«Terminal sterilization of duodenoscopes by Low Temperature Steam and Formaldehyde (LTSF) under extreme organic contamination conditions»

ABSTRACT

The sterilization of complex flexible endoscopes remains one of the most significant challenges in the reprocessing of reusable medical devices [1-3].

Building on Part I [4] of this series, which evaluated the efficacy of Low Temperature Steam and Formaldehyde (LTSF) sterilization on surfaces contaminated with organic matter and Hollow Process Challenge Devices (HPCDs), this White Paper goes a step further by assessing the microbiological efficacy of the LTSF process in complex endoscopes requiring advanced reprocessing. Specifically, Olympus duodenoscopes (EVIS EXERA III, model TJF-Q190V) were subjected to extreme organic contamination and microbiological challenge conditions.

Selected internal channels were inoculated with one million spores of Geobacillus stearothermophilus ATCC 7953, the reference microorganism used for evaluating LTSF sterilization processes. In addition, the biopsy channel was challenged with a protein load approximately 73 times higher than the action limit established by ISO 15883-5 for assessing cleaning efficacy in reusable medical devices.

Following three independent LTSF sterilization cycles at 60 °C in the 130LF® sterilizer using the three endoscopes, no microbiological growth was detected in any of the evaluated channels. Under the conditions tested, the results demonstrate the high capability of the LTSF process to achieve a Sterility Assurance Level (SAL) of 10⁻⁶ in a clinically representative device with highly complex internal geometries.

These findings reinforce the results presented in Part I and suggest that, for compatible complex devices processed using validated cycles, terminal sterilization by LTSF may provide an additional margin of microbiological safety, even under organic contamination conditions that are considerably more challenging than those typically encountered, without replacing the essential steps of cleaning and disinfection.

1. INTRODUCTION

The Challenge of Duodenoscope Sterilization

The difficulty in reprocessing flexible endoscopes stems both from their limited compatibility with high-temperature steam sterilization processes due to the presence of heat-sensitive materials and from the complex configuration of their internal channels, which may hinder the removal of residues following cleaning and microorganisms following disinfection and sterilization.

Within this group, duodenoscopes represent a particularly critical case due to the presence of movable distal mechanisms (including the elevator or Albarrán channel) and their long internal channels, features that may promote the persistence of residual contamination and biofilms following cleaning [1-3].

Following clinical use, organic and inorganic residues may remain, including proteins, biological fluids, salts, and other materials capable of interfering with subsequent reprocessing stages such as washer-disinfection and low-temperature sterilization. Furthermore, the presence of residual contamination or biofilm formation may compromise the effectiveness of disinfection and sterilization procedures if adequate cleaning is not performed [7,8].

The complexity of duodenoscope reprocessing has prompted extensive research and numerous safety communications in recent years. Several studies have documented microbiological transmission events associated with duodenoscopes and other highly complex endoscopes, including cases involving multidrug-resistant microorganisms, even after the implementation of reprocessing procedures consistent with current recommendations [7-9].

As a result, there has been growing interest in approaches capable of enhancing microbiological safety following reprocessing in these devices. These strategies are not intended to replace established cleaning, disinfection, quality control, and traceability procedures but rather to minimize the risks associated with residual contamination and improve the overall robustness of the reprocessing process.

In this context, LTSF sterilization, as described in ISO 25424 [5], represents an alternative for processing heat-sensitive devices such as duodenoscopes. The 130LF® sterilizer combines the action of low-temperature steam (60-78 °C) and formaldehyde (2%) for the inactivation of microorganisms and has demonstrated efficacy in devices with complex configurations and long internal channels subjected to particularly demanding microbiological challenge and organic contamination conditions.

Figure 1 shows the Olympus EVIS EXERA III TJF-Q190V duodenoscope used in the study and illustrates the complexity of the channels selected for microbiological evaluation.

Figure 1. Olympus EVIS EXERA III TJF-Q190V duodenoscope and characteristics of the channels evaluated. (A) Olympus EVIS EXERA III TJF-Q190V duodenoscope used in the study to evaluate the microbiological efficacy of the LTSF sterilization process. The biopsy channel (A.1) and the air/water channel (A.2) were evaluated, both of which are representative of complex configurations featuring long channels and demanding internal geometries for reprocessing and sterilization processes. (B) Geometrical characteristics of the channels evaluated microbiologically, including total length, internal diameter, and calculated internal surface area. Internal surface area calculated as π × internal diameter × channel length. †Confidential Olympus data.

