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Background: The newest method of treatment for patients with NSCLC (non-small cell lung cancer) is immunotherapy directed at the immune checkpoints PD-1 (Programmed Cell Death 1) and PD-L1 (Programmed Cell Death Ligand 1). PD-L1 is the only validated predictor factor for immunotherapy efficacy, but it is imperfect. Some patients do not benefit from immunotherapy and may develop primary or secondary resistance. This study aimed to assess the intestinal resistome composition of non-small cell lung cancer (NSCLC) patients treated with immune checkpoint inhibitors in the context of clinical features and potentially new prediction factors for assessing immunotherapy efficacy. Methods: The study included 30 advanced NSCLC patients, 19 (57%) men and 11 (33%) women treated with first- or second-line immunotherapy (nivolumab, pembrolizumab or atezolizumab). We evaluated the patient's gut resistome composition using the high sensitivity of targeted metagenomics. Results: Studies have shown that resistome richness is associated with clinical and demographic factors of NSCLC patients treated with immunotherapy. Smoking seems to be associated with an increased abundance of macrolides, lincosamides, streptogramins and vancomycin core resistome. The resistome of patients with progression disease appears to be more abundant and diverse, with significantly higher levels of genomic markers of resistance to lincosamides (lnuC). The resistance genes lnuC, msrD, ermG, aph(6), fosA were correlated with progression-free survival or/and overall survival, thus may be considered as factors potentially impacting the disease. Conclusion: The results indicate that the intestinal resistome of NSCLC patients with immune checkpoint inhibitors treatment differs depending on the response to immunotherapy, with several distinguished markers. Since it might impact treatment efficacy, it must be examined more deeply.
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Contaminations with cephalosporin-resistant Escherichia coli across the food chain may pose a significant threat to public health because those antimicrobials are critically important in human medicine. The impact of the presented data is especially significant concerning Poland's role as one of the leading food producers in the EU. This work aimed to characterize the genomic contents of cephalosporin-resistant Escherichia coli (n = 36) isolated from retail meat to expand the official AMR monitoring reported by EFSA. The ESBL mechanism was predominant (via blaCTX-M-1 and blaSHV-12), with the AmpC-type represented by the blaCMY-2 variant. The strains harbored multiple resistance genes, mainly conferring resistance to aminoglycosides, sulfonamides, trimethoprim, tetracyclines. In some isolates, virulence factors-including intimin (eae) and its receptor (tir) were detected, indicating significant pathogenic potential. Resistance genes showed a link with IncI1 and IncB/O/K/Z plasmids. Cephalosporinases were particularly linked to ISEc9/ISEc1 (blaCTX-M-1 and blaCMY-2). The association of virulence with mobile elements was less common-mostly with IncF plasmids. The analysis of E. coli isolated from retail meat indicates accumulation of ARGs and their association with various mobile genetic elements, thus increasing the potential for the transmission of resistance across the food chain.
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Periodontal disease in ruminants is common and occurs in farmed and wild animals. Periodontal lesions can result from the secretion of endotoxins by pathogenic bacteria and as consequences of immune system activity. Three main types of periodontitis have been described. The first is chronic inflammation involving mainly premolars and molars-periodontitis (PD). The second type is an acute inflammatory reaction occurring with calcification of the periosteum of the jawbone and swelling of the surrounding soft tissues (Cara inchada, CI-"swollen face"). Finally, a third type, similar to the first but located in the incisor area, is called "broken mouth" (BM). Etiological variation between the different types of periodontitis is indicated. This particularly manifests in the composition of the microbiome, which is characteristic of the different forms of periodontitis. The widespread detection of lesions has drawn attention to the current nature of the problem.
Subject(s)
Periodontal Diseases , Periodontitis , Animals , Periodontitis/pathology , Bacteria , RuminantsABSTRACT
For many years, ionophores have been used to control coccidiosis in poultry. However, misuse of ionophores can cause toxicity with significant clinical symptoms. The most critical factors influencing ionophores' toxicity are administration dose, species, and animal age. Although clinical signs of ionophore intoxication are well studied, the toxicity mechanisms of the ionophores at the molecular level still are not fully elucidated. This review summarizes the studies focused on polyether ionophores toxicity mechanisms in animals at the clinical and molecular levels. Studies show that ionophore toxicity mainly affects myocardial and skeletal muscle cells. The molecular mechanism of the toxication could be explained by the inhibition of oxidative phosphorylation via dysregulation of ion concentration. Tiamulin-ionophore interaction and the synergetic effect of tiamulin in ionophore biotransformation are discussed. Furthermore, in recent years ionophores were candidates for reprofiling as antibacterial and anti-cancer drugs. Identifying ionophores' toxicity mechanisms at the cellular level will likely help develop novel therapies in veterinary and human medicine.
