Detection of Brevetoxin in Human Plasma by ELISA.

Florida red tides have become more common and persistent in and around the Gulf of Mexico. When in bloom, red tides can produce brevetoxins in high concentrations, leading to human exposures primarily through contaminated food and ocean spray. The research described here includes adapting and validating a commercial brevetoxin water test kit for human plasma testing. Pooled plasma was fortified with a model brevetoxin, brevetoxin 3, at concentrations from 0.00500 to 3.00 ng/mL to generate calibration curves and quality control samples. The quantitative detection range was determined to be 0.0400-2.00 ng/mL brevetoxin 3 equivalents with inter- and intraday accuracies ranging from 94.0% to 109% and relative standard deviations <20%, which is within the US Food and Drug Administration guidelines for receptor-binding assays. Additionally, cross-reactivity was tested using 4 of the 10 known brevetoxins and 12 paralytic shellfish toxins. The cross-reactivity varied from 0.173% to 144% for the commercially available brevetoxin standards and 0% for the commercially available paralytic shellfish toxin standards. Fifty individual unexposed human plasma samples were measured to determine the limit of detection and endogenous interferences to the test. The validated method was used to test 31 plasma samples collected from humans potentially exposed to brevetoxins, detecting 11 positives. This method has been proven useful to measure human exposure to brevetoxins and can be applied to future exposure events.

A cluster of tetrodotoxin poisoning in Oman.

INTRODUCTION: Tetrodotoxin (TTX) is a potent sodium channel blocker, with significant neurotoxicity, found in marine animals like pufferfish and blue-ringed octopus. The severity of toxicity depends on the amount of toxin ingested and the outcome depends on the time-lapse to appropriate medical care. CASES REPORT: We report five patients who presented with tetrodotoxin poisoning after consuming fried internal organs of local pufferfish from the coast of Oman. The patients' clinical manifestations were consistent with the expected TTX toxidrome of perioral and generalized paresthesia, weakness of upper and lower extremities, gastrointestinal manifestations, dyspnea, dysarthria, ascending paralysis, hypotension, bradycardia and coma. The severity varied among the patients who recovered completely except one patient who developed a subarachnoid hemorrhage without underlying aneurysms on computed tomography-angiogram. This complication was potentially related to TTX poisoning and has not been previously reported. In addition to standard supportive management, patients with severe illness should potentially receive the intravenous acetylcholinesterase inhibitor neostigmine, and intermittent dialysis. Urine specimens were sent to CDC in Atlanta, where they were analyzed using online solid phase extraction (SPE) with LC-MS/MS and confirmed the diagnosis in all five cases. DISCUSSION: In general, the patients' clinical manifestations were consistent with the expected TTX toxidrome except patient 3 who developed a subarachnoid hemorrhage early during his clinical course. Two patients received neostigmine and underwent dialysis with complete recovery.

Investigation of dried blood sampling with liquid chromatography tandem mass spectrometry to confirm human exposure to nerve agents.

A method was developed to detect and quantify organophosphate nerve agent (OPNA) metabolites in dried blood samples. Dried blood spots (DBS) and microsampling devices are alternatives to traditional blood draws, allowing for safe handling, extended stability, reduced shipping costs, and potential self-sampling. DBS and microsamplers were evaluated for precision, accuracy, sensitivity, matrix effects, and extraction recovery following collection of whole blood containing five OPNA metabolites. The metabolites of VX, Sarin (GB), Soman (GD), Cyclosarin (GF), and Russian VX (VR) were quantitated from 5.0 to 500 ng mL-1 with precision of ≤16% and accuracy between 93 and 108% for QC samples with controlled volumes. For unknown spot volumes, OPNA metabolite concentrations were normalized to total blood protein to improve interpretation of nerve agent exposures. This study provides data to support the use of DBS and microsamplers to collect critical exposure samples quickly, safely, and efficiently following large-scale chemical exposure events.

Quantitation of saxitoxin in human urine using immunocapture extraction and LC-MS.

