Prevalence,seasonality and antibiotic susceptibility of Campylobacter spp. isolates of retail broiler meat in Iran

Campylobacter species, are the most common cause of bacterial gastroenteritis worldwide. The main route of transmission is generally believed to be via undercooked meat and meat products. This study was conducted to determine the prevalence, seasonality and antibiotic susceptibility of Campylobacter spp. isolates of retail broiler meat in Mashhad, Iran. From January 2013 through December 2013, 360 broiler meat samples were purchased in Mashhad, Iran. Identification of a presumptive Campylobacter species was performed using the cultural method and a polymerase chain reaction (PCR) assay. Antimicrobial susceptibility testing was performed using the disc diffusion method. Overall, 227 samples (63.1%) were positive for Campylobacter. The most prevalent Campylobacter spp. isolated was Campylobacter jejuni (88.1%). There was a significant seasonal prevalence of Campylobacter spp. in broiler meat in Mashhad, Iran (P < 0.0001). The highest isolation rate was also in summer (78.9%). The antimicrobial susceptibility test showed that 93.4% of the isolates were resistant to one or more antimicrobial agents. Resistances to tetracycline (87.2%) and ciprofloxacin (79.3%) were the most common resistances. The findings of this study showed a relatively high prevalence of Campylobacter contamination and antimicrobial resistance in broiler meats in Mashhad, Iran. To the authors' knowledge this is the first study on the seasonal prevalence and antibiotic susceptibility of Campylobacter spp. isolated from broiler meat in Iran.     

Assessment of the Campylobacter jejuni and C. coli in broiler chicken ceca by conventional culture and loop-mediated isothermal amplification method

In a two-year survey of the 24 Japanese broiler chicken flocks at 9 farms from 2013 to 2014, C. jejuni/C. coli prevalence was assessed in a total of 131 slaughtered broiler chicken cecal samples by conventional culture methods and loop-mediated isothermal amplification (LAMP) assay. While 93 samples were C. jejuni/C. coli-negative, 38 (29.0%) showed Campylobacter loads of between 6.4 and 9.0 log CFU/g of ceca in conventional culture methods. The performance of LAMP assay was 100% accurate in terms of diagnostic sensitivity (38/38), specificity (93/93). Furthermore, LAMP assay enabled direct screening of C. jejuni and C. coli in cecal samples from broiler chicken chickens as rapid and cost-effective detection within 90 min and less than 1 US dollar, which can help monitor release of Campylobacter-contaminated chicken into the food chain, thereby reducing the incidence and public health risk of campylobacteriosis. Seasonal changes in C. jejuni and C. coli prevalence in broiler chicken ceca were significantly correlated with the frequency of food poisoning incidents caused by these bacteria in Japan.     

Systematic review-meta-analysis of the effect of chilling on Campylobacter spp. during primary processing of broilers

Carcass chilling is a critical control point for Campylobacter spp. during the primary processing of broiler chickens. Our objective was to evaluate chilling intervention research that measured the change in Campylobacter prevalence and concentration on broiler chicken carcasses during primary processing using systematic review-meta-analysis (SR-MA) methodology. Experimental and observational research published in English that investigated impacts of chilling on Campylobacter spp. during primary processing of broiler chicken carcasses were considered. Random-effects MA of air chilling resulted in heterogenous summary effect estimates (mean reduction = 0.74 log₁₀ CFU/carcass, 95% CI: 0.32–1.17, I² = 91.3%; and odds ratio = 7.42, 95% CI: 0.32–174.05, I² = 92.3%). Random-effects MA of immersion chilling with chlorine resulted in heterogenous summary effect estimates (mean reduction = 1.74 log₁₀ CFU/carcass, 95% CI: 1.32–2.16, I² = 86.4%; and odds ratio = 0.50, 95% CI: 0.20–1.28, I² = 90.6%). Effects of immersion chilling with unspecified disinfectants were also determined and varied depending on study design. The SR-MA indicated that air chilling and immersion chilling reduce Campylobacter concentrations. Due to conflicting results across studies, the estimated average effect of air chilling on Campylobacter prevalence is not informative. Immersion chilling with chlorine demonstrated a trend towards reduced Campylobacter prevalence, but this result was not significant; results should be interpreted with caution because the overall methodological soundness of included studies was low. Existing research on the effectiveness of broiler carcass chilling on Campylobacter concentration or prevalence is limited and heterogenous. Results generated herein can inform decisions makers and stakeholders on potential effective chilling interventions, and can be used to inform quantitative microbial risk assessment to estimate processing measure impacts on public health.     

