Prevalence and Antimicrobial Resistance of Salmonella in Pork, Chicken, and Duck from Retail Markets of China.

Salmonella is one of the most important foodborne pathogens associated with animal and human diseases. In this study, 672 samples of fresh meat (pork, 347; chicken, 196; and duck, 129) were collected from retail markets in different provinces of China from 2010 to 2014. We identified 10 different serotypes among 80 Salmonella isolates, whereas 12 isolates were nonmotile precluding conventional identification of complete serotype. Among these 92 isolates, Salmonella enterica serovar Derby (n = 21) was the most prevalent serotype, followed by Salmonella Enteritidis (n = 17), Salmonella Typhimurium (n = 15), Salmonella Indiana (n = 9), Salmonella Agona (n = 7), and Salmonella Assinie (n = 5). Antimicrobial resistance testing for 18 antimicrobial agents revealed that all 92 isolates were resistant to at least 1 antimicrobial agent, and 39 different resistance profiles were identified. The highest resistance was to trimethoprim-sulfamethoxazole (n = 87), followed by tetracycline (n = 51), carbenicillin (n = 38), amoxicillin/A.clav (n = 30), and piperacillin (n = 24). Our results demonstrated that meats presented a potential public health risk, thereby underlining the necessity for local regulatory enforcement agencies in China to monitor salmonellosis.

Highly selective colorimetric bacteria sensing based on protein-capped nanoparticles.

A rapid and cost-effective colorimetric sensor has been developed for the detection of bacteria (Bacillus subtilis was selected as an example). The sensor was designed to rely on lysozyme-capped AuNPs with the advantages of effective amplification and high specificity. In the sensing system, lysozyme was able to bind strongly to Bacillus subtilis, which effectively induced a color change of the solution from light purple to purplish red. The lowest concentration of Bacillus subtilis detectable by the naked eye was 4.5 × 10(3) colony-forming units (CFU) mL(-1). Similar results were discernable from UV-Vis absorption measurements. A good specificity was observed through a statistical analysis method using the SPSS software (version 17.0). This simple colorimetric sensor may therefore be a rapid and specific method for a bacterial detection assay in complex samples.

Occurrence and spatial distributions of microcystins in Poyang Lake, the largest freshwater lake in China.

Occurrence and spatial distributions of microcystins (MCs; MC-RR, -YR, -LR, -LA, -LF, -LW) in Poyang Lake were studied during the period from July 6 to July 18, 2012, by using ultra-high-performance liquid chromatography-electrospray ionization tandem triple quadrupole/mass spectrometry (UPLC-MS/MS). MC-RR was the most dominant variant (94.70 and 84.73 % for intracellular (cellular MCs) and extracellular (dissolved MCs) MCs, respectively) in Poyang Lake, followed by MC-LR (4.65 and 13.17 %, respectively), MC-YR (0.8 and 2.63 %, respectively), and MC-LA (0.02 and 0.00 %), while MC-LW and MC-LF were not detected. Total MCs concentrations (intracellular +extracellular MCs) ranged between 0.0036 and 7.97 µg/L, with an average of 0.79 µg/L, and only two sampling stations with the total MCs concentrations exceeded the drinking water guideline level of 1 µg/L for MC-LR proposed by World Health Organization. The overall spatial pattern of intracellular and extracellular MCs in Poyang Lake demonstrates decreasing trends from east to west, and the south part higher than the north part. Intracellular MCs content was negatively correlated with total nitrogen (r = -0.34, p < 0.01) and NO3 (r = -0.35, p < 0.01), while no significant correlation was found between intracellular MCs concentration and total phosphorus, NH4, and NO2 (p > 0.05), suggesting that NO3 might be a regulating factor for MCs production in Poyang Lake. In addition, intracellular MCs concentrations were positively correlated with wind speed, Microcystis and Cyanobacteria biomass (r = 0.34-0.51, p < 0.05), indicating that wind speed plays an important role in the spatial distributions of MCs, and NO3, toxic cyanobacteria (mainly Microcystis), and wind speed seem to be the important forcing factors driving MCs spatial distributions in Poyang Lake.

Metal concentrations in various fish organs of different fish species from Poyang Lake, China.

Concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in the muscle of eleven fish species (bighead carp, bream, catfish, carp, crucian, Culter alburnus, grass carp, mandarin fish, white semiknife carp, silver carp, and yellow catfish) from Poyang Lake were analysed using inductive coupling plasma mass spectrometry. Metal levels in other organs (e.g., bladder, gill, kidney, liver, and spleen) of bighead carp, carp, grass carp, and silver carp were also determined. The results showed that metal concentrations in the muscle of all fish species were significantly lower than the proposed limits. Heavy metal concentrations were found to be substantially higher in benthic fish than in pelagic fish. Higher Hg contents were observed in predatory fish. In addition, various metals showed different affinity to fish organs. Hg was the most abundant in muscle, while Ni and Pb concentrations were highest in gills, Cd and Zn concentrations were highest in kidneys, and Cu was most commonly found in livers. Estimations of health risks revealed no evidence of potential threats to consumers.

Label-free fluorometric method for monitoring conformational flexibility of laccase based on a selective laccase sensor.

A facile and selective fluorescence sensor for laccase determination has been proposed depending on the interaction between 3-azidocoumarin and trametes versicolor (Tv) laccase in this paper. The azido group of 3-azidocoumarin that is electron-rich α-nitrogen can directly interact with histidines that coordinate to three copper sites through hydrogen bonds and forms a new complex, which decreases the electron-donating ability of the azido group, leading to enhance the fluorescence intensity of the sensing system. Also, other common proteins have no significant interference for the proposed laccase sensor. Additionally, the proposed fluorescence sensor is extended to demonstrate the conformational flexibility of Tv laccase by the urea denaturant. A good consistency of the results obtained with the presented laccase sensor and CD spectra is performed. Furthermore, the relationship between the catalytic activity and the unfolding percentage of the unfolded Tv laccase through the proposed laccase sensor is also elucidated well.

Colorimetric and fluorometric dual-readout sensor for lysozyme.

A novel, highly sensitive and selective dual-readout sensor (colorimetric and fluorometric) for the detection of lysozyme was proposed. The fluorescence of triazolylcoumarin molecules was quenched by Au nanoparticles (AuNPs) initially through the fluorescence resonance energy transfer (FRET), after the addition of lysozyme, the stronger binding of lysozyme onto the surfaces of AuNPs made triazolylcoumarin molecules remove from the AuNPs surface and led to the recovery of the fluorescence of triazolylcoumarin molecules, and accompanied by the discernable color change of the solution from red to purple. The lowest detectable concentration for lysozyme was 50 ng mL(-1) by the naked eye, and the limit of detection (LOD) was 23 ng mL(-1) by fluorescence measurements. In addition, satisfactory results for lysozyme detection in hen egg white were confirmed in the study. Moreover, the presented sensor provides a reliable option to determine lysozyme with high sensitivity and selectivity.

Pharmacokinetics, withdrawal time, and dietary risk assessment of enrofloxacin and its metabolite ciprofloxacin, and sulfachloropyridazine-trimethoprim in Taihe black-boned silky fowls.

Enrofloxacin (ENR) and sulfachloropyridazine combined with trimethoprim (TMP) were commonly used in poultries to treat bacterial infections. In this study, the pharmacokinetics of these antibiotics in four tissues of Taihe black-boned silky fowls was studied. The results showed that these drugs were absorbed and distributed rapidly, with the highest concentration showing in skin. Meanwhile, ENR and its metabolite ciprofloxacin (CIP) and TMP were depleted slowly, particularly in skin with the elimination half-lives being 37.1, 36.9, and 72.7 days, respectively. It may be attributed to the abundance of melanin in skin. The dietary risk assessment suggested that the long-term dietary intakes of ENR, CIP, and TMP showed a considerable threat to human health. Based on the experiment, the withdrawal times of 284 days for ENR + CIP and 159 days for TMP were acquired, which showed that these drugs are not appropriate for the application in Taihe black-boned silky fowls.

Pathological and biochemical characterizations of microcystin-LR-induced liver and kidney damage in chickens after acute exposure.