Subject(s)
Anti-Bacterial Agents , Coccidiosis , Animals , Humans , Ionophores/pharmacology , Ionophores/metabolism , Anti-Bacterial Agents/metabolism , Poultry/metabolismABSTRACT
The presented procedure combines experience from two LC-MS/MS methods previously developed by our team for NSAIDs determination in meat and milk. The novelty was a modification of sample preparation and combining LC-MS/MS method for milk and muscle. The clean-up procedure was investigated, leading to a change from SPE to dSPE with C18 bulk sorbent. Unlike most of the existing methods, chromatographic separation was achieved on a C8 chromatographic column. This method was developed and validated under European Commission Decision 2002/657/EC. Recovery for milk samples values between 86.3% to 108%, with the coefficient of variation, varied from 5.51% to 16.2%. The recovery for muscle was calculated to be between 85.0% and 109%, and the coefficient of variation was-4.73% to 16.6%. The validation results prove that the method is suitable for confirmatory purposes in milk and muscle. Of 452 samples tested in 2019 and 2020, two have been identified as non-compliant.
Subject(s)
Anti-Inflammatory Agents, Non-Steroidal/analysis , Chromatography, Liquid/methods , Drug Residues/analysis , Milk/chemistry , Muscles/chemistry , Tandem Mass Spectrometry/methods , Animals , Cattle , Horses , Milk/metabolism , Muscles/metabolism , SwineABSTRACT
A depletion study of toltrazuril and its metabolites was performed using 20 hens medicated via drinking water for two days in a dosage of 7 mg kg-1 per kg body weight. Afterward, eggs were collected for 42 days. Residues were analyzed in whole eggs and yolk and whites. Toltrazuril sulfone was found to be the most predominant in all matrices, the highest concentration was found in the yolk - 5567 µg kg-1, followed by whole eggs samples - 4767 µg kg-1 and egg whites - 532 µg kg-1. On last day toltrazuril sulfone were still detected - 22.5 µg kg-1. 70 days is required to concentration of toltrazuril sulfone reach zero. Administrating toltrazuril before the laying phase can pose a risk of residues of toltrazuril sulfone in eggs. Setting Maximum Residue Limit could reduce the risk of non-complaint samples and ensure the safety of consumers, but still requires 44 days of the withdrawal period.
Subject(s)
Chickens/metabolism , Drug Residues/analysis , Eggs/analysis , Triazines/analysis , Administration, Oral , Animals , Egg White/analysis , Egg Yolk/chemistry , Female , Sulfones/analysis , Triazines/administration & dosage , Triazines/metabolismABSTRACT
INTRODUCTION: The study measured the hormonal and protein markers of acute stress, those of oxidative stress and total antioxidant capacity (TAC) in swine oral fluid, determined which of these parameters would be the most appropriate for future livestock welfare assessment and established the time when the samples should be taken. MATERIAL AND METHODS: Stress was induced in 7 out of 14 castrated six-week-old Danbred×Duroc pigs by immobilisation on a nasal snare at 8 a.m., 1 p.m., and 6 p.m. and samples were taken both directly after the stressor was applied and 30 min later. The remaining pigs were the control group, which were not immobilised; their samples were taken at the same times. The concentrations of hormones and malondialdehyde (MDA) were measured using liquid chromatography with tandem mass spectrometry, while those of alpha-amylase and TAC were measured using spectrophotometry. RESULTS: The levels of cortisol and cortisone increased with statistical significance immediately after the acute stress response and 30 min later. A cut-off value set at 0.25 ng/mL cortisol concentration was capable of distinguishing between the stressed and control groups with 100% accuracy in evening samples and 95% accuracy overall. Prednisolone was not present, and the levels of testosterone and corticosterone were low and not distinctive. Alpha-amylase became significantly more concentrated during stress induction and 30 min later. The TAC and MDA levels rose after the stress but without statistical significance. CONCLUSION: The most suitable markers of acute stress were cortisol, cortisone and alpha-amylase. Oral fluid is a reliable material for monitoring the level of pigs' stress and should be collected in the evening.