The occurrence of Campylobacter spp. in Estonian broiler chicken production in 2002–2007

The aim of the present study was to monitor the occurrence of Campylobacter spp. in broiler chicken production in Estonia from 2002 to 2007. Campylobacter spp. was isolated in 163 (12.3%) of 1320 broiler chicken meat samples form 2002 to 2007 and in 115 (6.3%) of 1819 cecal samples in 2005–2007. Campylobacter jejuni was the most commonly isolated species (98.2%), followed by Campylobacter coli (1.4%) and Campylobacter lari (0.4%). The seasonal peak of Campylobacter contamination was from July to September. Our findings showed that Campylobacter contamination at all levels of broiler chicken production in Estonia was low.     

Protecting broilers against Campylobacter infection by preventing direct contact between farm staff and broilers

The objective of this study was to test the hypothesis that farm staff are the primary vector of Campylobacter transmission into broiler flocks. On 3 different farms and 5 different flocks (3 flocks on farm 1 and 1 flock on each of farms 2 and 3) a small section of the broiler house (3 × 2 m (farm 1) and 1 m × 1 m (farms 2 and 3)) was sectioned off using Perspex or plastic sheeting. This ‘biosecure cube’ (BC) was populated with 25–125 chicks (test birds), a small subset of the general population of up to 30,000 (control) birds in the broiler house. The BC area incorporated the water and feed-lines thus the test and control birds had access to the same feed, water and air. However, unlike in the general broiler house, the farm staff had no direct access to this sub-population. Dead birds were aseptically removed by the researchers. The birds were tested for Campylobacter (faecal and/or caecal samples), on the day of chick arrival and every 7 days thereafter. In farm 1-flock 1 the general broiler population was Campylobacter-positive after 21 days but the test birds remained negative until day 35. The general broiler population in the other 4 flocks were Campylobacter positive as early as day 14, but in all cases the test birds remained negative. Moreover BC broilers were significantly (P < 0.05) heavier than the control birds (400 g on average), at first thinning. It was therefore concluded that preventing direct contact between the farm staff and the broilers prevents Campylobacter infection in broilers.     

Multi-detection of mycotoxins by membrane based flow-through immunoassay

A membrane-based flow-through immunoassay for rapid non-instrumental multi-detection of ochratoxin A (OTA), zearalenone (ZEN) and fumonisin B1 (FB1) in cereal grains and silage was developed. The test is based on a direct competitive enzyme immunoassay performed on a membrane. Alkaline phosphatase was used as enzyme label to decrease matrix interference. The analytical method involved a fast extraction procedure (extraction with a mixture of methanol, water and acetic acid 79:20:1, v/v) followed by a multi-detection. The immunotest allows the visual estimation of the presence of three mycotoxins in less than 15 min. The cut-off limit of this test have been set at a value not higher than half of EU legislative limits (2.5, 50 and 1000 μg kg⁻¹ for OTA, ZEN and FB1 correspondingly in wheat; 2.5, 100 and 1000 μg kg⁻¹ in maize; 25, 125 and 2500 μg kg⁻¹ in silage). Evaluation and validation studies have been performed using spiked and naturally contaminated samples and results were compared with LC–MS/MS. Also the possibility of analyte detection in wheat at two concentration levels by the immunotest was demonstrated with OTA and ZEN as an example. In spite of the semiquantitative-qualitative character of the test, the results demonstrate that the test provides a very good estimation of the mycotoxins concentration in wheat, maize and silage. This test format could be adapted to the multi-detection of other contaminants in food and feed.     

