Detection Of Antibiotic Residues Research Articles

High throughput detection of antibiotic residues in milk by time-resolved fluorescence immunochromatography based on QR code

ABSTRACT Herein, we have successfully established a novel, rapid, and simple lateral-flow immunoassay based on time-resolved fluorescence and biotin-streptavidin to detect the residues of various antibiotics in milk. The fluorescence signal and sensitivity of immunochromatography were enhanced through biotinylated antibody coupled with streptavidin europium microspheres. Moreover, due to the use of a QR Code and fluorescent reader, quantitative detection and real-time data uploading can be achieved. Under the optimal conditions, the various antibiotic residues were detected in the milk samples. The results showed that the limits of detection of tylosin, lincomycin and doxycycline were 0.10, 0.06, and 0.27 ng/mL, respectively. The recoveries of the spiked milk samples were 88.9%~127%, with coefficients of variation less than 11%, and the test strip can be stored at room temperature for 12 months. This study shows that the proposed time-resolved fluorescence immunoassay is sensitive, rapid and reliable, and has the potential to be used for detection of veterinary antibiotic residues in food safety fields.

Fabrication of N-GQDs and AgBiS2 dual-sensitized ZIFs-derived hollow ZnxCo3-xO4 dodecahedron for sensitive photoelectrochemical aptasensing of ampicillin

A sensitive photoelectrochemical (PEC) aptasensing platform based on Nitrogen-doped graphene quantum dots (N-GQDs) and AgBiS2 dual-sensitized Zn/Co bimetallic oxide (ZnxCo3-xO4) dodecahedron as a matrix was constructed for the ultrasensitive detection of ampicillin (AMP). Concretely, the ZnxCo3-xO4 dodecahedron derived from ZnCo-ZIFs retained the unique hollow porous structure, which provided large specific surface and efficacious active sites, and thereby significantly enhancing the light utilization and shortening the photoelectrons transmission path. Both N-GQDs with the up-conversion effect and eco-friendly AgBiS2 with optimal band gap for solar absorption were utilized to dual-sensitize ZnxCo3-xO4 dodecahedron to further strengthen the PEC performance. Subsequently, the aptamer recognition technology was integrated with the modified photoelectrode, adopting AMP-aptamer to catch the target AMP, accompanied the hole oxidation of bind AMP causing the remarkable increase of photocurrent signal, the AMP could be specific and sensitive detect. Under optimized conditions, the photocurrent of developed aptasensor increased linearly displayed large liner response of 0.5 pmol/L – 10 nmol/L with a detection limit of 0.25 pmol/L (S/N = 3). Besides, the novel PEC AMP-sensoring exhibited excellent reproducibility, perfect stability and selectivity, which could open a potential avenue for antibiotic residues detection in environmental media.

Effective screening of antibiotic and coccidiostat residues in food of animal origin by reliable broad-spectrum residue screening tests

Foods of animal origin are controlled for antibiotic and coccidiostat residues. The rapid residue detection is possible using reliable broad-spectrum screening tests. This study’s objective using four microbial inhibition tests for the detection and identification of antibiotic and coccidiostat residues in different foods of animal origin: Premi®Test, EXP Ampulle test, Milchtest and Screening Test for Antibiotic Residues (STAR). Four hundred and thirty (430) food samples (165 animal tissues, 152 raw cow’s milk and 113 eggs) were randomly collected and screened. Using the Premi®Test, 18 samples were positive and 6 samples dubious. Using the EXP Ampulle test, 31 samples were positive and 2 samples dubious. Using the Milchtest, 15 samples were positive and 12 samples dubious. Using the STAR, 65 samples were positive with 62 samples positive on plates specific for beta-lactams and sulphonamides, 4 samples on plates specific for aminoglycosides, 8 samples on plates specific for macrolides and beta-lactams; and 7 samples on the plates specific for tetracyclines. Retesting using penicillinase and para-aminobenzoic acid (PABA) to confirm the presence of beta-lactams or sulphonamides all potentially positive tube test samples revealed 21 samples positive for beta-lactams and 27 samples positive for sulphonamides. Further testing of sulphonamide positive chicken samples revealed the positivity for coccidiostat salinomycin which was confirmed by testing with PABA, which counteracting salinomycin inhibition. Three hundred and sixty six (366) animal food samples were negative for antibiotic and coccidiostat residues. Microbial inhibition tests are preferred for initial antibiotic screening and have also proven useful for coccidiostat screening and post-screening. HIGHLIGHTS Foodstuffs of animal origin are subject to controls on antibiotic and coccidiostat residues. Microbial inhibition tests are still the preferred choice for the initial screening of antibiotic residues in food matrices and could become a useful tool for the screening of coccidiostat residues also. More specific post-screening analysis with PABA proved unexpectedly to be a reliable tool in the preliminary detection of coccidiostat residues in poultry meat and eggs.

