1. Janine Coetzer Integral Labs
Agar sterilization time, temperature and expiry dates for prepared media
Janine Coetzer Integral Labs

2. No matter how prepared you are for your next audit, there will always be something you missed, there is always something you can improve on and there are always ways to make your life easier and to work more efficient.
Working under conditions which does not allow for the preparation of media every day, it is necessary to prepare bigger batches of media when high volume of samples are expected.
Even though well maintained and calibrated equipment are being used, time and temperature limits are sometimes exceeded. This can become very expensive if this media has to be discarded.
These questions popped up in an Internal Audit
1. How long can you keep your prepared agar in the fridge.
2. How many degrees can you go above 121°C while sterilizing agar.
3. How much extra time can you allow at the required temperature with no effect to agar.
And off course there were no answers.
The idea behind this exercise was be to establish expiry dates for prepared agar,
Minimum/maximum time and temperatures for sterilization of agar that would not affect the integrity of the agar.

3. Question 1.
How long can we store prepared agar:
There is no data available under the manufacturers preparation procedures regarding the time prepared media can be stored.
The idea is to prepare a batch, and over a period of time perform:
1. Positive and negative controls
2. pH
3. Sterilities
to try and establish a suitable time media can be stored.
LAB M Harlequin e.coli/coliform Medium
Soak for 10min, swirl to mix.
Autoclave at 121°c for 15min.
pH7.2 ±0.2
Biolab Plate Count Agar for HPCs 1. Boil until completely dissolved Autoclave at 121°c for 15min. 3. pH 7.0 ±0.2

4. Harlequin coliform agar
Agar was also poured into 4 sterile containers to allow for pH’s to be performed over a period of 4 weeks.
Every week a pH would be run
Plates was poured into Petri dishes and stored in a sealed container at 2-8°C these were to be used as Positive and Negative controls.
Plate Count Agar for HPCs
Agar were stored in separate containers at 2-8°C, allowing it to be melted every week in order to perform positive controls, sterilities and pH

5. LAB M Harlequin e.coli/coliform Medium
Soak for 10min, swirl to mix.
Autoclave at 121°C for 15min.
pH7.2 ±0.2
Date Prep
Date Run
Steri Temp
Av time at Max temp
Steri Time 121 ±5°c
Agar/Media pH
pH range
Positive
Negative
Blank
Logger position
2016/09/14
123°c
12 min at 123°C
26 min
Harlequin
7.25
7.0 ± 0.2
Blue colonies
Pink colonies
No Growth
External
2016/09/20
2016/09/27
7.21
2016/10/03
7.23
2016/10/11
7.16

6. Biolab Plate Count Agar for HPCs 1. Boil until completely dissolved
Biolab Plate Count Agar for HPCs 1. Boil until completely dissolved Autoclave at 121°C for 15min pH 7.0 ±0.2
Date Prep
Date Run
Steri Temp
Av time at Max temp
Steri Time 121 ±5°C
Agar/Media pH
pH range
Pos
Blank
Logger position
2016/06/02
2016/6/02
123°C
11 min at 123°C
18 min
PCA
6.96
7.0 ± 0.2
Pass
No Growth
External
2016/06/08
6.93
2016/06/15
2016/06/22
2016/06/27
7.00

7. The next step was to run the plates in duplicate every week with our daily controls.
Every week I would prepare a freshly spiked sample using e.coli ATCC as a positive control and k.pneu ATCC as negative for e.coli and positive for total coliforms.
This spiked sample was then run on freshly prepared agar and the “old” agar, the results were compared and evaluated as per a 95% confidence table.
Total coliform
E Coli
Date
Dupl 1
Dupl 2
QC Indicator
Analyst/comments
UWL
UAL
08-May-17 68 81
ACCEPT 8 12
49.35
75.0
100.0
09-May-17
128
147 3 2
25.00
10-May-17
204
228
200
0.00
11-May-17 88 94
12-May-17 54 79 91
37.84
13-May-17 -
14-May-17
15-May-17 62 78 98
61.24
16-May-17 84 65
17-May-17
18-May-17
120
111 20 25
35.90

8. Harlequin Duplicates Fresh vs “Old”
Prepared: 14/9/2016
Run: 20/9/16
e.Coli ATCC 25922
k.Variicola ATCC 31488
Date
Dupl 1
Dupl 2
20-Sep-16
>200
#VALUE!
Date
Dupl 1
Dupl 2
20-Sep-16
>200
#VALUE!