Determination of fumonisin B1 in bovine milk by LC–MS/MS

The aim of the present work was to develop a sensitive and selective method for identification and quantification of fumonisin B1 (FB1) in bovine milk. FB1 was isolated by immunoaffinity column and was detected using liquid chromatography coupled with tandem mass spectrometry in positive electrospray ionization (ESI+).The LOQ of the method was 0.1 μg/kg that was lower than the others reported in the literature. The high coefficient of determination (R² > 0.99) obtained in the range of 0.1–10.0 μg/kg, the good recovery (84%) and relative standard deviation (7%) of the proposed method ensure correct fumonisin detection in milk even at relatively low concentrations.The developed method was applied on different commercial samples in order to test its efficacy. FB1 was found above the LOQ in eight out of 10 samples analysed and the average level of contamination found was 0.26 μg/kg.     

Derivation of performance objectives for Campylobacter in broiler carcasses taking into account impact of selected factors on pathogen prevalence and counts

Food safety standards in the European Union include microbiological criteria and targets in primary production. The current paper provides a strategy to elucidate risk-based metrics such a potential Food Safety Objective for Campylobacter used as benchmark to derive possible Performance Objectives for the pathogen in broiler carcasses tested after chilling. The Performance Objectives were developed using the EFSA data collected on broiler carcasses during the monitoring study performed in 2008 in the European Union according to the evaluation of the different risk factors included in the survey. The FSO for Campylobacter was set at −1.2 log₁₀ cfu/g (∼6 cfu/100 g). The Campylobacter concentrations after chilling resulting in a final concentration equal or below this proposed FSO were suggested as possible POs. The results obtained indicated that batches originating from previously thinned flocks can be more at risk of being colonized with Campylobacter. In fact, the estimated mean concentrations of Campylobacter on carcasses were 1.05 and 2.38 log₁₀ cfu/g for non thinned and thinned flocks, respectively. Further, the impact of high Campylobacter contamination on carcasses (>2.5 log₁₀ cfu/g) was shown since for those carcasses a reduction in PO values higher than 1.5 log₁₀ cfu/g is needed to meet the FSO. In contrast no significant differences for PO values estimated were found between slaughterhouses with different capacity and for carcasses tested at different times from collection. This study provides a validated methodology for the estimation of risk-based metrics based on a quantitative approach allowing food safety authorities to develop specific microbiological criteria.     

Optimal design of a novel oil–water separator for raw oil produced from ASP flooding

Oil recovery can be greatly enhanced with the ASP (Alkali/Surfactant/Polymer) flooding technology by increasing sweeping efficiency and displacing efficiency. But the emulsification of the residual chemical in the recovered oil from ASP flooding makes it very difficult to separate water from oil. To make the oil–water separation of ASP products more efficient to meet the discharge standards, some improvements need to be made on regular oil–water separators. Based on the physical properties of ASP products in Daqing Oilfield, novel packing and newly designed Crude oil–water separator are studied in this paper. Orthogonal test is used to optimize the design of the novel separator, including the structure and material of coalescent packing, as well as the operating conditions. Experiment results suggest that the separation efficiency of the new type separator is higher than 98%. Both the outlet oil phase and the water phase have met the corresponding standards. Oil concentration in the discharge water is reduced to 600 mg L^− 1 and average drop size is about 6 μm. It can be easily concluded that the new type separator has a better performance on the oil–water separation of ASP products. At the end of this paper, the drop size distribution (DSD) in the outlet water is analyzed to provide data for the wastewater treatment process following the crude oil–water separation.     

