Topic 8: Control of Microorganisms by Physical and Chemical Agents

Advantages

________: stable, persist for long times after applied and remain active in the presence of organic compounds.

Damages

________ DNA by producing thymine dimers, which cause mutations.

Organisms

________ can be in a viable but nonculturable (VBNC) conditon- may regain the ability to reproduce and cause infection.

effective disinfectants

Have antimicrobial activity and are ________, disrupt cell wall.

fluorine

Any of five elements: ________, chlorine, bromine, iodine, and astatine.

Disadvantages

________: damages skin and eyes; doesnt penetrate paper, glass, and cloth.

Reduces

________ /removes microbial population or sterlizes solutions of heat- sensitive materials by removing microorganisms.

disinfection of inanimate objects

Used as an antiseptic- toxic to cell; not good for open wounds because quickly broken down by catalzase present in human cells; effective in ________; used by food industry and to disinfect contact lenses.

Sterilization

destruction or removal of ALL viable organisms; usually used on inanimate objects

Disinfection

killing, inhibition, or removal of pathogenic, vegetative organisms

Disinfectants

agents, usually chemical, used for disinfection; usually used on inanimate objects

Chemotherapy

chemicals used internally to kill or inhibit growth of microorganisms within host tissues

Sanitization

reduction of microbial population to levels deemed safe (based on public health standards)

Antisepsis

prevention of infection of living tissue by microorganisms

Antiseptics

chemical agents that kill or inhibit growth of microorganisms when applied to tissue

Sepsis

microbial contamination

Asepsis

absence of significant contamination

Antimicrobial agents

agents that kill microorganisms or inhinit their growth

-cidal/-cide

agents that kill

Germicide

an agent that kills certain microorganisms

Bactericide

an agent that kill bacteria; most do not kill endospores

Viricide

an agent that inactivates virsuses

Fungicide

an agent that kills fungi

Sporicide

an agent that kills bacterial endospores or fungal spores

-static

agents that inhibit growth

Organisms can be in a viable but nonculturable (VBNC) conditon

may regain the ability to reproduce and cause infection

Three main microbial control methods

physical, chemical, and mechanical removal methods

Moist heat

kills microorganisms by coagulating (denaturing) their proteins, degrades nucleic acids, and disrupts membranes; more effective than dry heat

Autoclave sterilization

121 °C at twice atmospheric pressure

Boiling

heat to 100 °C or more at sea level; kills vegetative forms of bacterial pathogens, most viruses, and fungi and their spores within 10 min or less

Dry heat

kills by oxidation effects (ie bunsen burner)

Hot air sterlization

place objects in an oven

Freezing

temperatures below 0 °C

Flash freezing

does not kill most microbes

Slow freezing

more harmful becuae ice crystals disrupt cell structure

Ionizing radiation

gamma rays, x rays, electron beams, or higher energy rays; have short wavelengths (less than 1 nm)

Nonionizing radiation

ultraviolet light (UV); wavelength longer than 1nm

Disadvantages

damages skin and eyes; doesnt penetrate paper, glass, and cloth

Microwave radiation

wavelength ranges from 1 mm to 1 m

Cresols

derived from coal tar (lysol)

Biphenols (phsiohex)

effective against gram + staphylococci and streptococci; used in nursies but excessive use in infants may cause neurological damage

Advantages

stable, persist for long times after applied and remain active in the presence of organic compounds

Ethanol

drinking alcohol (optimum concentration 70%)

Any of five elements

fluorine, chlorine, bromine, iodine, and astatine

Iodine

Oxidized cell constituents and iodinates proteins; at high concentrations may kill spores; skin antiseptic

Cons

skin damage, staining, and allergies

Iodophor

iodine complexed with organic carrier

Chlorine

oxidizes cell constutuents; important in disinfection of water supplies and swimming pools; used in dairy and food industries; effective household disinfectant; destroys vegetative bacteria and fungi but not spores

Amphipathic

organic molecules with hydrophilic and hydrophobic ends

Formaldehyde gas

commonly used as formalin to preserve biological specimens and inactivate viruses and bacteria in vaccines; irritates mucous membranes and has strong odor; used in mortuaries for embalming

