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Histo-blood group antigens (HBGAs) comprise a family of cell-surface carbohydrates that are considered norovirus-specific binding receptors or ligands. HBGA-like molecules have also been detected in oysters as common norovirus carriers, although the pathway involved in the synthesis of these molecules in oysters has yet to be elucidated. We isolated and identified a key gene involved in the synthesis of HBGA-like molecules, FUT1, from Crassostrea gigas, named CgFUT1. Real-time quantitative polymerase chain reaction analysis showed that CgFUT1 mRNA was expressed in the mantle, gill, muscle, labellum, and hepatopancreatic tissues of C. gigas, with the hepatopancreas exhibiting the highest expression level. A recombinant CgFUT1 protein with a molecular mass of 38.0 kDa was expressed in Escherichia coli using a prokaryotic expression vector. A eukaryotic expression plasmid was constructed and transfected into Chinese hamster ovary (CHO) cells. The expression of CgFUT1 and membrane localization of type H-2 HBGA-like molecules in CHO cells were detected using Western blotting and cellular immunofluorescence, respectively. This study indicated that CgFUT1, expressed in C. gigas tissues, can synthesize type H-2 HBGA-like molecules. This finding provides a new perspective for analyzing the source and synthetic pathway of HBGA-like molecules in oysters.

Foodborne pathogens have caused many public health incidents and heavy economic burden. Endolysins have been proven to have efficient bactericidal activity against pathogens with low incidence of resistance. In this study, the recombinant endolysin LysSP1 encoded by Salmonella Typhimurium lytic bacteriophage SLMP1 was obtained by prokaryotic expression, and its characteristics were analyzed. Ethylenediaminetetraacetic acid (EDTA) can be used as the outer membrane permeabilizer to increase the bactericidal activity of LysSP1. Under the synergism of 5 mmol/L EDTA, LysSP1 exhibited a strong bactericidal activity against Salmonella Typhimurium ATCC14028. LysSP1 was stable at 4°C for 7 days and at -20°C for 180 days. LysSP1 remained the optimal activity at 40°C and was efficiently active at alkaline condition (pH 8.0-10.0). Divalent metal ions could not enhance the bactericidal activity of LysSP1 and even caused the significant reduction of bactericidal activity. LysSP1 not only could lyse Salmonella, but also could lyse other Gram-negative strains and Gram-positive strains. These results indicated that LysSP1 is a broad-spectrum endolysin and has potential as an antimicrobial agent against Salmonella and other foodborne pathogens. KEY POINTS: • Recombinant endolysin LysSP1 can be prepared by prokaryotic expression. • LysSP1 has stable nature and strong bactericidal activity on Salmonella Typhimurium with EDTA. • LysSP1 has a broad range of hosts including Gram-negative bacteria and Gram-positive bacteria.

Malondialdehyde (MDA) is one of the representative end products under lipid peroxidation, indicating the degree of lipid oxidation in foods. However, compounds in pickled products, especially the nitrite in salted lean pork can react with MDA under the acidic condition, leads to the loss of MDA and an underestimation on lipid oxidation through the conventional assay. In this study, the quantification for MDA in the sample containing sodium nitrite were found lacking accuracy by the thiobarbituric acid (TBA) assay and chromatography assay based on alkaline hydrolysis as the reaction between them were difficult to be completely inhibited. Among other trials, the improvement GC-MS analysis utilizing deuterium substituted MDA (MDA-d2) as an internal standard and applying perfluorophenylhydrazine (PFPH) as a derivative reagent can reduce the deviations from the presence of nitrite in the salted lean pork meat and the recovery is between 93.9% and 98.4% and coefficient of variation for the intermediate precision is between 1.1 and 3.5% using the method. The advanced gas chromatograph mass spectrometer (GC-MS) assay also has a very low detection limit (0.25 ng/mL) with both hydrolysis types.