Development of an immunochromatographic assay for rapid and quantitative detection of clenbuterol in swine urine

A lateral flow strip test was developed for quantitative detection of clenbuterol (CLE) in swine urine in a 10 min total assay time. This new quantitative system for CLE was developed based on the concept of using the ratio of the optical densities (ODs) of the test line (A_T) to that of the control line (A_C) to offset the inherent heterogeneity of lateral flow test strips (LFTS_AT/AC) and the effect of sample matrix. Various parameters such as immunoreaction time, the concentration of analyte, reaction temperature and pH of the reactions, as well as the ionic strength were optimized in urine samples. The assay kinetics based on the immunological reactions indicated achievement of constant signal within 5–10 min of incubation depending upon the CLE concentration. Using the optimized parameters, the linear range for the quantitative detection of CLE using the LFTS_AT/AC was between 100 pg/mL and 2500 pg/mL over a 10 min total assay time. The CLE LFTS_AT/AC showed a half maximal inhibitory concentration (IC₅₀) of 460 ± 60 pg/mL (n = 5) and a reliable coefficient of correlation (R² = 0.996). The CLE test strip exhibited insignificant cross-reaction (Cr) to mabuterol, isoproterenol, salbutamol, terbutaline, brombuterol, ractopamine and bambuterol. The limit of detection (LOD) for swine urine was 220 pg/mL, and recoveries for spiked sample were 102.35% ± 7.66% at 500 pg/mL, 95.07% ± 7.14% at 1000 pg/mL and 100.65% ± 10.21% at 1500 pg/mL, respectively. The intra-and inter-assay precision at 500–1500 pg/mL CLE concentrations showed coefficients of variation (CVs) at <11%. This rapid quantitative LFTS_AT/AC system for CLE in spiked urine samples exhibited a coefficient of correlation with traditional ELISA at 0.97 (N = 50). Furthermore, 96% of 90 samples gave a percent recovery of 100 ± 30%. These results indicated that the 10-min colloidal gold-based LFTS_AT/AC system is adaptive, sensitive, reproducible, and comparable to traditional ELISA method with the added advantage of being easy to use, inexpensive, and requires non-skilled personnel. The LFTS_AT/AC holds promise for field use an on-site detection of CLE in swine urine samples.     

Campylobacter species and their antimicrobial resistance in Latvian broiler chicken production

In the present study Campylobacter species and their antimicrobial resistance in Latvian broiler chicken production was determined. Furthermore, this is the first report on the antimicrobial resistance patterns for Campylobacter isolates from broiler chickens at slaughterhouse and retail level in Latvia. Two biggest Latvian broiler chicken meat producing company products were included in the study. Altogether, 74 randomly selected broiler chicken Campylobacter spp. isolates were analysed for species identification. Campylobacter isolates were obtained during a 12-month period within the Latvian Campylobacter prevalence study in 2010. Colony multiplex PCR was used for all isolates to identify Campylobacter species. Minimal inhibitory concentration (MIC) was determined for 58 Campylobacter spp. isolates. Resistance to one or more antimicrobials was detected in all 58 isolates (100%). A high proportion of the isolates were resistant to ciprofloxacin (100%) and nalidixic acid (87.9%). Multidrug resistance, which was determined as resistance to three or more unrelated antimicrobials, was detected in 39 isolates (67.2%). Moreover, all multiresistant isolates were resistant to ciprofloxacin and nalidixic acid. Analyses of Campylobacter isolates from two Latvian broiler chicken meat producing companies resulted with significant differences in Campylobacter species; from the company A mainly Campylobacter coli were found, while in the company B Campylobacter jejuni.     

A reliable screening of mycotoxins and pesticide residues in paprika using ultra-high performance liquid chromatography coupled to high resolution Orbitrap mass spectrometry

