Disinfectants and sterilisation Flashcards
What are some of the measures involved in disease control?
- Accurate ID of animals
- Restrictions on movement
- Lab testing for diagnosis
- Can allow for specific control vaccination, prophylaxis
- Infected animal may still shed pathogens into environment so control needs to both treat the animal and also ensure environment in clear
Name a bacteria with a poor survival rate in the environment
Mycoplasmas (quite sensitive)
Name a pathogen with an average survival rate and one with a good survival rate
- Average: salmonella, fungal spores
- Good= bacterial endospores (anthrax), Prions
What are the methods of sterilizing media and small equipment?
- Filtration (liquids): using um filters can remove pathogens and ultra filtrations can remove ions
- Heat inactivation (liquids/ solids): depends on solutions, sugars can caramelise, range of materials can require different temperatures
- Irradiation: used in medical filed plastics
- Chemical (surface decontamination)
What is the thermal inactivation range for different pathogens?
- Mycoplamas= 60 deg
- Canine parvovirus = 100 deg for 1 min
- Endospores= 121 deg for 15 mins
- Prions= 132 deg to 4.5 hours
Describe pasteurisation
- does NOT count as sterilisation, because it does NOT KILL all microbes in the food
- Instead it reduces number of sensitive viable pathogens
- 90% effective against vegetative (non sporulating) bacteria
- Involves rapid ehating. cooling of the food
- Process used because it has less of an effect on the quality of the food item.
What is the definition of disinfection?
Destruction of microorganisms by physical or chemical methods on surfaces of objects
What is the definition of antisepsis?
Destruction of micro organisms on tissues by chemical which are non toxic and non irritating to the tissue
What are some of the properties that make an ideal chemical disinfectant?
- Broad activity
- Absence of irritability, tetragenicicty or carcinogenicity
- Long shelf life
- Stable
- Water soluble
- Active in organic matter (faeces)
Describe the use of alcohols as a disinfectant
- Effective against mycoplasms, Gram + and gram - as well as some efficacy against enveloped viruses, fungal spores and acid fast bacteria
- Broad action
- Needs water to work
- Denatures proteins causing membrane damage
- Not active against spores
Discuss acids as a disinfectant
- effective against mycoplasms, gram +, gram -, enveloped viruses, fungal spores, bacterial spores
- Function is related to pH
- Destroys nucleic acid bonds
- Can be caustic and have unpleasant fumes, can damage surfaces
- Viruses can vary is susceptibility, HCl can destroy endospores
Which form of organic acids are able to cross the membrane?
- the associated form (HA)
- ionsised form, then becomes deiionised in the cell
Discuss the use of alkalis as disinfectants
- Action= saponifies lipids in cell membranes/ envelopes. Activity is low but increases with raised temp
- Effective against Mycoplasma, some efficacy against gram +, gram -, enveloped viruses, fungal spores, acid fast bacteria, bacterial spores, coccidia parasite
- Caustic and fumes, can cause corrosion.
- Ammonium hydroxide: effective against coccidial oocysts ( not considered effective against bacteria)
- Sodium carbonate: hot solution used to disinfect buildings. Not effective for most viruses but is approved for FMDV
- Calcium oxide (quick lime): used on surface/ the ground. Also used to slow down putrification of buried carcasses.
Discuss teh use of aldehydes as a disinfectant
- V effective against Mycoplasmas, Gram +,gram -, enveloped viruses, some efficacy against non enveloped viruses, fungal spores, bacterial spores, acid fast bacterial, coccidia
- Highly effective as very reactive compounds
- Denatures proteins and nucleic acids
- Active against bacteria (including spores)
- Non corrosive
- High toxic, irritating, carcinogenic
Discuss the use of biguanides as a disinfectant
- Effective against mycoplasma, gram+, gram-, enveloped viruses, fungal spores
- React with cell membranes altering permeability
- Limited in effectiveness against acid fast/ fungi/ viruses/ spores
- Inactivated by some anionic detergents
- Chlorhexidine (hand scrub)
Discuss the use of halogen compounds as a disinfectant
- Effective against mycoplasma, gram+, gram-, enveloped viruses, non enveloped viruses, fungal spores, acid fast, bacterial spores
- Broad spec
- 2 groups (Hypochlorite, iodine)
- Lose potency over time
- Not as active in organic matter, or sunlight
Discuss chlorine compounds as disinfectants?
- Function due to oxidising power, denaturing proteins
- Use in water treatment and the food industry
- NEVER MIX WITH ACIDS OR AMMMONIA= WILL CREATE CHLORINE GAS
- Low conc= vegetative bacteria, fungi, most viruses
- High conc= active against spores/ more resistant pathogens BUT problems with corrosion
Discuss iodine as a disinfectant
- Broad spec= bacteria, fungi, viruses
- Dentaures proteins
- Less active than chlorine but more toelrant of organic matter
- Low water solubility so often dissolved in alcohol
- Staining is a problem
- Iodophores: complexes with surfactant the increases solubility and sustained release of iodine
- Improved activity in presence of organics, dilution of iodophores increases the free iodine activity (common teat dip)
Discuss phenolic compounds as a disinfectant
- Broad spec
- Denaturing proteins
- Active in hard water and organic material
- Can cause irritation to skin
- Environmental problems
- Can taint food so NOT used in food industry
- VERY toxic to animals espesh cats
What are QACs are what are they used for?
- Quaternary ammonium compounds, sued as a disinfectant
- Cationic detergent: affects surface of microorganisms
- Easily inactivated by organic matter and hard water
- Not effective against non enveloped viruses, mycobacteria, spores
- Toxic to fish
Discuss hydrogen peroxide as a disinfectant
- Non polluting
- Oxidising agent, reacts with cell components
- +30%= sporocidal
- 5-20%= bacteriocidal, virucidal, fungicidal
What can be sued instead of formaldehyde?
Peroxide vapour
What disinfectant is often used in water systems for feeders?
Ozone- hyper oxygen species reacts with proteins and nucleic acids
Bacteriacidal, virucidal and sporicidal
