• Refers to microbial contamination

• The absence of significant contamination

• Prevent microbial contamination of wounds

• Removing all microbial life

• Killing C. Botulinum endospores

• removing pathogens

• removing pathogens from living tissue

• removing microbes from a limited area

• Lowering microbial counts on eating utensils

• killing microbes

• inhibiting, not killing, microbes

• Depends on:
• number of microbes
• environment
• time of exposure
• microbial characteristics 

• Alteration of membrane permeability
• Damage to proteins
• Damage to nucleic acids

• lowest temperature at which all cells in a culture are killed in 10 mins

• Time during which all cells in a culture are killed

• Minutes to kill 90% of a population at a given temperature

• Moist heat denatures proteins

• steam under pressure

• steam must contact item's surface

• Reduces spoilage organisms and pathogens
• Equivalent treatments
• 63^o C for 30 min
• High-temperature short-time: 72^o C for 15 sec
• Ultra-high-temperature: 140^o C for <1 sec
• Thermoduric organisms survive

• kills by oxidation
• dry heat 
• flaming
• incineration
• hot-air sterilization

• HEPA filters removes microbes >0.3 um
• Membrane filtration removes microbes >0.22 um

Physical methods of microbial control

• Low temperature: inhibits microbial growth
• refigeration
• deep-freezing
• lyophilization
• High pressure- denatures proteins
• Dessication- Prevents metabolism
• Osmotic pressure- causes plasmolysis

• Ionizing radiation: X-rays, gamma rays, electron beams
• ionizes water to release OH
• damages DNA
• Nonionizing radiation: UV, 260 nm
• damages DNA
• Microwaves: kill by heat; not especially antimicrobial

• Concentration of disinfectant
• Organic matter
• pH
• Time

• Metal rings dipped in test bacteria are dried
• Dried cultures are placed in didinfectant for 20 min at 20^o C
• Rings are transferred to culture media to determine whether bacteria survived treatment

• Disrupt plasma membranes

• Hexachlorophene, triclosan
• Disrupt plasma membranes

• Chlorhexidine
• disrupts plasma membranes

• Iodine
• Tinctures: in aqueous alcohol
• Iodophors: in organic molecules
• Alter protein sysnthesis and membranes
• Chlorine
• Bleach: hypochlorous acid (HOCl)
• Chloramine: chlorine + ammonia
• Oxidizing agents

• Ethanol, isopropanol
• Denature proteins, dissolve lipids
• Require water

• Ag, Hg, and Cu
• Silver nitrate may be used to prevent gonorrheal opthalmia neonatorum
• Silver sulfadiazine used as a topical cream on burns 
• Copper sulfate is an algicide
• Oligodynamic action
• Denature proteins

• Organic Acids
• inhibit metabolism
• sorbic acid, benzoic acid, and calcium propionate
• control molds and bacteria in foods and cosmetics
• Nitrate prevents endospore germination
• Antibiotics
• Nisin and natamycin prevent spoilage of cheese

• Inactive proteins by cross-linking with functional groups (-NH₂, -OH, -COOH, -SH)
• Use: medical equipment
• Glutaraldehyde, formaldehyde, and ortho-phthalaldehyde

• Denature proteins
• Use: heat-sensitive material
• Ethylene oxide

• Free radicals destroy microbes
• Use: tubular instruments

• CO₂ with gaseous and liquid properties
• Use: medical implants

• Oxidizing agents
• Use: contaminated surfaces
• O₃, H₂O₂, peracetic acid