Determination of penicillin G in heavy sow urine using immunochromatographic assay and microbial inhibition swab tests

Authors: Shelver, Weilin; Rahn, Kira; McGarvey, Amy; Holthusen, Jason; Smith, David

Submitted to: International Association for Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2016
Publication Date: 7/31/2016
Citation: Shelver, W.L., Rahn, K.L., Mcgarvey, A.M., Holthusen, J.E., Smith, D.J. 2016. Determination of penicillin G in heavy sow urine using immunochromatographic assay and microbial inhibition swab tests [abstract]. International Association for Food Protection Annual Meeting. 07/31/2016 - 08/03/2016. St. Louis, MO. P3-89.

Interpretive Summary: Introduction: Penicillin is a commonly used antibiotic in food animals. Unfortunately, violative penicillin residues in animal carcasses are sometimes identified by the USDA Food Safety and Inspection Service. Ante-mortem matrices such as urine could prove valuable for predicting possible violative tissue residues thus avoiding unnecessary carcass condemnation. Purpose: To evaluate an immunochromatographic assay and kidney inhibition swab (KIS™) test for the determination of penicillin G residues in sow urine. Methods: Sows (n=126; 228 ± 30.1 kg) were administered daily IM doses of penicillin G procaine (33,000 U/kg bw; 5x the label dose) for 3 consecutive days using 3 different administration patterns. Urine was screened for penicillin G using the KIS™ test as well as by an immunochromatographic assay. The urine samples were diluted with milk prior to processing for the immunochromatographic procedures. For the KIS™ test the presence of penicillin G was indicated by the development of a purple color. Results: Using a simple modification consisting of the addition of whole milk, we were able to adapt a commercially available immunochromatographic assay designed for use in milk for use in identifying penicillin G in sow urine. Immunochromatographic assay results were comparable with the KIS™ test results with 96% accuracy. When KISTM test accuracy was compared between assays performed in 2012 and 2015 there was 98% agreement, indicating stability of penicillin G in urine under storage conditions of -80 oC. LC-MS/MS results confirmed penicillin G concentrations did not differ between measurement years. Significance: Both KIS™ test and immunochromatographic assay methods can be performed “on-site” and produced similar results, but immunochromatographic assays provided “real time” (5 min testing time) answers in comparison to KIS™ test which require ~4 hours. Nevertheless, either rapid screening method could be used on-site to determine penicillin G residues in sow urine prior to marketing.

Technical Abstract: Introduction: Penicillin is a commonly used antibiotic in food animals. Unfortunately, violative penicillin residues in animal carcasses are sometimes identified by the USDA Food Safety and Inspection Service. Ante-mortem matrices such as urine could prove valuable for predicting possible violative tissue residues thus avoiding unnecessary carcass condemnation. Purpose: To evaluate an immunochromatographic assay and kidney inhibition swab (KIS™) test for the determination of penicillin G residues in sow urine. Methods: Sows (n=126; 228 ± 30.1 kg) were administered daily IM doses of penicillin G procaine (33,000 U/kg bw; 5x the label dose) for 3 consecutive days using 3 different administration patterns. Urine was screened for penicillin G using the KIS™ test as well as by an immunochromatographic assay. The urine samples were diluted with milk prior to processing for the immunochromatographic procedures. For the KIS™ test the presence of penicillin G was indicated by the development of a purple color. Results: Using a simple modification consisting of the addition of whole milk, we were able to adapt a commercially available immunochromatographic assay designed for use in milk for use in identifying penicillin G in sow urine. Immunochromatographic assay results were comparable with the KIS™ test results with 96% accuracy. When KISTM test accuracy was compared between assays performed in 2012 and 2015 there was 98% agreement, indicating stability of penicillin G in urine under storage conditions of -80 oC. LC-MS/MS results confirmed penicillin G concentrations did not differ between measurement years. Significance: Both KIS™ test and immunochromatographic assay methods can be performed “on-site” and produced similar results, but immunochromatographic assays provided “real time” (5 min testing time) answers in comparison to KIS™ test which require ~4 hours. Nevertheless, either rapid screening method could be used on-site to determine penicillin G residues in sow urine prior to marketing.