In this study, an ultra-high performance liquid chromatography (UHPLC) coupled to a high resolution Orbitrap mass spectrometry (Orbitrap-HRMS) was demonstrated as a promising technique in high-throughput method development for the routine analysis and contamination control of mycotoxins and pesticide residues in spices. The method was applied for the analysis of fifty ground paprika samples containing blends of sweet and hot paprika harvested in Brazil and China. The efficiency and detection sensitivity of the used UHPLC-Orbitrap-HRMS technique were compared to the results obtained using a triple quadrupole tandem mass spectrometric detector (UHPLC-QqQ-MS/MS). The values of recovery (75–120%) and repeatability (8–15%) for both methods, calculated as the average (n = 5) from the results of spiked (10–500 μg kg⁻¹), paprika samples, were in good conformity to the relevant EU guidelines. The high resolution of the used Orbitrap-HRMS technique provided a better sensitivity for quantitative determination of several pesticide contaminants in paprika, compared to the results obtained by the QqQ-MS/MS method and were comparable in case of mycotoxins. The results of analysis demonstrated the ubiquitous presence of three mycotoxins (fumonisin B₁, ochratoxin A, and sterigmatocystin) and twelve pesticide residues in paprika. The concentrations of determined contaminants were below the MRLs set by the Regulations of the European Union with exception of iprovalicarb, which violated the EU MRL in two samples of hot paprika. In addition, a notable difference in the concentration of fumonisin B₁ was determined depending on the harvest period (2009–2013), reaching the maximum concentrations of 33 μg kg⁻¹ in sweet paprika and 140 μg kg⁻¹ in hot paprika. There was no significant correlation found between the determined mycotoxin contamination levels and the pesticide residues, with the sole exception of decreased fumonisin B₁ content in samples with an elevated concentration of metalaxyl fungicide.     

Effect of UV-C irradiation on the inactivation of inoculated pathogens and quality of chicken breasts during storage

In this study, we evaluated the inactivation of foodborne pathogens inoculated on chicken breasts by UV-C treatment. Chicken breasts were inoculated with Campylobacter jejuni, Listeria monocytogenes, and Salmonella enterica serovar Typhimurium at 6–7 log CFU/g. The inoculated chicken breasts were then irradiated with UV-C light of dose 0, 0.5, 1, 3, and 5 kJ/m². Microbiological data indicated that the populations of the foodborne pathogens decreased significantly (p < 0.05) with increasing UV-C irradiation. In particular, UV-C irradiation at 5 kJ/m² reduced the initial populations of C. jejuni, L. monocytogenes, and S. typhimurium by 1.26, 1.29, and 1.19 log CFU/g, respectively. After UV-C irradiation, the samples were individually packed using polyethylene terephthalate containers and stored at 4 ± 1 °C for 6 d. The pH of the control increased more than the samples irradiated at 0.5, 1, 3, and 5 kJ/m², while TBARS values increased during storage regardless of UV-C irradiation. UV-C irradiation caused negligible changes in Hunter L, a, and b values. These results suggest that UV-C irradiation can be useful in improving the microbial safety of chicken breasts during storage, without impairing quality.     

Recovery of associated and internalized Salmonella in broiler skin by stomaching and grinding

The objective of this study was to evaluate the recovery of associated and internalized Salmonella by stomaching and grinding broiler skin during exposure at 4 °C and at room temperature, using a two-strain green fluorescent protein (GFP) labeled cocktail of Salmonella Enteritidis. In the first experiment, broiler skins were immediately taken from eviscerated carcasses and exposed to a Salmonella cocktail containing ∼1 × 10⁹ CFU/ml for 0.5, 6, 12, 24, and 48 h at 4 °C. After each exposure, two 1-min stomachings and subsequent grinding of the stomached skin were conducted to quantify loosely associated (from two stomachings) and tightly associated (from grinding) Salmonella on the skin, respectively. Broiler skins exposed to Salmonella for 24 and 48 h were also examined by confocal microscopy before and after the two stomachings. The 1st and 2nd stomachings recovered an average of 71 and 17% of the Salmonella population, respectively, with an additional 12% of the cells recovered after subsequent grinding, regardless of incubation time. Based on the confocal images, most Salmonella were removed after two stomachings, however a few cells further penetrated from 9 to 29 μm into the skin. In the second experiment, broiler skins were immersed in the same two-strain Salmonella cocktail (∼1 × 10⁸ cells/ml) and dip-inoculated for 2 min with/without stomaching at room temperature. Based on the confocal images, Salmonella penetrated the flat skin surfaces and crevices up to 10 and 68 μm without stomaching, respectively, and up to 62 and 132 μm with stomaching. The presence of free-floating Salmonella cells in the skin crevices indicates that entrapped water is important for bacterial translocation in poultry skin. These findings indicated that extent of observable Salmonella association, penetration, and subsequent recovery from poultry skin is related to both surface topography of poultry skin and method of sample processing.     

