Chapter 5

Sterilization

Destroying all forms of microbial life

Disinfection

Destroying pathogens and growing cells but not necessarily spores

Germicide

A chemical that quickly kills microbes but not necessarily spores

Bactericide

Kills bacteria

Fungicide

Kills fungi

Virucide

Kills viruses

Bacteriostasis

Inhibits bacterial growth, doesn’t kill cells

Antiseptics

Antimicrobial chemicals that are non toxic enough to use of body surfaces

Asepsis

The absence of pathogens from an object or area

Degerming

The temporary removal of microbes

Sanitizing

Reducing pathogens to safe levels for the general public

Bio safety level 1

Sterile techniques for microbes that don’t cause disease in healthy people

Bio safety level 2

Moderate risk microbes, lab coats, eye and face protection, doors that automatically close

Bio safety level 3

For pathogens that cause serious or possibly fatal disease, hoods, controlled airflow, double door entry

Bio safety level 4

Deadly pathogens, sophisticated body suits, hoods, decontamination chambers, controlled airflow, separate building or restricted section

Opportunistic pathogen

Causes disease under unusual conditions

Most common method to kill microbes

Thermal death point

The lowest temperature required to kill all the microbes in 10 minutes

Thermal death time

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

Decimal reduction time

The time required for 90% to be killed at a certain temperature

Critical risk for transmitting infectious agents

Comes into direct contact with body tissues, so they must be sterile

Semicritical risk for transmitting infectious agents

Contact mucous membranes but don’t penetrate body tissue, should be free of microbes but can contain a few spores

Noncritical risk for transmitting infectious agents

Contact broken skin so no standard germicidal procedures

Moist heat

Kills quicker than dry heat because water breaks bonds

Autoclave

Applies steam, heat, and pressure to tools

Pasteurizing

63 degrees c for 30 minutes fir 72 degrees c for 15 seconds

Dry heat sterilization

Direct flame or incineration

Filtration

Passing through small pores that don’t allow microbes

Effect of freezing on bacteria

Slow freezing form ice crystals that pierce the membrane of cells and damage them

Desiccation

Drying out

Ionizing radiation

Short wavelength high energy

Non ionizing radiation

Long wavelength such as UV light; they damage the DNA or heat the water inside cells

Alcohols

Kill bacteria and fungi, but not spores or virus; Disrupts, membranes and proteins

Aldehydes

Inactive proteins; kill bacteria and viruses and minutes, but kills spores in a few hours

Chlorhexidine

Damages the micro cell membrane, but not spores

Ethylene oxide

A gas denatures proteins; kills all microbes and spores, can cause cancer

Halogens

React with water to form acids also damage; amino acids and fatty acids and kills bacteria, fungi, spores, and some viruses

Metal compounds

High atomic weight elements, such as Ag, Hg, Cu, Zn, Pb; damage proteins and have variable effects on microbes

Ozone peroxide

Produces toxic oxygen molecules that kills microbes and some spores

Phenol

Damages, cell membranes, and proteins; kills mostly everything (lysol)

Benzalkonium chloride

Positively charged detergent changes, cell permeability, and causes cytoplasm to leak; affective against fungi amoebas and viruses

Phenol coefficient

Compare the affects of a test chemical against phenol

Use dilution test

Bacteria are added to serial dilutions of a chemical, the amount of growth is observed

Filter paper test

A piece of filter paper soaked with the chemical is placed on top of growing bacteria in a petri plate and the zone of inhibition is measured

Methods to slow microbial growth in perishable products

Freeze drying

Sugar and salt to draw water out of bacteria and kill it

Refrigeration and freezing

Benzoic acids, nitrates, and nitrites inhibit bacteria in processed meat