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Salicylates are among the most known anti-inflammatory drugs, used both in human and veterinary medicine. They also occur naturally in plants. Residues of salicylic acid in tissues and eggs may occur after drug administration or exposure of animals to feed material with high salicylate content. An animal study was performed on laying hens. The birds received sodium salicylate or acetylsalicylic acid (10 mg/kg b.w.) for 7 days or were given corn containing 1.18 mg/kg of salicylic acid. Samples of liver, muscle and plasma were collected at 0, 4, 8, 24 and 72 h after treatment; eggs were collected daily for 14 days. Salicylic acid and its metabolites: gentisic acid, salicyluric acid and gentisuric acid were determined using liquid chromatography coupled with tandem mass spectrometry. In both liver and muscle, the residues after administration of sodium salicylate were initially higher than for acetylsalicylic acid but they depleted at the same time. The deposition and depletion profile of salicylic acid in eggs was similar for groups receiving both drugs; the plateau level reached 248 ± 61.5 µg/kg and 275 ± 82.1 µg/kg. The concentration of salicylic acid in tissues and eggs of animals receiving salicylic acid was low. Gentisic acid was found in individual samples of liver, muscle and eggs from all treated groups. The exposure of hens to the salicylates at feed additive levels and to naturally occurring salicylates results in low residue concentrations and fast depletion of salicylic acid. The eggs do not pose any risk to consumers sensitive to salicylates.
Subject(s)
Drug Residues/analysis , Food Analysis , Food Contamination/analysis , Hippurates/chemistry , Ovum/chemistry , Salicylic Acid/analysis , Administration, Oral , Animals , Chickens , Hippurates/administration & dosage , Liver/chemistry , Muscles/chemistry , Salicylic Acid/administration & dosage , Salicylic Acid/metabolismABSTRACT
Salinomycin is a polyether antibiotic showing anticancer activity. There are many reports of its toxicity to animals but little is known about the potential adverse effects in humans. The action of the drug may be connected to its metabolism. That is why we investigated the cytotoxicity of salinomycin and pathways of its biotransformation using human primary hepatocytes, human hepatoma cells (HepG2), and the mouse fibroblast cell line (Balb/c 3T3). The cytotoxicity of salinomycin was time-dependent, concentration-dependent, and cell-dependent with primary hepatocytes being the most resistant. Among the studied models, primary hepatocytes were the only ones to efficiently metabolize salinomycin but even they were saturated at higher concentrations. The main route of biotransformation was monooxygenation leading to the formation of monohydroxysalinomycin, dihydroxysalinomycin, and trihydroxysalinomycin. Tiamulin, which is a known inhibitor of CYP450 izoenzymes, synergistically induced cytotoxicity of salinomycin in all cell types, including non-metabolising fibroblasts. Therefore, the pharmacokinetic interaction cannot fully explain tiamulin impact on salinomycin toxicity.
Subject(s)
Anti-Bacterial Agents/metabolism , BALB 3T3 Cells/metabolism , Drug Resistance , Hep G2 Cells/metabolism , Hepatocytes/metabolism , Pyrans/metabolism , Animals , Anti-Bacterial Agents/pharmacology , Cell Line , Diterpenes/metabolism , Diterpenes/pharmacology , Hepatocytes/drug effects , Humans , Mice , Prednisolone/metabolism , Prednisolone/pharmacology , Pyrans/pharmacologyABSTRACT
INTRODUCTION: Some azo dyes, including Sudans I-IV and Para Red, are genotoxic and may be biotransformed to cancerogenic aromatic amines. They are banned as food and feed additives, but their presence has been detected in food. Aromatic amines are also considered potentially toxic. Online EC-MS is a promising tool to study the transformation mechanisms of xenobiotics such as azo dyes. The aim of the study was to investigate emulation of how azo dyes are enzymatically transformed to amines with EC-MS. MATERIAL AND METHODS: The reduction reactions of five azo dyes (Sudans I-IV and Para Red) were conducted using a glassy carbon working electrode and 0.1% formic acid in acetonitrile. Reduction results were compared with the literature and in silico to select preliminary candidates for metabolites. The LC-MS/MS method was used to confirm results obtained by electrochemical reactor. RESULTS: A limited number of pre-selected compounds were confirmed as azo dyes metabolites - aniline for Sudan I, aniline and 4-aminoazobenzene for Sudan III, o-toluidine for Sudan IV, and 4-nitroaniline for Para Red. No metabolites were found for Sudan II. CONCLUSIONS: Electrochemistry-mass spectrometry was successfully applied to azo dyes. This approach may be used to mimic the metabolism of azo dyes, and therefore predict products of biotransformation.
