Micro chapter 11 microbial control

What is microbial control

physical and chemical methods to destroy or reduce undesirable microbes in a given area by altering enzyme function

Decontamination

Physical, chemical, and mechanical methods to destroy or reduce undesirable microbes in a given area

What are the microorganism capable of causing

infection or spolage

Types of microorganism that are dangerous

Vegetative bacterial cells and endospores•

- Fungal hyphae and spores, yeast

• Protozoan trophozoites and cysts

• Worms

• Viruses

• Prions

Physical agents of microbial control

Heat•

Dry

• Incineration

• Sterilization•

Dry oven

• Sterilization•

Moist•

Steam under pressure

• Sterilization

• Boiling water, hot water, pasteurization•

Disinfection

Radiation control methods

Ionizing

-X-RAY , cathode(High velocity electron), gamma

-Sterilization

-Non ionizing

-Uv Disinfection

Mechanical removal methods

-Filtration

-Air

-Disinfection

-Liquids

-Sterliziation

-Chemical agents

-Gases

-Sterlization

-Disinfection

Liquid control methods

-Anitsepsis (Animate)

-Inanmate

-Disinfection

-Sterilization

Disinfection

The destruction or removal of vegetativepathogens but not bacterial endospores. Usually used onlyon inanimate objects

Sterilazation

The complete removal or destruction of allviable microorganisms. Used on inanimate objects.

Antisepsis

Removing pathogens from living tissue/ Chemicals applied to body surfaces to destroyor inhibit vegetative pathogens.

Highest resistance bacteria

Prions

Bacterial endospores (Bacillus, clostridium)

Moderate resistance

-Protozoan cysts; naked viruses

Bacteria with no endospores but resistant walls

• Mycobacterium, Pseudomonas, Acinetobacter, other gram(-)•

-Staphylococcus (most heat- and chemical-resistant bacteria)

least resistance

most bacterial vegetative cell

Fungal spores and hyphae

yeast

enveloped viruses (Covid-19)

protozoan trophozoites

Heat (moist) endospore kill temp

120 C

Heat (moist) vegetative forms kill temp

80C

Heat (moist) relative resistance

1.5x

Radiation dosage endospores

4,000 grays

Radiation dosage vegetative

1000 grays

Sterilizing gas (ethylene oxide) endospores

1,200 mg/l

Sterilizing gas (ethylene oxide) vegetative

700 mg/l

Sporicidal liquid (2% glutaraldehyde) endospore resistance

3 hours

Sporicidal liquid (2% glutaraldehyde) vegetative resistance

10 mins

What is sterilization?

Process to destroy all viable microbes.

What are microbicidal agents?

Antimicrobial agents aimed at destroying a certain group of microorganisms (bactericide, fungicide, virucide, sporicidal).

What is disinfection?

Use of a physical process or a chemical agent (disinfectant) to destroy vegetative pathogens but not bacterial endospores.

What is antisepsis?

Application of chemical agents (antiseptics) directly to exposed body surfaces, wounds, and surgical incisions to destroy or inhibit vegetative pathogens.

What are germicides?

Microbicidal agents (germicides) are antimicrobial agents aimed at destroying a certain group of microorganisms (bactericide, fungicide, virucide, sporicidal).

Cide

to kill

Static

stop reproduction

What are agents that cause microbistasis?

Antimicrobial agents

What is the aim of antimicrobial agents?

To temporarily prevent microbes from multiplying

What are methods that reduce the numbers of microorganisms?

Sanitation and degermation

What is sanitation?

Any cleansing technique that removes microorganisms from inanimate surfaces to reduce the potential for infection and spoilage

What is degermation?

Reduction of microbial load from living tissue by mechanical means

What is decontamination?

Destruction, removal, or reduction of undesirable microbes

Name some methods of decontamination/ examples

Asepsis, disinfection, sanitization, degermation, sterilization

What is sepsis?

The growth of microorganisms in the tissues

Give examples of sepsis.

Presence of infected wounds, blood infection

What are asepsis techniques?

Techniques that prevent the entry of microorganisms into sterile tissues

Provide an example of asepsis technique.

Cleansing the skin with iodine prior to surgery, using sterile needles

What are antiseptics?

Chemicals applied to body surfaces to destroy or inhibit vegetative pathogens

Name some examples of antiseptics.

Iodophors, antibacterial soap, chlorhexidine

What is disinfection?

Destruction of vegetative pathogens on inanimate objects

Give an example of disinfection.

5% bleach, boiling water

What is sanitization?

Cleansing technique that removes microorganisms and debris from inanimate surfaces

Provide an example of sanitization.

Dishwashing, laundering clothes

What is degermation?

Cleansing technique that removes microorganisms and debris from living tissue

Give an example of degermation.

Surgical handscrub, alcohol wipes

What is sterilization?

The removal or destruction of all viable microbes

Name some methods of sterilization.

Autoclaving, ionizing radiation (correctly applied)

What are some factors that affect microbial death?

Number of microbes, Nature of microbes, Temperature and pH, Concentration or dosage of agent, Mode of action of the agent, Presence of solvents, organic matter, or inhibitors

What is the term for permanent loss of reproductive capability in microbes?

Sterilization

What is related to microbes that are hard to detect?