Protecting Consumer Health By Developing a Multiplex Amperometric Immunosensor for the Detection of Banned Antibiotic Residues in Milk

Introduction Chemical (eg pesticides, veterinary drugs, etc.) and bacteriological contaminants (eg. foodborne pathogens) could contaminate animal and plant derived food products for human consumption. Some antibiotic residues (eg. chloramphenicol, nitrofuran metabolites, dyes) are banned in foodstuffs of animal origin (eg. milk, meat, eggs, etc.) in European Union because of toxicological risks for the consumer. The European Regulation has set Minimum Required Performance Limits (MRPL) [1] or Reference Point for Action (RPA) for banned substances [2]. Food containing residues of substances at or above the MRPL or RPA are declared non-compliant and consignments are rejected from the consumer’s market.Screening methods are the first stage of food control and so are essential for food safety monitoring. Conventional screening methods are microbiological methods (eg. plate tests, tube tests), immunological methods (eg. ELISA, radioimmunoassays) or physico-chemical methods (Thin Layer Chromatography, High Performance Liquid Chromatography (HPLC), liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS)). These methods sometimes lack of sensitivity or specificity; they also could be time and money consuming. There is thus a need to develop novel screening methods for antibiotic residues detection, preferably with the potential for the field-testing (eg. farm control, self-control). Electrochemical biosensors make it possible to develop a promising and economically interesting approach. Electrochemical immunosensor An innovative electrochemical method based on disposable Screen Printed Carbon Electrodes (SPCE), coupled to magnetic beads (MB), allowing the simultaneous detection of 3 families of antibiotics in milk, was published by a Spanish academic team [3]. This technique presents major advantages: low cost (eg. disposable electrodes, potentiostat), promising detection limits, portability, and possible automatisation. Our laboratory has evaluated the transferability of the method. An electrochemical immunosensor has been developed for the detection of chloramphenicol residues in milk as a proof of concept. The matrix effect (milk samples) was high and so sample preparation has to be improved to reduce matrix effects.The objective is to develop an amperometric bead-based immunosensor for the multiplex detection of banned antibiotics (eg. chloramphenicol, nitrofuran metabolites, dyes) in bovine milk. Method Antibodies (Abs) against antibiotics are grafted on the surface of magnetic beads (MBs). Milk samples and antibiotic conjugated with Horseradish peroxidase (HRP) are mixed with MBs-Abs. A competition occurs between the HRP conjugates and the antibiotic residues if present in the sample, for the binding to the antibody. The MBs are washed to remove free antibiotics and conjugates. Then, a Screen Printed Carbon Electrode (SPCE) with MBs on its surface (maintained by a magnet) is soaked into a buffer solution containing hydroquinone; when adding hydrogene peroxide (H2O2) to the solution, an amperometric signal is produced, due to the enzymatic activity of HRP and measured. The amperometric signal is inversely proportional to the antibiotic concentration in the sample. Results and Conclusions Screening methods for the detection of veterinary drugs in food products have to be validated according to the European regulation [1] and to the European guideline for the validation of screening methods [4]. After the development and the optimization of the analytical parameters (eg. sample preparation, HRP concentration, incubation time, applied potential, etc), the methods developed for single compounds will be evaluated and validated according to the European regulations. Then the single compound methods will be merged into one multiplex method if possible. The results will be presented to the conference, discussing the advantage sand drawbacks of amperometric biosensors for the screening of antibiotic residues in food products.