2. STUDY DESIGN

The microbiological efficacy of the LTSF sterilization process was initially evaluated to determine its Sterility Assurance Level (SAL) on protein-contaminated metal surfaces, representing the potential persistence of residual organic matter following cleaning. This evaluation was conducted in accordance with ISO 25424 [16], which describes the validation procedures for LTSF sterilization. For this study, Geobacillus stearothermophilus ATCC 7953 spores were used as the biological indicator.

The objective of the study was to verify the ability of the 130LF® LTSF process to achieve a SAL of 10⁻⁶, defined as a probability of one in one million of finding a viable microorganism after sterilization, under conditions that greatly exceed the levels of residual contamination considered acceptable following cleaning procedures.

The microbiological efficacy of the LTSF sterilization process was evaluated using three Olympus EVIS EXERA III TJF-Q190V duodenoscopes as test devices [10]. The internal channels selected for microbiological evaluation were the biopsy channel and the air/water channel, the characteristics of which are summarized in Figure 1 and Table 1.

The channels evaluated were inoculated with a biological challenge of 1 × 10⁶ spores of Geobacillus stearothermophilus ATCC 7953, the reference microorganism specified in ISO 11138-5 [11] for the evaluation and monitoring of LTSF sterilization processes.

In addition, to assess the robustness of the process under particularly demanding conditions, a high protein load was applied to the biopsy channel. The contamination level reached 466 µg/cm², a value 72.8 times higher than the 6.4 µg/cm² action limit established in ISO 15883-5 [6] for evaluating cleaning efficacy in reusable medical devices.

Table 1. Characteristics of the test device, applied contamination conditions, and key microbiological parameters used throughout the study.

* Confidential Olympus data.

Following microbiological inoculation and the application of organic contamination, the duodenoscopes were sterilized using the LTSF process with the 130LF® sterilizer (Matachana). The study was conducted in three independent sterilization cycles at 60°C, with an exposure time of 30 minutes. During each cycle, the three duodenoscopes and two channels per device were evaluated, resulting in a total of 18 microbiological assessments of internal channels.

The load configuration and barrier systems used during the testing are shown in Figure 2.

Subsequent microbiological evaluation made it possible to determine the presence or absence of growth of the inoculated spores within the channels examined after the sterilization process.

Figure 2. Sterile barrier system and load configuration used during duodenoscope sterilization. The figure shows the Aesculap PrimeLine® sterile container system equipped with a single-use filter and loaded into the 130LF® sterilizer for the 60 °C LTSF cycle. The duodenoscopes were placed inside the containers. The location of the chemical indicator, positioned within a Helix Process Challenge Device (PCD) to verify exposure to the sterilization process, is also shown.

3. RESULTS

Following completion of each sterilization cycle, a microbiological evaluation of the channels under study was performed through recovery and incubation of microorganisms (58-60 °C, 7 days).

The microbiological results obtained from the biopsy and air/water channels are summarized in Table 2. In both cases, complete inactivation of the inoculated spores was observed, demonstrating achievement of a SAL 10⁻⁶.

Table 2. Microbiological Efficacy Results

CFU – Colony-Forming Units.

4. MICROBIOLOGICAL ROBUSTNESS OF THE LTSF PROCESS

The microbiological efficacy of the process was analyzed by considering the resistance of the G. stearothermophilus spores used in the study (D-value). The D-value corresponds to the time required to achieve a 90% reduction in a microbial population. In this study, the duodenoscope channels were inoculated with G. stearothermophilus spores exhibiting a D_{FA 60°C} value of 20.2 min.

For reference, in Part I of this series, the efficacy of the LTSF technology was evaluated using Hollow Process Challenge Devices (HPCDs) inoculated with spores exhibiting a D_{FA 60°C} value of 17.2 min [4]. Although lower, both values are considerably higher than the D_{FA 60°C} value of 6 min specified in ISO 25424 [5] as guidance for the validation of LTSF sterilization processes.