9. Prepared: 14/9/2016 Run: 27/9/16 e.Coli ATCC 25922
k.Variicola ATCC 31488
Date
Dupl 1
Dupl 2
27-Sep-16 1 2
ACCEPT
Date
Dupl 1
Dupl 2
27-Sep-16
121
113
ACCEPT

10. Prepared: 14/9/2016 Run: 3/10/16 e.Coli ATCC 25922
k.Variicola ATCC 31488
Date
Dupl 1
Dupl 2
03-Oct-16 9 8
ACCEPT
Date
Dupl 1
Dupl 2
03-Oct-16
236
203
ACCEPT

11. Prepared: 14/9/2016 Run: 11/10/16 e.Coli ATCC 25922
k.Variicola ATCC 31488
Date
Dupl 1
Dupl 2
11-Oct-16
>200
ACCEPT
Date
Dupl 1
Dupl 2
11-Oct-16
>200
#VALUE!

12. PCA Duplicates Fresh vs “Old”
Fresh Agar
e.Coli ATCC 25922
Prepared: 2/6/2016
Run: 8/6/2016
pH: 6.93
e.Coli ATCC 25922
Date
No.
Dupl 1
Dupl 2
08-Jun-16 1 24 22

13. Fresh Agar e.Coli ATCC 25922 Prepared: 2/6/2016 Run: 15/6/2016
pH: 6.96
e.Coli ATCC 25922
Date
No.
Dupl 1
Dupl 2
08-Jun-16 1 24 22
15-Jun-16 2
1000

14. Fresh Agar e.Coli ATCC 25922 Prepared: 2/6/2016 Run: 22/06/2016
pH: 6.96
e.Coli ATCC 25922
Date
No.
Dupl 1
Dupl 2
08-Jun-16 1 24 22
15-Jun-16 2
1000
22-Jun-16 3
253
274

15. Fresh Agar e.Coli ATCC 25922 Prepared: 2/6/2016 Run: 29/06/2017
pH: 7.00
e.Coli ATCC 25922
Date
No.
Dupl 1
Dupl 2
08-Jun-16 1 24 22
15-Jun-16 2
1000
22-Jun-16 3
253
274
29-Jun-16 4 18 17

16. Decision:
Looking at the results obtained during the 4 weeks, all checks passed and the agar was still in good condition( no visible deterioration).
We’ve settled on a 4 week storage time for prepared plates, but prepared [plates hardly lasts longer than 1 week. At least this means business has picked up a lot.

17. Question 2.
What time is acceptable at 121°C, and what temperature deviation would be tolerated by the media?
Sterilization Time and Temperature is still a bit of a Toffee.
On all the manufacturers preparation steps it states autocalve at 121°C for 15 minutes, no +/- this way or that. I’ve never seen a run this specific.
With a SANAS audit it was noted that the temperature logger was not submerged in the media during the sterilization process, and that different volumes were sterilized at the same time.
Subsequently all autoclaves have been re-calibrated with Loaded and Unloaded runs, and sterilizing of media and glassware etc. has been separated.
The temperatures on most of our runs are fairly regular and hardly ever exceeding 124°C.
On the odd occasion where the temperature was over 124°C no failures were noted on controls or pH.
The average run time at 121°C after the last calibration sits roughly at 22 minutes, with no failures and very similar readings on controls and pH.
We have also started to run a pH with the daily controls with each batch of Plate Count Agar used.

18. No failures were detected on any of these checks.
The pH is very consistent and within range.
A duplicate was run on a weekly basis to compare freshly prepared agar with the stored plates.
All these duplicates passed as per the 95% Confidence range that we use to check our duplicates on.