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INTRODUCTION: Salicylic acid is a derivative of benzoic acid and occurs in nature. The main target of this study was to develop the liquid chromatography coupled with tandem mass spectrometry technique as a method for determination of salicylic acid in feed materials and compound feed. MATERIAL AND METHODS: Salicylic acid was extracted from feed with 0.1% hydrochloric acid in methanol. Separation was achieved in 8 min in a gradient elution using 0.1% formic acid and acetonitrile. The analyte was detected using negative electrospray tandem mass spectrometry. The procedure was validated to the specifications of the European Commission Decision No. 2002/657/EC. RESULTS: The validation results showed the repeatability of the method, which was evaluated at three levels (0.25, 0.5, and 1.0 mg/kg). Calibration curves for the working ranges were linear (R2 0.9911 to 0.9936), and recoveries ranged from 98.3% to 101%. The LOD and LOQ for compound feed were 0.02 and 0.05 mg/kg, respectively. Salicylic acid was found mostly in corn, and its concentrations differed depending on whether it was young or fully grown (5.30-12.8 mg/kg and 0.13-1.01 mg/kg, respectively). CONCLUSIONS: A sensitive and reliable method for the determination of salicylic acid in feed and compound feed using LC-MS/MS was developed.
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Salinomycin (SAL) is a polyether antibiotic, which is commonly used as a coccidiostat and has recently shown to exhibit anticancer activity. The toxic action of the drug may be connected with the extent and routes of its biotransformation. The cytotoxic potential of SAL and its combination with tiamulin and prednisolone was investigated using three cell models from rat: primary hepatocytes, hepatoma cells (FaO) and myoblasts (L6). The four biochemical endpoints were assessed: mitochondrial and lysosomal activity, total cell protein content and membrane integrity. The metabolites of SAL in the medium from cell cultures were determined using LC-MS/MS. The cytotoxicity of SAL was time-, concentration- and cells dependent. The most sensitive endpoint was the inhibition of lysosomal activity. Tiamulin increased SAL cytotoxicity, whereas the opposite results were observed for prednisolone. Primary hepatocytes were the most efficient in SAL biotransformation both in terms of its intensity and number of produced metabolites. The range of the cytotoxicity and mode of salinomycin interaction with tiamulin and prednisolone cannot be explained by the biotransformation alone.
Subject(s)
Anti-Bacterial Agents/toxicity , Antineoplastic Agents/toxicity , Hepatocytes/drug effects , Pyrans/toxicity , Animals , Cell Survival/drug effects , Cells, Cultured , Diterpenes/toxicity , Drug Interactions , Lysosomes/drug effects , Male , Mitochondria/drug effects , Prednisolone/toxicity , Rats, WistarABSTRACT
A confirmatory multi-residue method was developed for the determination in milk of 19 coccidiostats (amprolium, arprinocid, clazuril, clopidol, decoquinate, diclazuril, ethopabate, halofuginone, lasalocid, maduramicin, monensin, narasin, nicarbazin, nequinate, robenidine, salinomycin, semduramicin, toltrazuril sulfone and toltrazuril sulfoxide). Sample preparation utilising extraction with organic solvent and clean up by SPE and freezing was found reliable and time-efficient. Optimised chromatography and MS conditions with positive and negative ESI achieved sufficient sensitivity and selectivity. Validation experiments has proven method usefulness for routine analysis of coccidiostats in milk samples. An on-farm study conducted on dairy cows fed with experimentally contaminated feed with salinomycin and lasalocid showed negligible transfer to milk. No residues of lasalocid were found in collected samples. Salinomycin was found only in 5 of 168 samples analysed, while the concentrations of salinomycin in those samples (0.119-0.179 µg kg-1) was significantly below the limit of salinomycin in milk set by European Union legislation. Such low concentrations of both coccidiostats cannot be explained by conjugation during dairy cows' metabolism, as shown by experiments with enzymatic hydrolysis.
