Upper Midwest Environmental Sciences Center
PSR 2002-02 October 2002
Food Safety Research Associated with a Proposed Drug for Fish
by Jeffery R. Meinertz, Shari L. Greseth, and Guy R. Stehly
Bacterial gill disease (BGD) is a disease of fish cultured in crowded and stressful rearing conditions and is responsible for substantial production losses on federal, state, and commercial hatcheries. The disease is caused by a slow growing, Gram-negative bacterium that most commonly affects fry, but also causes the disease in older fish. The disease is characterized by flared gills, increased respiration, decreased fright response, and reduction in feed intake.
Chloramine-T is a disinfectant that is effective in reducing fish mortalities caused by BGD. Legal use of chloramine-T as a drug in fish culture depends on approval by the U.S. Food and Drug Administration (FDA). An attribute of a drug that must be characterized before the drug is approved is depletion of all the drugs residues from fillet tissue. By characterizing the drugs depletion, the FDA can establish a withdrawal time for fish exposed to chloramine-T ensuring that drug residues reach safe levels before the fillets are consumed by humans.
A metabolite of chloramine-T in fillet tissue, para-toluenesulfonamide (p-TSA), was chosen by the FDA as a marker to represent all chloramine-T residues in fillets. Use of p-TSA as the marker for chloramine-T was based on an early study where the chemistry methods used to determine p-TSA concentrations were time consuming and cumbersome. Since that study, a simple and widely applicable improved method for p-TSA has been developed. This new method, using modern chemistry techniques, was planned for use during chloramine-T depletion studies, but before it could be used, the method had to be tested against FDA criteria for accuracy and precision. In addition, since the selection of p-TSA as the marker for chloramine-T was based on the earlier method, the FDA required that the new method be compared to the earlier method to prove that the methods produced similar results.
Accuracy and Precision of the Modern Method
The new method successfully recovered 86% to 97%
of the p-TSA in fillet tissue from channel catfish Ictalurus punctatus,
rainbow trout Oncorhynchus mykiss, and walleye Stizostedion
vitreum vitreum fortified at 70 to 2,000 ppb. The new methods
precision was remarkable with the variability among repeated analyses
less than 8%. These data exceed FDA requirements for measuring a
Concentrations of p-TSA in fillet tissue determined with the new method were similar to concentrations determined with the earlier method (Table 2), i.e., the p-TSA concentrations at each sample time were not statistically different.
An analytical method validated against FDA criteria can now be used in studies critical to the pursuit of allowing public and private hatcheries to use chloramine-T to combat bacterial diseases in fish.
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