Cyanobacteria contains considerable amounts of protein and other nutritive materials and are considered to be high-quality protein source and feed additive for livestock and poultry. However, some species of cyanobacteria are also able to produce toxins, and exposure to these toxins represents health risks to animals. In the present study, pathological changes and biochemical responses were examined in the liver and kidney of the Chongren chicken (Gallus gallus domesticus) after intraperitoneal (i.p.) injection with microcystin-LR (MC-LR) at dose of 5 µg kg-1 (Low dose group, LD group), 10 µg kg-1 (Medium dose group, MD group), and 20 µg kg-1 (High dose group, HD group), respectively. Results revealed that the high dose of MC-LR led to the irreversible liver damage, which was characterized by mononuclear infiltrations，necrotic changes and blood congestion, and obvious recovery of hepatocytes was observed in the low and medium dose groups. Across all groups, the MC-LR-induced injuries in the kidney were prominent since the first hour, and it did not get any better at the end of the experiments. The MC-related detoxification and antioxidant components (GSH, GPX, GST) in the liver made positive responses, which helped to alleviate the cytotoxicity of MC-LR. Our results showed that even at low concentrations of MCs (produced by cyanobacteria), pathological changes (such as necrosis and inflammation) were observed in liver and kidney of birds.

Triazole-stabilized fluorescence sensor for highly selective detection of copper in tea and animal feed.

A triazole-stabilized fluorescence sensor is developed for copper detection in the study. Tris-(benzyltriazolylmethyl)amine (TBTA) is used to improve the sensitivity and stability for the sensing system. A series of comparative experiments are performed with and without TBTA. In the presence of TBTA, the fluorescence decrease ratio is enhanced from 2.46 to 118.25; the detection limit is reduced from 67 nM to 3.6 nM; the higher selectivity toward copper compared to the other metal ions is verified, including K+, Ca2+, Cd2+, Zn2+, Mg2+, Mn2+, Pb2+, Hg2+, Fe3+ and Cr3+. Besides, the sensing system is successfully applied for copper determination in complex tea samples and chicken feed samples with the recovery range of 91.67-116.8%. A good consistency between the presented sensor and the flame atom absorbance spectrometry (FAAS) is confirmed by the low relative errors with the range from -2.39% to 7.02%.

DNA template-mediated click chemistry-based portable signal-on sensor for ochratoxin A detection.

A novel signal-on portable sensing system has been developed for OTA detection using personal glucose meter (PGM) as signal transducer. In the study, we explore the potential of using a short dsDNA as template to trigger the "click" ligation of two DNA strands, further improve the stability of DNA strand on the magnetic beads (MBs) surface, and thereby reduce the background signal. Compared with no "click" ligation, the background signal decreases 7.5 times. Both the sensitivity and selectivity are greatly promoted. A high sensitivity with OTA detection down to 72 pg/mL is achieved, which is comparable with several existing detectors, such as fluorescence-based detectors and electrochemical detectors. The feasibility of the strategy in real samples is well verified and evaluated by detecting OTA in feed samples, indicating the potential application in the food safety field.

[Seasonal and Spatial Variations of Microcystins and Their Relationships with Physiochemical and Biological Factors in Poyang Lake].

