microbio ch. 11

decontamination methods include

chemical or physical agents to destroy microorganisms

primary targets of microbial control are microorganisms that cause

food spoilage, disease

contaminants that have far-reaching effects if not properly contained

bacterial vegatative cells, fungal hypgae and spores

inhibition of bacterial growth

bacteriostatic

antimicrobial drugs target

complex mixtures of microbes and microbes with variable resistance

bacterial agents that are least resistant to control methods

bacterial vegatative cells, enveloped viruses

chemical agents used to disinfect microbes on the skin

antiseptics

microbial agent most resistant to physical and chemical control methods

bacterial endospores

disinfection destroys

only vegetative cells

the roots that indicate ability to prevent microbial growth

stais, static

reduction of microbial load on living tissues through mechanical means

degermation

examples of antisepsis

swabbing a wound with hydrogen peroxide, hand washing with a germicidal soup, and preparing the skin with iodine compounds before a surgical incision

practical definition of microbial growth

inability to reproduce/multiply/replicate even under optimal growth conditions

factors that influence the action of antimicrobial agents

temperature of the environment, the presence of interfering matter, a microbial load

disinfectants are normally only used on inanimate objects for what reason

the high concentrations needed are harmful to living tissues

how do surfactants work

they cause leaky membranes

what is involved in the process of degermation

mechanical scrubbing, immersion in chemicals

the levels of protein structure that are disrupted in denaturation

secondary and tertiary

most widely used antimicrobial physical agent

heat

factors which may influence the action of antimicrobial agents

concentration and action of the agent and the temperature and pH of the environment

agents that work by lowering the surface tension of cell membranes

surfactants

disruption of proteins from their native state

denaturation

moist heat forms

boiling water, steam, hot water

examples of physical and mechanical means

radiation, heat, filtration

moist heat

lower temperatures for shorter times

dry heat

higher temps and longer exposure time

heat treatment of perishible liquids to destroy heat-sensitive vegetative cells and prevent infection and spoilage

pasteurization

a closed container’s pressure can be adjusted in order to regulate the temperature of

steam when it is used as microbial control measure

main effect of cold temperatures

to slow the activity of microbes

least resistant to moist and dry heat

vegetative states of both bacteria and fungi

process that avoids the formation of ice crystals, which can damage cells

lypholization

goals of pasteurization

reduction of microbial load and retention of liquid qualities

radiation wavelength rage

electromagnetic spectrum

method to preserve microorganisms by freezing and drying them directly from their frozen state

lyophilization

effects of ionizing radiation on cellular targets

damage to DNA, possible production of toxins

advantages of ionizing radiation

rapid results and high penetration power

most lethal non-ionizing raditaion has lethal wavelengths from 240-280

ultraviolet

radiation that consists of short wave electromagnetic waves that cause the ejection of electrons from target molecules and the creation of ions

ionizing

disadvantages of UV radiation

low penetration power and damage to human tissues

disadvantages of ionizing radiation include

concerns for the safety of operators, possible material damage

straining of a fluid or air through a membrane to trap microorganisms

filtration

non-ionizing radiation 100-400 and readily induces mutations

UV

what states can antimicrobial chemicals exist

gas liquid solid

disadvantages of UV radiation

inability to penetrate deep substances and the damaging effect on human tissue/skin

chemical agents that can destroy all forms of life, including _ are called sterilants

endospores/spores

the effect of a germicide is affected by the time of

exposure

small volume of a liquid chemical that is dissolved in a large volume of solvent is usually

less germicidal than a small volume dissolved in a small volume

why arent bromine and fluorine routinely used in germicidal preparations

dangerous to handle

medical devices that require high-level control using sterilants

catheters, endoscopes, implants

factors that affect the activity of a germicide

chemical action and concentration, material being treated, nature of microbial population, time of exposure

solutions of which general dilution are less germicidal

low

not a form of chlorine used in microbial control

chloride

halogens routinely used in germicidal preparations

chlorine and iodine

alcohols effective in microbial control

ethly, isopropyl

effects on 100% alcohol on cells

disruption of cell membranes, inhibition of growth

almost all microorganisms except endospores are killed by chlorine in how many minutes

30

alcohols are colorless hydrocarbons with one or more

-OH/OH/hydroxyl functional groups

50% concentraion of alcohol usually affects microbes by doing

disrupting cell membranes

what do microbes produce to try to inactivate hydrogen peroxide

catalase

a chemical officially accepted as a sterilant and high-level disinfectant is an aldehyde called

glutaraldehyde

disadvantages of using ETO

explosiveness, damages mucous membranes if in direct contact, rated as a carcinogen by the government

typical action of cationic detergents

disrupting the cell membrane

germicidal effects of hydrogen peroxide are due to the direct and indirect actions of

oxygen

mechanisms of glutaraldehyde

disrupting enzyme function, altering amino acids

disadvantages of quaternary ammonium compounds

unreliable against resistant bacteria, effectiveness is lowered by the presence of organics

ETO is a strong alkylating agent that blocks

DNA synthesis, enzymatic reactions

cationic detergents disrupt

the cell membrane

NOT disadvantages of using quats

irritation, unstable

soaps alone are weak

microbicides

antimicrobial copper and silver that is added to clothing items is

lost after a few washes

soaps can be used at home as

sanitizers

uses of heavy metals

prevention of infection, control of microbial growth on objects

sanitization

remove microbes and debris from inanimate objects, ex dishwashing and laundry

degerm

remove microbes and debris from living tissue, eg surg handwashing and alcohol wipes

disinfect

control vegetative pathogens on inanimate objects, eg bleach and boiling water

antisepsis

control vegetative pathogens on living tissues, eg antibacterial soap

sterlization

remove or destroy ALL VIABLE microorganisms, including endospores. not always necessary or possible, either sterile or not (binary)

decontamination

destruction, removal, or reduction

sepsis

growth of microorganisms in tissues

asepsis

prevents sepsis eg. iodine before surgery

easiest to destroy

enveloped viruses, most gram positive, most gram negative

moderate to destroy

nonenveloped viruses, acid fast bacteria

most resistant

bacterial endosopres (sterilization standard) prions (proteins that need special protocols)

reduction is usually a combination of

all types of methods. for example handwashing

physical methods

moist heat, autoclave, boiling/pasteurization, UHT/dry heat, cold/drying, radiation, filtration

chemical agents

halogens, phenolics, alcohols, oxidizers, aldehydes/gases, quats/soap, chlorexidine

halogens

bleach for water/surfaces, iodine for skin. organic matter can impair chlorine

phenolics

surface disinfectants, disrupt membranes and proteins, generally not sporicidal

alcohol

ethanol/isopropanol for skin and small surfaces, 70% often works best, no spores

oxidizers

hydrogen peroxide damages proteins and DNA. strong validated formulations can kill spores

aldehydes/gases

glutaraldehyde (cidex) for heat-sensitive instruments, ethylene oxide sterlizers for packaged devices

quats/soap

quats disrupt membranes but not spores. soap mainly removes organisms mehcanically

chlorhexidine

common skin antiseptic for preoperative preparation, actively depends on formulation

microbial death

permanent loss of reproduction even under optimal conditions, hard to detect

static vs cidal

inhibit vs death

factors that affect microbial death

number of microbes, nature of microbes, temp/pH of environment, concentration/dose of agent, mode of action of agent, presence of solvents/organic matter/inhibitors

bacteria are not killed instantly! it occurs

exponentially

measures agents killing efficiency

decimal reduction time (time to kill 90%)

what takes the longest to kill

larger populations. and vegetative is shorter than spores

what temperatures are agents usually less effective

colder, just needs a little longer