Control Flashcards
History
Pasteur> microorganisms can live on nonliving and destroyed by heat
Lister> chloride of lime for aseptic surgeries
Antisepsis
Destruction of vegetative bacteria on living tissue
Degerming
Removal from limited area
Sanitisation
Lowering microbial count on food handling equipment to minimise transmisssion
Why control
Quality control
Food preservation
Prevent disease
Factors
No. Of microbes
Environmental factors
Time of exposure
Microbial characteristics
How affect
Alter membrane permeability
Damage to proteins(hydrogen and disulfide bonds )
Damage to nucleotides(no replication/ metabolic functions)
Physical
Temperature (high/ low)
Desiccation
Osmotic pressure
Filtration
Radiation
High heat
Dry»flame/oven
Moist»autoclave/boiling/pasteurization
Low heat
Refrigerator except listeria
Freezing> flash/slow
Chemical control rules
High stability
Non toxic
Non corrosive
Broad spectrum
Fast acting
For water and lipids
Environmentally friendly
Evaluating efficiency
Dilution tests>culture+ disinfectant then agar
Disk diffusion>disk soaked with disinfectant on agar previously inoculated.
The agents
Phenols and phenolics
Halogens
Alcohols
Heavy metals
Aldehydes
Gaseous sterilisers
Oxidising agents
Why phenol no longer used
Irritates skin
Bad odour
Examples of phenolics
Mechanism
Biphenol(against staphylococcus in infants) (Phisohex)
cresols(floor cleaning)(lysol)
Disrupt cell membrane
Halogens are…used for…
Iodine(betadine ) skin and wound all even endospores
Chlorine gas>hypochlorous acid
Liquid>calcium hypochlorite(water drink)
Sodium hypochlorite/clorox for swimming pools and dialysis and bleach
Alcohols
Isopropanol better than ethanol but more expensive and poisonous
Why 70% ethanol
Why not for open wounds
As denaturation need water
Forma coagulation under which bacteria grow
Heavy metals combine with….
Are…
Sulfhydryl groups
Silver nitrate
Mercury chloride (toxic)
Copper sulfate (algicide )
Zinc chloride (mouthwash)
Aldehydes work by…
Are..
Covalent cross links = protein inactivation
Formaldehyde> formalin for tissue preservation inactivated bacteria 37%
Glutaraldehyde > cidex steriliser for endoscopes and respiratory therapy
Gaseous depend on…are..
Alkylation replacing H with alkyl group
Cross linking nucleic acids and proteins
Ethylene oxide> needs time , explosive so mixed with CO2
Chlorine dioxide>endospores of anthrax
Oxidising agents
Hydrogen peroxide> sporicidal, inanimate
Not for open wounds as it breaks down to H2O and O2
Ozone> highly reactive, O2 through hugh voltage, disinfect water, neutralise taste
