asepsis 3 Flashcards
what is bioburden?
•Most items come with a limited number of microbes already on them (bioburden)
what are the categories in viable counting between alive and dead?
actively metabolising cell
cell with reduced metabolic activity
some metabolic activity and plasma membrane intact, but RNA content is reduced
plasma membrane intact,but no detectable metabolic activity
extensive damage to plasma membrane
cellular DNA degraded
cell fragments
define sterile
sterile: An absolute term meaning free from all viable microorganisms–Not possible to have degrees of sterility
define sterilisation
The process by which sterility is achieved, usually through the application of a biocidal agent or physical microbial removal
define disinfection
The reduction of microorganisms on an inanimate surface
what is a survivor curve?
Microorganism viability lost in exponential fashion following exposure to a killing process (not just a sterilization process)
•Independent of the starting number of organisms
what do the 3 lines represent on a survivor curve?
•Continuous (A)•Initial reduced rate of kill during early stages (B)•Reduced rate of kill at low survivor levels (C)
what microorganisms are the most resistant to sterilisation?
prions spores gram negative bacterial small non-envoloped viruses fungi large non-envloped viruses gram positive bacteria lipid envloped viruses
what are the 5 processes with standard methods for sterilisation?
steam( autoclave) filtration dry heat ( oven) gas sterilisation ionising radiation
what happens in practical sterilisation?
procedures are designed and validated with “Overkill” in mind
•Start with a measurable amount and extrapolate
in most cases what is the initial bioburden?
lower than the required level of kill needed (i.e. a 6 log reduction)
what is the D value?
The decimal reduction time (D-value) originated from assessing the thermal resistance of microbes
•The D-value is the amount of time required to reduce the number of viable organisms by 10% (a 1 log reduction) at defined experimental conditions
•Only true in steam sterilization
how is the D value usually quoted?
•Usually quoted with reference to the temperature tested•i.eD121of 5 minutes
when do D values increase/decrease?
- D-value increases at lower temperatures
* D-Value decreases at higher temperatures
how can D values also be quoted?
- D-values can be quoted for other sterilisation methods as well
- In these cases it may not be based on exposure time
what is a z value?
change in temperature that produces a tenfold (1 log reduction) change in D value
For named microorganisms a Z value is a measure of its resistance to heat
what do physical and chemical indicators show?
they do not guarantee sterilization only show procedural error/ equipment malfunctions
what is a physical indicator of a preformance verification test?
- Measurement of physical parameters with mechanical or electronic recorders
- Includes things like temperature sensors, pressure sensors
- Will provide some form of log for quality documentation
how many different classes of chemical indicators are there for steam sterilisation?
there are 6 different classes
what do the different classes in steam sterilisation show?
class 1 only shows exposure to process- e.g. autoclave tape class 5 is designed to react with all essential variables during a cycle e.g. thermalog colour change is directly related to death curve of B
What is the only type of indicator that shows that a process has killed organisms?
biological process
this is uaully for high resistance organisms
what are the two different techniques used for sterility testing?
- Direct Inoculation
* Membrane filtration
what media is used for sterility testing?
Soya-bean casein digest medium (or as you know it TSB)
•Allows for the growth of anaerobic and aerobic organisms
when there is no growth over a 14 day period the product is sterile unless:
- Environmental monitoring of facility shows a fault
- There is a fault in the testing procedure
- There is growth in the negative control
