Ciguatoxin in Hawai'i: Fisheries forecasting using geospatial and environmental analyses for the invasive Cephalopholis argus (Epinephelidae).

Invasive species can precede far-reaching environmental and economic consequences. In the Hawai'ian Archipelago Cephalopholis argus (family Serranidae) is an established invasive species, now recognized as the dominant local reef predator, negatively impacting the native ecosystem and local fishery. In this region, no official C. argus fishery exists, due to its association with Ciguatera seafood poisoning (CP); a severe intoxication in humans occurring after eating (primarily) fish contaminated with ciguatoxins (CTXs). Pre-harvest prediction of CP is currently not possible; partly due to the ubiquitous nature of the microalgae producing CTXs and the diverse bioaccumulation pathways of the toxins. This study investigated the perceived risk of CP in two geographically discrete regions (Leeward and Windward) around the main island of Hawai'i, guided by local fishers. C. argus was collected and investigated for CTXs using the U.S. Food and Drug Administration (FDA) CTX testing protocol (in vitro neuroblastoma N2a-assay and LC-MS/MS). Overall, 76% of fish (87/113) exceeded the FDA guidance value for CTX1B (0.01 ng g-1 tissue equivalents); determined by the N2a-assay. Maximum CTX levels were ≅2× higher at the Leeward vs Windward location and, respectively, 95% (64/67) and 54% (25/46) of fish were positive for CTX-like activity. Fisher persons and environmental understandings, regarding the existence of a geographic predictor (Leeward vs Windward) for harvest, were found to be (mostly) accurate as CTXs were detected in both locations and the local designation of C. argus as a risk for CP was confirmed. This study provides additional evidence that supports the previous conclusions that this species is a severe CP risk in the coastal food web of Hawai'i, and that ocean exposure (wave power) may be a prominent factor influencing the CTX content in fish within a hyperendemic region for CP.

Analysis of Chloramphenicol and Two Metabolites in Crab and Shrimp Following Waterborne Exposure.

The use of chloramphenicol (CAP) in aquaculture products is banned in many countries, including the United States, due to human health issues. Very few depletion and metabolism studies of CAP in seafood have been performed. Current detection methods for CAP residues in food are directed toward the parent drug molecule, but rapid elimination following treatment suggests the need for an alternative marker residue. We identified, characterized, and determined the persistence of two CAP metabolites, CAP-base (CAP-B) and CAP-alcohol (CAP-OH), in crab and shrimp. Interday recoveries of CAP, CAP-B, and CAP-OH in muscle fortified ( n = 9) at levels of 0.15 to 0.60 ng/g ranged from 95 to 127% and 101 to 119% for crab and shrimp, respectively, with repeatability ranging from 4 to 19%. The limit of detection for CAP and metabolites in crab and shrimp ranged from 0.05 to 0.11 ng/g. We also monitored the depletion of CAP, CAP-B, and CAP-OH in crab following waterborne exposures. To our knowledge, we present the first CAP depletion and metabolite study following waterborne exposure in crabs, with the aim of identifying alternative marker residues.

Performance Assessment and Comparability of a Commercial Enzyme-Linked Immunosorbent Assay Kit with Liquid Chromatography-Tandem Mass Spectrometry for Chloramphenicol Residues in Crab and Shrimp.

Monitoring for chloramphenicol (CAP) in aquaculture products is primarily performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), which requires expensive equipment and specialized training. Many laboratories prefer to screen samples with facile and high-throughput enzyme-linked immunosorbent assay (ELISA) kits for CAP residues before submitting samples for LC-MS/MS quantification and confirmation. We evaluated the performance of a Ridascreen (R-Biopharm) ELISA kit for CAP in spiked and incurred crab and shrimp muscle at levels bracketing the minimum required performance level for analysis (0.3 ng/g). The Ridascreen ELISA kit incorporates antibody directed against CAP. Incurred CAP levels in crab and shrimp muscle were verified using LC-MS/MS. We found good repeatability (relative standard deviation) of the ELISA in spiked and incurred crab and shrimp muscle samples, with values ranging from 6.8 to 21.7%. Recoveries of CAP from tissues spiked at 0.15 to 0.60 ng/g ranged from 102 to 107%. Minimal cross-reactivity with blank crab and shrimp muscle matrix components was observed. ELISA data were highly correlated with those of LC-MS/MS for CAP in incurred muscle tissue. We believe this study to be the first evaluation of the performance and comparability of a CAP ELISA kit and LC-MS/MS for determination of CAP residues, as well as their elimination, in crab muscle. Our findings support the use of this ELISA kit for screening purposes and, when used in conjunction with validated instrumental methods, for regulatory monitoring of CAP in these species.