Used as an antiseptic

toxic to cell; not good for open wounds because quickly broken down by catalzase present in human cells; effective in disinfection of inanimate objects; used by food industry and to disinfect contact lenses

What is sterilization?

destruction or removal of all viable organisms; usually used on inanimate objects

What is disinfection?

killing, inhibition, or removal of pathogenic, vegetative organisms

What is disinfectants?

agents, usually chemical, used for disinfection; usually used on inanimate objects

What is chemotherapy?

chemicals used internally to kill or inhibit growth of microorganisms within host tissues

What is sanitization?

reduction of microbial population to levels deemed safe (based on public health standards)

What is antisepsis?

prevention of infection of living tissue by microorganisms

What is antiseptics?

chemical agents that kill or inhibit growth of microorganisms when applied to tissue

What is sepsis?

microbial contamination

What is asepsis?

absence of significant contamination

What is antimicrobial agents?

agents that kill microorganisms or inhibit their growth

What is an antimicrobial agent that ends in -cidal/-cide?

kills microbe

What is a germicide?

an agent that kills certain microorganisms

What is a bactericide?

an agent that kill bacteria; most do not kill endospores

What is a viricide?

an agent that inactivates virsuses

What is a fungicide?

an agent that kills fungi

What is a sporicide?

an agent that kills bacterial endospores or fungal spores

What is an antimicrobial agent that ends with -static? (i.e. bacteriostatic)

inhibits growth of microbe

True or False - Microorganisms are killed instantly.

False - not killed instantly

Microbial population death occurs ___.

exponetially

When microbial death occurs, organisms can be in a ___ but not ___ conditon, but may regain the ability to reproduce and cause infection.

viable but nonculturable (VBNC)

What are conditons that influence the effectiveness of antimicrobial agent activity?

population size, population composition, concentration or intensity of antimicrobial agent, duration of exposure, temperature, and local environment

Larger populations take ___ to kill than smaller populations.

longer

True or False: Microorganisms differ in their sensitivity to antimicrobial agents.

True

True or False: Higher concentrations/intensities of antimicrobial agent kills more rapidly, depicting a linear relationship.

False - higher concentrations do kill more rapidly but it is not a linear relationship

The longer the exposure of the antimicrobial agent, the ___ organisms killed.

more

Does an increase or decreae in temperature usually increase microbe death?

increase

What factors in the local environment can affect the effectiveness of antimicrobial agent activity?

pH, viscosity, concentration of organic matter

What does viscosity mean?

the state of being thick, sticky, and semifluid in consistency

Organisms that are in ___ are physically alterted and less susceptible to many antimicrobial agents.

bioflims

What are the three main microbial control methods?

physical, chemical, and mechanical

What are the two types of heat?

moist and dry

How does moist heat kill microorganisms?

by coagulating (denaturing) their protein, degrades nucleic acids, and disrupts membranes

Is moist or dry heat more effective in killing microorganisms?

moist heat

Boiling and autoclave sterilization is a type of ___ control.

moist heat or physical

What are the conditions for autoclave sterilization?

121 °C at twice atmospheric pressure

What temperature does boiling have to be to kill vegetative forms of bacterial pathogens, most viruses, and fungi and their spores within 10 min or less?

heat to 100 °C or more at sea level

How long can the hepatitis virus survive boiling?

up to 30 min

How long can endospores survive boiling?

up to 20 hrs or more

How does dry heat kill microbes?

kills by oxidation effects - disrupt cell structure

What is direct flaming?

used to sterlize inoculating loops and needles - heat until it has a red glow

What is incineration?

effective way to sterlize diposable items and biological waste

What is hot air sterlization?

place objects in an oven for 2 hrs at 170 °C

True or False: Dry heat transfers heat less effectively to a cooler body than moist heat.

True

Direct flaming, incineration, and hot air sterlization are examples of ___ control.

dry heat or physical

What does refrigeration do to microbes?

bacteriostatic effect - reduces metabolic rate of most microbes therefore they cannot reproduce or produce toxins (in some)

What temperature does refrigeration have to be to have a bacteriostatic effect?

0 - 7 °C

What temperatures does freezing occur at?

below 0 °C

Does flash freezing kill most microbes?

no

Is flash freezing or slow freezing more harmful to microbes and why?

slow freezing - ice crystals disrupt cell structure