Analysis of antibiotic resistance phenotypes and genes of Escherichia coli from healthy swine in Guizhou, China.

This study was carried out to investigate the resistance phenotypes and resistance genes of Escherichia coli from swine in Guizhou, China. A total of 47 E. coli strains isolated between 2013 and 2018 were tested using the Kirby-Bauer (K-B) method to verify their resistance to 19 common clinical antimicrobials. Five classes consisting of 29 resistance genes were detected using polymerase chain reaction. The status regarding extended-spectrum ß-lactamase (ESBL) and the relationship between ESBL CTX-M-type ß-lactamase genes and plasmid-mediated quinolone resistance (PMQR) genes were analysed. A total of 46 strains (97.9%) were found to be multidrug resistant. Amongst them, 27 strains (57.4%) were resistant to more than eight antimicrobials, and the maximum number of resistant antimicrobial agents was 16. Twenty antibiotic resistance genes were detected, including six ß-lactamase genes blaTEM (74.5%), blaCTX-M-9G (29.8%), blaDHA (17.0%), blaCTX-M-1G (10.6%), blaSHV (8.5%), blaOXA (2.1%), five aminoglycoside-modifying enzyme genes aac(3')-IV (93.6%), aadA1 (78.7%), aadA2 (76.6%), aac(3')-II c (55.3%), aac(6')-Ib (2.1%) and five amphenicol resistance genes floR (70.2%), cmlA (53.2%), cat2 (10.6%), cat1 (6.4%), cmlB (2.1%), three PMQR genes qnrS (55.3%), oqxA (53.2%), qepA (27.7%) and polypeptide resistance gene mcr-1 (40.4%). The detection rate of ESBL-positive strains was 80.9% (38/47) and ESBL TEM-type was the most abundant ESBLs. The percentage of the PMQR gene in blaCTX-M-positive strains was high, and the detection rate of blaCTX-M-9G was the highest in CTX-M type. It is clear that multiple drug resistant E. coli is common in healthy swine in this study. Extended-spectrum ß-lactamase is very abundant in the E. coli strains isolated from swine and most of them are multiple compound genotypes.

Investigations on residual elimination of altrenogest oral solution in pigs and the withdrawal time.

The residual elimination of altrenogest in swine was investigated, preparing for the determination of withdrawal time. The residues of altrenogest in sebum, muscle, liver and kidney were extracted by optimized methods and further analyzed by UPLC-MS/MS. Under experimental conditions, the LOD and LOQ of altrenogest in sebum, muscle, liver and kidney were 0.5 and 1.0 µg/kg, respectively. The recoveries were in the range of 65 and 95% and the inter- and intra-RSD were less than 15%. The established method for the extraction, purification and detection of altrenogest is suitable for the determination of the residue of altrenogest in edible tissues of pigs. It was showed that altrenogest had the highest residual concentration level in liver, followed by kidney, sebum and muscle. Then withdrawal time was set at 9 days. The study provides an effective basis for elimination of altrenogest in swine.

Comparative pharmacokinetic study of two kinds of altrenogest oral solutions for sows.

This study was to compare the pharmacokinetic characteristics of domestic altrenogest oral solution (DAOS) or imported altrenogest oral solution (IAOS) in healthy sows. A single administration (1 mg/kg body weight) of DAOS or IAOS was performed in sixteen healthy sows according to a two-period crossover design. Plasma concentrations of altrenogest (AT) were measured by high performance liquid chromatography coupled to a tandem mass spectrometer (HPLC-MS/MS) and the concentration-time data of AT was analyzed by WINNONLIN 5.2. It was suggested that the main pharmacokinetic parameters of DAOS and IAOS were as follows: Cmax was 227.59 ± 83.35 ng/mL and 152.83 ± 80.34 ng/mL, Tmax was 1.16 ± 0.52 h and 1.58 ± 0.85 h, t1/2 was 3.63 ± 0.72 h and 3.45 ± 0.63 h, MRT was 5.02 ± 0.79 h and 5.21 ± 0.87 h, AUC0-t was 1050.23 ± 409.80 h·ng/mL and 778.22 ± 397.84 h·ng/mL, and AUC0-∞ was 1060 h·ng/mL and 786 h·ng/mL, respectively. The relative bioavailability of DAOS was 134.9%. Above results indicated that oral DAOS was better absorbed than IAOS, Cmax of DAOS was higher than that of IAOS (p < 0.05). However, there was no significant difference in the main pharmacokinetic parameters between oral DAOS and IAOS (p > 0.05). Our data confirmed that the absorption, fast elimination and bioavailability of DAOS in sows were better than those of IAOS.

Pharmacokinetics and residues elimination of diclofenac sodium administration in pigs by a new HPLC/MS method.