Poyang Lake is the largest freshwater lake in China and an important drinking water source for Jiangxi Province. Since the year 2000, toxic cyanobacteria have been observed frequently in Poyang Lake. In this study, water samples were collected in the lake quarterly (April 2012, August 2012, October 2012, and January 2013) to examine the spatial and seasonal variations in the concentrations of microcystins (MCs; MC-RR, -YR, and -LR) and their relationships with physiochemical and biological factors. MCs were determined by ultra-high-performance liquid chromatography-electrospray ionization tandem triple quadrupole/mass spectrometry (UPLC-MS/MS). MC-RR (accounting for 75.01% and 71.34% of intracellular MC (IMC) and extracellular MC (EMC) concentrations, respectively) was the most dominant variant in Poyang Lake, followed by MC-LR (accounting for 21.95% and 24.97% of IMC and EMC concentrations, respectively), while MC-YR was detected in low concentrations (accounting for 3.01% and 3.69% of IMC and EMC concentrations, respectively). Total MC concentrations (IMC + EMC, TMC) ranged from 0.49 to 3517.85 ng·L-1, with an average of 337.43 ng·L-1 and only 2.53% (2 out of 79 water samples) of the water samples contained MCs concentrations exceeding the drinking water guideline level of 1 ng·L-1 for MC-LR proposed by World Health Organization (WHO). IMC concentrations showed significant relationships with Microcystis biomass (r=0.47, P<0.01), Oscillatoria biomass (r=0.68, P<0.01), Cyanobacteria biomass (r=0.56, P<0.01), and Chl-a (r=0.28, P<0.01), but no significant correlation was found between intracellular MC concentration and Anabena biomass (P>0.05), suggesting that Microcystis and Oscillatoria might be the main MCs-producing cyanobacteria in Poyang Lake. In addition, IMC concentrations were positively correlated with water temperature (r=0.51, P<0.01), transparence (r=0.69, P<0.01), Fe (r=0.43, P<0.01), and Zn contents (r=0.43, P<0.01), and negatively correlated with TN (r=-0.44, P<0.01), TP (r=-0.29, P<0.01), NH4+-N (r=-0.33, P<0.05), NO2--N (r=-0.28, P<0.05), Ca (r=-0.34, P<0.01), and Mg(r=-0.35, P<0.05), while no significant correlations were observed between IMC concentrations and pH, PO43--P, NO3--N, electrical conductivity, permanganate index, and Cu content (P>0.05). These results indicated that light intensity (represented by transparence), nitrogen, phosphorus, and water temperature might be the regulating factors of MCs production in Poyang Lake and trace elements (Fe, Zn, Ca, and Mg) can influence the MC production to a certain extent. IMCs and EMCs exhibited similar seasonal variations in Poyang Lake. The highest values of IMCs (531.87 ng·L-1) and EMCs (232.44 ng·L-1) were observed in summer. The concentrations of IMCs and EMCs in autumn were 31.97 ng·L-1 and 6.49 ng·L-1, respectively. Low concentrations were observed in spring (0.55 ng·L-1 and 0.88 ng·L-1 of IMCs and EMCs, respectively) and winter (0.69 ng·L-1 and 4.14 ng·L-1 of IMCs and EMCs, respectively). The highest IMCs and EMCs values of Poyang Lake in summer were 2298.08 ng·L-1 and 1219.77 ng·L-1, respectively, and the lowest values were 92.53 ng·L-1 and 38.80 ng·L-1, respectively. Overall, the concentrations of IMCs in eastern bays, the vicinity of Songmen Mountain, Banghu Lake, and its outlet were higher than those in other regions. However, the spatial distributions of EMCs in Poyang Lake were different from those of IMCs. EMCs concentrations in the vicinity of Songmen Mountain, Banghu Lake, and its outlet were higher than those in other regions.

Seasonal and spatial variations of microcystins in Poyang Lake, the largest freshwater lake in China.

Poyang Lake is the largest freshwater lake in China and an important drinking water source. Since the year 2000, toxic cyanobacteria have been observed frequently in Poyang Lake. In the present study, spatial and seasonal variations of microcystins (MCs; MC-RR, MC-YR, and MC-LR) in water column were examined monthly from January to December (except the months of March, May, and November) in 2013, by using ultra-high-performance liquid chromatography-electrospray ionization tandem triple quadrupole/mass spectrometry (UPLC-MS/MS). MC-RR was the most dominant variant, followed by MC-LR, while MC-YR was detected in low concentration. Total MC concentrations (intracellular + extracellular MCs) ranged from 1.26 to 9916.05 ng/L, with an average of 469.99 ng/L, and only 3.14% (6 out of 192 samples) of the water samples contained MC concentrations that exceeded the drinking water guideline level of 1 µg/L for MC-LR proposed by the World Health Organization (WHO). MC concentrations in water column showed obvious seasonal variations in Poyang Lake. Intracellular and extracellular MCs were both at a low level from January to April but increased quickly from June to August and decreased dramatically thereafter. Intracellular MCs exhibited similar spatial distribution pattern with extracellular MCs. Both intracellular and extracellular MC concentrations in eastern bays and around Songmen Mountain of Poyang Lake were higher than other regions. Intracellular MC concentrations were positively correlated with Chl a (r = 046, P < 0.01), pH (r = 0.25, P < 0.01), cyanobacterial biomass (r = 0.40, P < 0.01), and temperature (r = 0.36, P < 0.01) but negatively correlated with TN (r = - 0.28, P < 0.01), suggesting that TN, cyanobacteria biomass, pH, and temperature might be regulating factors for MC production in Poyang Lake.

[Analysis of heading time genotype for a rice photoperiod and thermo--sensitive male sterile line PeiAi64S].

