Control of microbes

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People will be able to understand concept of D-value,Z-value,F0 and different methods to kill microbes

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Control of Microorganism Prepared By: Dr.Jaydeep Patel, Lecturer, B.K.Mody Govt. Pharmacy college, Rajkot. :

Control of Microorganism Prepared By: Dr.Jaydeep Patel, Lecturer, B.K.Mody Govt. Pharmacy college, Rajkot.

Terminologies:

2 Terminologies Sterilization – a process that destroys or removes all viable microbes, including viruses and endospores ; microbicidal Disinfection – a process to destroy vegetative pathogens, not endospores ; inanimate objects (may remain viable) Antiseptic – disinfectants applied directly to exposed body surfaces Sanitization – any cleansing technique that mechanically removes microbes

Terminologies:

3 Terminologies Degermation – mechanically removing microbes form surface (skin) Germicide- kill growing form but not resistant spore Sepsis – bacterial contamination Asepsis – absence of significant contamination Bacteriocidal ( microbiocidal ) - cidal means kill (Like fungicide,virucide,sporicide ) Bacteriostatic ( microbiostatic ) -static means inhibition of growth and multiplication Sterility- no living organisms on/in object

What is the definition of “sterile”?:

What is the definition of “sterile”? Free from microorganisms In practice no such absolute statement regarding absence of microorganisms can be proven Defined as the probability of 1 in a million of a container being contaminated (10 -6 ) This referred to as the Sterility Assurance Level (SAL) Organisms are killed in an exponential fashion

Survivor curve:

Survivor curve Population generally loose their viability in an exponential fashion(independent of initial number) Plot of logarithm of fraction of survivors against exposure time or dose.

D-Value:

D-Value The resistance to the organism can be understood by D-value Time taken at fixed temperature or the radiation dose required to achieve a 90% reduction in viable cells( i.e a 1 log cycle reduction in survivors It only refers to particular M.O at particular Temp.

Z-Value:

Z-Value In order to assess the influence of temperature changes on thermal resistance a relationship B/N Temp. and log D-value can be leading to express as Z-value Increase in temperature needed to reduce the D-value of an organism by 90% ( i.e 1 log cycle reduction)

D-value & Z-value calculation:

D-value & Z-value calculation

Concept of Fo :

Concept of F o Lethality factor equivalent to time at 121°C 1 minute at 121°C is equivalent to F o of 1. Lethality can accumulate during heat up and cool down phases Typical temperature profile of a heat sterilization process What would be the Fo of a cycle at 121°C for 15 minutes?

Concept of Fo :

Concept of F o F o is calculated using the following equation: F o = ΔtΣ10 (T-121/Z) where: “ Δt ” is the time interval between measurements of temperature (T) “T” is the temperature of sterilized product at time (t) “Z” is a temperature coefficient which measures the number of degrees required to change the D-value of an organism by 1 log

Concept of Fo :

Concept of F o The minimum F o required by a sterilzation process is related to the resistance of the bioburden (D-value) F o = D 121 (LogA - Log B) where: “D 121 ” is equal to the time at 121°C to reduce the population of the most resistant organism in each product container by 90% (or 1 log) “A” is the number of microoganisms per container “B” is the maximum acceptable probability of survival (Sterility Assurance Level , 10 -6 )

PowerPoint Presentation:

Two approaches to sterilization Overkill Probability of survival Overkill approach used when the product can withstand excessive heat treatment without adverse effects Cycle should deliver an F o of at least 12 This will achieve a 12 log reduction of microorganisms with a D-value of 1 minute ( Assuming each product unit contains 10 6 organisms a 12 log reduction will result in 10 -6 organisms per unit or probability of survival (SAL) of 1 in a million ) ( Normal bioburden is usually much lower and the organisms normally much less resistant than this )

Sterility Assurance Level (SAL):

Sterility Assurance Level (SAL) The sterility assurance level (SAL) of a sterilizing process is the degree of assurance with which the process in question renders a population of items sterile. The SAL for a given process is expressed as the probability of a non-sterile item in that population. An SAL of10 -6 , for example, denotes a probability of not more than one viable micro-organism in 1x10 6 sterilized items of the final product. The SAL of a process for a given product is determined by appropriate validation studies.

Sterility assurance. At Y, there is (literally) 10-1 bacterium in one bottle, i.e. in 10 loads of single containers, there would be one chance in 10 that one load would be positive. Likewise, at Z, there is (literally) 10-6 bacterium in one bottle, i.e. in 1 million (106) loads of single containers, there is one chance in 1 million that one load would be positive.:

Sterility assurance. At Y, there is (literally) 10 -1 bacterium in one bottle, i.e. in 10 loads of single containers, there would be one chance in 10 that one load would be positive. Likewise, at Z, there is (literally) 10 -6 bacterium in one bottle, i.e. in 1 million (10 6 ) loads of single containers, there is one chance in 1 million that one load would be positive.

Sterility Assurance Level (SAL):

Sterility Assurance Level (SAL) A sterilization process must deliver a Sterility Assurance Level (SAL) of 1 in a million (10 -6 ) It is not possible to measure “10 -6 ” The required SAL can be achieved by applying a process that will reduce the number of organisms to zero and then apply a safety factor that will deliver an extra 6 log reduction

Methods of Sterilisation:

Methods of Sterilisation

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