AIM: An immunomagnetic capture protocol for use with LC-MS was developed for the quantitation of saxitoxin (STX) in human urine. MATERIALS & METHODS: This method uses monoclonal antibodies coupled to magnetic beads. STX was certified reference material grade from National Research Council, Canada. Analysis was carried out using LC-MS. RESULTS: With an extraction efficiency of 80%, accuracy and precision of 93.0-100.2% and 5.3-12.6%, respectively, and a dynamic range of 1.00-100 ng/ml, the method is well suited to quantify STX exposures based on previously reported cases. CONCLUSION: Compared with our previously published protocols, this method has improved selectivity, a fivefold increase in sensitivity and uses only a third of the sample volume. This method can diagnose future toxin exposures and may complement the shellfish monitoring programs worldwide.

Bridging the Gap between Sample Collection and Laboratory Analysis: Using Dried Blood Spots to Identify Human Exposure to Chemical Agents.

Public health response to large scale chemical emergencies presents logistical challenges for sample collection, transport, and analysis. Diagnostic methods used to identify and determine exposure to chemical warfare agents, toxins, and poisons traditionally involve blood collection by phlebotomists, cold transport of biomedical samples, and costly sample preparation techniques. Use of dried blood spots, which consist of dried blood on an FDA-approved substrate, can increase analyte stability, decrease infection hazard for those handling samples, greatly reduce the cost of shipping/storing samples by removing the need for refrigeration and cold chain transportation, and be self-prepared by potentially exposed individuals using a simple finger prick and blood spot compatible paper. Our laboratory has developed clinical assays to detect human exposures to nerve agents through the analysis of specific protein adducts and metabolites, for which a simple extraction from a dried blood spot is sufficient for removing matrix interferents and attaining sensitivities on par with traditional sampling methods. The use of dried blood spots can bridge the gap between the laboratory and the field allowing for large scale sample collection with minimal impact on hospital resources while maintaining sensitivity, specificity, traceability, and quality requirements for both clinical and forensic applications.

Detection of human exposure to saxitoxin and neosaxitoxin in urine by online-solid phase extraction-liquid chromatography-tandem mass spectrometry.

Saxitoxin (STX) and neosaxitoxin (NEO) are potent neurotoxins that cause paralytic shellfish poisoning (PSP). PSP typically occurs through the ingestion of bivalve shellfish that have consumed toxin producing dinoflagellates. Due to initial presentation of symptoms being nonspecific, a clinical measurement is needed to confirm exposure to these toxins. Our group has developed an online solid phase extraction hydrophilic interaction liquid chromatography (HILIC) method for the analysis of STX and NEO in human urine with tandem mass spectrometry. A unique feature of this online method is the incorporation of a new synthetic (15)N4-STX labeled internal standard used for quantitation. Manual sample preparation time was reduced by approximately 70% for 98 urine samples as compared to a previously reported method. The lowest reportable limit for STX was improved from 5.0 ng/mL to 1.01 ng/mL and from 10.0 ng/mL to 2.62 ng/mL for NEO. Three analysts validated the method with 20 calibration curves total over 30 days with precision and accuracy within ±15% for all QCs. This new online method rapidly identifies STX and NEO exposure with improved sensitivity, which can facilitate the work of public health authorities to confirm the cases of PSP, complementing the many shellfish monitoring programs worldwide.

Quantitation of five organophosphorus nerve agent metabolites in serum using hydrophilic interaction liquid chromatography and tandem mass spectrometry.

Although nerve agent use is prohibited, concerns remain for human exposure to nerve agents during decommissioning, research, and warfare. Exposure can be detected through the analysis of hydrolysis products in urine as well as blood. An analytical method to detect exposure to five nerve agents, including VX, VR (Russian VX), GB (sarin), GD (soman), and GF (cyclosarin), through the analysis of the hydrolysis products, which are the primary metabolites, in serum has been developed and characterized. This method uses solid-phase extraction coupled with high-performance liquid chromatography for separation and isotopic dilution tandem mass spectrometry for detection. An uncommon buffer of ammonium fluoride was used to enhance ionization and improve sensitivity when coupled with hydrophilic interaction liquid chromatography resulting in detection limits from 0.3 to 0.5 ng/mL. The assessment of two quality control samples demonstrated high accuracy (101-105%) and high precision (5-8%) for the detection of these five nerve agent hydrolysis products in serum.