Control Of Microbial Growth Flashcards
Sterilisation
The killing or removal or all living organisms and their viruses.
Disinfection
The elimination of microorganisms from inanimate objects
Antibiotic
A chemical substance produced by a microorganism that kills or inhibits the growth of another microorganism
What should microbial control agents be like?
- Inexpensive
- Fast acting
- Stable during storage
- Control all microbial growth while being harmless to humans, animals and objects
Moist heat - autoclave
- Sealed chamber
- Steam under pressure = higher temperature than boiling water. Higher the pressure = higher the temperature
- E.g, Steam at 1000C at 15 psi (pounds/square inch) pressure, temperature rises to 1210C = all organisms killed in 15 mins (20 psi, 1260 C)
Dry heat
- Used when moist heat can’t be used
- Higher temperatures/longer time than moist heat - used for glassware
- Incineration of infected material
Filtration
- Used to sterilise liquids e.g, antibiotic solutions
- Membrane filters with pores small enough to keep bacteria in
- Air filters in operating theatres
Radiation
- Shorter wavelength = more energy + greater penetration
- Radiation is described as ionising or non ionising according to effects on cellular chemicals
Chemical control
Static - bacteria static
Vidal - viricidal, sporicidal
Disinfectant
A chemical used to disinfect a surface or non living object
Antiseptic
Disinfection of living tissue - same chemical may be a disinfectant and an antiseptic
Chemical methods of microbial control
- Phenols
- Alcohols
- Halogens
- Oxidising agents
- Surfactants
- Heavy metals
- Aldehydes
Phenols
- First surgical antiseptics - carbolic acid
- Commonly used in health care settings, labs and homes
- Smelly and have side effects
Alcohols
- Kill bacteria and fungi, but not spores or viruses
- Protein denaturation or membrane disruption
- Used for rapid disinfection of surfaces e.g. swabbing of skin with 70% ethanol prior to injection - evaporate rapidly
Halogens
- Chlorine used to treat drinking water and in swimming pools
- Hypochlorite used for cleaning baby bottles, surface etc
- Iodine used as antiseptic for wounds
- Povidone iodine (betadine) used as preoperative skin preparation but can cause allergies
Oxidising agents
- Hydrogen peroxide disinfects and sterilises surfaces of objects - not useful for treating open wounds
- Ozone treatment of drinking water
Surfactants
Soaps and detergents have limited biocidal action but can assist in the removal of microorganisms through scrubbing
