Residue depletion in tissues and fluids from swine fed sulfamethazine, chlortetracycline and penicillin G in combination

Inhalation anesthesia induced by isoflurane alters penicillin disposition in swine tissues

Twelve healthy swine were dosed with penicillin G intramuscularly. Fluids and tissues samples were collected at the end of two periods of general anesthesia, performed 24 h apart. Tissue samples were collected by minimally invasive laparoscopy under general anesthesia at 8 and 28 h postdose. Four nonanesthetized, penicillin-treated pigs were euthanized at 8 h postdose, and a second set of four similarly treated control pigs were sacrificed 28 h postdose. Liver penicillin tissue concentrations from animals that underwent anesthesia and laparoscopic tissue collection had tissue concentrations that were higher than nonanesthetized pigs at both time points. Urine, plasma, kidney, skeletal, and cardiac muscle showed no differences between the two groups. Laparoscopic tissue collection under general anesthesia in swine induces physiological changes that cause alterations in tissue pharmacokinetics not seen in conscious animals.

Antibiotic residue monitoring results for pork, chicken, and beef samples in Vietnam in 2012-2013

A monitoring plan of residual antibiotics in food of animal origin was conducted in Vietnam from 2012 to 2013. Meat samples were collected from slaughterhouses and retail stores in Ho Chi Minh City and Nha Trang. A total of 28 antibiotics were analyzed using a LC-MS/MS screening method. Sulfonamides, fluoroquinolones, and tilmicosin were detected in some of the samples. Sulfaclozine and fluoroquinolones were mainly detected in chicken samples, and sulfamethazine was mainly detected in pork samples. High levels of sulfonamide residues, ranging between 2500 and 2700 μg/kg sulfaclozine and between 1300 and 3600 μg/kg sulfamethazine, were present in two chicken and three pork samples, respectively. Tilmicosin was detected at ranges of 150-450 μg/kg in 10 chicken samples. Positive percentages were 17.3, 8.8, and 7.4% for chicken, pork, and beef, respectively, for an average of 11.9%. The results suggest an appropriate withdrawal period after drug administration had not been observed in some livestock.

Evaluation of the chemical residue monitoring in animal-derived products in Switzerland

This paper evaluates whether the Swiss monitoring programme for foreign substances in animal products fulfils basic epidemiological quality requirements, and identifies possible sources of bias in the selection of samples. The sampling was analysed over a 4-year period (2002-05). The sampling frame in 37 participating abattoirs covered 51% of all slaughtered pigs, 73% of calves, 68% of beef and 36% of cows. The analysis revealed that some sub-populations as defined by the region of origin were statistically over-represented while others were under-represented. The programme that is in accordance with European Union requirements contained some relevant bias. Patterns of under-sampled regions characterized by management type differences were identified. This could lead to an underestimate of the number of contaminated animals within the programme. Although the current sampling was stratified and partially risk-based, its efficiency could be improved by adopting a more targeted approach.

Preliminary evaluation of a lateral flow immunoassay device for screening urine samples for the presence of sulphamethazine

A lateral flow immunoassay (LFIA) device was developed and applied to testing urine samples for residues of the antimicrobial sulphamethazine (SMZ). This report describes the preparation of a rat monoclonal antibody to SMZ and its characterisation in an ELISA format. Apart from SMZ, the antibody showed high (> or =50%) cross-reactivity to N4-acetyl-sulphamethazine (55%), sulphamerazine (59%) and sulphisoxazole (50%) and lower cross-reactivity of 18% to sulphachlorpyridazine and sulphadiazine. The LFIA device consisted of a nitrocellulose membrane spotted with SMZ-ovalbumin and goat anti-mouse antibody as capture line and control line, respectively. Mouse anti-rat IgG F(ab')2 fragment specific antibody, adsorbed to colloidal carbon, was used as the detection ligand in the LFIA. The LFIA device had a cut-off value of 6.3 ng/ml in diluted (1/10) urine. Urine samples from SMZ-treated pigs, and bovine and porcine urine samples fortified with SMZ were used for a blind, four-laboratory evaluation of the performance of the LFIA device. Concentrations of SMZ in the test samples (n=29), as determined by LC-MS/MS, ranged from 0 (<3) to 1174 ng/ml. The evaluation of the LFIA device showed an overall sensitivity of 100%, a specificity of 71%, and positive and negative prediction values of 73% and 100%, respectively. The LFIA device has been fabricated as a test kit for determining SMZ residues in animals produced for slaughter.

Rapid and sensitive screening of sulfamethazine in porcine urine with an enzyme-linked immunosorbent assay and a field-portable immunofiltration assay

An enzyme-linked immunosorbent assay (ELISA) and an enzyme-linked immunofiltration assay (ELIFA) were developed for the screening of sulfamethazine (SMZ) in porcine urine. Incurred urine samples were measured by ELISA with a working range of 0 to 10 ng of SMZ per ml. The assay showed good accuracy and precision, with recoveries above 99.8% and intra- and interassay coefficients of variation (CVs) ranging from 2.6 to 5.6% and from 5.9 to 12.7%, respectively. Good agreement was observed when the results of the immunoassay were compared with those of liquid chromatography/tandem mass spectrometry analysis. For the ELIFA, a nylon membrane is placed on top of an absorbent material and covalently coated with rabbit anti-rat immunoglobulins. Free binding sites are blocked, and monoclonal anti-SMZ antibodies, SMZ standard or urine, and SMZ-horse radish peroxidase conjugate are subsequently dropped onto the membrane. During the assay, the reactants are drawn through the membrane because of its close contact with the absorbent pad. Finally, a substrate solution is added for blue color development. The blue spot produced can be visually evaluated or instrumentally measured (numeric deltaE*ab value), and the intensity of its color is inversely proportional to the analyte concentration. When a blue dot appears on the membrane, even if its color is less intense than that of the negative control, the sample is considered "negative," i.e., it is thought to contain a concentration of SMZ that is below the visual detection limit. If no color appears on the test membrane, the sample is considered "positive," i.e., it is thought to contain a concentration of SMZ that is equal to or above the visual detection limit. Validation of the assay showed good inter- and intra-assay precision (CV < 10%). Because samples can be analyzed after a simple dilution in <30 min with this assay format, it has strong potential for application in the field.

Conditional gene expression in the respiratory epithelium of the mouse

Transgenic mouse models mediating conditional temporal and spatial regulation of gene expression to the respiratory epithelium were developed utilizing the reverse tetracycline transactivator (rtTA) expressed under the control of SP-C and CCSP promoters. Luciferase activity was detected in the lungs of fetal and adult double transgenic mice but was not detected in other tissues or in single transgenic mice. In adult mice, maximal luciferase activity was detected 16 h after the administration of doxycycline in the drinking water, or 2 h after the injection of doxycycline. Activation of the transgene was observed after the administration of doxycycline in food pellets. After prolonged exposure to doxycycline, luciferase activity decreased slowly following removal of doxycycline, suggesting the importance of tissue pools which maintained expression of the transgene. In SP-C-rtTA mice, exposure of the pregnant dam to doxycycline induced luciferase activity in fetal lung tissue as early as E10.5. Luciferase activity was maintained in the lung tissue of pups during the period of lactation when the mother received doxycycline in the drinking water. In the CCSP-rtTA mice, luciferase was not detected in the absence of doxycycline. In the SP-C-rtTA mice, luciferase activity was detected in the absence of doxycycline but was enhanced approximately 10-fold by administration of drugs. The SP-C-rtTA and CCSP-rtTA activator mice control the expression of transgenes in the developing and mature respiratory epithelium, and will be useful for the study of gene function in the lung.