fast. -organic material present in environment, saliva, pus, blood, urine. will make it harder to access microbes.

What are the physical methods of microbial growth control?

1 Heat 2 Cold 3 Drying 4 Filtration 5 Osmotic pressure 6 Radiation (2 types) - Ionizing radiation - Non-Ionizing radiation

Would a chemical microbial control agent that affects plasma membranes affect humans?

A microbial agent that targets the plasma membrane of the microorganism would not be advised because humans also have a plasma membrane. For this reason, it is important to develop a microbial agent that targets components of the microorganism that are not present in the host cell. For example, penicillin is an antibiotic that targets the cell well. Since the cell wall is not present in human cells, penicillin causes no damage to the host cell.

What characteristics make surface-active agents attractive to the dairy industry?

Acid-Anionic Sanitizers: important in cleaning dairy utensils and equipment; Non-toxic; non-corrosive; and fast acting.

Physical methods of microbial control: Heat Action:

Action: denatures proteins, widely applicable, inexpensive, fast, reliable. (The higher the temp decreases the time.)

Chemical methods of microbial growth control: Gaseous Sterilizers For the test you do have to know the different chemicals, the way they work, who they work against.

Action: Denatures proteins. Effective against: ALL MICROBES. STERILIZERS. Effectiveness: HIGH LEVEL Examples: -Ethylene Oxide -Chlorine dioxide

Chemical methods of microbial growth control: Hydrogen Peroxide For the test you do have to know the different chemicals, the way they work, who they work against.

Action: The free radicals that are produced harm cell components. -carbohydrates, lipids, fats, and nucleic acids. Effective against: broad range of microbes. -Especially: OBLIGATE ANAEROBES. Effectiveness: ONLY a disinfectant.

Chemical methods of microbial growth control: phenol/phenol derivatives In 1857 Dr. Lister used phenol on his patients. Had to use a 5-10% solution, caustic to skin, damaged lungs, toxic, nervous system damage

Action: alters membrane permeability. Effective against: some bacteria, viruses, fungi Effectiveness: low effectiveness, ONLY disinfectant. Examples: surface cleaners for hospitals, personal care products, MOST COMMON: Triclosan, now less effective

Physical methods of microbial control: Radiation:

Action: damage is done to the DNA. 2 types: 1.Ionizing radiation: X-Rays, Gamma Rays. -Used: to preserve food. Popular in Europe. Doesn't make food nuclear. 2.Non-Ionizing radiation: Ultra Violet Light -Used: in labs, and morgues, operating rooms.

Physical methods of microbial control: Cold Action:

Action: decreases metabolism, growth, reproduction. -most pathogens (mesophiles = moderate temp loving microbes)

Chemical methods of microbial growth control: Aldehydes For the test you do have to know the different chemicals, the way they work, who they work against.

Action: denatures proteins Effective against: ALL MICROBES, STERILANT. Effectiveness: high level Examples: -Formaldehyde. Is a gas, expensive. -Glutaraldehyde chemical relative of formaldehyde/formalin.

Chemical methods of microbial growth control: Alcohol

Action: denatures proteins, damages membrane (dissolves lipids). -needs H2O to be effective, 70% best. Effective against: Most bacteria, viruses, and fungi. Effectiveness: Medium level. Examples: -Skin antiseptic, duration of exposure problem. 30 seconds before blood draw.

Chemical methods of microbial growth control: Chlorine For the test you do have to know the different chemicals, the way they work, who they work against.

Action: denatures proteins. Effective against: a broad range of microbes Examples: bleach has Sodium hypochlorite (house hold bleach) 10% bleach and 90% water = decontamination 100% needed for C-deff.

Chemical methods of microbial growth control: Iodine and Iodine derivatives (Iodophores) For the test you do have to know the different chemicals, the way they work, who they work against.

Action: denatures proteins. Effective against: board range of microbes. -used as skin antiseptic. Examples: -Betadine = pre-op skin antiseptic -wescodyne = surface disinfectant, Iodophore based.

Chemical methods of microbial growth control: Heavy metals

Action: denatures proteins. Effective against: some bacteria and fungi. Effectiveness: low level of activity.

