We use self-contained biological indicators (BIs) for the monitoring of each autoclave run, and two such BIs (test: put in autoclave and control: one normal BI from the same batch as test) are sent to the department of medical microbiology for verification of the sterility test reporting. The change in color from the usual purple to yellow along with turbidity of the media is reported as failure of sterility test after necessary incubation at 55°C.
We report a case of apparent failure of sterility test of one of the autoclaves. A root cause analysis was conducted; after all steps were examined in sequence, it was found that there was no deviation from any step as per the standard operating procedure (SOP). The BI being used was EZ Test (Lot: S-507, Exp: January 5, 2020), Mesa Labs, France. The color change of the autoclave tape was satisfactory as documented in the register of the autoclave record, indicating that the temperature of 121°C was achieved. This can also be verified on the tape on the BI, brownish black (a) color change (in test) from light navy blue (in control) as depicted in Figure 1.
Figure 1.
The control (purple) and test (brownish black) biological indicators. (A) Test biological indicator (right side) demonstrating the change in color of the autoclave tape from light navy blue to brownish black. (B) Test biological indicator (right side) demonstrating the change in color of thermoplastic culture tube from purple to light brown
On detailed discussion with staff, it was noted that there was preanalytical change in color from purple to light brown (b) in the thermoplastic culture tube [Figure 1] of the BI after it was taken out from the autoclave, which was not documented on the sterility test requisition form. The change in color is due to caramelization of the tryptic soy broth, also described as nonenzymatic browning of media or Maillard-type reaction, which does not affect the performance of the BI.[1,2]
A demo run was sent after duly acknowledging the preanalytical change to simulate the usual practice, without any change, which to our expectation was reported as satisfactory.
The case emphasizes the importance of documentation of the preanalytical variables on the test requisition form, with sensitization of staff involved, and incorporation of this change in the SOP for the monitoring of autoclave usage in accordance with the Standards for Autoclaving of Bio-Medical Wastes, Bio-Medical Waste Management Rules, 2016 in India.[3]
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Conflicts of interest
There are no conflicts of interest.
References
- 1.Caramelization or Darkening in the Color of Autoclaved Liquid BI Ampoules. Spore News™, Mesa Labs. Volume Number. [Last accessed date 05 May 2019]. Available from: https://biologicalindicators.mesalabs.com/wp-content/uploads/sites/31/2014/07/Spore-News-Vol-8-No. 3.pdf .
- 2.Maillard-Type Reaction or Nonenzymatic Browning of Media. General Information, Media Preparation and Quality Control, Microbiological Laboratory Best Practices. The United States Pharmacopeial Convention. 2011. [Last accessed date 05 May 2019]. Available from: https://www.drugfuture.com/Pharmacopoeia/usp35/pdf/0707-0712%20%5b1117%5d%20microbiological%20best%20laboratory%20practices.pdf .
- 3.Standards for Autoclaving of Bio-Medical Wastes. Standards for Treatment and Disposal of Bio-Medical Wastes Bio-Medical Waste Management Rules Ministry of Environment, Forest and Climate Change, Government of India. 2016. [Last accessed date 05 May 2019]. Available from: http://cpcbnicin/bio-medical-waste-rules/