DEtecting paralytic shellfish toxins in oysters - initial assessment of aquabc rapid test kit
BUDGET EXPENDITURE: $29,845
PRINCIPLE INVESTIGATOR: Andreas Seger
ORGANISATION: IMAS - UTAS
PROJECT CODE: 2023-103
PROJECT STATUS: Completed
WHY WAS THE RESEARCH UNDERTAKEN?
Reliable detection of marine biotoxins is a critical requirement for any effective biotoxin monitoring program, requiring any analytical technique to be properly validated. The Neogen rapid test kit for the detection of paralytic shellfish toxin (PSTs) was successfully validated in both single lab and inter-lab validations for use in oysters, offering rapid (within 20 min) on farm results. The test was used in Tasmania to reduce business risk, (i.e. frequent testing of shellfish that can rapidly accumulate PST within a week) and employed in South Australia for regulatory purposes (low frequency of PST detection in this region).
A key factor influencing the suitability of antibody based rapid test kits is the PST profile present in the sample to be analysed. The term PST profile describes the relative concentrations of different PST analogues that might be present in each seafood sample. These profiles differ between toxic algal species, different seafood species and their tissues. Not all PST analogues are equally detected by the antibodies of different test kits (quantified as the % cross-reactivity). These cross-reactivities are critical for ensuring reliable detection across different combinations of PST analogues that might be present in shellfish.
To determine if the AquaBC rapid test kit is suitable replacement for routine monitoring, a full validation for each seafood tissue matrix would normally be conducted to determine the probability of detection curve (probability of detection across a range of PST concentrations) for multiple PST profiles, ideally followed by an inter-laboratory validation (as was conducted for the Neogen test). However, a full validation study requires repeat testing of hundreds of samples and is therefore expensive. From our previous work with the Neogen test kit, we have identified some key performance indicators that would allow for a quick initial assessment of the new AquaBC test kit, using much reduced sample numbers. These small pilot trials would include testing the most commonly encountered PST profiles (i.e. which PST toxin analogues are present) and their relative concentrations (i.e. can we reliably detect the presence of PST at the regulatory level without obtaining too many positive results at PST levels below concern?). Rather than conducting a full validation, this project provided an initial assessment of these parameters in regard to the PST profiles commonly encountered in TAS, SA and NSW.
OBJECTIVES:
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Review & identify different PST profiles that may be encountered in TAS, SA and NSW oysters.
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Challenge the AquaBC test kit against a range of different PST concentrations and profiles to provide an initial assessment of its suitability for detecting PST in Australian oyster tissues.
FINDINGS
The project ended up trialling two rapid test kits for rapid detection of PST's in oysters (AquaBC and SensoReal).
The trials showed that both the AquaBC and SensoReal test kit require additional work before they can meet five performance criteria:
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Provide fast sample turnaround (prep & analysis time) and be simple enough to be used on farm.
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Provide very low, or no false detections of PST.
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Yield a positive result for all samples above the bivalve regulatory level across all toxin profiles.
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Have a high probability of detection at PST levels at half the regulatory level.
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Have a low probability of detection at low PST level.
The AquaBC test kit met the first four criteria, but proved overly senstiive at low PST levels. Vise versa, the SensoReal test kit provied not sensitive enough and requires further method development before being suitable for use for all Australian toxin profiles.
As the project was ending, two alterantive testing approaches were identified as promising alterantives (Attogene and Toranelli Moana). The Attogene kit is of particular interest as it's already commercially available and showing promising results in New Zealand.
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