Sensitive and selective electrochemical aptasensor via diazonium-coupling reaction for label-free determination of oxytetracycline in milk samples

As one kind of tetracycline antibiotics, oxytetracycline (OTC) residues in animal-derived foods can do serious harm to human health. Though aptasensors for the detection of OTC are widely reported, label-free electrochemical aptasensor with low cost, simple preparation and good applicability should be further explored to meet the current urgent needs. In this study, a label-free electrochemical aptasensor for OTC determination was designed. The detection was based on specific recognition by the aptamer covalently-bound on the sensing interface via diazonium coupling reaction, which was verified by computer simulation. Experiment results showed that the differential pulse voltammetry (DPV) current response of the constructed electrochemical aptasensor was linear with the logarithm of OTC concentration in the range of 1.0 × 10−9 g mL−1–1.0 × 10−4 g mL−1 (R2 = 0.9897) with the limit of detection of 2.29 × 10−10 g mL−1. The proposed aptasensor indicated good selectivity, reproducibility and stability, which could be attributed to the stable modification of aptamer on the sensing interface. The OTC in the milk sample was detected by the spiked recovery method, and good results were obtained, with the recovery rate being 87.0%-99.3%. The proposed label-free electrochemical aptasensor can provide methods for low-cost, accurate and rapid detection of antibiotic residues.

Detection of antibiotic residues in Cow's milk: A theoretical and experimental vibrational study

The presence of antibiotic residues in milk has been one of the biggest challenges for public health agencies. When these residues are above the established maximum limits, it becomes worrying as they may have consequences for human health. Inadequate amounts of these substances may also impair the production of cheese, yogurt and other dairy products.Through vibrational spectroscopy and DFT theoretical calculations β−lactam antibiotics were investigated in bovine milk. For thus, structural and spectroscopic information of penicillin and ampicillin were obtained in different reaction media.Our methodology allowed the establishment of spectroscopic patterns of the antibiotics isolated and in the presence of milk. This work is expected to contribute another tool for the detection of minimal amounts of these compounds quickly and accurately.

A coupled method of on-line solid phase extraction with the UHPLC‒MS/MS for detection of sulfonamides antibiotics residues in aquaculture

The use of a variety of antibiotics in fish farming raises serious concern about the development of antibiotic resistance. Sulfonamides antibiotics (SAs), which are widely used in aquaculture and generate large eco‒toxicological effects with significant mutagenicity and teratogenic consequences, are still difficult to determine in aquatic organisms. In this study, an automatic technology was developed by coupling on‒line solid phase extraction system (on‒line SPE) with ultra‒high‒performance liquid chromatography spectrometry‒mass spectrometry (UHPLC‒MS/MS). Particularly, using a single on‒line column in the process of sample pretreatment, e.g., HLB or C18, phospholipids that potentially caused the matrix effect cannot be removed form biological sample. We applied a mixed cation exchange column (Oasis® MCX) connected with a hydrophilic lipophilic balance column (Oasis® HLB) in series in on‒line SPE clean‒up to remove interferences and finally obtained a clear and stable eluant. The on‒line SPE working conditions and UHPLC‒MS/MS parameters were optimized for their sensitivity, accuracy, decision limit, and detection capability, which were further calibrated for fish, shrimp and crab. The results showed that the limits of detection and limits of quantification ranged from 1.46 to 15.5 ng/kg, and 4.90–51.6 ng/kg, respectively. Accuracy values covered 71.5%–102% at the three concentration levels (0.1, 0.5, 1.0 μg/kg) for all compounds and average repeatability (relative standard deviation, RSD%) ranged from 3.47% to 14.2%. This on‒line SPE coupled with UHPLC‒MS/MS method is a way forward for an automatic, powerful detection technology for determination of antibiotics from complex matrix.

Microwave method synthesis of magnetic ionic liquid/gold nanoparticles as ultrasensitive SERS substrates for trace clopidol detection.

