Vibrio parahaemolyticus is recognized as one of the most important foodborne pathogens responsible for gastroenteritis in humans. The bla CARB-17 gene is an intrinsic β-lactamase gene and a novel species-specific genetic marker of V. parahaemolyticus. In this study, a loop-mediated isothermal amplification (LAMP) assay combined with a lateral flow dipstick (LFD) was developed targeting this bla CARB-17 gene. The specificity of LAMP-LFD was ascertained by detecting V. parahaemolyticus ATCC 17802 and seven other non-V. parahaemolyticus strains. Finally, the practicability of LAMP-LFD was confirmed by detection with V. parahaemolyticus-contaminated samples and natural food samples. The results showed that the optimized reaction parameters of LAMP are as follows: 2.4 mmol/l Mg 2+ , 0.96 mmol/l dNTPs, 4.8 U Bst DNA polymerase, and an 8:1 ratio of inner primer to outer primer, at 63 o C for 40 min. The optimized reaction time of the LFD assay is 60 min. Cross-reactivity analysis with the seven non-V. parahaemolyticus strains showed that LAMP-LFD was exclusively specific for V. parahaemolyticus. The detection limit of LAMP-LFD for V. parahaemolyticus genomic DNA was 2.1 × 10 -4 ng/μl, corresponding to 630 fg/reaction and displaying a sensitivity that is 100-fold higher than that of conventional PCR. LAMP-LFD in a spiking study revealed a detection limit of approximately 6 CFU/ml, which was similar with conventional PCR. The developed LAMP-LFD specifically identified the 10 V. parahaemolyticus isolates from 30 seafood samples, suggesting that this LAMP-LFD may be a suitable diagnostic method for detecting V. parahaemolyticus in aquatic foods.
The complete mitochondrial genome of the Chinese lake gudgeon Sarcocheilichthys sinensis was first determined in this study. It is a circular DNA double strand of 16,684 bp in length, encodes genes for 13 proteins, 2 ribosomal RNA subunits, 22 transfer RNAs and an A + T-rich control region with the typical gene order in vertebrate mitogenomes. Overall nucleotide composition is 30.5% A, 26.6% C, 16.7% G and 26.3% T. Three start codons (ATG, GTG and ATA) and three stop codons (TAG, TAA and T) were found in all protein-coding genes. The tRNA-Ser(AGY) lacked the dihydrouridine arm and could not fold into typical cloverleaf secondary structure. The origin of L-strand replication was identified between the tRNA-Asn and tRNA-Cys genes.
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