Micro Ch 5--Control of Microbial Growth

sterilization

destroying all forms of microbial life

disinfection

kills pathogens and growing cells

may or may not kill viruses

germicide

kills microbes

bacteriacide

kills bacteria

fungicide

kills fungi

viruscide

kills viruses

bacteriostasis

inhibiting bacterial growth

antiseptics

antimicrobial chemicals that are non toxic enough to use on body surfaces

asepsis

the absence of pathogens from an object or area

degerming

the temporary removal of microbes

sanitizing

reduces pathogens to safe levels for the general public

biosafety levels

guidelines for working with microbes

1. sterile techniques for microbes that dont cause disease in healthy people

2. moderate risk microbes, lab coats, eye and face protection, doors that automatically close

3. pathogens that cause serious or fatal disease, ventilated hoods, controlled airflow, double door entry

4. deadly pathogens, body suits, hoods, decontaimination chambers, controlled airflow, separate building or section

opportunistic pathogen

cause disease under unusual conditions

what is the most common method used to kill microbes

heat

thermal death point

lowest temperature requires to kill all the microbes in 10 minutes

thermal death time

the minimum time needed to kill all microbes at a given temperature

decimal reduction time

the time required for 90% of microbes to be killed at a certain temperature

critical

comes into direct contact with body tissues so they must be sterile

semicritical

contact mucus membranes but dont penetrate body tissue, sjould be free of microbes but can contain a few spores

noncritical

contact unbroken skin so no standard germicidal procedures

moist heat

kills more quickly than dry heat because the water helps break bonds

3 kinds of moist heat

boiling, autoclaving, and pastuerization

temperatures for pasturization

normal: 30C for 30 mins

high temp: 72C for 15 sec

ultra high temp: 140C for 1 sec

two types of dry heat sterilization

direct flaming or incinerator

hot air

filtration

pass a suspension or liquid through a filter that has small pores

the water passes through and the microbes do not

slow freezing

ice crystals that pierce the membrane of bacteria

dessication

drying out

ionizing radiation

short wave length and high energy rays; gamma rays, x-rays, electrons

react with water to form toxic oxygen molecules

nonionizing radiation

long wavelength; ultraviolet light and microwaves

damage DNA or heat the water inside of the cell

alcohols

kills bacteria and fungi, but not spores or viruses

disrupts membranes, proteins, and DNA

70% is better than 100% because the water helps break bonds

aldehydes

inactive proteins, kill bacteria and viruses in minutes and spores in a few hours, also kills fungi

ex. formaldehyde

chlorhexidine

damages the microbe cell membrane and not spores

better known as hibiclens

ethylene oxide

a gas that denatures proteins, kills all microbes and spores

can cause cancer

halogens

react with water to form acids

damage amino acids and fatty acids

kills bacteria, fungi, spores, and some viruses

examples of halogens

tincture, iodophore, betadine

heavy metals

high atomic weight elements

ozone and hydrogen peroxide

product toxic oxygen molecules that kill microbes and small spores

phenol

damages cell membrane and proteins

found in lysol and phisoHe

in some alcohols, can cause cancer

also called carbolic acid

benzalkonium chloride

changes cell permeability causing the cytoplasm to leave out

against Gram + and ameobas

phenol coefficient test

compare the effect of a new disinfectant to phenol

less than 1 means not as strong and greater than one means stronger

dilution test

diluting a substance and then testing it to determine its concentration or other properties

filter paper test/Kirby Baeur test

piece of filter paper soaked in bacteria and drops of antibiotic are applied

methods to slow microbial growth in perishable products

chemicals like benzoic acid, nitrates/nitrites

refrigeration and freezing

sugar and salt to draw out water

freeze drying