Screening for petrochemical contamination in seafood by headspace solid-phase microextraction gas chromatography-mass spectrometry.

A headspace solid-phase microextraction gas chromatography-mass spectrometry (SPME GC-MS) method is described, to screen seafood for volatile organic compounds (VOCs) associated with petrochemical taint. VOCs are extracted from the headspace of heated sample homogenates by adsorption onto a SPME fiber and desorbed for analysis by GC-MS. Targeted compounds are determined semi-quantitatively using representative calibration standards for the various classes (alkanes, alkylbenzenes, indanes/tetralins, and naphthalenes) of VOCs analyzed. Sample preparation is minimal, and the analyses are rapid and automated with a capacity of 50 samples per day. The method was optimized in terms of headspace temperature, sample heating time, extraction time, and desorption time using oyster samples fortified with target compounds. Calibrations for hydrocarbon components were linear in the range of 8.3-167 ng/g; the limit of detection ranged between 0.05 and 0.21 ng/g, and the limit of quantitation between 0.16 and 0.69 ng/g. Good precision (RSD < 10 % at 16.7 ng/g for individual VOCs) and accuracy (recovery range 89-118 % at 25 ng/g) were obtained in oyster, crab, shrimp, and finfish matrices. The trueness of the method was demonstrated by quantifying VOCs at 1-2-ppb levels in oyster fortified with certified reference material NIST SRM 1491a. Following single laboratory validation, the method was employed for the determination of VOCs in seafood exposed to oil contaminated seawater and for the determination of background VOC levels in seafood species from the Gulf of Mexico and local food stores. The method as described can be used to supplement human sensory testing for petrochemical taint in seafood.

Biomarkers of brevetoxin exposure and composite toxin levels in hard clam (Mercenaria sp.) exposed to Karenia brevis blooms.

Brevetoxins in clams (Mercenaria sp.) exposed to recurring blooms of Karenia brevis in Sarasota Bay, FL, were studied over a three-year period. Brevetoxin profiles in toxic clams were generated by ELISA and LC-MS. Several brevetoxin metabolites, as identified by LC-MS, were major contributors to the composite brevetoxin response of ELISA. These were S-desoxyBTX-B2 (m/z 1018), BTX-B2 (m/z 1034), BTX-B5 (m/z 911), open A-ring BTX-B5 (m/z 929), and BTX-B1 (m/z 1018). Summed values of these metabolites were highly correlated (R(2) = 0.9) with composite B-type brevetoxin measurements by ELISA. S-desoxyBTX-B2, BTX-B2, and BTX-B1 were the most persistent and detectable in shellfish for several months after dissipation of blooms. These metabolites were selected as LC-MS biomarkers of brevetoxin exposure and reflective of composite B-type brevetoxins in hard clam. ELISA and LC-MS values were moderately correlated with toxicity of the shellfish by mouse bioassay. ELISA and LC-MS methods offer rapid screening and confirmatory determination of brevetoxins, respectively, as well as toxicity assessment in clams exposed to K. brevis blooms.

Performance evaluation of commercial ELISA kits for screening of furazolidone and furaltadone residues in fish.

