Elisa

S. aureus 311-327

C. botulinum 328-338

C. perfringen 339-344

E. coli 345-350

selected publications of IAs for detection of bacterial toxins. The table lists the type of assay, the species of bacterium that the assay was developed to detect, and references. It does not describe which S. aureus toxin or toxins are detected in the assays. Some assays only detect en-terotoxin B, while others detect A and B or A, B, C, and D. To provide information on other agents that are considered to be endangering the food supply only a general list of sources has been provided. Information on risks associated with vehicles of food-borne pathogens and toxins is available (353).

To detect Salmonella in foods, investigators have relied on culture procedures that enable growth, selection, isolation, and identification of isolated organisms (354). The length of time needed to obtain a negative reading has always posed a problem. To overcome this disadvantage, numerous rapid testing methods have been proposed. They have not found wide acceptance due to problems with sensitivity and specificity (355). Two reports indicated the potential for use of EIA for screening for Salmonella (356,357) in foods. Since then there have been other reports of Salmonella detection using EIAs (358-363).

Listeria detection using an immunobased test requires highly specific antibodies because Listeria species have been shown to be antigenically related to other grampositive organisms, namely Staphylococcus, Streptococcus, Erisipelothrix, and Bacillus species (364-368). Several groups have been successful at producing monoclonal antibodies to a genus-specific antigen (369-371).

There are several commercial kits available for toxin and pathogen detection. Oxoid Ltd. (Hampshire, UK) sells revised passive latex agglutination assays for detection of S. aureus toxins A, B, C, and D; Clostridium perfringens enterotoxin; Vibrio chlorae and E. coli heat-labile entero-toxin; and S. aureus toxic shock syndrome toxin. Organon Teknika Corp. (Durham, N.C.) sells Salmonella-Tek and Listeria-Tek which are ELISAs.

CHEMICAL AGENTS Pesticides

Pesticides are used to produce high-quality, inexpensive food. With the use of pesticides, agricultural residues can be expected to occur in foods. Regulation of pesticides is shared by three federal agencies. The U.S. Environmental protection Agency (EPA) is responsible for registering or approving the use of pesticides and to setting tolerance, if residues will occur in food. The USDA is responsible for pesticides used on meat and poultry, and the FDA is responsible for enforcing tolerances for foods shipped in interstate commerce (372). Many states, including California, Florida, and Michigan, have pesticide analytical programs.

The FDA carries out a large-scale monitoring program, the objective of which is to prevent foods that contain illegal residues from entering interstate commerce. Testing of raw agricultural commodities is the focus of the moni toring. To date about 15,000 samples, 8,000 imported and 7,000 domestic (372), are collected and analyzed by the 21 field offices.

There are 300 pesticides and active ingredients with tolerances in or on foods in addition to other pesticides and related chemicals that can exist as residues (373). The EPA has supplied data showing that 53 of these pesticides have active ingredients that have been shown to be oncogenic or potentially oncogenic (351).

Gas chromatography has been used for analysis of pesticides (352,374-376). These methods were developed by the early 1960s. The use of immunoassays has spread into the area of pesticide analysis. A brief summary of chemicals that control weeds or pests in agricultural crops will be provided. There have been IAs described in the literature since the mid-1970s (Table 7). Prior to 1982 the majority of IAs described for pesticide analysis were rias and since that date there have been reports of EIAs. Much less attention has been given to development of fluoroimmu-noassays for pesticide analysis.

With a few exceptions, the majority of tests developed for pesticide analysis employ polyclonal antibodies raised in rabbits. There have been some monoclonal antibodies produced against pentachlorophenol (406), surflan (407), malic hydrazide (399), paraquat (403), and paraoxon (401).

Table 7. Immunochemical Methods for Detection of Pesticides

Assay

Pesticide

Ref.

Radioimmunoassay

Aldrin

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