Control of Control of Microbial GrowthMicrobial Growth
How to kill them once you How to kill them once you grow themgrow them
The Control of The Control of Microbial GrowthMicrobial Growth
Sepsis refers to microbial Sepsis refers to microbial contamination.contamination.
Asepsis is the absence of Asepsis is the absence of significant contamination.significant contamination.
Aseptic surgery techniques Aseptic surgery techniques prevent microbial prevent microbial contamination of wounds.contamination of wounds.
Sterilization: Removal of all microbial lifeSterilization: Removal of all microbial life Commercial Sterilization: Killing Commercial Sterilization: Killing C. botulinumC. botulinum
endosporesendospores Disinfection: Removal of pathogensDisinfection: Removal of pathogens Antisepsis: Removal of pathogens from living tissueAntisepsis: Removal of pathogens from living tissue Degerming: Removal of microbes from a limited Degerming: Removal of microbes from a limited
areaarea Sanitization: Lower microbial counts on eating Sanitization: Lower microbial counts on eating
utensilsutensils Biocide/Germicide: Kills microbesBiocide/Germicide: Kills microbes Bacteriostasis: Inhibiting, not killing, microbesBacteriostasis: Inhibiting, not killing, microbes
TerminologyTerminology
Filtration removes microbesFiltration removes microbes Low temperature inhibits microbial Low temperature inhibits microbial
growthgrowth RefrigerationRefrigeration Deep freezingDeep freezing LyophilizationLyophilization
High pressure denatures proteinsHigh pressure denatures proteins Desiccation prevents metabolismDesiccation prevents metabolism Osmotic pressure causes plasmolysisOsmotic pressure causes plasmolysis
Physical Methods of Physical Methods of Microbial ControlMicrobial Control
Radiation damages DNARadiation damages DNA Ionizing radiation (X rays, gamma rays, Ionizing radiation (X rays, gamma rays,
electron beams) electron beams) Nonionizing radiation Nonionizing radiation
UV UV Microwaves kill by heat; not especially Microwaves kill by heat; not especially
antimicrobialantimicrobial
Physical Methods of Physical Methods of Microbial ControlMicrobial Control
Evaluating a disinfectantEvaluating a disinfectant Use-dilution testUse-dilution test
1. 1. Metal rings dipped in test bacteria Metal rings dipped in test bacteria are driedare dried
2. 2. Dried cultures placed in Dried cultures placed in disinfectant for 10 disinfectant for 10 min at 20°Cmin at 20°C
3. 3. Rings transferred to culture media Rings transferred to culture media to to determine whether determine whether bacteria survived bacteria survived treatmenttreatment
Chemical Methods of Chemical Methods of Microbial ControlMicrobial Control
ChemicalChemical Methods of Methods of Microbial ControlMicrobial Control
Figure 7.6
Evaluating a disinfectantEvaluating a disinfectant Disk-diffusion methodDisk-diffusion method
Types of DisinfectantsTypes of Disinfectants
Figure 7.7
Phenol Phenol Phenolics. LysolPhenolics. Lysol Bisphenols. Bisphenols.
HexachloropheneHexachlorophene, Triclosan, Triclosan Disrupt plasma Disrupt plasma
membranesmembranes
BiguanidesBiguanides ChlorhexidineChlorhexidine Disrupt plasma membranesDisrupt plasma membranes
Types of DisinfectantsTypes of Disinfectants
Halogens. Iodine, ChlorineHalogens. Iodine, Chlorine Oxidizing agentsOxidizing agents Bleach is hypochlorous acid (HOCl)Bleach is hypochlorous acid (HOCl)
Types of DisinfectantsTypes of Disinfectants
Types of DisinfectantsTypes of Disinfectants
Table 7.6
AlcoholsAlcohols EthanolEthanol isopropanolisopropanol Denature Denature
proteins, proteins, dissolve lipidsdissolve lipids
Heavy Metals. Ag, Hg, CuHeavy Metals. Ag, Hg, Cu Oligodynamic actionOligodynamic action Denature proteinsDenature proteins
Types of DisinfectantsTypes of Disinfectants
Surface-Active Agents or SurfactantsSurface-Active Agents or Surfactants
Types of DisinfectantsTypes of Disinfectants
SoapSoap DegermingDegerming
Acid-anionic detergentsAcid-anionic detergents SanitizingSanitizing
Quarternary ammonium Quarternary ammonium compoundscompoundsCationic detergentsCationic detergents
Bactericidal, Denature Bactericidal, Denature proteins, disrupt plasma proteins, disrupt plasma membranemembrane
Chemical Food PreservativesChemical Food Preservatives Organic Acids Organic Acids
Inhibit metabolismInhibit metabolism Sorbic acid, benzoic acid, calcium propionateSorbic acid, benzoic acid, calcium propionate Control molds and bacteria in foods and Control molds and bacteria in foods and
cosmeticscosmetics Nitrite prevents endospore germinationNitrite prevents endospore germination Antibiotics. Nisin and natamycin prevent Antibiotics. Nisin and natamycin prevent
spoilage of cheesespoilage of cheese
Types of DisinfectantsTypes of Disinfectants
AldehydesAldehydes Inactivate proteins by cross-linking with Inactivate proteins by cross-linking with
functional groups functional groups (–NH(–NH22, –OH, –COOH, —SH), –OH, –COOH, —SH)
Glutaraldehyde, formaldehydeGlutaraldehyde, formaldehyde
Types of DisinfectantsTypes of Disinfectants
Gaseous SterilantsGaseous Sterilants Denature proteinsDenature proteins Ethylene oxideEthylene oxide
Types of DisinfectantsTypes of Disinfectants
PeroxygensPeroxygens Oxidizing agentsOxidizing agents OO33, H, H22OO22, peracetic acid, peracetic acid
Types of DisinfectantsTypes of Disinfectants
Microbial Microbial Characteristics and Characteristics and Microbial ControlMicrobial Control
Figure 7.11
Bacterial populations die at a constant Bacterial populations die at a constant logarithmic rate.logarithmic rate.
Figure 7.1a
Number of Number of microbesmicrobes
Environment Environment (organic (organic matter, matter, temperature, temperature, biofilms)biofilms)
Time of Time of exposureexposure
Microbial Microbial characteristiccharacteristicss
Effectiveness of antimicrobial Effectiveness of antimicrobial treatment depends on:treatment depends on:
Figure 7.1b
Microbial Microbial Characteristics and Characteristics and Microbial ControlMicrobial Control
Chemical Chemical agentagent Effectiveness againstEffectiveness against
EndosporesEndospores MycobacteriMycobacteriaa
PhenolicsPhenolics PoorPoor GoodGood
QuatsQuats NoneNone NoneNone
ChlorinesChlorines FairFair FairFair
AlcoholsAlcohols PoorPoor GoodGood
GlutaraldehydeGlutaraldehyde FairFair GoodGood