Regulatory monitoring for nitrofuran drug residues in aquaculture products has largely focused on LC-MS/MS. In addition, there is a need for facile and high-throughput screening methods for monitoring programs. We evaluated the performance of Ridascreen (R-Biopharm) ELISA kits for nitrofuran drug residues in fish muscle, with verification by LC-MS/MS. Kits were available for 3-amino-2-oxazolidinone (AOZ) and 3-amino-5-morpholino-methyl-2-oxazolidinone (AMOZ) side-chains of furazolidone and furaltadone, respectively. We found good repeatability in fortified and incurred muscle samples, with RSDs ranging from 1.8% to 7.6%. Recoveries of AOZ and AMOZ from muscle fortified at levels of 0.5-2 ng/g ranged from 98% to 114%. Excellent selectivity was demonstrated. The minimum detection limits (MDLs) for AOZ and AMOZ in muscle were 0.05 and 0.2 ng/g, respectively. ELISA data were highly correlated with those of LC-MS/MS. Results of this study support the use of these kits as screening assays for nitrofuran residues in fish muscle.

Invasive lionfish (Pterois volitans): a potential human health threat for ciguatera fish poisoning in tropical waters.

Invasive Indo-Pacific lionfish (Pterois volitans) have rapidly expanded in the Western Atlantic over the past decade and have had a significant negative impact on reef fish biodiversity, habitat, and community structure, with lionfish out-competing native predators for resources. In an effort to reduce this population explosion, lionfish have been promoted for human consumption in the greater Caribbean region. This study examined whether the geographical expansion of the lionfish into a known ciguatera-endemic region can pose a human health threat for ciguatera fish poisoning (CFP). More than 180 lionfish were collected from waters surrounding the US Virgin Islands throughout 2010 and 2011. Ciguatoxin testing included an in vitro neuroblastoma cytotoxicity assay for composite toxicity assessment of sodium-channel toxins combined with confirmatory liquid chromatography tandem mass spectrometry. A 12% prevalence rate of ciguatoxic lionfish exceeding the FDA guidance level of 0.1 µg/kg C-CTX-1 equivalents was identified in fish from the U.S. Virgin Islands, highlighting a potential consumption risk in this region. This study presents the first evidence that the invasive lionfish, pose a direct human health risk for CFP and highlights the need for awareness and research on this food safety hazard in known endemic areas.

Ciguatera fish poisoning on the West Africa Coast: An emerging risk in the Canary Islands (Spain).

Ciguatera fish poisoning (CFP) is endemic in certain tropical and subtropical regions of the world. CFP had not been described on the West Africa Coast until a 2004 outbreak in the Canary Islands. In 2008-2009, two additional outbreaks of ciguatera occurred. Individuals afflicted had consumed lesser amberjack (Seriola rivoliana) captured from nearby waters. Caribbean ciguatoxin-1 (C-CTX-1) was confirmed in fish samples by LC-MS/MS. Ciguatoxic fish in this region may pose a new health risk for the seafood consumer.

Cyano metabolite as a biomarker of nitrofurazone in channel catfish.

The use of nitrofuran drugs in food-producing animals continues to attract international concern as a food safety issue. Methods for monitoring nitrofuran residues have been directed to the intact side chain of tissue-bound metabolites. Semicarbazide, the side chain of nitrofurazone (NFZ), can enter food products from non-NFZ sources, suggesting the need for an alternative biomarker for confirmatory purposes. We characterized a cyano derivative as a major metabolite of NFZ in channel catfish (Ictalurus punctatus). The depletion of cyano metabolite was examined in the muscle of channel catfish after oral dosing (10 mg of NFZ/kg of body weight). Parent NFZ was rapidly eliminated in muscle, with a half-life of 6.3 h. The cyano metabolite was detected for up to 2 weeks, with an elimination half-life of 81 h. The cyano metabolite represents an alternative biomarker for confirming the use of NFZ in channel catfish.

Monitoring of brevetoxins in the Karenia brevis bloom-exposed Eastern oyster (Crassostrea virginica).

