Endotoxin is the lipopolysaccharide (LPS) associated with the cell membrane of Gram-negative bacteria and is released into the environment from bacterial growth and when bacteria are disrupted or lysed. High levels of endotoxin in the environment, food or water correspond with high levels of human or animal gut-derived (enteric) bacteria which can lead to serious illness. Research by MolEndoTech has shown that endotoxin is a convenient and reliable marker for faecal contamination in bathing water (Figure 1). We have developed and tested an endotoxin assay (Siren BW) which is accurate, simple, fast and can be performed in real time in-situ.
The quality of bathing water in the UK and Europe is governed by the European Bathing Water Directive, which sets legislation and defines standards that all beaches and bathing waters must comply with in order to be considered as a designated bathing water. The presence of faecal contamination is an indicator that a potential health risk exists for individuals exposed to this water. Faecal Indicator Bacteria (FIB), (Escherichia coli (E. coli) and enterococci) are types of bacteria used to detect and estimate the level of faecal contamination of water. FIB are currently determined by microbial analysis of water by taking samples and sending them to a microbiology laboratory for culture. However, such current quantitative culture-based FIB methods have drawbacks as results are retrospective, taking at least 24-48 hours to inform regulatory bodies, require microbiology laboratory facilities and trained technical staff with associated costs. Regulators and authorities require an efficient, rapid, point-of-use test to determine marine bathing water quality. This will allow them to make more informed decisions about the use of bathing beaches and the ability for multiple testing will allow for source tracking of pollution to be determined. Moreover, marine recreational water users need an instant, qualitative indication of possible bacterial pollution events in order to make an informed decision on whether to undertake an activity.
Research by MolEndoTech has shown that endotoxin is a convenient and reliable marker for faecal contamination in bathing water. We have developed a modified Limulus amebocyte lysate (LAL)-based assay (Siren BW) as a novel screening technology that is fast (<1 hour), simple to use and economical. The assay can semi-quantitatively test for faecal contamination using endotoxin (lipopolysaccharide (LPS)) as a biomarker detected by means of an optimised chromogenic assay. In our simplified assay water samples are diluted and incubated with appropriate enzyme and substrate to which colour reagents are added, leading to a colour change proportional to the concentration of LPS. This colour change can be conveniently measured and quantified using a portable spectrophotometer. (Figure 2).
The kit for the rapid detection of faecal contamination of bathing water (Siren BW) is produced and distributed by Palintest Ltd. Click here to visit Siren BW Website.
Figure 1. correlation of LPS with traditional culture-based detection of the faecal indicator bacteria E.coli and Enterococci.
Figure 2. Application of Siren BW assay to measure faecal contamination in three test samples of bathing water.