When and Why Do You Need Endotoxin Testing?
Endotoxins, which are strong pyrogens, are a component of the outer membrane of gram-negative bacteria. They are shed by gram-negative bacteria primarily during cell lysis and are widespread in the environment. In addition, endotoxins are highly resistant to heat and desiccation, allowing them to remain stable for prolonged periods of time.
If they enter the human bloodstream, endotoxins can lead to severe consequences, including inflammation, fever, and organ failure. Considering the dangers associated with endotoxin exposure, endotoxin testing plays a key role for ensuring the safety of medicines administered via injection and the raw materials used in their manufacturing. However, endotoxin testing has also found applications in various other fields. The most widely established method for endotoxin testing is the Limulus amebocyte lysate (LAL) assay, which is characterized by high sensitivity and specificity. The LAL reagent is extracted from amebocytes of the horseshoe crab (Limulus polyphemus). If the LAL reagent encounters endotoxin, an enzymatic cascade is initiated leading to a measurable change in viscosity, turbidity or colour depending on the assay format [1]. In addition, recombinant assays for endotoxin testing (including recombinant cascade and recombinant Factor C reagents) and tests for the detection of both endotoxin and non-endotoxin pyrogens have been developed, e.g., the monocyte activation test (MAT).
Some of the fields in which endotoxin testing has found broadest applications include [2]:
Injectable pharmaceutical products – The endotoxin testing of injectable pharmaceutical drugs, vaccines, gene and cell therapies, and the raw materials used for their manufacturing plays a critical role in ensuring patient safety. In these cases, endotoxin testing should comply with strict regulatory requirements and pharmacopeial guidelines.
Medical devices that interact with the human bloodstream or tissues, such as surgical instruments, implants, and dialysis products as well as the raw materials used for their production, should also undergo strict endotoxin testing in compliance with regulatory and pharmacopeial guidelines to ensure patient safety. Patients undergoing dialysis may be immunosuppressed and thus particularly vulnerable to endotoxin effects, further emphasising the importance of endotoxin testing.
Water monitoring – Endotoxin testing can help to assess the purity of water used not only for the manufacturing of pharmaceutical drugs and medical devices, but also for various other applications, including as a drinking supply. In contrast to time-consuming, culture-based methods for detecting microbial contamination, endotoxin testing provides rapid information for contamination with endotoxin, and indirectly, gram-negative bacteria [3].
Laboratory reagents – Maintaining reagents used for the manufacturing of pharmaceutical drugs and medical devices endotoxin-free is key to ensuring patient safety. In addition, an endotoxin-free environment is very important for cell based-experiments, as endotoxins can negatively impact cell cultures. Endotoxin contamination can lead to unreliable experimental results, especially when investigating cell signaling and inflammatory and immune responses, emphasising the importance of endotoxin-free lab reagents.
Saliva swabs – Gram-negative bacteria have been implicated in the development and progression of gingivitis and periodontitis and release endotoxin, which promotes gum inflammation. The released endotoxin can indirectly (via inflammatory mediators) or directly contribute to systemic diseases, including cardiovascular disease and diabetes mellitus [4]. Therefore, endotoxin testing of saliva swabs can help gain important insights into oral health.
References
Skalski H (2021). Endotoxin testing - why and how the industry seeks improvements. American Pharmaceutical Review. https://www.americanpharmaceuticalreview.com/Featured-Articles/581814-Endotoxin-Testing-Why-and-How-the-Industry-Seeks-Improvements/#:~:text=The%20industry%20seeks%20to%20improve,patients%20more%20efficiently%20and%20safely.
Tamura H, Reich J and Nagaoka I (2021). Outstanding contributions of LAL technology to pharmaceutical and medical science: review of methods, progress, challenges, and future perspectives in early detection and management of bacterial infections and invasive fungal diseases. Biomedicines, 9(5): 536.
Sattar AA, Good CR, Saletes M, Brandão J and Jackson SK (2022). Endotoxin as a Marker for Water Quality. International Journal of Environmental Research and Public Health, 19(24): 16528.
Zenobia C and Darveau RP (2022). Does oral endotoxin contribute to systemic inflammation? Frontiers in Oral Health, 3: 911420.