Brevetoxin uptake and elimination were examined in Eastern oyster (Crassostrea virginica) exposed to recurring blooms of the marine alga Karenia brevis in Sarasota Bay, FL, over a three-year period. Brevetoxins were monitored by in vitro assays (ELISA, cytotoxicity assay, and receptor binding assay) and LC-MS, with in vivo toxicity of shellfish extracts assessed by the traditional mouse bioassay. Measurements by all methods reflected well the progression and magnitude of the blooms. Highest levels recorded by mouse bioassay at bloom peak were 157 MU/100g. Oysters were toxic by mouse bioassay at levels >or=20 MU/100g for up to two weeks after bloom dissipation, whereas brevetoxins were measurable by in vitro assays and LC-MS for several months afterwards. For the structure-based methods, summed values for the principal brevetoxin metabolites of PbTx-2 (cysteine and cysteine sulfoxide conjugates), as determined by LC-MS, were highly correlated (r(2)=0.90) with composite toxin measurements by ELISA. ELISA and LC-MS values also correlated well (r(2)=0.74 and 0.73, respectively) with those of mouse bioassay. Pharmacology-based cytotoxicity and receptor binding assays did not correlate as well (r(2)=0.65), and were weakly correlated with mouse bioassay (r(2)=0.48 and 0.50, respectively). ELISA and LC-MS methods offer rapid screening and confirmation, respectively, of brevetoxin contamination in the oyster, and are excellent alternatives to mouse bioassay for assessing oyster toxicity following K. brevis blooms.

Biomarkers of neurotoxic shellfish poisoning.

Urine specimens from patients diagnosed with neurotoxic shellfish poisoning (NSP) were examined for biomarkers of brevetoxin intoxication. Brevetoxins were concentrated from urine by using solid-phase extraction (SPE), and analyzed by enzyme-linked immunosorbent assay (ELISA) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Urine extracts were fractionated by LC, and fractions analyzed for brevetoxins by ELISA. In subsequent LC-MS/MS analyses, several brevetoxin metabolites of B-type backbone were identified, with elution profiles consistent with those of ELISA. The more abundant brevetoxin metabolites in urine were characterized structurally by LC-MS/MS. With the exception of BTX-3, brevetoxin metabolites in urine differed from those found in shellfish and in shellfish meal remnants. Proposed structures of these major urinary metabolites are methylsulfoxy BTX-3, 27-epoxy BTX-3, and reduced BTX-B5. BTX-3 was found in all specimens examined. BTX-3 concentrations in urine, as determined by LC-MS/MS, correlated well with composite toxin measurements by ELISA (r(2)=0.96). BTX-3 is a useful biomarker for confirmation of clinical diagnosis of NSP.

Saxitoxin puffer fish poisoning in the United States, with the first report of Pyrodinium bahamense as the putative toxin source.

BACKGROUND: From January 2002 to May 2004, 28 puffer fish poisoning (PFP) cases in Florida, New Jersey, Virginia, and New York were linked to the Indian River Lagoon (IRL) in Florida. Saxitoxins (STXs) of unknown source were first identified in fillet remnants from a New Jersey PFP case in 2002. METHODS: We used the standard mouse bioassay (MBA), receptor binding assay (RBA), mouse neuroblastoma cytotoxicity assay (MNCA), Ridascreen ELISA, MIST Alert assay, HPLC, and liquid chromatography-mass spectrometry (LC-MS) to determine the presence of STX, decarbamoyl STX (dc-STX), and N-sulfocarbamoyl (B1) toxin in puffer fish tissues, clonal cultures, and natural bloom samples of Pyrodinium bahamense from the IRL. RESULTS: We found STXs in 516 IRL southern (Sphoeroides nephelus), checkered (Sphoeroides testudineus), and bandtail (Sphoeroides spengleri) puffer fish. During 36 months of monitoring, we detected STXs in skin, muscle, and viscera, with concentrations up to 22,104 microg STX equivalents (eq)/100 g tissue (action level, 80 microg STX eq/100 g tissue) in ovaries. Puffer fish tissues, clonal cultures, and natural bloom samples of P. bahamense from the IRL tested toxic in the MBA, RBA, MNCA, Ridascreen ELISA, and MIST Alert assay and positive for STX, dc-STX, and B1 toxin by HPLC and LC-MS. Skin mucus of IRL southern puffer fish captive for 1-year was highly toxic compared to Florida Gulf coast puffer fish. Therefore, we confirm puffer fish to be a hazardous reservoir of STXs in Florida's marine waters and implicate the dinoflagellate P. bahamense as the putative toxin source. CONCLUSIONS: Associated with fatal paralytic shellfish poisoning (PSP) in the Pacific but not known to be toxic in the western Atlantic, P. bahamense is an emerging public health threat. We propose characterizing this food poisoning syndrome as saxitoxin puffer fish poisoning (SPFP) to distinguish it from PFP, which is traditionally associated with tetrodotoxin, and from PSP caused by STXs in shellfish.