Evaluation of dispersive liquid–liquid microextraction for the determination of patulin in apple juices using micellar electrokinetic capillary chromatography

Patulin (PAT) is a mycotoxin naturally found in fruits, including apples. Its occurrence as a natural contaminant of fruit juices is indicative of fruit quality in production. The European Union has set the maximum content of patulin in 50 μg kg⁻¹ for fruit juices and 10 μg kg⁻¹ for infant fruit juices. In this paper, dispersive liquid–liquid microextraction (DLLME) has been proposed for the extraction and preconcentration of PAT in apple juice, followed by its determination by micellar electrokinetic chromatography (MEKC) with diode-array detection. PAT has been analyzed in the presence of 5-hydroxymethylfurfural (HMF), which is the main interference in this kind of matrix. Variables affecting DLLME efficiency were optimized and the calibration curve was established for PAT in analyte standard solutions, applying the DLLME–MEKC procedure. The limit of detection was 0.6 μg L⁻¹ and recoveries obtained for spiked freshly-made apple juice samples at four different concentration levels (5, 20, 50 and 75 μg L⁻¹), were above 75% with RSD lower than 9%. This method can be classified as a green alternative, being successfully applied to the measurement of 19 apple juice samples obtained from different suppliers and supermarkets. The optimized DLLME–MEKC method is free from matrix effects and avoids the tedious matrix-matched or standard addition calibration method. Almost fifty percent of the samples were contaminated with a PAT content greater than the maximum content established by the European regulation.     

Case-by-case risk assessment of broiler meat batches: An effective control strategy for Campylobacter

In 2006, the Danish government decided to take new measures to control Salmonella and Campylobacter in Danish and imported retail meat. The legal basis for these new measures was article 14 in the EU food law, which states that food shall not be placed on the market if it is unsafe, among others, for reasons of contamination. This provision allows each member state to make a specific risk assessment of food batches, and decide whether a batch poses an unacceptable risk to the consumer or not. Here we present the basis for the risk assessment model on Campylobacter used in this new approach and the results of more than 3000 batches of broiler meat tested since 2007. The risk was assessed for batches with one or more samples positive for Campylobacter (>100 cfu/g). Reductions in the number of positive batches from 2007 to 2010 were observed for both domestic (from 17% to 7%, p = 0.01) and imported broiler meat (from 39% to 18%, p < 0.0001). During 2007–2010, only relatively few batches were deemed unsafe due to the presence of Campylobacter. The proportion of batches of domestic and imported broiler meat deemed unsafe varied from 0.3% to 1.0% for Danish broiler meat and from 0.2% to 7.7% for imported broiler meat. Still this initiative has been successful in significantly reducing the occurrence of Campylobacter in fresh meat available on the Danish retail market.To our knowledge, this is the first example of a risk based control system that enables quantitative day to day risk assessment of food batches.     

Automotive Gasolines. Long-Term Requirements for Composition and Properties

The requirements for the composition and quality of automotive gasolines by 2010 for reducing the toxicity of exhaust gases are examined. Data on the component composition and environmental indexes of all brands of gasoline manufactured in 2002–2003 and tested with a set of qualification evaluation methods are generalized. The possibility of meeting the demand of Russian motor vehicles for Euro–2 and Euro–3 gasolines in 2005 is demonstrated. Expansion of manufacture of these gasolines is limited by the total aromatic hydrocarbon content, including benzene. The use of iron– and manganese–containing antiknock compounds at a maximum metal concentration of 18 mg/dm³ could be a temporary measure.     