Figure 3 illustrates the theoretical microbiological reduction associated with these three resistance levels. While the HPCD studies already represented a microbiological challenge exceeding the requirements established by the standard, the duodenoscope trials were conducted using spores with even greater resistance, thereby constituting a particularly demanding evaluation condition for the sterilization process.

Figure 3. Theoretical evaluation of the microbiological reduction of Geobacillus stearothermophilus spores over time during the LTSF process at 60 °C. The lines represent the calculated microbiological reduction using different D-values under formaldehyde conditions: D_{FA 60°C} = 6 min (ISO 25424 reference value), D_{FA 60°C} = 17.2 min (spores used in the HPCD studies presented in Part I), and D_{FA 60°C} = 20.2 min (spores used in the Olympus TJF-Q190V duodenoscope studies). The vertical dashed line indicates the exposure time of the LTSF cycle (30 min).

5. CLINICAL IMPLICATIONS

Cleaning and disinfection remain fundamental and irreplaceable steps in endoscope reprocessing. The effective removal of organic residues and microorganisms is the foundation for reducing the risk of infection transmission associated with reusable medical devices [7,8].

In addition, the reprocessing of these devices involves multiple manual and automated steps, the outcome of which may be influenced by both the complexity of the device itself and the nature of the biological contamination, as well as by the high clinical workload encountered in healthcare settings [2,3,8]. This aspect is especially relevant for highly complex devices, whose design may complicate reprocessing and promote the persistence of residual contamination [2,3,8].

The significance of these findings becomes even greater when considering that certain low-temperature sterilization technologies may exhibit limitations in the presence of residual organic matter, proteins, salts, or complex luminal configurations. Such limitations have been reported particularly for H₂O₂-based technologies, including Vaporized Hydrogen Peroxide (VHP) and Hydrogen Peroxide Gas Plasma (HPGP), when challenged by combinations of organic contamination and restrictive geometries [12-16].

In this context, the results obtained reinforce the value of terminal sterilization using LTSF as part of a comprehensive infection prevention and control strategy.

The principal implications of these findings include:

• Enhanced microbiological safety. Despite the presence of organic residues, any remaining pathogens are not protected by the organic matrix, reducing the likelihood of survival and potentially decreasing the risk of microbial persistence and biofilm formation associated with residual organic contamination.
• Applicability to devices with complex internal configurations. Effective sterilization of devices with long and difficult-to-access internal channels.
• Potential utility as a terminal sterilization strategy for highly complex reusable medical devices, particularly in scenarios where other low-temperature technologies may present limitations.

6. CONCLUSIONS

The 130LF® LTSF sterilization process developed by MATACHANA demonstrated high microbiological efficacy in Olympus EVIS EXERA III TJF-Q190V duodenoscopes subjected to organic and microbial contamination conditions considerably more demanding than those typically considered acceptable following cleaning procedures.

Consistent with the findings presented in Part I, the results further reinforce the microbicidal potential of the 130LF® sterilizer, even under conditions of high microbiological complexity. Moreover, these findings open new avenues for research aimed at evaluating the performance of this technology against what remains the greatest challenge in endoscope reprocessing: biofilms. This topic will be specifically addressed in Part III of this series.