19. 95% Confidence Index Observed Lower Upper Count (CFU) Acceptable count50 32 72 51 33 73 52 75 53 34 76 54 35 77 55 36 78 56 37 79 57 38 80 58 82 59 39 83 60 40 84 61 41 85 62 42 86 63 88 64 43 89 65 44 90 66 45 91 67 46 92 68 47 93 69 95 70 48 96 71 49 97 98 99 74
100

20. Question 2.
What time is acceptable at 121°C, and what temperature deviation is acceptable?
Date Prep
Date Run
Steri Temp
Av time at Max temp
Steri Time 121 ±5°C
Agar pH
pH range
Positive
Negative
Blank
Logger position
2016/06/14
122°c
12 min at 122°c
15 min
Harlequin
7.11
7.0 ± 0.2
Blue colonies
Pink colonies
No Growth
External
2016/06/21
7.15
2016/06/27
7.18
2016/07/04
7.24
2016/07/11
7.20
2016/08/19
123°c
18 min at 123°c
26 min
7.12
2016/08/29
2016/09/05
7.21
2016/09/12
2016/09/20
7.26
2016/09/14
12 min at 123°c
7.25
2016/09/27
2016/10/03
7.23
2016/10/11
7.16
2016/12/01
124.51°c
16 min at 124°c
49 min
7.34
Submerged
7.36
2016/12/07
122°
9 min at 122°c
23 min
7.39
2017/01/19
125.5°c
25 min at 125°c
34 min
7.22
2017/01/20
125.75°c
21 min at 125°c
2017/03/07
123.08°c
7 min at 123°c
16 min
7.17

21. Date Prep
Date Run
Steri Temp
Av time at Max temp
Steri Time 121 ±5°c
Agar/Media ph
ph range
Positive
Negative
Blank
Logger position
2016/06/02
123°c
11 min at 123°
18 min
PCA
6.96
7.0 ± 0.2
Pass
N/A
No Growth
External
2016/06/08
6.93
2016/06/15
2016/06/22
2016/06/29
7.00
2016/12/01
124.51°c
16 min at 124°c
49 min
7.12
Submerged
2016/12/7
7.06
2016/12/14
2016/12/06
124.56°c
17 min at 124°c
41 min
7.09
7.08
2017/01/19
125.5°c
25 min at 125°c
34 min
7.03
7.02
2017/01/20
125.75°c
21 min at 125°c
6.92
2017/03/06
2017/03/03
123.79°c
11 min at 123°c
19 min
6.97

22. Harlequin coliform agar
Date Prep
Date Run
Steri Temp
Av time at Max temp
Steri Time 121 ±5°c
Agar/Media ph
ph range
Positive
Negative
Blank
Logger position
2016/06/30
123.3°c
11 min at 123°c
22 min
PCA
6.89
7.0 ± 0.2
Pass
N/A
No Growth
Submerged
2017/07/03
6.91
123.79°c
20 min
6.97
2017/07/10
6.90
2017/07/13
123.06°c
4 min at 123°c
18 min
6.96
2017/07/18
6.94
2017/07/20
8 min at 123°c
2017/07/25
20min
7.00
2017/06/30
Harlequin coliform agar
7.14
Blue colonies
Pink colonies
External
7.12
7.21
7.15
7.11
7.16

23. Decision:
Temperature:
Looking at historical sterility checks we’ve always been working on a 121°C ±3°C, and our recent data shows that we have been maintaining the required temperature.
Sterilization time:
The data shows that we have times ranging from minutes at 121°C ±3°C, and that the agar is still performing very well under these conditions.
No failures were detected on controls or pH’s.
Sterilization time is set at minutes.

24. NLA Results
Looking at our NLA results, we’ve had very good results over the past couple of years.
Agar used in Round :
Both Harlequin and PCA was prepared on the same day, 2/09/2016 and the NLA was run on 9/09/2016.
Temperature: °C
Sterilization 121°C ±3°C: 26 minutes
Harlequin pH: (7.0 ± 0.2)
PCA pH: 6.97 (7.2 ± 0.2)

25. NLA Results 2016 Round 5