Clopidol is one of the most widely used anti-coccidiosis drugs. Its residues in poultry products and the environment pose a serious threat to human health. In this work, microwave-assisted synthesis of magnetic ionic liquid/gold nanoparticles (MIL-Au NPs) as the SERS substrates were first designed for sensitive and reliable determination of clopidol residue in egg samples. The experiment shows that MIL(1-methyl-3-hexyl imidazole ferric tetrachloride ([C6mim]FeCl4)) and microwave play a key role in the dispersion and morphology of Au NPs. Under the optimal conditions, the as-prepared MIL-Au NPs were applied to the SERS detection of clopidol in methanol and egg solution and its detection limits can be as low as to 0.5μg/kg (equal to 0.5ppb) in both solutions. The standard curves with regression coefficients of 0.9298 and 0.93496 were constructed in the linear range of 100-1000ppb and 0.5-50ppb for clopidol in egg solutions. Moreover, satisfactory recoveries (97.5-103.2%) were obtained for egg samples. The developed SERS method provides a way for quantitation of clopidol and can be applied for the convenient, reliable, and highly sensitive detection of antibiotic residues in food and environment, which has great potential in food safety and biological monitoring. Graphical abstract.

Detection of tetracycline antibiotics in honey using high-performance liquid chromatography

It is hard to overestimate the value of honey since the constituent substances in it are of great importance in the food industry and medicine. The quality of honey is established by the legislation of the Russian Federation (GOST). But the levels of these standards are regulated by outdated methods of analysis, which can not give reliable results. The detection of antibiotic residues in honey is a central issue in the quality and safety control of this product. Accumulation of drugs in honey used to treat bee colonies can cause allergies and dysbiosis in people who have eaten such honey, as well as develop antibiotic resistance in microorganisms. At present, one of the promising directions in the field of detecting medicines in honey is the use of high-performance liquid chromatography (HPLC). It helps selectively and accurately detect antibiotic substances in honey bee products. In Russia, the HPLC method is used with mass spectrometry to detect tetracycline residues in honey. A significant drawback with this method that limits the widespread use of it is the application of expensive, technically sophisticated equipment that needs high-quality reagents and consumables. The purpose of this work was to develop the simultaneous identification of tetracycline antibiotics in honey and carry out their quantitative analysis by a reversed-phase HPLC method. A sample preparation algorithm was developed, and the conditions for chromatographing combined indication of tetracyclines in honey at an acceptable concentration according to the MRL (0.01 mg/kg) with Agilent 1260 Infiniti liquid chromatograph equipped with a column thermostat, a gradient pump, and a UV detector were selected. According to the results of the research, the most optimal condition for the simultaneous analysis of oxytetracycline, tetracycline hydrochloride, chlortetracycline in honey by HPLC method with ultraviolet detection was a wavelength of 254 nm, a flow rate of 0.5 ml/min and a column temperature of 25° C. Under these conditions, the antibiotic retention time was determined: 4.069 minutes for oxytetracycline, 4.331 minutes for tetracycline hydrochloride, 4.642 minutes for chlortetracycline. The developed HPLC method for the simultaneous determination of tetracycline antibiotics in honey was tested on honey bee products from the regions of the Republics of Tatarstan and Bashkortostan.

Detection of penicillin G residues in milk based on dual-emission carbon dots and molecularly imprinted polymers

Instant detection of antibiotic residues in dairy products has been remained a challenge. Current methods require careful samples storage and handling, skilled personnel, and expensive instrumentations. Herein, we report the preparation of a ratiometric fluorescent sensor that contains different colored Carbon dots (CDs) as dual fluorophores, and a mesoporous structured molecularly imprinted polymer as a receptor (B/YCDs@mMIP) for penicillin-G (PNG) detection in milk. Upon PNG addition, only the fluorescence of yellow emissive CDs was quenched due to analyte blockage, while that of the blue emissive CDs stayed almost constant, which led to an obvious change in the fluorescence color from the yellow to blue. A linear response in the range of 1–32 nM with a detection limit of 0.34 nM and excellent recognition specificity for PNG over its analogs were also observed. Comparing our sensor with its counterparts, it exhibited a promising potential in the in-situ PNG detection in milk.