The aim of this study was to evaluate the effectiveness of bacteriophage (phage) SLMP1 to reduce Salmonella Typhimurium on contaminated raw salmon fillets and scallop adductors as a function of Salmonella inoculum level, phage dose, storage temperature, and storage time. Samples were inoculated with 102 and 104 CFU/g Salmonella and then treated with different concentrations of phage SLMP1, followed by incubation at 4, 15, and 25°C, respectively. The results showed that 108 PFU/g was the optimal concentration of phage for the control of Salmonella, which was applied in the following storage experiments over a 7-day period at 4°C, a 4-day period at 15°C, and a 2-day period at 25°C. For the salmon fillets samples, 102 CFU/g Salmonella could be reduced below the detection limit at all three temperatures, whereas 104 CFU/g Salmonella was first decreased and then increased at 15 and 25°C. For the scallop adductors samples, 102 CFU/g Salmonella could be reduced below the detection limit first and then i...

Vibrio parahaemolyticus is an important foodborne pathogen which commonly inhabits estuarine and marine environments and seafood. In the present study, 90 V. parahaemolyticus isolates from the main seafoods from three coastal provinces surrounding Bohai Sea and Yellow Sea, China were analyzed to elucidate their antimicrobial resistance, virulence and genetic relationship by multilocus sequence typing (MLST). The results showed that the virulence genes tdh and trh were detected in one isolate and five isolates respectively. Most of isolates showed resistance to ampicillin (86/90) and cephazolin (75/90). Some isolates were resistant to amikacin (27/90), cefuroxime sodium (18/90), tetracycline (16/90), sulphamethoxazole/trimethoprim (16/90) and streptomycin (13/90). Forty isolates (44.4%) possessed multiple antimicrobial resistance to at least three antimicrobials. The V. parahaemolyticus population was composed of 68 sequence types, of which 41 were novel to the pubMLST database, displaying a high level of genetic diversity. The phylogenetic relatedness of V. parahaemolyticus isolates was irrelevant to the collection sources. Moreover, there were no associations of antimicrobial resistance and trh positive virulence with genetic population of V. parahaemolyticus isolates. These results indicated that the diversity of antimicrobial-resistant or pathogenic V. parahaemolyticus isolates from coasts of Bohai Sea and Yellow Sea, China could pose a potential risk to human health.

UNLABELLED This study was aimed to evaluate the antimicrobial resistance and molecular resistance mechanisms of 87 Vibrio parahaemolyticus isolates from cultured sea cucumbers (Apostichopus japonicus). The results showed that all isolates were resistant to ampicillin and cephazolin, fewer of them were resistant to streptomycin (43·7%), cefuroxime sodium (18·4%), tetracycline (4·6%), sulphamethoxazole/trimethoprim (2·3%) and four quinolones (2·3%). More than half (56·2%) of the isolates displayed multiple resistance to at least three antimicrobials. The resistance genes were detected in all antimicrobial-resistant isolates except two tetracycline-resistant isolates. Among all these tested resistance genes, blaTEM , sul2, strA and strB were predominant, and none of blaSHV , blaCTX-M , blaOXA , sul1, sul3, tetA, tetM and tetQ genes was detected. Point mutations were found in quinolone resistance-determining regions of gyrA and parC genes in quinolone-resistant isolates. All isolates harboured class 1 integrons but only one carried gene cassette without any resistance genes, and none of them was positive to class 2, 3 integrons and SXT constins. These results indicate that the antimicrobial-resistant V. parahaemolyticus isolates from sea cucumbers and resistance genes could be potential risks to public health or other environments. SIGNIFICANCE AND IMPACT OF THE STUDY This study is the first report on characterization of antimicrobial resistance of Vibrio parahaemolyticus from sea cucumbers (Apostichopus japonicus). Our findings reveal a high level of resistance to some antimicrobials and prevalence of the resistance genes in V. parahaemolyticus isolates from sea cucumbers and underline the need for prudent use of antimicrobials in aquaculture to minimize the spread of antimicrobial-resistant V. parahaemolyticus.