Subject(s)
Animal Feed/analysis , Coccidiostats/analysis , Food Contamination/analysis , Lasalocid/analysis , Milk/chemistry , Pyrans/analysis , Animals , Cattle , Coccidiostats/metabolism , Drug Residues/chemistry , Drug Residues/metabolism , Lasalocid/metabolism , Milk/metabolism , Pyrans/metabolismABSTRACT
RATIONALE: Salinomycin is an ionophore antibiotic with potential anticancer activity. The history of its use in veterinary medicine shows large differences in species susceptibility to its toxicity. At the same time, the results of research to date suggest a correlation between the extent and pathways of ionophore biotransformation and its toxicity. The biotransformation pattern of salinomycin has not been studied so far. METHODS: Extracts from culture media of human hepatoma cells (HepG2) exposed to salinomycin were analysed with two mass spectrometry techniques. For the first one, micro-liquid chromatography coupled with a quadrupole time-of-flight (Q-TOF) mass spectrometer was used. In the second approach, high-performance liquid chromatography was coupled with a hybrid triple quadrupole linear ion trap. Both experiments were operated in positive electrospray ionization mode. To identify unknown salinomycin metabolites, information-dependent acquisition was applied. RESULTS: Metabolites identified with tandem mass spectrometry included hydroxylated, demethylated and hydroxylated-demethylated derivatives, in total 14 compounds. Using high resolution, only eight isomers of hydroxysalinomycin were detected. The efficiency of biotransformation was low, and so was the abundance of the signals; only for two metabolites did the signal exceed 1% of the salinomycin signal. The analysis of fragmentation patterns narrowed the structure combinations but the actual modification site could not be specified. CONCLUSIONS: Tandem mass spectrometry was more sensitive in the identification of salinomycin metabolites in comparison to the Q-TOF approach. Because of low efficiency of biotransformation of the applied model, the obtained fragmentation data are not sufficient to fully characterize the detected compounds. A study with more metabolically active primary hepatocytes is needed.
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Sudan I is a carcinogenic industrial azo-dye, forbidden for use in food. However, it has been detected in food on several occasions, such as in paprika, used in animal husbandry to enhance egg yolk colour. Therefore, an animal experiment was designed to simulate the transfer of Sudan I to eggs after its unintentional administration to laying hens. A group of laying hens (n=18) received feed contaminated with Sudan I at the raising concentrations: 0.45mg/kg, 4.97mg/kg and 42.1mg/kg. Residues of Sudan I were detected in egg yolks (0.29±0.03µg/kg, mean±SD) only after the administration of the feed contaminated with the dye at the highest concentration. The determined concentrations were much lower than expected based on the compound's lipophilicity. In conclusion, the transfer of Sudan I to eggs was limited and strongly dependent on its concentration in feed.
Subject(s)
Eggs , Animal Feed , Animals , Chickens , Female , NaphtholsABSTRACT
INTRODUCTION: The paper presents the method of simultaneous determination of 10 illegal azo dyes in feed by ultra-high performance liquid chromatography coupled with tandem mass spectrometry technique. MATERIAL AND METHODS: The dyes were extracted with hexane, evaporated to dryness, and analysed. Separation was achieved in 7 min in a gradient elution using acetonitrile (A) and 0.1% formic acid (B) as a mobile phase. RESULTS: The validation results showed the repeatability of the method, which was evaluated at three levels (50, 500, and 5,000 µg/kg). All the matrix calibration curves for the working ranges were linear (R2 0.9904 to 1.0), the repeatability was between 2.1% and 24%, and recoveries ranged from 77.9% to 120%. The LOD and LOQ were at 1-2 and 5-10 µg/kg for different dyes, respectively. Furthermore, the method was applied in the homogeneity tests of the in-house prepared feed containing Sudan I at the levels of 0.5, 5, and 50 mg/kg. CONCLUSIONS: A sensitive, selective, and fast multiresidue method was successfully developed and validated. Its robustness was confirmed by the analysis of an experimental feed containing Sudan I.
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A multi-residue method has been developed and validated for the simultaneous determination of authorized (decoquinate, diclazuril, halofuginone, lasalocid, maduramicin, monensin, narasin, nicarbazin, robenidine, salinomycin and semduramicin) and non-authorized (amprolium, clopidol, ethopabate and toltrazuril) coccidiostats in animal feed. Feed samples were extracted with basic followed by acidified solution in methanol and, after centrifugation, were injected directly into LC-MS/MS system. Detection was performed in selected reaction monitoring mode with both positive and negative electrospray ionization. The time efficient validation experiment has verified the robustness of a method in different types of feed and on two separate LC-MS/MS instruments. The comparison of different quantification methods demonstrated that, against expectations, the standard addition did not prove better in comparison with matrix-matched calibration curve. Although the sample preparation was very easy, the observed matrix effects were not significant for the most part but they could explain the problems with the quantification of some coccidiostats.