PeiAi64S, a photoperiod and thermo-sensitive genic male sterile, has been wildly applied to hybrid rice seed production in China, but its photoperiod-sensitivity gene for heading date in this sterile line was still unknown. This definitely limited the further use of this sterile line in breeding practice and re-production of hybrid seeds. To solve this problem, using heading time nearly isogenic lines EGO - EG7, ER - LR, T65 - T65m and six heading date QTL-isogenic lines, NIL (Hd1) - NIL (Hd6) with the genes of Nipponbare but Hd1 - Hd6 genes from Kasalath respectively, we performed a genetic analysis of PeiAi64S with special reference to photoperiod-sensitivity loci, in natural long days at Nanjing (32 degrees N) where the average day-length is about 14 h and in natural short days at Linshui county, Hainan province(18 degrees 29'N), where the average day-length is about 11.6 h during the course of rice growing respectively. The F1 and F2 generations from the crosses 'PeiAi64S x heading time nearly isogenic lines' were subjected to genetic analyses. Experimental results showed that PeiAi64S carries photoperiod-sensitivity allele gene E1 and E3 and dominant earliness gene Ef-1 in E1 and E3 and Ef-1 loci, respectively, and a photoperiod insensitivity allele Se-1 degrees in Se-1 locus. Meanwhile, the photoperiod-sensitivity gene E1 and photoperiod-insensitivity gene Se-1e in PeiAi64S were also identified by crossing with the NIL(Hd1) and NIL(Hd4). In addition, a recessive inhibitor for photoperiod-sensitive gene E1 or Se-1(n) and other modified photoperiod-sensitive genes: i-Se-1, E3, Hd3 (En-Se-1), Hd5 and Hd6, were identified in PeiAi64S by crossing with QTL nearly isogenic lines: NIL(Hd2), NIL (Hd3), NIL (Hd5) and NIL( Hd6), The results indicated that the genotype of PeiAi64S's heading date was: E1E1e2e2E3E3Se-1(e)Se-1(e)Ef-1 Ef-1 i-Se-1 i-Se-1.

[Analysis of photoperiod-sensitivity genes in Minghui63, an restorer line of indica rice(Oryza sativa L.)].

Hybrid rice is very important in agriculture production in China. Its selecting property makes it significant to study the genetic performance of F1's date to heading (DH). Minghui63, an indica rice restorer line, has been widdly applied to hybrid rice seed production in China, but the photoperiod-sensitivity gene of heading date in this restorer line is still unknown. This definitely limited the further use of this restorer line in breeding practice and re-production of hybrid seeds. To solve this problem, using heading time nearly isogenic lines EGO-EG7, ER-LR and two heading date QTL-isogenic lines, NIL (Hd1) and NIL (Hd4), with the genes of Nipponbare but Hd1 (Se-1) and Hd4 (E1) genes from Kasalath, respectively, we performed a genetic analysis of Minghui63 with special reference to photoperiod-sensitivity loci, using natural long days in Nanjing(32 degrees N) and natural short days in Linshui county, Hainan province (18 degrees 29'N), where the average day-length is about 14 h and 11.6 h during the course of rice growing, respectively. The F1 and F2 generations from the crosses "heading time nearly isogenic lines x Minghui63" were subjected to genetic analyses. Experimental results showed that Minghui63 carries photoperiod-sensitivity allele gene E1 and E3 in E1 and E3 loci, respectly, and a photoperiod insensitivity allele Se-1e in Se-1 locus, and it also carries a recessive inhibitor for photoperiod-sensitivity gene E1. Meanwhile, the photoperiod-sensitive genes, E1 and the photoperiod-insensitive genes, Se-1e, in Minghui63 were also identified by crossing with the nearly isogenic lines for heading time QTLs, NIL (Hd1) and NIL(Hd4). The results indicated that Minghui63's genotype of heading date was: E1E1e2e2E3E3Se-1eSe-1e. The result from this research indicated that Minghui63 carries a major dominant photoperiod-sensitive gene E1 in E1 locus, and our previous researches indicated that Zhenshan97A carried a major dominant photoperiod-sensitive gene Se-1n in Se-1 locus and a recessive inhibitor gene i-Se-1. The DH of the hybrid rice "Shanyou63" is 94.7 in Nanjing, lying between Zhenshan97A's and Minghui63's, but more nearer to late maturity parent Minghui63. It has been not expressed that E1 gene usually prolongs days to heading by about 20 days when coexisting with Se-1u or Se-1n. This is possibly made by that inhibitor genes exist in respective parents, which make DH transgression of "Shanyou63" not appear. This phenomenon indicated that the heading date of indica hybrid rice is resulted from the interaction among the photoperiod-sensitive genes and their inhibitor genes in the sterile and the restorer lines.