Ultrafiltration improves ELISA and Endopep MS analysis of botulinum neurotoxin type A in drinking water

• Published in: Journal of microbiological methods 2012-09, Vol.90 (3), p.267-272
• Main Authors: Raphael, Brian H., Lautenschlager, Matthew, Kahler, Amy, Pai, Suresh, Parks, Bryan A., Kalb, Suzanne R., Maslanka, Susan E., Shah, Sanjiv, Magnuson, Matthew, Hill, Vincent R.
• Format: Article
• Language: English
• Subjects: analytical methods; Animals; Biological and medical sciences; botulinum toxin; Botulinum Toxins, Type A - analysis; Botulinum Toxins, Type A - chemistry; Botulism; Calibration; Detection; detection limit; Drinking Water - analysis; ELISA; Enzyme Assays; Enzyme Stability; enzyme-linked immunosorbent assay; Enzyme-Linked Immunosorbent Assay - standards; Fundamental and applied biological sciences. Psychology; Limit of Detection; Linear Models; Mass Spectrometry; Mice; Mice, Inbred ICR; Microbiology; monitoring; Reference Standards; tap water; Toxin; Ultrafiltration; Water Microbiology; Water quality
• ISSN: 0167-7012; 1872-8359; 1872-8359
• DOI: 10.1016/j.mimet.2012.05.020

The objective of this study was to adapt and evaluate two in vitro botulinum neurotoxin (BoNT) detection methods, including the Botulinum Toxin ELISA and the Endopep MS (a mass spectrometric-based endopeptidase method), for use with drinking water samples. The method detection limits (MDL) of the ELISA and Endopep MS were 260pg/mL and 21pg/mL of BoNT/A complex toxin, respectively. Since toxin could be present in water samples at highly dilute concentrations, large volume (100-L) samples of municipal tap water from five US municipalities having distinct water compositions were dechlorinated, spiked with 5μg BoNT/A, and subjected to tangential-flow ultrafiltration (UF) using hollow fiber dialyzers. The recovery efficiency of BoNT/A using UF and quantified by ELISA ranged from 11% to 36% while efficiencies quantified by MS ranged from 26% to 55%. BoNT/A was shown to be stable in dechlorinated municipal tap water stored at 4°C for up to four weeks. In addition, toxin present in UF-concentrated water samples was also shown to be stable at 4°C for up to four weeks, allowing holding of samples prior to analysis. Finally, UF was used to concentrate a level of toxin (7pg/mL) which is below the MDL for direct analysis by both ELISA and Endopep MS. Following UF, toxin was detectable in these samples using both in vitro analysis methods. These data demonstrate that UF-concentration of toxin from large volume water samples followed by use of existing analytical methods for detection of BoNT/A can be used in support of a monitoring program for contaminants in drinking water. ► ELISA and MS methods were adapted for quantification of botulinum toxin type A in water. ► Toxin in highly dilute water samples was concentrated using ultrafiltration. ► Recovered toxin was stable up to 4weeks at 4°C. ► Various water quality parameters are correlated with toxin recovery.