Detection of Antibiotic Residues in Chicken Meat and Eggs from Traditional Markets at Yogyakarta City Using Bioassay Method

Studies on antibiotic residues content in food of animal origin are currently needed to support veterinary public health programs. The present study was described bioassay method for the detection of antibiotic residues in chicken meat and eggs from traditional market at Yogyakarta City. A number of twenty-four chicken meat samples and 24 egg samples were taken from 8 traditional markets in Yogyakarta city. Samples were examined at Centre for Veterinary Wates, Yogyakarta, Indonesia using bioassay method for screening detection of penicillin, aminoglycoside, macrolide and tetracycline residues. This bioassay method using some bacteria, such as Bacillus stearothermophillus, B. cereus, B. subtilis, and Kocuria rizophila. A percentage of the results showed that 8.33% (2/24) samples of chickens tested positively contained the oxytetracycline antibiotic residues. Meanwhile, as much as 75% (18/24) samples of positive eggs contain penicillin antibiotic residues, positive residues of aminoglycoside amounted to 12.5% (3/24) and the positive residues of oxytetracycline also amounted to 12.5% (3/24).

3-D DNA nanodevices for on-site sensitive detection of antibiotic residues in food.

Developing convenient and sensitive detection methods for antibiotic residues in food is beneficial for ensuring food quality and human health. The tough challenges that limit the development of sensitive, quantitative, portable, on-the-spot antibiotic detectors are the lack of simple and effective target recognition and signal amplification strategies, and direct digital quantification. Herein, we developed a visual digital quantitative aptasensor, based on a binding-induced 3-D DNA nanomachine signal probe, for the simple and sensitive, on-the-spot detection of antibiotics.

Antibiotic Residue in Marketed Broiler Meat of Kathmandu Metropolitan City

Broiler meat is the most consumed poultry product in Nepal. To increase the productivity and met the demand there is high use of antibiotics for prophylactic and as growth promoter in poultry industry. Continuous use of Antibiotic in broiler and supplying them in market before with-drawl period had led to development of Antibiotic Residue. This study aims for detection of antibiotic residue in marketed broiler meat of Kathmandu Metropolitan City. A total of 150 meat samples were taken (75 liver +75 breast muscle), and 300 tests performed for two group of antibiotics Group A(Tetracyclines) and Group B (macrolides, aminoglycosides and sulphonamides). Purposive and randomized sampling procedure was done and commercially available test kit was used. 74 tests were found to be positive for antibiotic residue and 53 of them were above the Minimum residue level. The true prevalence was found to be 28.25%. The presence of antibiotic residue in meat found to be statistically significant(p<0.05). Antibiotic residue was found higher in liver than in muscle. This study concluded that antibiotics residue was found higher than recommended in poultry meat of Kathmandu metropolitan city, which could expose serious human health hazard. Hence to mitigate the situation one health and multisectoral approach guiding for safe and rational use of antibiotics should be implemented.

Şanlıurfa İlinde Satışa Sunulan Kıymalarda Premi®Test ile Antibiyotik İlaç Kalıntılarının Tespiti

Hayvanlarda antibiyotik ilaçların uygun olmayan şekilde kullanılması, antibiyotik dirençli mikroorganizmaların gelişimini ve yayılmasını kolaylaştırabilir ve ayrıca hayvansal gıdalarda antibiyotik kalıntı oluşumunu hızlandırabilir. Bu çalışmanın amacı, Şanlıurfa ilinde kasaplarda satışa sunulan sığır ve koyun kıymalarında antibiyotik ilaç kalıntılarının varlığını tespit ederek halk sağlığı açısından risk oluşturup oluşturmadığını değerlendirmektir. Bu çalışma kapsamında farklı zaman aralıklarında kasaplardan rastgele 20 sığır, 20 koyun olmak üzere toplam 40 kıyma örneği Premi®Test ile antibiyotik ilaç kalıntılarının tespiti amacıyla analiz edilmiştir. Sığır kıyma örneklerinin 10 adedinde (%50) pozitif, koyun kıyma örneklerinin 12 adedinde (%60) pozitif sonuç görülmüştür. Çalışma bulgularına göre Şanlıurfa ilinde kasaplarda satışa sunulan sığır ve koyun kıymalarında antibiyotik ilaç kalıntısının olduğu tespit edilmiş olup bu kıymaların tüketilmesinin halk sağlığı açısında risk oluşturabileceği kanaatine varılmıştır.

