In order to efficiently conduct validation of diluted disinfectant storage condition and period, ensure that the following requirements are fulfilled –
· Validated Laminar air flow
· Calibrated Incubators
· Soybean casein digest agar
· Approved Test Methods for Swab testing and Plate Exposure
· Test Organisms – E. coli, Salmonella abony, Staph. aureus, C. albicans, and Wild culture – WC1
Before proceeding for Validation of Shelf Life for diluted disinfectant solution, following parameters are checked –
· Each lot of dehydrated media used for validation, the medium must be tested for its growth promoting qualities.
Validation of diluted disinfectant storage conditions are done by following methods
· Surface swab test Method
· Settle Plate Method
1. Prepare 70% v/v solution of Isopropyl Alcohol.
2. Carry out the sterility of diluted IPA solution by Membrane filtration method.
3. Store the disinfectant solution at room temperature, and analyze the sample on the day of preparation, after 24 hrs, 48 hrs, 72 hrs and 96 hours by Surface swab test, Settle Plate Method
SURFACE SWAB METHOD
Remove following culture slant from the refrigerator and allow it to attain room temperature.
· Staphylococcus aureus
· Escherichia coli
· Pseudomonas aeruginosa
· Salmonella, and
· Wild culture
1. Inoculate loop full of the culture from each slant separately into 50 ml of sterile Soyabean casein digest medium and incubate at 32.5 ± 2.5°C for 24 – 48 hrs.
2. Transfer 1.0 ml of the broth culture into 9.0 ml of sterile saline solution (0.9% sodium chloride solution) to obtain a test dilution of 10-1.
3. Transfer 1.0 ml of the 10-1 dilution into 9.0 ml of sterile saline solution to give 10-2 dilution.
4. Similarly serially dilute the culture suspension to obtain dilution of 10-3 , 10-4, 10-5 and 10-6
5. Plate 1.0 ml of the culture suspension from dilution 10-3, 10-4, 10-5 and 10-6 in duplicate into sterile petri dishes.
6. Pour approximately 15-20 ml of sterile Soyabean Casein Digest Agar cooled to about 45°C in each plate. Incubate at 32.5 ± 2.5°C for 24 to 48 hours.
7. Count the number of colonies on each plate and Select the dilution, which gives a count of not less than 10-5.
8. Apply 1.0 ml of each culture suspension containing cell concentration not less than 10-5 cfu/ml, separately on the floor approx 25 cm2 area, and allow to air dry.
9. After drying, take a surface swab as per latest SOP for Swab Testing, and carry out the determination of total aerobic count per cm2 withing 4 hours of sampling.
10. Immediately clean the floor with IPA 70% v/v solution and allow to stand for 30 minutes to facilitate the action of disinfectant solution on the challenge test organisms.
11. After 30 minutes, take a swab and detect the bacterial count as per SOP for swab testing.
12. Repeat the same procedure, step no. 9 to 12 to determine the efficacy of 70% IPA solution after 24 hrs, 48 hrs, 72 hrs and 96 hours at room temperature.
SETTLE PLATE METHOD
1. Expose the pre-incubated sterile Soybean casein digest agar plate for 2 hours.
2. After plate exposure time, immediately clean the floor with IPA 70% v/v solution.
3. After proper cleaning, spray the area with IPA 70 % v/v solution and immediately close the room 30 minutes to facilitate the action of disinfectant solution.
4. After 30 minutes of contact time, immediately expose the plate as per latest SOP for plate exposure and detect the bacterial count per location per 2 hours.
5. Repeat the same procedure, step no. 1 to 4 to determine the efficacy of IPA 70% v/v solution after 24 hrs, 48 hrs, 72 hrs and 96 hours at room temperature
Diluted disinfectant solution, which is stored at room temperature, is effective when the test result of surface swab and Settle plate shows 90% reduction of the challenged microorganisms.
Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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