REFERENCES

1. Heuvelmans M, Wunderink HF, van der Mei HC, Monkelbaan JF. A narrative review on current duodenoscope reprocessing techniques and novel developments. Antimicrob Resist Infect Control. 2021;10(1):171. doi:10.1186/s13756-021-01037-z.
2. Rutala, U.S. Food and Drug Administration. Infections associated with reprocessed duodenoscopes [Internet]. Silver Spring (MD): FDA; 2022.
3. Prüfert-Freese, U.S. Food and Drug Administration. Supplemental measures to enhance duodenoscope reprocessing: FDA safety communication [Internet]. Silver Spring (MD): FDA; 2015.
4. Carreras N, Vázquez DA, Ramirez A, von den Hagen T. VBTF: alcanzando la esterilidad donde otros fracasan. Parte I. La ventaja de la esterilización por VBTF de superficies y dispositivos canulados contaminados con materia orgánica: un estudio in vitro [White Paper]. Matachana; 2025.
5. International Organization for Standardization. ISO 25424:2018. Sterilization of health care products — Low temperature steam and formaldehyde — Requirements for development, validation and routine control of a sterilization process for medical devices. 2nd ed. ISO; 2018.
6. International Organization for Standardization. ISO 15883-5:2021. Washer-disinfectors — Part 5: Performance requirements and test method criteria for demonstrating cleaning efficacy. ISO; 2021.
7. Percival SL, Suleman L, Vuotto C, Donelli G. Healthcare-associated infections, medical devices and biofilms: risk, tolerance and control. J Med Microbiol. 2015;64:323-334. doi:10.1099/jmm.0.000032.
8. Pineau L. Endoscope reprocessing: retrospective analysis of 90,311 samples. Endosc Int Open. 2023;11(3):E247-E257.
9. Southworth PM. Infections and exposures: reported incidents associated with unsuccessful decontamination of reusable surgical instruments. J Hosp Infect. 2014;88(3):127-131. doi:10.1016/j.jhin.2014.08.007.
10. SMP GmbH. Examination of low-temperature formaldehyde sterilizer 130 LF with the rapid cycle program 60 °C using Olympus Video Duodenoscope EVIS EXERA III TJF-Q190V as load. Project No. P22138. Test report. Tübingen: SMP GmbH; 2024.
11. International Organization for Standardization. ISO 11138-5:2017. Sterilization of health care products — Biological indicators — Part 5: Biological indicators for low-temperature steam and formaldehyde sterilization processes. ISO; 2017.
12. Alfa MJ, DeGagne P, Olson N, Puchalski T. Comparison of ion plasma, vaporized hydrogen peroxide and 100% ethylene oxide sterilizers to the 12/88 ethylene oxide gas sterilizer. Infect Control Hosp Epidemiol. 1996;17(2):92-100.
13. Diab-Elschahawi M, Blacky A, Bachhofner N, Koller W. Challenging the Sterrad 100NX sterilizer with different carrier materials and wrappings under experimental “clean” and “dirty” conditions. Am J Infect Control. 2010;38(10):806-810. doi:10.1016/j.ajic.2010.05.023.
14. Diab-Elschahawi M, Blacky A, Bachhofner N, Koller W. Lumen claims of the Sterrad 100NX sterilizer: testing performance limits when processing equipment containing long, narrow lumens. Am J Infect Control. 2011;39(9):770-774. doi:10.1016/j.ajic.2011.01.010.
15. Prüfert-Freese U. H2O2 Sterilisationsprozesse — neue Erkenntnisse. Presented at: 11. ÖGSV-Fachtagung; 2019; Hafnersee, Austria.
16. Rutala WA, Gergen MF, Sickbert-Bennett EE, Weber DJ. Comparative evaluation of the microbicidal activity of low-temperature sterilization technologies to steam sterilization. Infect Control Hosp Epidemiol. 2020;41(4):391-395. doi:10.1017/ice.2020.2.

La entrada LTSF: REACHING STERILITY WHERE OTHERS FAIL. PART II se publicó primero en Matachana.

Within this framework, the first two awards were presented to the Hospital General Universitario Gregorio Marañón, recognising both its Sterilization Central and its Advanced Planning and 3D Manufacturing Unit (UPAM3D). This award recognises its active involvement in promoting knowledge, operational excellence and collaboration in educational and scientific initiatives, in which MATACHANA’s MATEC has played a key role.

The event took place as part of an institutional visit organised under the Marañón Valley initiative, during which professionals from the hospital and the MATACHANA team shared experiences, identified synergies and explored new avenues for collaboration in key areas such as the in-house manufacture of medical devices using 3D printing technologies, their reprocessing and innovation in hospital care.

The meeting highlighted the enormous value of public-private partnerships as a driving force for transformation in the healthcare system, demonstrating how such partnerships can accelerate the development of innovative solutions that have a direct impact on clinical practice and patient safety.

Furthermore, this type of recognition plays a crucial role in highlighting the strategic role of the RUMED in preventing infections and ensuring the quality of care.