Diclofenac sodium (DS) was the third generation non-steroidal drugs with analgesic and antipyretic properties. Owing to taking action faster, long lasting potency, good efficacy and low side effects, DS was widely used in the pharmaceutical industry. To further ensure animal food safety and consumer health, the rational usages regulations of DS and DS withdrawal time should be provided. In the present study, a new high performance liquid chromatography tandem mass spectrometry (HPLC/MS) method was first established for extracting and validating diclofenac sodium levels in edible porcine tissues. Meanwhile, the pharmacokinetics characteristics and residue elimination of intramuscular DS administration in pigs were also studied. We found DS eliminated quickly and the distribution was poor in vivo. After a single dose of 2.5 mg/kg body weight per day for continuous 3 days, the withdrawal time in the tissues of liver, kidney, sebum, muscle and administration site were 9.892 days, 5.116 days, 14.205 days, 5.444 days and 8.818 days, respectively. According to the double-sided 95% confidence interval, DS withdrawal period should be 15 days. These experiment evidences lay a good foundation on the rational usages regulations of DS and DS withdrawal time, which will be helpful for the animal food safety and consumer health.

Determination of sulphachloropyrazine-diaveridine residues by high performance liquid chromatography in broiler edible tissues.

Diaveridine (DVD) is used in combination with sulphachloropyrazine (SPZ) as an effective antibacterial agent and antiprotozoal agent, respectively, in humans and animals. To gain a better understanding of the metabolism of SPZ and DVD in the food-producing animals, a high performance liquid chromatography (HPLC) method to determine and quantify sulphachloropyrazine (SPZ) and diaveridine (DVD) suspension residues from broilers is reported. Thirty healthy chickens were orally administered with sulphachloropyrazine-diaveridine (SPZ-DVD) suspension in water of 300 mg/l (SPZ) per day for seven successive days. Six chickens per day were slaughtered at 0, 1, 3, 5 and 7 days after the last administration. This procedure permitted SPZ and DVD to be separated from muscle tissue, liver, kidneys and skin with fat after extraction with acetonitrile and acetone under slightly acidic conditions. From the detected residuals in different tissues, we found that SPZ was quickly eliminated in liver and muscle, and slowly eliminated in kidney and skin with fat. DVD was quickly eliminated in liver and slowly eliminated in kidney. The withdrawal period of SPZ was 3.26, 3.72, 4.39 and 5.43 days in muscle, liver, kidney and skin with fat, respectively. The withdrawal period of DVD was 4.77, 4.94, 6.74 and 4.58 days in muscle, liver, kidney and skin with fat, respectively. Therefore, the suggested withdrawal period for SPZ-DVD suspension should be 7 days after dosing for seven successive days.

Silibinin in vitro protects A549 cells from Staphylococcus aureus-mediated injury and in vivo alleviates the lung injury of staphylococcal pneumonia.

In this study, hemolysis, Western blot, and real-time RT-PCR assays were performed to evaluate silibinin's activity against S. aureus α-toxin secretion. In addition, live/dead cell staining and lactate dehydrogenase activity assays were introduced to examine the influence of silibinin on α-toxin-induced cell injury in human alveolar epithelial cells. Furthermore, we tested the influence of silibinin on S. aureus pneumonia in a mouse model. We show that silibinin inhibits the expression of α-toxin in a dose-dependent manner and alleviates α-toxin-induced lung cell injury. The IC50 of silibinin that inhibits the hemolytic activity of S. aureus was 14.33 µg/mL for strain 8325-4. Moreover, this compound provides effective protection on the lung injury of staphylococcal pneumonia.

Simple, cheap and effective high-performance liquid chromatographic method for determination of praziquantel in bovine muscle.

A simple high-performance liquid chromatographic method using ultraviolet detection was developed for the determination of praziquantel in bovine muscle. The sample was extracted with ethyl acetate, cleaned up by alumin B cartridge. Analyses were run at a flow-rate of 0.8 ml/min with the detector operating at a detection wavelength of 220 nm. The method is specific and sensitive, with a quantification limit of 0.02 mg/kg and a detection limit of 0.01 mg/kg. The standard calibration curve of drugs solution was linear in the range of 0.02-2.0 µg/ml (r² = 0.9999). At the fortified levels of 0.02, 0.05, 0.2 mg/kg, the mean recoveries of praziquantel ranged from 75% to 85%, while the intra-day and inter-day coefficient of variation (CV) of the assay were all less than 9%.

[Simultaneous extraction and determination of nine chemically synthetic anticoccidial drug multi-residues in chicken meat using high performance liquid chromatography-tandem mass spectrometry].

A high performance liquid chromatography-tandem mass spectrometric (HPLC-MS/ MS) method was developed for the simultaneous extraction and determination of multi-residues of nine chemically synthetic anticoccidial drugs in chicken meat. Toltrazuril-D3 was used as the internal standard. The sample was extracted by 15 mL acetonitrile/dimethyl sulfoxide (4:1, v/ v, containing 2% acetic acid), cleaned-up by a QuEChERS (quick, easy, cheap, effective, rugged and safe) clean-up tube with 150 mg octadecylsilyl (ODS), 100 mg Florisil and 100 mg graphitized carbon black (GCB). After the concentration, the extract was analyzed by HPLC-MS/MS. The results showed that good linearity in the range of 20 - 150 microg/L for each target compound. The recoveries were between 81.5% and 103. 6% with the relative standard deviations lower than 15%. The method is simple, rapid, and suitable to detect the chemically synthetic anticoccidial drug residues with high throughput.