Microbiology Chapter 13: Controlling Microbial Growth

Fomite

• An inanimate object that can be contaminated

- Ex: Door knob

Sterilization

• The complete removal or destruction of all vegetative, endospores, and viruses on an object

Commercial Sterilization

• The removal or destruction of all vegetative, endospores, and viruses on an object that are relevant to the process happing

Asepsis

• Lack of contamination

Microbial Growth

• The number of bacterial cells that are present

BSL Levels

• “Biosafe level”

• Classification level of safety required in a lab

Disinfection

• Inactivation most microbes on the surface of inanimate objects

Antisepsis

• Inactivation most microbes on the surface of tissues objects

Degerming

• Mechanical removal of microbes

Sanitization

• Removal of enough microbes to meat public safety standards

“-cidal”

• Suffix to indicate the method kills microbes

“-static”

• Suffix to indicate the method prevents growth of the microbe

BSL-1

• Lab safety designation

• Non pathogenic organism

• Lowest level of safety protocol

- Door with barriers

- PPE only used as needed

BSL-2

• Lab safety designation

• Human pathogens that are treatable or preventable by vaccine

• Second level of safety protocol

- Self closing doors

- Restricted area

- Eye-wash station

- Safety cabinets

- Autoclave

BSL-3

• Lab safety designation

• Potentially lethal human pathogens

• Third level of safety protocols

- Self locking doors

- Medical supervision

- Respirators

- Microbes under a hood at all times

- Hands free wash station

BSL-4

• Lab safety designation

• Most dangerous pathogens

- No treatments or vaccines

• Safety promotions

- Special clothes going in

- Shower going out

- Full body pressurized protective suit

- Full decontamination of materials

Heat

• Permanent method to control bacterial

• Denatures the proteins, leading to death

• Moist heating methods

- Boiling

- Autoclave

- Pasteurization

• Dry

- Flaming

Cooling

• Method to control bacterial

• Not typical way to control bacteria

• Does not have a -cidal effect

- Slow freezing has a very small -cidal effect, ice crystals penetrate cell membrane

• Doesn’t effect psychrophiles

Autoclave

• Method to control bacteria

• Combines both heat and pressure

Pascalization

• Method to control bacteria

• Used in food stuffs to kill bacteria without taking away quality of food

Desiccation

• Method to control bacteria

• Removes water molecules

• Does not have a -cidal effect

Lyophilization

• Method to control bacteria

• Similar to freeze drying

- Combines cold and water removal

Osmotic Pressure Manipulation

• Method to control bacteria

• Preserving food with salt or sugar

Ionizing Radiation

• Method of controlling bacteria

• Uses x-rays, gamma rays, high energy beams

• Used to sterilize foods wrapped in plastics and equipment that is sensitive to heat

• Causes DNA mutations

Nonionizing Radiation

• Method of controlling bacteria

• Uses UV radiation

• Can’t penetrate plastic

• Causes thymine dimers, type of DNA mutations

Filtration

• Method of controlling bacteria

• Uses tiny pores to physically remove bacteria

Phenols

• Chemical first used by Joseph Lister to clean wounds and sterilize instruments

• Skin irritant so it isn’t ideal

• Functions by denaturing proteins and disrupting membranes

Bisphenols

• Two phenols bound together

• Far less toxic to human tissue

• Functions by denaturing proteins and disrupting membranes

Heavy Metals’ Effect on Bacterial

• Inhibits enzymes of microbes and other cells

• Bioaccumulates

Bioaccumulates

• Substance that accumulate in the body over time

Mercury

• Heavy metal

• Used in the form of mercuric chloride

• Used to be used to treat syphilis

- Not anymore as it’s toxic

Silver

• Heavy metal

• Falling out of favor

Copper

• Heavy metal

• Used in the form of copper sulfate

• Lines incubators to prevent contamination

Zinc

• Heavy metal

• Uses in mouthwashes along with alcohol

Iodine

• Halogen

• Antiseptic

• Great for wound care and as surgical scrub

• Used in Betadine

Chlorine Gas

• Halogen

• Disinfectant

• Great for sanitizing pools

- Becomes hypochlorite in water

Alcohols

• Material that disrupts microbial growth

• Coagulates proteins, disrupts membranes, strips viruses of their envelopes

Surfactants

• Classification of material used to control bacteria

• Works by disruptive membranes

• Has polar and non-polar groups

- Allows interaction in with phospholipids of membranes

Bisbiguanides

• Classification of material used to control bacteria

• Broad spectrum

- G+, G-, yeast, envelope of viruses

• Disrupts cell membrane

• Ex: Chlorohexidine

Aldehydes

• Material that controls bacteria

• Akylating agent

• Crosslinks proteins

• Irreversible effects

Peroxygens

• Classification of material used to control bacteria

• Produces free radicals that damage macromolecules

- If organism already makes peroxides its more resistant

• Debated if its an antiseptic or disinfectant

- Skin irritant

• Ex: Hydrogen peroxide

Supercritical Fluids

• Classification of material used to control bacteria

• Penetrates cells and forms acids

• Non toxic, nonreactive, nonflammable

- Used on sensitive medical equipment

Sorbic Acid

• Food preservative

• Prevents mold in acidic food

- Inhibits critical enzymes

Sulphur dioxides

• Food preservative

• Used in fruit

Nitrates

• Food preservative

• Stop generation of clostridium botulinum spores

• Keeps red meat red

Testing Anti-microbial effectiveness

• Put dots of antimicrobial in a completely infected agar plate

• Measure the diameter of the uninfected area around anti-microbe

- Larger the area the better the effectiveness

Thymine dimers

• Genetic mutation

• Causes two adjacent thymine (T) nucleotides to bind to one another

- Opposed to their opposite adenine (A) counterpart

Broad Spectrum

• Reference to how specific a means of controlling bacteria is

• Effective against many different types of bacteria

Narrow Spectrum

• Reference to how specific a means of controlling bacteria is

• Effective against only a few types of bacteria

Thermal Death Point (TDP)

• The point at which microbial life will die in 10 minutes

Thermal Death Time (TDT)

• The amount of time needed to kill all microbial life at a given temperature

Decimal Reduction Time (D-value)

• The time required to reduce a microbial population by 90% (1 log reduction)

• Given a specific variable

- Ex: Temp.