BIOL229: Chapter 9

antisepsis

reduction of microbes on living tissue

aseptic

environment free of microbes

degerming

removing microbes mechanically

disinfection

reducing microbes on non-living surfaces

pasteurization

use of heat to destroy pathogens and reduce number of spoilage microbes in food/beverages

sanitization

removing pathogens to meet public health standards

sterilization

destruction of all microbes on an object (surgical instrument)

decimal reduction time

time required to destroy 90% of microbes in a sample under a specific temperature (smaller time = stronger reagent)

cell wall (antimicrobial agents)

if compromised, cannot prevent cell from bursting

cytoplasmic membrane (antimicrobial agents)

if compromised, cell contents leak out

viral envelope (antimicrobial agents)

damage interrupts viral replication

proteins (antimicrobial agents)

denature 3D shape (enzymes don’t work = cell death)

most susceptible/resistant?

most susceptible = enveloped virus, most resistant = prions

thermal death point

lowest temperature that kills all cells in broth in 10 minutes

thermal death time

time to sterilize volume of liquid at a set temperature

moist heat

best type of heat for killing

boiling

increased elevation = decreased boiling temperature

autoclaving

increased boiling temperature = increased pressure

dry heat

needs higher temperature and longer time (ex. incinerator)

refrigeration

slows metabolism

desiccation

removes H2O to inhibit growth

lyophilization

freeze dry

osmotic pressure

cell loses H2O in hypertonic environment (fungi can withstand due to cell wall)

ionizing radiation

wavelengths shorter than 1 nm, disrupts H-bonds, oxidize covalent bonds

non-ionizing radiation

wavelength greater than 1 nm, uv lights, creates thymine-thymine dimers

thymine-thymine dimers

cause mutations and non-functional DNA

phenol

phenol coefficient

alcohol

evaporates easily, need to add H2O

halogens

iodine, chlorine, bromine

oxidizing agents

hydrogen peroxide is not effective (2H2O2 —> 2H2O + O2)

surfactant

reduces surface tension (soap, detergents, quats)

soap

emulsifier, hydrophilic/phobic nature

detergents

(+) charged, organic

quat

ammonia + carbon chain

heavy metals

low level bacteriostatic and fungistatic agents

aldehydes

ex. glutaraldehyde, formalin

gaseous agents

hazardous, carcinogenic

enzymes

act against microorganisms (ex. lysosome, prionzyme)

lysosome

digest peptidoglycan wall

prionzyme

remove/kill prions

antimicrobials

disease treatment, synthetic/semi-synthetic

phenol coefficient

compares efficacy to phenol

• 1.0 = equal

• > 1.0 = better

• < 1.0 = worse

use dilution test

metal dipped in bacteria, dried, put in disinfectant for 10 minutes, washed, put in clean TSB and incubated for 48 hours to test for turbidity

kelsey-sykes capacity test

(look at diagram)

minimum inhibitory concentration (MIC)

lowest concentration of antimicrobial that prevents growth after incubation

minimum bacteriocidal concentration (MBC)

lowest concentration of antimicrobial that kills 99.9% of original population

in-use test

swabs taken before/after disinfectant, incubated and monitored for growth