In this context, it is also worth highlighting the valuable contribution made by the team at Gregorio Marañón to the latest issue of MATACHANA Magazine, in which they share their experience as a leading example of the integration of in-hospital manufacturing and sterilization – an innovative approach that enhances safety and traceability throughout the entire process.

We at MATACHANA would like to extend our most sincere congratulations to Hospital Gregorio Marañón, and in particular to the teams at UPAM3D and at the Sterilization Central, for their leadership, their commitment to excellence and their capacity for innovation. Their work not only drives medical progress, but also contributes directly to improving the safety and quality of life of many patients.

La entrada MATACHANA recognises the Hospital General Universitario Gregorio Marañón in the first edition of its “Aliados Clínicos” programme se publicó primero en Matachana.

The programme combined 8 hours of theoretical training with 4 hours of practical work carried out in the sterilization central of the Hospital Materno Infantil, which allowed the participants to consolidate their knowledge directly in a real environment.

After reviewing the exercises, the overall score of the group was excellent, with an average mark of 9.2/10. It is particularly noteworthy that the training was well received by the operating theatre staff, who described it as “essential” and even “compulsory” for professionals involved in sterilization and the surgical block.

Among the main conclusions, participants underlined the need to promote continuous training, standardise protocols and strengthen communication between services. Opportunities for improvement in infrastructure, equipment and human resources are also identified, together with a growing interest in quality control and technological innovation.

The experience has not only reinforced technical knowledge, but has also generated motivation and commitment to continuous improvement, consolidating training as a key pillar to ensure patient safety.

La entrada SPECIALISED TRAINING IN REPROCESSING AT THE VALL D’HEBRON UNIVERSITY HOSPITAL, BARCELONA se publicó primero en Matachana.

As usual, our cover is linked to one of the featured articles in this edition. This year, we travel to Lisbon, a city that symbolizes the coexistence of tradition and innovation, reflecting the technological and organizational evolution that is transforming healthcare environments.

We are confident that this issue will surprise and inspire you, while offering a closer look at some of the projects shaping the present and future of the sector.
 

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The congress brought together 556 participants and more than 200 scientific papers under the motto “Surgical nursing: leading, transforming and caring”.

Elena Lorenzo took part in Round Table No. 4 (Thursday 23, 17:00 h), dedicated to patient safety and advanced practice, together with leading professionals from the sector. Her presentation, “Innovation and sustainability in Reprocessing Units for Medical Devices”, highlighted the impact of technology and process optimization on the safety and efficiency of reprocessing units, generating considerable interest among the audience. As she underlined during her intervention: “Innovating in reprocessing is not only about advancing technologically, but also about ensuring safer, more sustainable and patient-centered processes”.

We would like to express our sincere thanks to the moderator, Ms. Cristina Herguera García, and her colleagues at the table for the enriching professional exchange.

We would also like to thank Ms. Amparo Rubio San Pedro for her tireless work at the head of the AEEQ in recent years and warmly welcome the new president, Ms. Lucía Fernández Yagüe, head of the nursing unit of the Surgical Block of the Hospital del Mar in Barcelona. We are confident that Reprocessing Units for Medical Devices will continue to be recognised as a critical element within the surgical ecosystem, due to their direct impact on infection prevention, traceability and quality assurance of the care process, maintaining their prominence in the scientific agenda of future editions.

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The event featured international speakers of a very high scientific level, who shared evidence, experiences and current perspectives on the challenges and advances in the reprocessing of medical devices.

During the meeting, MATACHANA actively participated in the academic activities as well as in the training and interaction spaces with the attending professionals.

One of the highlights was the exhibition of around 20 scientific posters. Among them, three were selected for oral defence in the plenary hall, including the paper presented by our colleague, Mr. Nelson Carreras, who was awarded the first prize thanks to the essay “Sterilization efficiency of the MATACHANA 130LF® sterilizer”, including extremely challenging conditions. Congratulations, Nelson, on this great achievement and that of your entire team!

Likewise, together with our distributor in Colombia KAIKA, the workshop “Steam Sterilization: CONTROL 360º, Rigorous Process Monitoring”, a multidisciplinary space, focused on the integral control of the Steam sterilization process, patient safety, traceability, efficiency and sustainability within medical devices reprocessing centrals.