They often reveal no conspicuous vital signs

What are some factors that can affect the effectiveness of a microbial death

Number of microbes•

Nature of microbes in the population

• Temperature and pH of environment

• Concentration or dosage of agent•

Mode of action of the agent•

Presence of solvents, organic matter, or inhibitors

microbistatic

the quality of inhibiting the growth of microbes

Microbicidal

kills microbes

Practical considerations in microbial control

-Does the application require sterilization?•

Is the item to be reused?•

Can the item withstand heat, pressure, radiation, orchemicals?

Is the method suitable?•

Will the agent penetrate to the necessary extent?•

Is the method cost- and labor-efficient and is it safe?

What are the physical and chemical agents target

Cell wall

Cell membrane

Protein and nucleic acid synthesis

Protein function

Cell wall

becomes fragile and cell lyses (some antimicrobial drugs, detergents, and alcohol)

Cell membrane

loses integrity (surfactants from agents break the lipids and dissolve the membrane)

Protein and nucleic acid synthesis

prevention of replication, transcription, translation, peptide bond formation, protein synthesis (chloramphenicol, ultraviolet radiation, formaldehyde)

Protein function

Disrupt or denature proteins (alcohols ,phenols, acids, heat)

What happens to a native state of protein once it is introduced to agents?

Phosphodiester bonds break and can either

-Denature

-Change shape

-Or active sites of protein will be blocked

This prevents active site from accepting substrate and enzymes needed for metabolic processes

What is cystine responsible for

Forms phosphodiester bonds

physical methods of control

Heat (moist and dry)•

-Dry heat: Oven/baking

Cold temperatures•

Desiccation• (Drying out)

Radiation•

Filtration

Bacterial activity in colder enviornments

Doubling decreases, and enzymes are not operable

Can viruses pass through filtration?

Yes since they are nanometers small

moist heat

lower temperatures and shorter exposure time; coagulation and denaturation of proteins, which halts cellular metabolism

Dry heat

moderate to high temperatures; dehydration, alters protein structure; incineration

When is a bacteria most resistant

When bacteria is an endospore

When is bacteria least resistant

When bacteria is vegetative

Thermal death time (TDT)

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

Thermal death point (TDP)

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

Methods of moist heat control

1. Sterilization with Steam Under Pressure

2. Nonpressurized Steam

3. Boiling Water: Disinfection

4. Pasteurization

Sterilization with steam under pressure

The autoclave: (15 psi/121oC/10-40min) Pressure increases steam temperature

-The pressure raises the steam temperature, ensuring it reaches the surface of the item.

-This method is suitable for items that can withstand heat and moisture, leading to protein denaturation, membrane destruction, and DNA breakdown

What can you not autoclave

Plastics!!!!!!!!!!!!!!

nonpressurized steam

-Tyndallization - intermittent sterilization for substances that cannot withstand autoclaving

-Items exposed to free-flowing steam for 30-60 minutes, incubated for 23-24 hours and then subjected to steam again

-Repeat cycle for 3 days

-Used for some canned foods and laboratory media

-Disinfectant

If pressure is higher

There is a high boiling temp

If pressure is lower

There is a lower boiling temp

1 Atmosphere

Ambient

2 Atmosphere

absolute

Pasteurization

Heat is used to eliminate potential infection-causing agents and spoilage while preserving food flavor and value.

-The flash method involves heating to 71.6°C for 15 seconds, reducing microbe count but not sterilizing.

-Non sterilization kills non spore forming pathogens and lowers overall microbe count (Does not kill endospores or many nonpathogenic microbes)

Ultrapasteurization (UHT) at 134°C for 2-5 seconds produces sterile milk

Boiling water: Disinfection

Boiling at 100°C for 30 minutes to destroy non-spore-forming pathogens

A small flash pasteurizer

used by dairies for calves' milk.

Dry heat uses ______ temperatures than moist heat:

higher

Incineration

Flam, electric heating coil, infrared incinerators

-Ignites and reduces microbes and other substances

-Very common in microbio lab

Hot air( dry) ovens

- heated,

circulated air (150oC-180oC,

12min-4h)

- Coagulate proteins

Dry heat incinerator

Infrared incinerator with shield toprevent spattering of microbial samples during flaming

Cold

Microbiostatic- slows the growth of microbes

Refrigeration 0-15C and freezing < 0C

-USED TO PRESERVE FOOD, MEDIA AND CULTURES

Desiccation

Gradual removal of water from cells, leads to metabolic inhibition

• Not effective microbial control – many cells retain ability to grow when water is reintroduced•

Lyophilization – freeze drying; preservation

Lyophilization

freeze drying; preservation

Radiation

Energy emitted from atomic activities anddispersed at high velocity through matter or spaceTypes of radiation suitable for microbial control

Types of radiation microbial control

-Ionizing radiation

-Non iodizing radiation

Types of ionizing radiation

-Gamma rays

-X Rays

-Cathode rays

Types of non-ionizing radiation

UV light (Thyamine dimer)

Energy in relation to wavelenght

Wavelength is inversely proptional to energy

Shorter wavelength= more energy

Longer wavelength= Less energy

What do gamma rays do

blow apart proteins

Ionizing radiation

deep penetrating power sufficient energy to cause electrons to leave their orbit•

Gamma rays, X rays, cathode rays•

Breaks DNA

Non ionizing radiation

little penetrating power

-UV light creates pyrimidines dimer

-Interferes with replication