Control of Microbial Growth Gabriella Gita Febriana NIM : 10406002

Control of Microbial GrowthGabriella Gita FebrianaNIM : 10406002

Control of Microbial Growth

Introduction

Louis Pasteur Joseph Lister

•Pasteur : invisible microbes could cause disease

• Lister : found the modern antiseptic for surgery

•Used a solution of carbolic acid (phenol)



•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


Methods of SterilizationI. Heat•Incineration

▫Burns organisms and physically destroys them

•Boiling▫100ᵒC, 30 minutes kills everything except

endospores▫Intermitent boiling (>6hours) to kill endospores


Methods of SterilizationI. Heat (cont.)•Autoclaving

▫Most effective and efficient▫Usual standard temperature/pressure :

121ᵒC/15psi for 15 minutes▫Using steam under pressure as the

sterilizing agent▫Thermal Death Time

•Dry heat ▫Not as effective as moist heat


Methods of SterilizationII. 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


Methods of SterilizationII. Irradiation (cont.)•Electron Beam Radiation (e-beam

radiation)▫Low penetration and high dose rates.▫Similar to Gamma radiation


Methods of SterilizationIII. 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


Methods of SterilizationIV. 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


ETO Sterilization Gas Chamber


Methods of SterilizationIV. 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


Methods of SterilizationIV. Gas & Chemicals (cont.)•Low Temperature Gas Plasma (LTGP)

▫Alternative to ethylene oxide▫Uses small amount of hydrogen peroxide

(H2O2)

energized with radio frequencies waves into gas plasma

▫Generation of free radicals destroy microorganisms


Non Sterilizing MethodsI. 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 63ᵒC, 30 min (batch method) or 71ᵒC 15 sec

(flash method)• Ultrapasteurization• Milk is heated to temperature of 140ᵒC


Non Sterilizing MethodsII. Low Temperature•Refrigeration & Freezing

▫non bactericidal▫most foods are preserved against microbial

growth in the household freezer


Non Sterilizing MethodsIII. Drying•Removal of H2O

▫often used to preserve foods ▫removal of water heat, evaporation,

freeze-drying, and addition of salt or sugar


Non Sterilizing MethodsIV. 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 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.


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




Types of Antimicrobial Agents (cont.)

•Preservatives▫static agents used to inhibit the growth of

microorganisms▫nontoxic




•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



•Semi-synthetic Antibiotics▫molecules produced by a microbe that are

subsequently modified by an organic chemist to enhance their antimicrobial properties





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


Mode of Actions

•Cell wall synthesis inhibitor▫Beta-lactams antibiotics▫Natural Penicillins▫Semi-synthetic penicillins▫Clavulanic Acid▫Cephalosporins▫Bacitracin

•Cell membrane inhibitor▫Polymyxin


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


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


Bacterial Resistance to Antibiotics•Inherent (natural) resistance•Acquired resistance•Vertical evolution•Horizontal Gene Transmission (HGT)

▫Bacteria exchange genes by 3 process : Conjugation Transduction Transformation


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


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Control of Microbial Growth Gabriella Gita Febriana NIM : 10406002