At MATACHANA, we are all MIEC and we are committed to continuous training, the generation of evidence and the strengthening of the Sterilization Sciences, moving forward under the approach of “Transforming Conscience with SCIENCE” and with means that favour that all these processes are carried out in the most sustainable and balanced way possible.

Thank you Colombia for having us. We extend special recognition and thanks to Ana Eva Monterroza, founder and organiser of CIBE, as well as to all the organisers and members who made this important meeting possible for the sector.

See you next time!

More about our participation and the scientific poster presented in plenary:

• Congreso Iberoamericano y taller CONTROL 360º
• MATACHANA en el III Congreso Iberoamericano
• Participación MATACHANA en Cartagena 2026
• Póster científico premiado sobre tecnología 130LF®

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During the event, new developments related to sterilization technologies, engineering and sustainability were shared, addressing the current needs of our customers from a technical point of view and aligned with the challenges of the area.

The MIEC and MATEC departments also stressed the importance of accompanying innovation and technology with continuous training, generation of scientific evidence and a vision of reprocessing focused on patient safety, protection of medical devices and commitment to the environment.

The convention also included a space to recognise outstanding distributors in the region, highlighting the work and trajectory of all the teams.

We appreciate the energy, dedication and participation of all the distributors who, day by day, continue to strengthen and position the MATACHANA brand in their markets.

A regional meeting to continue moving forward together!

…We continue, Transforming conscience…

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The discussion compared LTSF, VH2O2, and EO, using a data-driven approach to evaluate safety and performance. During the session, actionable insights to optimize their CSSD workflows were provided to the healthcare professionals.

Key pillars of the presentation included:

• Efficacy: Proven 2% LTSF penetration in complex, narrow-lumen instruments.
• Safety : Protecting staff, patients, and the environment from risks.
• Standards : Aligning regional practices with international sterilization benchmarks.

“Our attendees’ energy highlights a simple truth: to trust advanced medical tech, people need clear and honest scientific facts.”

We remain dedicated to supporting the APAC healthcare sector through clinical excellence and specialized knowledge transfer.

More information:

Francisco Fernández-Cabrera’s LinkedIn post

Deby Saji’s LinkedIn post

PT Airindo Sentra Medika’s LinkedIn post

La entrada Scientific Insights into MATACHANA LTSF 2% sterilization in Bandung city, Indonesia se publicó primero en Matachana.

We are delighted to welcome Marc Perez, who is joining the MATACHANA General Management.

His vision, international experience and leadership will be key to driving MATACHANA’s development in this new phase, reinforcing our commitment to excellence, innovation and the development of our team.

We are convinced that his leadership and vision will be fundamental to keep on building the future of the MATACHANA GROUP, together with everyone who is part of this project.

We welcome Marc and wish him every success in this new challenge.

Welcome to MATACHANA!

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Technical participation was a cornerstone of the event. MIEC delivered impactful presentations on pre-cleaning and automated cleaning of robotic devices, as well as providing an in-depth look at Low-Temperature Steam with Formaldehyde (LTSF) technology. Giovanna Ruiz, clinical specialist for LATAM at MATACHANA, was responsible for delivering these presentations.

The industry supported the event with a first-class trade exhibition, facilitating the exchange between technology and clinical practice. In our case, MATACHANA, together with its local distributor INTERNATIONAL CLINICS, presented a large part of its portfolio of solutions for effective, efficient and sustainable reprocessing.

The congress reached its most emotional moment as it coincided with the International Day of Sterilization Sciences. Being part of such a powerful educational event on 10 April was an energising experience, once again highlighting the value of human talent as the driving force behind success in every process.

We congratulate the participants for their massive turnout and commitment to continuous professional development. We also congratulate SPECH for leading these initiatives that promote excellence and the exchange of knowledge in the region.

The journey of training never stops; we will continue to meet in academic settings and are already preparing to celebrate the Panamericano Congress in Costa Rica in 2027.

At MIEC, we remain firmly committed to continuing to Transform-with-CONCIENCE and Transforming RUMED for a sustainable future.

 
REFERENCE POST

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