Microbiology Exam 3

Sterilization

A process that destroys or removes all viable microorganisms including bacterial endospores and all viruses

Disinfection

A process that destroys vegetative pathogens but not bacterial endospores

Antisepsis (degermination)

a process that reduces the number of microbes on the human skin

Decontamination (sanitization)

A process that mechanically removes microorganisms as well as other debris to reduce contamination to safe levels

sterilization key points

no such thing as slightly sterile, generally reserved for inanimate objects such as surgical instruments, syringes, commercially packaged food

ex:heat, sterilants (chem agents that destroy endospores)

disinfection key points

normally used on inanimate objects because of concentration of disinfections to be effective, common uses boiling food utensils, 5% bleach solution to exam table, thermometer in iodine solution

ex:bleach, iodine, heat (boiling)

decontamination (sanitization) key points

restaurants, dairies, breweries, and other commercial entities that handle a lot of soiled utensils/containers. common uses include: cooking utensils, dishes, bottle and cans

ex: soaps, detergents, commercial dishwashers

antisepsis (degermation) key points

scrubbing of the skin or immersing it in chemicals

ex: alcohol, surgical hand scrubs

bacteri-STATIC vs bacteri-CIDAL

a -CIDAL agent does not necessarily result in sterilization

critical medical devices

-expected to come into contact with sterile tissues

-must be sterilized before use

semi critical devices

-come into contact with mucosal membranes

-must receive high-level disinfection, preferably sterilized

non critical devices

-do not touch the patient or only touch intact skin

-require only low-level disinfection unless they become contaminated with blood or body fluids

factor influencing action of antimicrobe agent- number of microbes

-higher load of contaminants takes longer to destroy

-microbial death continues in a logarithmic manner as the time or concentration is increased: active cells tend to die more quickly than less metabolically active cells

the nature of the microorganisms in the population

target population is usually a mixture of bacteria fungi, spores, and viruses with broad spectrum of resistance

temperature and pH of enviroment

influence action of antimicrobial agents

concentration of agent

-UV radiation is most effective at 260nm

-most disinfectants are more active at higher concentrations

mode of action of the agent

-how does it kill or inhibit the microorganism: -cidal vs -static

the presences of solvents, interfering organic matter and inhibitors

-saliva, blood, feces can inhibit actions of disinfectants and even heat

modes of action of antimicrobial agents

-antimicrobials have a range of cellular targets

-cellular targets of a physical and chemical agents: cell wall, cytoplasmic membrane, cellular synthetic processes (DNA, RNA), proteins

cell wall

chemical agents can damage this by blocking its synthesis or digesting it

ex:chemicals, detergents, alcohol

cytoplasmic membrane

agents disrupt the lipid layer of the this. this gets opened up and allows damaging chemicals to enter the cell and important ions to exit the cell

ex: detergents, alcohol

cellular synthesis

agents can interrupt the synthesis of proteins via the ribosomes. agents can change genetic codes (mutations)

ex: formaldehyde, radiation, ethylene oxide

proteins

some agents are capable of denaturing this (breaking of these bonds, which result in breakdown of this structure. agents may attach to the active site of this, preventing it from interacting with its chemical substrate.

ex:moist heat, alcohol, phenolics

Mode of Action of Surfactants on the Cytoplasmic Membrane

-Alcohol-based hand sanitizers are a mainstay of disinfection of surfaces and antisepsis of hands during the COVID-19 pandemic

-SARS-CoV-2 is an enveloped virus, and its envelope is susceptible to both detergents and alcohol

high temperatures are _________, low temperatures are __________

microbicidal; microbistatic

moist heat

-penetrates the microbial cell better: lower temps and shorter exposure times to achieve the same effectiveness as dry heat

-microbicidal effect is the coagulation and denaturation of proteins

ex: hot water, boiling water or steam between 60°C and 135°C

dry heat