Lumen claims of the STERRAD 100NX Sterilizer: Testing performance limits of this technology

Transcription

1 Lumen claims of the STERRAD 100NX Sterilizer: Testing performance limits of this technology Magda Diab-Elschahawi, Alexander Blacky, Walter Koller Clinical Institute of Hospital Hygiene Medical University of Vienna

2 STERRAD 100NX Sterilizer

3 STERRAD 100NX Full Cycles Standard Cycle 47 minutes Sterilization of most surgical instruments including Inox lumened devices AND Flex Cycle 42 minutes Sterilization of flexible endoscopes only

4 Study Background A main drawback in the past has been the reliable sterilization of devices featuring long narrow lumens. According to the manufacturers information the STERRAD 100NX Sterilizer can adequately process 0.7mm X 500mm Inox lumened devices. We placed inoculated carriers at the midpoint position of lumens, which were then submitted to half-cycle sterilizing conditions in the STERRAD 100NX Sterilizer. In order to simulate insufficient cleaning of instruments or crystalline residues we added organic and inorganic challenges respectively to our inoculated carriers.

5 Aim of the study The aim of this study was to qualify the performance of the STERRAD 100NX Sterilizer under different experimental settings* representing worst case conditions. Protocol: 1. Stainless steel lumens of 0.7mm x 500mm 2. Wrapping (1 X) 3. Flex Scope conditions 4. Organic and inorganic burdens * These conditions do not correspond to the manufacturer s instructions for use

6 Test Conditions Manufacturer s IFU University Worst Case Test Condition Lumen Claim 0.7 mm X 500 mm Inox 0.7 mm X 500 mm Inox* Instrument Condition Must be clean and dry Contaminated with inorganic and organic material Load Arrangement Arranged pouches on edge Sterilization Cycle STANDARD FLEX Pouches stacked on top of each other * 0.7 mm X 500 mm Inox are validated for sterilization only in the STERRAD 100NX STANDARD cycle. Do not process these devices in the FLEX cycle.

7 Rationale for Worst Case Conditions Cleaning process not validated >> sub-standard washing or rinsing Simulated by use of inorganic and organic soils Human Error >>Improper loading Simulated by stacking pouched lumens on top of each other Human Error >> selecting the wrong cycle for the devices to be processed Simulated by use of FLEX cycle for sterilization of a rigid lumen

8 Test load Test load upper shelf Test load lower shelf

9 Manfacturer s Recommendation Place pouches on edge

10 Experimental setting

11 Titer verification BI (condition) Mean spore count/ml SD Final titer (mean) unchallenged 5,08E+00 ± 2,81 5,08E ppm 1,23E+01 ± 4,01 1,23E ppm 1,77E+01 ± 4,63 1,77E ppm 1,37E+01 ± 2,77 1,37E+06 5%FBS 1,88E+01 ± 4,07 1,88E+06

12 Qualitative Results condition position number untreated cycle 2 ng G ng ng G G ng ng ng ng cycle 3 ng G ng ng ng ng ng G ng ng cycle 4 ng G ng ng ng ng ng ng ng ng negative (%) 100% 0% 100% 100% 66% 66% 100% 66% 100% 100% 300ppm cycle 2 G G G G G G G G G G cycle 3 G G G G G G G G G G cycle 4 G G G G G G G G G G negative (%) 0% 0% 0% 0% 0% 0% 0% 0% 0% 0% 600ppm cycle 2 G ng ng G ng ng G G ng ng cycle 3 G G G G G G G G G G cycle 4 G G G G G G G G G G negative (%) 0% 33% 33% 0% 33% 33% 0% 0% 33% 33% 1200ppm cycle 2 G G G G G G ng G G G cycle 3 G G G G G G G G G G cycle 4 G G G G G G G G G G negative (%) 0% 0% 0% 0% 0% 0% 33% 0% 0% 0% 5% FBS cycle 2 G G G G G G G G G G cycle 3 G G ng G ng G G G G G cycle 4 ng G G ng G G G G G G negative (%) 33% 0% 33% 33% 33% 0% 0% 0% 0% 0%

13 log reduction/wire Quanitative results wires 7,00 6,00 5,00 4,00 3,00 2,00 untreated 300ppm 600ppm 1200ppm 5%FBS 1,00 0, position numbers

14 log reduction/bi Besides the protocol: Untreated wires: Heatshock vs. non Heatshock 7,00 6,00 5,00 4,00 untreated 3,00 untreated HS 2,00 1,00 0, position numbers

15 Discussion The titer determination of the inoculated wires in unchallenged condition provided by ASP showed a titer of only 5.08 x As our quantitative results showed that CFU counts of unchallenged wires found after sterilization were below detection limit, the actual log reduction rate can only be stated as Though one can assume, that a SAL of 10-6 could be achieved, a positive verification would have required a higher inoculation of the BI s.

16 Discussion We also cannot rule out that an effect known as inoculum effect would not influence the test results had we had a higher initial test inoculum. The inoculum effect refers to a decrease of the effect of a microbicide associated with a higher inoculum as described for antibiotics and certain disinfectants. The increase in bio-burden going along with an increasing inoculum size would decrease the amount of available sterilant per bacterial cell. Hence in our case H2O2 might fail to kill all test-organisms, thus resulting in inadequate sterilization especially in situations with heavy contamination and insufficient previous cleaning.

17 Discussion Inoculum effects must be considered relevant in all situations where biocides are not abundant in relation to microbial inocula.

18 Recommendations regarding the STERRAD 100NX strictly adhere to the manufacturer s recommendations specified in their user guide correct cycle (Standard or Flex Scope) and permitted dimensions for the processing of medical devices with lumens in the STERRAD 100NX Sterilizer.

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20 Thank you for your attention!