Chemical methods of microbial growth control: Soap/Detergents

Action: detergents break up oil on our skin, this decreases surface tension, more easily to wash off microbes. Effective against: broad range of microbes. -polar end sticks to H2O, non-polar end grabs microbes. like bile for GI. -microbes use oil to stick to skin.

Physical methods of microbial control: Filtration

Action: filter traps microbes Examples: -water filtraiton, beverages (beer) -hospital surgical mask -blood products, vaccines.

Physical methods of microbial control: Osmotic pressure:

Action: shrivel or burst microbe. Examples: jam, jelly, maple, syrup.

Physical methods of microbial control: Drying Action?

Action:removing water, decrease metabolism. -Lyophilization, removal of H2O under vacuum. -dried things have longer shelf life.

Is Betadine an antiseptic or a disinfectant when it is used on skin?

An antiseptic. Anything that is applied to the skin will be an antiseptic and anything applied to objects is considered a disinfectant.

What does Action of antimicrobial control agents mean?

Definition: How do they actually kill microbes.

Why is alcohol effective against some viruses and not others?

Denature proteins, dissolve lipids Require water

Which is more likely to be used in a medical clinic laboratory, a use-dilution test or a disk-diffusion test?

Disk-diffusion test. Because this is what is used to measure the effectiveness of specific antibiotics on certain microbes. -A use-dilution test would be more appropriate in industrial uses because it measures what is the lowest amount of chemical needed in a solution to effectively kill microbes.

How is microbial growth in canned foods prevented?

Drying is often used to preserve foods (e.g. fruits, grains, etc.). Methods involve removal of water from commercial sterilization: product by heat, evaporation, freeze-drying, and addition of salt or sugar.

What chemicals are used to sterilize?

Ethylene Oxide is the gas most frequently used for sterilization.

Chemical methods of microbial growth control: Heavy metals types: silver uses For the test you do have to know the different chemicals, the way they work, who they work against.

Examples: -silver nitrate drops used in newborns eyes to protect against STD's -Silver ointment for burns and wounds. silvadine. -silver particles in some workout clothes/plastic storage containers. -silver is in catheters. Foley's

T/F: It is not better to use H2O2 if you are treating a deep wound because obligate anaerobes are not effected by hydrogen peroxide?

FLASE! Obligate anaerobes are especially affected by H2O2.

T/F: Ethylene Oxide is not toxic to humans, does not need to be used in a closed system?

False! -Duration of exposure is 1-3 hours.

T/F: Chlorine dioxide is not very dangerous. It is not toxic to humans, and is not highly explosive/expensive?

False! Used during the 911 attacks of anthrax.

How Does H2O2 work: summary

If you do aerobic energy production you produce free radicals. Including superoxides and peroxides. you produce an oxidase that beaks these free radicals apart. -if not broke apart would cause damage to macromolecules of life. -H2O2 via oxidase breaks up into 2H + O2

What does it mean when you spray H2O2 on a wound and it starts to fizz?

It means that the bacteria present produce the enzyme oxidase and are able to break apart the free radicals being produced so that their macromolecules are not effected by them.

Chemical methods of microbial growth control: Heavy metals types: 3

Mercury Zinc Silver

Chemical methods of microbial growth control: types most commonly used -Organics (blood, saliva, pus, feces, and vomit) will decrease effectiveness of most chemicals. For the test you do have to know the different chemicals, the way they work, who they work against.

Most commonly used: -phenol/phenol derivatives -Soap/Detergents -Alcohol -Heavy metals -Chlorine -Iodine and Iodine derivatives (Iodophores) -Aldehydes -Gaseous Sterilizers -Hydrogen peroxide

What chemical disinfectants can be considered sporicides?

Phenols; Glutaraldehyde; B-Propiolactone; Ethylene oxide ;Peroxy acids

Usual definition of sterilization is the removal or destruction of all forms of microbial life; how could there be practical exceptions to this simple definitions?

Prions have a high resistance to all forms of sterilization; sterilization implies to the absence of prions.

How is it possible that a solution containing a million bacteria would take longer to sterilize than one containing a half-million bacteria?

