Control of Microbial Growth Gabriella Gita Febriana NIM :

Introduction Louis PasteurJoseph Lister Pasteur : invisible microbes could cause disease Lister : found the modern antiseptic for surgery Used a solution of carbolic acid (phenol) Control of Microbial Growth

To INHIBIT or PREVENT growth of microorganisms Affected in 2 basic ways : ▫By killing microorganisms (cidal agents) ▫By inhibiting the growth of microorganisms (static agents) Sterilization : complete destruction or elimination of all viable microorganisms in a sterilized substance Control of Microbial Growth

Methods of Sterilization I. Heat Incineration ▫Burns organisms and physically destroys them Boiling ▫100 C, 30 minutes kills everything except endospores ▫ Intermitent boiling (>6hours) to kill endospores Control of Microbial Growth

Methods of Sterilization I. Heat (cont.) Autoclaving ▫Most effective and efficient ▫Usual standard temperature/pressure : 121C/15psi for 15 minutes ▫Using steam under pressure as the sterilizing agent ▫Thermal Death Time Dry heat ▫Not as effective as moist heat Control of Microbial Growth

Methods of Sterilization II. Irradiation Ultraviolet ▫Causes adjacent thymine molecules on DNA to dimerize inhibiting DNA replication Gamma Radiation ▫Break chemical bonds by interacting with the electrons of atomic constituents ▫Highly effective in killing microorganisms Control of Microbial Growth

Methods of Sterilization II. Irradiation (cont.) Electron Beam Radiation (e-beam radiation) ▫Low penetration and high dose rates. ▫Similar to Gamma radiation Control of Microbial Growth

Methods of Sterilization III. Filtration Exclusion of all cells in a liquid or gas For sterilization of solution which would be denatured by heat. eg: antibiotics, injectable drugs, amino acids, vitamins, etc. Millipore membrane Control of Microbial Growth

Methods of Sterilization IV. Gas & Chemicals Ethylene oxide (ETO) ▫Most commonly used form of chemical sterilization ▫Reacts with amino acids, protein, and DNA to prevent microbial reporduction ▫Used for cellulose and plastic irradiation Control of Microbial Growth

ETO Sterilization Gas Chamber Control of Microbial Growth

Methods of Sterilization IV. Gas & Chemicals (cont.) Ozone Sterilization ▫Uses oxygen that is subjected to an intense electrical field that separates oxygen molecules into atomic oxygen. ▫Used as disinfectant for water and food Ozone fogger Ozone sterilizer Control of Microbial Growth

Methods of Sterilization IV. Gas & Chemicals (cont.) Low Temperature Gas Plasma (LTGP) ▫Alternative to ethylene oxide ▫Uses small amount of hydrogen peroxide (H 2 O 2 ) energized with radio frequencies waves into gas plasma ▫Generation of free radicals destroy microorganisms Control of Microbial Growth

Non Sterilizing Methods I. Application of Heat Boiling ▫Inactivates viruses ▫Giardia cysts can survive in this process Pasteurization ▫Use of mild heat to reduce the number of microorganisms in products or foods. ex: milk ▫Milk 63 C, 30 min (batch method) or 71C 15 sec (flash method) Ultrapasteurization Milk is heated to temperature of 140 C Control of Microbial Growth

Non Sterilizing Methods II. Low Temperature Refrigeration & Freezing ▫non bactericidal ▫most foods are preserved against microbial growth in the household freezer Control of Microbial Growth

Non Sterilizing Methods III. Drying Removal of H 2 O ▫often used to preserve foods ▫removal of water heat, evaporation, freeze- drying, and addition of salt or sugar Control of Microbial Growth

Non Sterilizing Methods IV. Irradiation UV, X-ray, Gamma Radiation ▫destroys microorganisms ▫fruits and vegetables are irradiated to increase their shelf life up to 500 percent ▫According to the FDA, irradiation does not make food radioactive, nor does it noticeably change taste, texture, or appearance. Control of Microbial Growth

Control of Microbial Growth by Chemical Agents Antimicrobial Agents ▫chemicals that kill or inhibit the growth microorganisms ▫may be of natural or synthetic origin, and they may have a static or cidal effect on microorganisms. Control of Microbial Growth

Types of Antimicrobial Agents Antiseptics ▫microbicidal agents harmless enough to be applied to the skin and mucous membrane ▫should not be taken internally Disinfectants ▫agents that kill microorganisms, but not necessarily their spores ▫not safe for application to living tissues ▫used on inanimate objects Control of Microbial Growth

Types of Antimicrobial Agents (cont.) Preservatives ▫static agents used to inhibit the growth of microorganisms ▫nontoxic Control of Microbial Growth

Types of Antimicrobial Agents (cont.) Chemoterapeutic Agents (synthetic antibiotics) ▫antimicrobial agents of synthetic origin useful in the treatment of microbial or viral disease ▫Ex : sulfonilamides, isoniazid, ethambutol, AZT, nalidixic acid and chloramphenicol Antibiotics ▫antimicrobial agents produced by microorganisms that kill or inhibit other microorganisms ▫low molecular-weight (non-protein) molecules produced as secondary metabolites, mainly by microorganisms that live in the soil Control of Microbial Growth

Types of Antimicrobial Agents (cont.) Semi-synthetic Antibiotics ▫molecules produced by a microbe that are subsequently modified by an organic chemist to enhance their antimicrobial properties Control of Microbial Growth

Antimicrobial Agents in Treatment of Infectious Diseases Selective Toxicity ▫acts in some way that inhibits or kills bacterial pathogens ▫has little or no toxic effect on the animal taking the drug Spectrum of Action ▫Narrow spectrum ▫Broad spectrum ▫Limited Spectrum Control of Microbial Growth

Mode of Actions Cell wall synthesis inhibitor ▫Beta-lactams antibiotics ▫Natural Penicillins ▫Semi-synthetic penicillins ▫Clavulanic Acid ▫Cephalosporins ▫Bacitracin Cell membrane inhibitor ▫Polymyxin Control of Microbial Growth

Mode of Actions (cont.) Protein synthesis inhibitor ▫Tetracyclines, e.g : tetracycline, chlortetracycline, doxycycline ▫Chloramphenicol ▫Macrolides, e.g : erythromycin, azythromycin ▫Aminoglycosides, e.g : streptomycin ▫Kanamycine ▫Gentamicin, Tobramycin Control of Microbial Growth

Mode of Actions (cont.) Effects of Nucleic Acids ▫Quinolones, e.g : nalidixic, ciprofloxacin ▫Rifamycins, e.g : rifampicin Competitive inhibitors ▫Sulfonamides, e.g : sulfanilamide, gantrisin and trimethoprim Control of Microbial Growth

Bacterial Resistance to Antibiotics Inherent (natural) resistance Acquired resistance Vertical evolution Horizontal Gene Transmission (HGT) ▫Bacteria exchange genes by 3 process :  Conjugation  Transduction  Transformation Control of Microbial Growth

Alternative to Antibiotics Phage Therapy ▫use of lytic bacteriophages to treat pathogenic bacterial infections ▫Benefit : derived from the observation that bacteriophages are much more specific than most antibiotics that are in clinical use ▫Negative effect : phages are self-replicating in their target bacterial cell a single, small dose is theoretically efficacious Control of Microbial Growth

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