Characterization of polar brevetoxin derivatives isolated from Karenia brevis cultures and natural blooms.

Several novel brevetoxin derivatives were isolated and identified in Karenia brevis cultures and natural blooms by using solid phase extraction (SPE) and LC/MS(MS) techniques. These analogs were more polar compared with previously described brevetoxins, and were poorly extractable by conventional non-polar solvent (chloroform) partitioning. Brevetoxin analogs were structurally confirmed as hydrolyzed (open A-ring) forms of brevetoxins PbTx-1, PbTx-7, PbTx-2, and PbTx-3, and of oxidized PbTx-1 and PbTx-2. Some of these open A-ring derivatives were in greater abundance than their non-hydrolyzed counterparts. All were in much greater abundance in bloom water filtrate compared with cell-rich fractions. Open A-ring compounds were cytotoxic in mouse neuroblastoma (N2a) cell assay. In the K. brevis bloom-exposed Eastern oyster, brevetoxin metabolites with opened A rings were identified (e.g., open-ring cysteine-PbTx conjugates), contributing to their overall toxin burden.

Brevetoxin metabolism and elimination in the Eastern oyster (Crassostrea virginica) after controlled exposures to Karenia brevis.

The metabolism and elimination of brevetoxins were examined in the Eastern oyster (Crassostrea virginica) following controlled exposures to Karenia brevis cultures in the laboratory. After a 2-day exposure period ( approximately 62 million cells/oyster), elimination of brevetoxins and their metabolites was monitored by using liquid chromatography/mass spectrometry (LC/MS). Composite toxin in oyster extracts was measured by in vitro assay (i.e. cytotoxicity, receptor binding, and ELISA). Of the parent algal toxins, PbTx-1 and PbTx-2 were not detectable by LC/MS in K. brevis-exposed oysters. PbTx-3 and PbTx-9, which are accumulated directly from K. brevis and through metabolic reduction of PbTx-2 in the oyster, were at levels initially (after exposure) of 0.74 and 0.49 microg equiv./g, respectively, and were eliminated largely within 2 weeks after dosing. PbTx-7 and PbTx-10, the reduced forms of PbTx-1, were non-detectable. Conjugative brevetoxin metabolites identified previously in field-exposed oysters were confirmed in the laboratory-exposed oysters. Cysteine conjugates of PbTx-1 and PbTx-2, and their sulfoxides, were in the highest abundance, as apparent in LC/MS ion traces, and were detectable for up to 6 months after dosing. Composite toxin measurements by in vitro assay also reflected persistence (up to 6 months) of brevetoxin residues in the oyster. Levels of cysteine conjugates, as determined by LC/MS, were well correlated with those of composite toxin, as measured by ELISA, throughout depuration. Composite toxin levels by cytotoxicity assay were well correlated with those by receptor binding assay. Cysteine-PbTx conjugates are useful LC/MS determinants of brevetoxin exposure and potential markers for composite toxin in the Eastern oyster.

LC/MS analysis of brevetoxin metabolites in the Eastern oyster (Crassostrea virginica).

Brevetoxin (PbTx) metabolism was examined in the Eastern oyster (Crassostrea virginica) following exposure to a Karenia brevis red tide, by using LC/MS(/MS) and cytotoxicity assay. Metabolites observed in field-exposed oysters were confirmed in oysters exposed to K. brevis cultures in the laboratory. Previously, we identified a cysteine conjugate and its sulfoxide (MH(+): m/z 1018 and 1034) as metabolites of the brevetoxin congener PbTx-2. In the present study, we found a cysteine conjugate and its sulfoxide with A-type brevetoxin backbone structure (MH(+): m/z 990 and 1006), as probable derivatives of PbTx-1. We also found glycine-cysteine-PbTx (m/z 1047 and 1075), gamma-glutamyl-cysteine-PbTx (m/z 1147), and glutathione-PbTx (m/z 1176 and 1204) conjugates with A- and B-type backbone structures. Amino acid-PbTx conjugates react with fatty acids through amide linkage to form a series of fatty acid-amino acid-PbTx conjugates. These fatty acid conjugates are major contributors to the composite cytototoxic responses obtained in extracts of brevetoxin-contaminated oysters. Other brevetoxin derivatives found in oysters are consistent with hydrolytic ring-opening and oxidation/reduction reactions.

