Development of a liquid chromatography-tandem mass spectrometry method to determine colistin, bacitracin and virginiamycin M1 at cross-contamination levels in animal feed

Determination of four aminoglycoside antibiotics and spectinomycin in feed at cross-contamination level: Development and in-house validation of a LC-MS/MS method for enforcing EU Regulation

Combating antimicrobial resistance is a top priority worldwide involving a concerted action by several high-level institutions and organisations in the health sector. To ensure that a meaningful progress is achieved, several campaigns and political initiatives have been launched targeting the health professionals, the industry, the farmers, and the general public. The Regulation (EU) 2019/4 on medicated feed contains provisions for the limitation and control of the contamination of non-target compound feed with 24 antimicrobials. The purpose of this work was to develop a reliable and effective method for the determination of four aminoglycoside antibiotics (apramycin, paromomycin, tobramycin and neomycin) and spectinomycin in feed at cross-contamination level, where an absolute lack of suitable methods was identified. Four candidate methods described in the literature failed to provide adequate recoveries of all analytes. Therefore, an in-depth investigation was carried out to identify the bottleneck variable. The optimised method was then in-house validated and showed performance features appropriate for the intended purpose. The selected compounds could be analysed by LC-MS/MS in five animal feeds with LOQs between 2.6 and 9.2 μg kg-1 for the AGs and between 28 and 86 μg kg-1 for spectinomycin. Using isotopically labelled internal standards, the recovery rates varied from 63 % to 103 % and the intermediate precision (RSDip) varied from 1.1 % to 14 %. This work represents a step forward in the reliable determination of antibiotics in compound feed as the developed method has shown to be precise and sensitive. It is expected that this method gains wide acceptance and can supplement the legislation with effective control tools for antibiotic residues.

Applications of tandem mass spectrometry (MS/MS) in antimicrobial peptides field: Current state and new applications

Antimicrobial peptides (AMPs) constitute a group of small molecular peptides that exhibit a wide range of antimicrobial activity. These peptides are abundantly present in the innate immune system of various organisms. Given the rise of multidrug-resistant bacteria, microbiological studies have identified AMPs as potential natural antibiotics. In the context of antimicrobial resistance across various human pathogens, AMPs hold considerable promise for clinical applications. However, numerous challenges exist in the detection of AMPs, particularly by immunological and molecular biological methods, especially when studying of newly discovered AMPs in proteomics. This review outlines the current status of AMPs research and the strategies employed in their development, considering resent discoveries and methodologies. Subsequently, we focus on the advanced techniques of mass spectrometry for the quantification of AMPs in diverse samples, and analyzes their application, advantages, and limitations. Additionally, we propose suggestions for the future development of tandem mass spectrometry for the detection of AMPs.

Analysis of virginiamycin M1 in swine feed, muscle and liver samples by quantum dots-based fluorescent immunochromatographic assay

Based on a highly sensitive and specific monoclonal antibody (mAb) against virginiamycin M1 (VIR M1), a quantum dots-based fluorescent immunochromatographic assay (QDs-ICA) for quick and sensitive analysis of VIR M1 was established for the first time. The mAb showed a half-maximal inhibitory concentration (IC₅₀) of 0.5 ng/mL and cross-reactivity (CR) values below 0.1% for other three analogues when used in enzyme-linked immunosorbent assay (ELISA). The mAb was conjugated to ZnCdSe/ZnS (core/shell) QDs with maximum emission wavelength of 610 nm (orange-red) which was selected as fluorescent probe to increase QDs-ICA sensitivity. The cut-off value of QDs-ICA was 12.5 ng/mL. QDs-ICA showed a linear range from 0.7 to 14.5 ng/mL with a limit of quantification of 0.7 ng/mL. Compared with existing methods for the analysis of VIR M1, the QDs-ICA exhibited higher sensitivity. For analysis of VIR M1 concentrations spiked into swine feed, muscle and liver samples, recovery rates ranged from 94.0% to 111.6% with the highest coefficient of variation (CV) of 6.7% for intra-assay, and for inter-assay ranged from 94.7% to 107.6% with the highest CV of 9.4%. In conclusion, the QDs-ICA could be a potential method for analyzing VIR M1 in animal feed and animal-derived food.

Influence of Endogenous Factors of Food Matrices on Avidin—Biotin Immunoassays for the Detection of Bacitracin and Colistin in Food

(Strept)avidin–biotin technology is frequently used in immunoassay systems to improve their analytical properties. It is known from clinical practice that many (strept)avidin–biotin-based tests provide false results when analyzing patient samples with a high content of endogenous biotin. No specific investigation has been carried out regarding possible interferences from avidin (AVI) and biotin (B₇) contained in food matrices in (strept)avidin–biotin-based immunoanalytical systems for food safety. Two kinds of competitive ELISAs for bacitracin (BT) and colistin (COL) determination in food matrices were developed based on conventional hapten–protein coating conjugates and biotinylated BT and COL bound to immobilized streptavidin (SAV). Coating SAV–B₇–BT and SAV–B₇–COL complexes-based ELISAs provided 2- and 15-times better sensitivity in BT and COL determination, corresponding to 0.6 and 0.3 ng/mL, respectively. Simultaneously with the determination of the main analytes, these kinds of tests were used as competitive assays for the assessment of AVI or B₇ content up to 10 and 1 ng/mL, respectively, in food matrices (egg, infant milk formulas enriched with B₇, chicken and beef liver). Matrix-free experiments with AVI/B₇-enriched solutions showed distortion of the standard curves, indicating that these ingredients interfere with the adequate quantification of analytes. Summarizing the experience of the present study, it is recommended to avoid immunoassays based on avidin–biotin interactions when analyzing biosamples containing these endogenous factors or enriched with B₇.