Detection of several quinolone antibiotic residues in water based on Ag-TiO2 SERS strategy

Herein, a surface-enhanced Raman scattering (SERS) strategy based on semiconducting substrate was exploited for detection of several antibiotic residues both in ultrapure water system and in actual water system. The as-prepared Ag-TiO2 (Ag synchronously deposited and doped TiO2) nanoparticle SERS-active substrate can achieve high sensitive SERS detection for difloxacin hydrochloride, ciprofloxacin, enrofloxacin, danofloxacin and enoxacin (five widely used quinolone antibiotics) in actual water samples, and the detection limits are as low as 4.36 × 10−12, 7.08 × 10−11, 3.94 × 10−11, 3.16 × 10−11 and 3.15 × 10−10 mol/L, respectively. These detection limits are far below the maximum of residue limit (3.01 × 10−7 mol/L) stipulated by the European Union. And, the desirable quantitative relationships can be obtained in a wide concentration range. The recoveries of five antibiotic residues from spiked actual water samples are found to be more than 80.8% with the relative standard deviations between 2.1% and 4.7%. Even, the proposed SERS method can accurately distinguish every antibiotic species from a mixed antibiotic residue sample with multiple antibiotics. And, Ag-TiO2 nanoparticles can also serve as an efficient photocatalyst for photocatalytic degradation of these antibiotic residues, which provides a multi-functional platform for synchronous determination and degradation of antibiotic residues in real environment.

Determination of antibiotic residues in Indian honeys and assessment of potential risks to consumers

Honey, being a healthy and natural product, is considered a valuable food commodity across the globe. However, injudicious use of antibiotics to prevent and control bacterial foulbrood diseases of honey bees not only contaminate honey but may also pose potential risks to human health. In this context, 150 commercial honey samples from India were investigated for the presence of oxytetracycline, erythromycin and chloramphenicol residues. The competitive immunoassay and chromatographic methods used for detection of antibiotic residue were validated as per European Commission decision. Oxytetracycline and erythromycin with concentrations above tolerance limits established by FSSAI were detected in 15.3% and 5.3% samples, respectively. Majority of oxytetracycline contaminated samples were uncertified branded (21.4%) and unbranded honeys (14.3%) sold in retail markets trailed by certified branded honeys (10.2%). All the erythromycin positive samples were uncertified ones. The honey samples screened by competitive ELISA were found to be free from chloramphenicol residues. Further, potential human health risks associated with exposure to antibiotics detected in honey were also evaluated. Although, estimated daily intakes of antibiotic residues were found to be lower than the established acceptable daily intakes but the presence of antibiotics in honey is a considerable public health concern especially for children, old and ill people. The results of present study suggests that continuous residue monitoring programs, accompanied by educational programs to the beekeepers’ on beehive management are indispensable to meet the expectations of food safety and public health at both national and international fronts.

Robust and selective electrochemical detection of antibiotic residues: The case of integrated lutetium vanadate/graphene sheets architectures

Lutetium vanadate (LuVO4) is a promising material for electrochemical application owing to its good conductivity and electrocatalytic activity. Herein, we demonstrate a facile technique for the synthesis of a LuVO4/ graphene sheet (GRS) nanocomposite where LuVO4 is encapsulated with an ultrathin GRS to form a hierarchical structure (LuVO4/GRS). The resulting hierarchical LuVO4/GRS architecture was characterized by several analytical and spectroscopic techniques. The resultant electrocatalyst shows superior electrochemical sensing for nitrofurantoin (NFT) with a low detection limit (0.001 μM), wide linear range (0.008–256.0 μM) and excellent sensitivity (1.709 μA μM−1 cm-2). It has been demonstrated that the enhanced electrocatalytic performance of LuVO4/GRS nanocomposite is due to their excellent electrical conductivity, suitable surface area, high redox reaction and large number of electron transport. In addition, the LuVO4/GRS nanocomposite exhibited excellent response towards NFT detection with adequate reproducibility, good repeatability, long-term stability and excellent selectivity over its structural analogs and common interferents. Furthermore, the practical applicability of the proposed electrochemical sensor was successfully applied for determination of NFT in environmental samples with satisfactory results. The LuVO4/GRS nanocomposite presented here can serve as a favorable candidate for developing electrochemical sensor and plays an important role in widespread fields.