Multi-Laboratory Study of Five Methods for the Determination of Brevetoxins in Shellfish Tissue Extracts.

A thirteen-laboratory comparative study tested the performance of four methods as alternatives to mouse bioassay for the determination of brevetoxins in shellfish. The methods were N2a neuroblastoma cell assay, two variations of the sodium channel receptor binding assay, competitive ELISA, and LC/MS. Three to five laboratories independently performed each method using centrally prepared spiked and naturally incurred test samples. Competitive ELISA and receptor binding (96-well format) compared most favorably with mouse bioassay. Between-laboratory relative standard deviations (RSDR) ranged from 10 to 20% for ELISA and 14 to 31% for receptor binding. Within-laboratory (RSDr) ranged from 6 to 15% for ELISA, and 5 to 31% for receptor binding. Cell assay was extremely sensitive but data variation rendered it unsuitable for statistical treatment. LC/MS performed as well as ELISA on spiked test samples but was inordinately affected by lack of toxin-metabolite standards, uniform instrumental parameters, or both, on incurred test samples. The ELISA and receptor binding assay are good alternatives to mouse bioassay for the determination of brevetoxins in shellfish.

A rapid assay for the brevetoxin group of sodium channel activators based on fluorescence monitoring of synaptoneurosomal membrane potential.

A functional pharmacologically-based assay for the brevetoxin group of sodium channel activators was developed using synaptoneurosomes isolated from the brains of CD1 mice. The assay can detect the depolarizing effect of brevetoxin congeners PbTx-2 and PbTx-3 as enhancements of the veratridine-dependent increase in fluorescence of the voltage-sensitive fluorescent probe rhodamine 6G. The assay is relatively rapid and can detect brevetoxin activity in the nanomolar range. The synaptoneurosomal assay has been used to analyse mussel tissue extracts spiked with PbTx-2, and composite toxicity, expressed as PbTx-3 equivalents in extracts of oysters naturally exposed to brevetoxins. In this latter context, the synaptoneurosomal technique was shown to compare favorably with the cytotoxicity assay, the receptor binding assay and HPLC/MS. Our results support the concept that this membrane potential assay detects brevetoxins based on their interaction with sodium channels.

Confirmation of brevetoxin metabolism in the Eastern oyster (Crassostrea virginica) by controlled exposures to pure toxins and to Karenia brevis cultures.

Previously, we analyzed Eastern oysters (Crassostrea virginica) naturally exposed to a Karenia brevis red tide and found that brevetoxins (PbTx) are rapidly accumulated and metabolized. Several metabolites were isolated and later identified, including a cysteine-PbTx conjugate (MH(+): m/z 1018) and its sulfoxide product (m/z 1034). In the present study, we confirm and extend those findings by examining PbTx metabolism and elimination in oysters exposed to pure toxins (PbTx-2 and -3) under controlled conditions. Waterborne PbTx-3 was rapidly accumulated, but not metabolized, in the oyster and was largely eliminated within 2 weeks after exposure. In contrast, PbTx-2 was accumulated and rapidly metabolized. Metabolites of PbTx-2 included the reduction product PbTx-3 (m/z 897), and the cysteine conjugates (m/z 1018 and 1034) isolated previously from the field samples. Levels of the metabolite PbTx-3 in PbTx-2-exposed oysters were highest immediately after exposure and declined at a rate similar to parent PbTx-3 in PbTx-3-exposed oysters. Cysteine-PbTx persisted for 8 weeks after exposure. The same metabolites were confirmed in oysters exposed to laboratory cultures of K. brevis. PbTx metabolites contribute to neurotoxic shellfish poisoning (NSP) and should be included in analytical protocols for monitoring shellfish toxicity after a K. brevis red tide event.