Subject(s)
Animal Feed/analysis , Coccidiostats/chemistry , Chromatography, Liquid/methods , Tandem Mass Spectrometry/methodsABSTRACT
Decoquinate, a chemical coccidiostat used as a feed additive, can occur in eggs due to cross-contamination of feedstuffs for laying hens. An experiment was designed to assess the transfer of decoquinate to hen eggs and its distribution between egg yolk and egg white. Hens were given the feed containing decoquinate at a cross-contamination level (0.34 mg kg(-1)) and collected eggs were analysed using an LC-MS/MS method. The plateau level was reached on the eighth day of the experiment and averaged 8.91 µg kg(-1), which is far below the maximum level established at 20 µg kg(-1) for whole eggs. Decoquinate was deposited mostly in egg yolks (26.2 µg kg(-1)) and did not deplete completely during 14 days of administration of decoquinate-free feed. The results confirmed that administration of cross-contaminated feed is associated with very low risk of non-compliant residue levels of decoquinate in eggs.
Subject(s)
Animal Feed/analysis , Chickens , Decoquinate/pharmacokinetics , Drug Residues/pharmacokinetics , Eggs/analysis , Food Contamination/analysis , Animals , Coccidiostats/chemistry , Coccidiostats/metabolism , Coccidiostats/pharmacokinetics , Decoquinate/chemistry , Decoquinate/metabolism , Drug Residues/chemistry , Drug Residues/metabolism , FemaleABSTRACT
INTRODUCTION: Freshwater sponges are common animals of most aquatic ecosystems. They feed by filtering small particles from the water, and so are thought to be sensitive indicators of pollution. Sponges are strongly associated with the abiotic environment and are therefore used as bioindicators for monitoring of water quality in water habitats. Among the freshwater sponges, Spongilla lacustris is one of the classic models used to study evolution, gene regulation, development, physiology and structural biology in animal water systems. It is also important in diagnostic of aquatic environments. The aim of this study was to characterize and visualize three-dimensional architecture of sponge body and measure skeleton elements of S. lacustris from Goczalkowice reservoir for identification purposes. MATERIAL AND METHODS: The scanning electron microscopy with an energy dispersive X-ray microanalysis (SEM- -EDS) and X-ray micro computed tomography (micro-CT) were used to provide non-invasive visualization of the three-dimensional architecture of Spongilla lacustris body. RESULTS: We showed that sponge skeleton was not homogeneous in composition and comprised several forms of skeleton organization. Ectosomal skeleton occurred as spicular brushes at apices of primary fibres with cementing spongin material. Choanosomal skeletal architecture was alveolate with pauci- to multispicular primary fibres connected by paucispicular transverse fibres, made by megascleres embedded in a scanty spongin matrix both in the choanosome and at the sponge surface. In contrast, microscleres were irregularly scattered in choanosome and skeletal surface. Furthermore, SEM-EDS studies showed that the distribution of silica in megascleres and microscleres was observed along the spicules and sponge surface areas. CONCLUSIONS: In conclusion, we showed that the combination of SEM-EDS and micro-CT microscopy techniques allowed obtaining a complete picture of the sponge spatial architecture.
Subject(s)
Porifera/ultrastructure , Animals , X-Ray MicrotomographyABSTRACT
Semduramicin is an ionophore coccidiostat used in the poultry industry as a feed additive. Cross-contamination of feeds for non-target animals with semduramicin is unavoidable. However, it is not known whether undesirable residues of semduramicin may occur in food after cross-contaminated feed is administered to animals. The aim of the work was to determine the levels of semduramicin in hen eggs (yolks and albumen) and tissues (liver, muscle, spleen, gizzard, ovarian yolks and ovaries) after administration of feed contaminated with 0.27 mg kg(-1) of this coccidiostat. The residues were determined using LC-MS/MS. The distribution pattern confirmed the high lipophilicity of semduramicin. Residues were found mainly in egg yolks (28.8 µg kg(-1)), ovarian yolks (19.5 µg kg(-1)) and liver (2.57 µg kg(-1)), while hens' muscle was free from semduramicin (LOD = 0.1 µg kg(-1)). Among edible tissues, the maximum level (2 µg kg(-1)) was exceeded only in the liver.