Broad Spectrum Detection of Antibiotic Residues in Poultry Meat by a Multi-Plate Assay

Abstract The objective of this study was to use the “Screening test for antibiotic residues” (STAR) as a broad-spectrum detection method for antibiotic residues in poultry meat. The STAR method is a microbiological inhibition assay (a five plate test) where the development of inhibition zones (IZs) indicates the presence of antibiotic residues in meat samples. By using the STAR method, in a total of 13 poultry products providing 18 meat samples (14 muscle and 4 skin) and 18 corresponding juice samples, 11 out of the 18 samples were positive for containing antibiotic residues. Based on muscle alone (which is the matrix validated for use in the STAR method), 6 of the 14 muscle samples were positive for antibiotic residues. The STAR method as a screening technique proves advantageous as it is relatively easy to perform and of a low cost. Furthermore, the STAR method not only indicates the presence or absence of antibacterial substances, but simultaneously, a positive sample gives an indication of the antibiotic family present due to the use of five different bacterial test organisms. Families of antibiotics pre-identified due to positive samples in the results of this study include aminoglycosides (one out of 18), beta-lactams and sulphonamides (6 out of 18), and macrolides (5 out of 18). Such pre-identification of the antimicrobial families allows for a targeted confirmatory analysis. However, one could argue that the STAR method is laborious and time consuming. Overall, given the potential for false positive/negative results, further confirmatory method analysis of the samples must be performed to ensure that the results and conclusions drawn here are true.

Conductive imprinted polymers for the direct electrochemical detection of β-lactam antibiotics: The case of cefquinome

A biomimetic sensor for cefquinome (CFQ) was designed at multi-walled carbon nanotubes modified graphite screen-printed electrodes (MWCNTs-G-SPEs) as a proof-of-concept for the creation of a sensors array for β-lactam antibiotics detection in milk. The sensitive and selective detection of antibiotic residues in food and environment is a fundamental step in the elaboration of prevention strategies to fight the insurgence of antimicrobial resistance (AMR) as recommended by authorities around the world (EU, WHO, FDA). The detection strategy is based on the characteristic electrochemical fingerprint of the target antibiotic cefquinome. A conductive electropolymerized molecularly imprinted polymer (MIP) coupled with MWCNTs was found to be the optimal electrode modifier, able to provide an increased selectivity and sensitivity for CFQ detection. The design of CFQ-MIP was facilitated by the rational selection of the monomer, 4-aminobenzoic acid (4-ABA). The electropolymerization process of 4-ABA have not been fully elucidated yet; for this reason a thorough study and optimization of electropolymerization conditions was performed to obtain a conductive and stable poly(4-ABA) film. The modified electrodes were characterized by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and cyclic voltammetry (CV). CFQ-MIP were synthesized at MWCNT-G-SPEs by electropolymerization in pH≈1 (0.1 M sulphuric acid) with a monomer:template ratio of 5:1. Two different analytical protocols were tested (single and double step detection) to minimize unspecific adsorptions and improve the sensitivity. Under optimal conditions, the lowest CFQ concentration detectable by square wave voltammetry (SWV) at the modified sensor was 50 nM in 0.1 M phosphate buffer pH 2.

The Effect of Boiling on Stability of Oxytetracycline and Sulfamethazine Residues in Raw Milk using HPLC Method

Two hundred raw milk samples (250 ml of each) were collected from small dairy farms, street peddlers and dairy shops in Mansoura Governorate. These samples were screened using Bacillus Subtilis Diffusion Assay for qualitative detection of antibiotics residues; where the percentage of suspected positive samples was 12.5%. High Performance Liquid Chromatography – Ultra Violet detector (HPLC- UV) method was developed and validated to determine the amount of oxytetracycline (OTC) and sulfamethazine (SMZ) residues in raw milk before and after boiling. The results revealed that 8.5 % of the raw milk samples were containing (OTC) residues (6.5 % of them exceed MRL) while, (SMZ) was detected in4 % of the raw milk samples (3 % of them exceed MRL). Upon applying heat treatment, the reduction in the (OTC) content in milk boiled for 2 minutes was 30.5% but boiling for 5 minutes was accompanied with 54.1% reduction. On the other hand, the percentage of (SMZ) reduction was 1.7% and 9.5% in milk boiled for 2 and 5minutes respectively which could be attributed to the low heat stability of (OTC) and high stability of (SMZ).