Control of Microbial Growth Chapter 11 I. Introduction Vocabulary Sterile Disinfect Antisepsis Sanitization Pasteurization - cide - stasis Degerming Resistance to microbial control Endospores, protozoan cysts, naked virus, M.tuberculosis, S.aureus, Pseudomonas, vegetative cells, fungal spores, enveloped viruses, yeast, trophozoites Factors that influence death rate 1.) 2.) 3.) 4.) II. # of microbes nature of microorganisms, population, know the enemy conditions – temp, pH, concentration, mode of action presence/amount of organic material Figure ll.1 – Physical methods of control – mechanical A.) Heat 1.) 2.) autoclave – steam under pressure 121°C 15psi, 15-20 min, times vary depending on size of autoclave and sizes of the load. kills everything – sterilizes except prions Applications: any items – media that can withstand the pressure and temperature such as glass, cloth, gloves, med./surgical instruments, paper, heat res. Plastics (forceps we used). : not oil, wax, powder boiling: moist heat without pressure 100°C for 30' (liquids). Sanitize, disinfection most vegetative bacterial cells including Mycobacterium & Staphylococcus, and some viruses H20, food, clothing/bedding disadvantages: easily recontaminated H:\Biology\Stewart\Outlines|control of Microbial Growth 10 17 07 Notes 1 3.) Pasteurization – lower # of pathogens without affecting the flavor classical batch 63°C for 30 minutes flash 71.6°C for 15 seconds sterilize UHT ---134°C or 1-2 seconds, lower pathogens non-spore forms, viruses, enterics beverages – milk, wine, beer, fruit juice 4.) incineration - flame or electric heat coil 800°C – 6,500°C - kills everything-sterilizes - including loops/needles / incinerators – syringes, needles, biomedical waste, bedding 5.) dry oven 150°C - 180°C for 2-4 hours sterilization glassware, powder, oils – not plastics, paper, liquids which evaporate B.) Low temperatures and Desiccation- bacteriostatic 1.) refrigeration 4°C freezing 20°C, -70°C - 135°C (deep freezing all pathogens slowed down, some pathogens killed Food preservation – culture preservation/mammalian cells 2.) freeze drying – lyophilization no ice crystals/preservation food – cultures natural desiccation of some pathogens kills them but not endospores, like refrigeration and freezing slows/inhibits growth due to lack of H2O C.) Radiation 1.) ionizing radiation – gamma rays, x-rays, (sterilize) damages DNA, mutations, cell death food must be labeled, no radioactivity passed on to consumers drugs, vaccines, instruments, plastics, gloves, tissue for transplant operators must wear protective clothing non ionizing radiation - U.V. light 240nm – 280nm non penetrating (damage to human cells – skin, retina causes pyrimidine dimmers T-T, interferes with replication, transcription fungal cells, vegetative bacterial cells, protests, viruses, endospores (time of exposure) disinfection surfaces, public spaces, and food processing plants liquids - H2O, milk, juice 3.) microwaves- do not sterilize, the heat from raising the temperature of the food or liquid is similar to boiling Filtration - liquids Course 8m – 0.02 m & smaller pores can sterilize and catch some proteins but not some toxins Vacuum pump/presterilized container Serum blood products, milk, beer, H2O HEPA filters for air sterilizing 2.) D.) H:\Biology\Stewart\Outlines|control of Microbial Growth 10 17 07 Notes 2 Chemical methods of microbial control desirable qualities of chemical disinfectants- pg rapid action, solubility in water or alcohol, stability, non-toxic to tissues, penetrates inanimate surfaces, active in the presence of organic material, noncorrosive, nonstaining, deodorizing, affordable, inexpensive to manufacture Chemicals 1. Halogens- Chlorine and Iodine Chlorine-many forms, gas, liquid, hypochlorites, chloramines kills vegetative pathogens, viruses, fungi, endospores with long exposure disadvantages-inactivated by organic material and sunlight applicationsgas/liquid-large scale, water, sewage, wastewater hypoclorites-food equipment, dairies, canneries, pools, -treat wounds, disinfect bedding, instruments chloramines- water treatment, wounds, skin surfaces Iodine-free iodine and iodophors kills everythings, slowly sporocidal sensitive to pH and organic matter, but not as much as chlorine applications2% iodine-topical antiseptic prior to surgery, 5-10%- not safe for skin, but ok to use for plastics, gloves, inanimate items iodophors-iodine complexed to polyvinylalcohol-allows for slow release and less irritating to tissues, Betadine and Isodine 2. Phenol and derivatives-coal tar kills-above 1% kills everything but very irritating to the skin, phenolics- kill vegetative bacteria, fungi and many viruses but not endospores continue activity in the presence of organic material applicationsphenol- drains, sewage, animal facilities phenolics- disinfectant aerosol sprays, Lysol, triclosan chlorhexidine-bacteriosidal for gm+/gm-, some fungus and viruses, not endospores but mild and low toxicity so handscrub, neonatal wash, preservative for eye solutions 3. Alcohols-ethyl alcohol and isopropanol kills-vegetative bacteria, enveloped viruses, and fungus but not endospores and nonenveloped viruses must be mixed with water to be effective- 50%-95% applicationscheap degerming agent thermometers, electrodes 4. Hydrogen peroxide-colorless, caustic liquid decomposes in the presence of light, metals and catalase kills-bacteriocidal, virocidal, sporocidal, fungicidal applications3%-wound cleansing, mouthwash, deep wounds(anaerobes) H:\Biology\Stewart\Outlines|control of Microbial Growth 10 17 07 Notes 3 35% or 35% peracetic acid- sterilizing cabinets for delicate, tubing instruments-endoscopes, dental instruments ozone- disinfect air, water, cooling towers, industrial AC 5. Surface acting agents, detergents, soap Quaternary ammonium compounds- cationic detergent kills gram positive, viruses, fungi, algae low toxicity, stable, cheap, tasteless, odorless applications-restaurants, food processing equipment, clothing, mouthwash Soap-sudsing and wetting properties, mechanical removal of oil, grease, debris 6. Heavy Metal compounds high molecular weight metals in aqueous, tinctures, ointments,soap kills- vegetative bacteria, fungal cells, viruses, algae, protozoa but not endospores disadvantages- toxic, allergic reactions, neutralized by biological fluids and bacteria develop resistance, environmental considerations limit use applicationsmercurochrome-useless silver nitrate- newborn’s eyes, now topical germicides in the mouth silver sulfadiazine-ointment added to dressings, burns silver ions incorporated into many plastics and steel 7. Aldehydes-formaldehyde and gluteraldehyde gluteraldehyde-liquid with mild odor kills-everything, sporcidal in 3hours, noncorrosive, works in the presence of organic matter Cidex-2% applications-respiratory equipment, dialysis, dental instruments, poultry carcasses, cow’s teats formaldehyde-irritating gas, 37% formalin carcinogen and irritating the skin and mucous membranes 8. Gaseous sterilants- ethylene oxide(ETO) and chlorine dioxide ETO sterilizes 90 minutes-3hours time necessary and residual gas must be dissipated disadvantages- explosive and carcinogen applications-plastics, delicate intstruments, pre-packaged supplies, food and drugs Chlorine dioxide sterilizes applications: drinking water, industrial waste water, food processing equipment, Senate offices 9. Organic acids and alkalis prevents spore germination, bacteriostatic, fungistatic, making food safe to eat application: food preservation H:\Biology\Stewart\Outlines|control of Microbial Growth 10 17 07 Notes 4