Detection of aflatoxin M1 in milk products from China by ELISA using monoclonal antibodies

A rapid and sensitive indirect competitive enzyme-linked immunosorbent assay (ELISA) method using monoclonal antibody for measuring aflatoxin M1 (AFM1) in milk and milk products has been described. One monoclonal antibody was isolated and characterized after fusion of myeloma cells with spleen cells isolated from BALB/c mice that had been immunized with AFM1 carboxymethyl oxime conjugated with bovine serum albumin (BSA). Cross-reactivities of the anti-AFM1 monoclonal antibody clone were 100, 13.9, 6.7 and <1% against AFM1, aflatoxin B1 (AFB1), aflatoxin G1 (AFG1) and deoxynivalenol (DON), respectively. Assays of milk samples mixed with AFM1 ranging in concentration from 0.1 to 3.2 ng/ml gave mean ELISA recovery of 98%. The limit of detection concentration of AFM1 was 0.04 ng/ml. AFM1 contamination was measured in 12 samples of raw milk, 15 samples of powdered milk, 104 samples of liquid milk and four cheese samples collected from different supermarkets in Northeast of China. Of 135 milk samples tested, 55 (41%) samples contained AFM1 at levels that ranged from 0.32–0.50 ng/ml, 24 (18%) samples contained 0.16–0.32 ng/ml, and 18 (13%) samples contained 0–0.16 ng/ml; in 38 (28%) samples AFM1 was not detected. The results indicate that the necessary precaution will have to be taken to minimize the AFM1 contamination in milk and milk products from Northeast of China.     

Development and validation of a new qualitative ELISA screening for multiresidue detection of sulfonamides in food and feed

An indirect competitive enzyme-linked immunosorbent assay (ELISA) to screen sulfonamide residues in food (muscle, eggs, milk and honey) and feed has been developed and validated according to Commission Decision 2002/657/EC. The immunoreagents were appropriately produced to detect a wide range of sulfonamide antibiotic congeners, obtaining half-maximum inhibition concentration (IC₅₀) values below 10 μg L⁻¹ for 11 sulfonamides widely used in veterinary practices. Taking into account the complexity of involved matrices, specific sample preparation protocols have been optimised combining high method throughput with low detectable concentrations. Accordingly, depending on the congener, the obtained detection capabilities (CCβs) were lower or equal to 20 μg kg⁻¹ (muscle, eggs and milk), 10 μg kg⁻¹ (honey) and 2 mg kg⁻¹ (feed). Finally the developed qualitative test was applied to real samples collected within the official monitoring programmes: results exceeding the established screening cut-off were re-analysed with a suitable confirmatory method. The presence of one or more sulfonamides was found in all the suspect screening samples thus demonstrating that the proposed ELISA can be successfully applied in class-specific detection of sulfonamides in food and feed.     

Development of an aptasensor for electrochemical detection of tetracycline

Developing the rapid, simple and sensitive biosensor system for tetracycline detection is very important in food safety. In this paper, we developed a label-free aptasensor for electrochemical detection of tetracycline. The reorganization of tetracycline binding aptamer was confirmed by Isothermal Titration Calorimetry, Kd = 5.18 × 10⁻⁵ mol L⁻¹. According to the electrochemical impendence spectroscopy (EIS) analysis, there was a linear relationship between the log concentration of tetracycline and the charge transfer resistance (ΔRet) from 5.0 to 5.0 × 10³ ng mL⁻¹ of the tetracycline conc. The detection limit was 1.0 ng mL⁻¹ within a detection time of 15 min. The average of assemble rate Q was at 82.4% with a differential batches' RSD of 4.6%. The current change of this aptasensor lies within at 8.5% after a storage of 15 days under 4 °C. The result aptasensor had shown a good reproducibility with an acceptable stability in tetracycline detection. The recoveries of TET in spiked milk samples were in the range of 90.0–95.7%.