Test kits Charm

A wide variety of commercial LFIA kits for the detection of antibiotic residues is available and the most well-characterised of these are summarized in Table 5.4, including the rapid one-step assay (ROSA) range from Charm Sciences Inc., and the Tetrasensor, Twinsensor, Trisensor, and Sulfasensor from Unisensor SA and the Betastar from Neogen Corporation. Other LFIA assays have been reported in the scientific literature for the detection of antimicrobial residues, including a lateral-flow device for nicarbazin detection in animal feedstuffs. However, at present these are not commercially available. These LFIA tests incorporate either a receptor protein or an antibody as the specific capture molecule and operate in the competitive assay format (most applicable for small-molecule detection). The sample preparation protocols are based on either direct analysis of the liquid sample (e.g., milk) or a simple extraction step for solid or complex matrices using buffer(s) supplied in the test kit. In general, the time required to perform these tests is less than 30 min with only basic laboratory equipment, if any, required. 

TABLE 5.5 Range of Charm II Test Kits and Their Applications Currently Available for Antibiotic Residue Screening from Charm Sciences Inc. 

Charm II Tests for Antibiotics Test Kits Available (number of individual compounds for which detection concentration are quoted) Application(s) Sample Preparation Time (minutes) Assay Time (minutes)... 

On the farm, a test kit may be used. The test organism is inoculated in tablet form into liquid medium in a test tube with a sample of the milk. An indicator in the buffer changes color if the bacteria are able to grow (i.e., no antibiotic is present). The Charm analyzer can be used for several different tests (Figure 2). 

As occurred with the other antibiotics, commercial immunoassay formats, also available as kits for tetracyclines and penicillins such as the Parallux, the LacTek, or the Charm II, have also been placed on the market for the analysis of sulfonamides (see Table 4). Thus, the Parallux detects sulfamethazine and sulfadimethoxine in raw milk with a LOD of 10 pg L1. The Charm II detects almost all sulfonamides in honey and milk with a LOD in the range from 1 to 10 pg L, whereas LacTek is able to detect sulfamethazine. Moreover, the 5101SULlp and 5101SUDAlp tests reach LOD values for sulfamethazine and sulfadiazine of around 0.2 pg L 1 and they have been applied to the analysis of urine, milk, and plasma. These tests have proved to be efficient as a point of care for on-site applications on farms. Moreover, commercially available antibodies can be found from several sources such as Silver Lake Research, US Biological, Cortex Biochem. Inc., Accurate Chemical Scientific, Fitzgerald Industries International Inc., and Biotrend Chemikalien GmbH. 

Regarding commercially available immunochemical kits, we could mention the Charm ROSA Enrofloxacin Test that detects ciprofloxacin and enrofloxacin equally (see Table 4) and the 5101ERFXlp test. This last one is a direct competitive ELISA, which uses MAbs and has a LOD of 3 ng g1 in tissues. Some other companies do have antibodies available as reagents for different applications such as Biodesign International and QED Bioscience Inc. 

The range of kits currently available for the Charm II system and their applications are given in Table 5.5. The test manufacturer claims that the Charm II tests are capable of detecting compounds belonging to the antimicrobial class at or below their defined MRLs (or USFDA tolerances, as indicated) within the relevant matrix, including, milk, urine, serum, animal tissue, honey, and other substances at concentrations of interest to regulatory agencies. 

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