Health risk associated with pesticide residues in vegetables from Incheon region of Korea.

This study was conducted to investigate the pesticide residue concentrations and assess potential human health risks from vegetable consumption in Incheon. A total of 960 samples were collected from the Incheon areas of Korea in 2019. The pesticide residues were analyzed by the multi-residue method of the Korean Food Code for 373 different pesticides using GC-MS/MS, LC-MS/MS, GC-ECD/NPD, and HPLC-UVD. Among the vegetable samples, 869 samples (90.5%) were free from detectable residues, while 91 samples (9.5%) contained residues, and 16 samples (1.7%) had residues exceeding the Korean maximum residue limit (MRLs). A total of 33 different pesticide residues were found, and 11 residues exceeded MRLs. The most frequently detected pesticide residues were chlorfenapyr, fludioxonil, pyridalyl, hexaconazole, and procymidone. Samples exceeding the MRLs were found in aster scaber, coastal hog fennel, lettuce (leaves), mustard green, mustard leaf, perilla leaves, Pimpinella brachycarpa, radish leaves, shepherd' purse, spinach, and winter-grown cabbage. The potential health risk assessment of pesticides was estimated by calculating the estimated daily intake (EDI) and the acceptable daily intake (ADI). The range of HQs was 0.002-90.621%, which was below 100%. Therefore, the results of this study show that the detected pesticide could not be considered a serious public health problem through the consumption of vegetables.

Genetic analysis of phosphomannomutase/phosphoglucomutase from Vibrio furnissii and characterization of its role in virulence.

The pmm gene from Vibrio furnissii, which encodes phosphomannomutase (PMM), was cloned and sequenced. The open reading frame consisted of 1,434 bp, encoding a polypeptide of 477 amino acids with a molecular mass of 53,325 Da. The predicted amino acid sequence of V. furnissii PMM showed high similarity with PMMs from other enteric bacteria, such as V. cholerae, Salmonella sp. and Escherichia coli. The PMM protein was overexpressed in E. coli as a His(6)-tagged recombinant protein. The estimated apparent K(m )and k(cat) values of the purified recombinant protein for mannose 1-phosphate were about 60 microM and 800 min(-1), respectively. To investigate the biochemical functions and the role of pmm in the virulence of V. furnissii, a pmm knock-out mutant was constructed by homologous recombination mutation. Under the various physical conditions, cell numbers of the wild-type and the mutant did not differ. Oral introduction of bacterial suspensions to a mouse model showed that the pmm-deficient mutant decreased in viability at the intestine. Microscopy of the isolated intestines from mice revealed significant damage after 3 days in intestinal mucosa infected with the wild-type as compared with the mutant. The pmm-deficient mutant caused a reduction of virulence in mice and the loss of O-antigen polysaccharide, and showed low resistance relative to the wild-type when incubated with normal human serum.

Characterization of Vibrio mimicus phospholipase A (PhlA) and cytotoxicity on fish cell.

Vibrio mimicus is a typical strain of Vibrio cholerae and produces a phospholipase (PhlA) which shares a highly conserved amino acid sequence with the lecithinase (Lec) of V. cholerae. The recombinant protein (rPhlA) produced from the phlA gene of V. mimicus was expressed in Escherichia coli as His-tag fused protein. The rPhlA was purified by gel filtration and Ni-metal affinity chromatographies. When the action mode was investigated by TLC and GC-MS, the purified rPhlA protein showed a phospholipase A activity, which cleaved the fatty acids at the sn-1 and sn-2 positions of phosphatidylcholine. However, it did not show lysophospholipase, sphingomyelinase, and phospholipase C activities. The rPhlA showed maximum activity at temperature of about 40 degrees C and pH around 8-9. Some divalent cations could affect the activity of PhlA. The addition of Co(2+) increased the activity, whereas Mg(2+) and Zn(2+) did not enhance the enzyme activity. The rPhlA could lyse the erythrocytes obtained from the fish such as rainbow trout and tilapia. A significant cytotoxic activity on a fish cell line, CHSE-214, was observed after 24h exposure to 40 microg rPhlA protein.