Rate of microbial death: The number of microbes. The more microbes to begin with, the longer it takes to eliminate the entire population. other factors: environment influences; time of exposure; microbial characteristics.

What is the difference between soaps and detergents?

Soap made of: lye + animal fat; pH 9-10 -Very expensive, not common. Detergent made of: a petroleum products, more soluble in water than soap. -We use detergents not soap.

Why would a can of pork take longer to sterilize at a given temperature than a can of soup that also contained pieces of pork?

Solid foods heat unevenly because of the uneven distribution of moisture.

F/T: Chlorine dioxide is good for use on entire buildings, and when we send out things into space?

TRUE

T/F: A phenolic derivatives is a chemically altered phenol to decrease the bad side effects. This decreased the expense and side effects

TRUE

T/F: Formalin is a 37% aq solution of this?

TRUE

T/F: obligate anaerobes are able to use O2 if there is not sulfate/nitrate available?

TRUE

T/F: Glutaraldehyde is less expensive, safer, less irritating, more effective option than formaldehyde? USED FOR?

TRUE Used for: -histology to fix slides. -embalming. -cleaning respiratory therapy equipment. -Dialysis equipment. -Fiber optic endoscope. -instruments.

T/F: Both soaps and detergents are surfactants? What are surfactants?

TRUE surfactants = decrease surface tension in water.

T/F: Iodophores are chemically altered Iodine that decrease surface tension, staining, and irritation?

TRUE! Iodophores are better antiseptics than iodine alone due to the improved chemical qualities.

The presence or absence of endospores has an obvious effect on microbial control, but why are gram-negative bacteria more resistant to chemical biocides than gram-positive bacteria?

The characteristics of the gram-negative bacteria makes it more susceptible to chemical biocides due to it's physical characteristics. form endospores during adverse conditions; waxy lipid like membrane; thick cells. Mycobacteria, endospores, and protozoan cysts and oocysts are very resistant than enveloped viruses to disinfectants and antiseptics.

What is the connection between the killing effect of radiation and hydroxyl radical forms of oxygen?

These radicals are produced from ionizing radiation that take electrons from other molecules.

T/F: Ethylene oxide is good for things that are heat sensitive?

True. -Used for plastics, suture, artificial heart valves, heart-lung machines, mattresses.

What does Disinfection mean? Types of Disinfection ?

Use of a chemical agent OR physical agent (disinfectant) to inhibit/destroy microbes on inanimate objects or surfaces. -Not all of the pathogens are eliminated. Types of Disinfection : -Antisepsis -Sanitization -Pasteurization

Chemical methods of microbial growth control: Heavy metals types: Zinc Uses?

Used in several dandruff shampoos, effective in controlling fungus (dandruff). Head & shoulders Used in mouth wash. No alcohol present in the solution. (Biotene has enzymes as alternative no Zinc based)

Chemical methods of microbial growth control: Heavy metals types: Mercury Uses/example

can be used as a skin antiseptic. ( Not sold in the USA ) unless in the hospital or clinical settings. used as a preservative. -Thimerosol Example: eye solutions, anti-venoms, tattoo ink, was used in vaccines (people are stupid).

What does Sterilization mean?

destruction of all microbes. Pathogens are dead.

Types of Disinfection: Antisepsis

disinfection of tissue via a chemical agent (antiseptic). Must be safe to use on human/animal tissue. Examples: H2O2, Alcohol, bacterial cream.

What are obligate anaerobes?

microbes that are poisoned by oxygen.

If you wanted to disinfect a surface contaminated by vomit and a surface contaminated by a sneeze, why would your choice of disinfectant make a difference?

no single chemical is good for all applications. It would depend on what the situation dictates. Use of Biguanides would be useful on the sneeze because of chlorhexidine.

Types of Disinfection: Sanitization

reduce the number of pathogens on a surface to meet public health standards.

Why is it that obligate anaerobes are especially affected by hydrogen peroxide?

they do not produce the enzyme needed to break apart the free radicals (oxidase). the free radicals build up, damaging macromolecules. -This will first INHIBIT, then KILL them.

Types of Disinfection: Pasteurization

use heat to kill pathogens and reduce the number of spoilage organisms.