A total of 489 Vibrio parahaemolyticus isolates from patients in Thailand with diarrhea was examined for the presence of thermostable direct hemolysin (TDH) and TDH-related hemolysin genes (tdh and trh, respectively), their serovars, TDH production, and urease activity. Of the strains, 81% were positive only for the tdh gene, 6% for both trh and tdh genes, and 2% for the trh gene only. Thirty-seven (8%) of the 489 isolates were positive for urease production. Of special interest, all urease-positive strains possessed the trh gene, and conversely, urease-negative strains lacked the gene, indicating that urease production by V. parahaemolyticus strains strongly correlates with the possession of the trh gene. Thus, the urease-positive phenotype of V. parahaemolyticus can be considered an indication of virulent (trh-possessing) V. parahaemolyticus strains in clinical diagnosis.
Antimicrobial resistance (AMR) is a major threat to global health. Understanding the emergence, evolution, and transmission of individual antibiotic resistance genes (ARGs) is essential to develop sustainable strategies combatting this threat. Here, we use metagenomic sequencing to analyse ARGs in 757 sewage samples from 243 cities in 101 countries, collected from 2016 to 2019. We find regional patterns in resistomes, and these differ between subsets corresponding to drug classes and are partly driven by taxonomic variation. The genetic environments of 49 common ARGs are highly diverse, with most common ARGs carried by multiple distinct genomic contexts globally and sometimes on plasmids. Analysis of flanking sequence revealed ARG-specific patterns of dispersal limitation and global transmission. Our data furthermore suggest certain geographies are more prone to transmission events and should receive additional attention.
e Vibrio parahaemolyticus is a seafood-borne pathogenic bacterium that is a major cause of gastroenteritis worldwide. We investigated the genetic and evolutionary relationships of 101 V. parahaemolyticus isolates originating from clinical, human carrier, and various environmental and seafood production sources in Thailand using multilocus sequence analysis. The isolates were recovered from clinical samples (n ؍ 15), healthy human carriers (n ؍ 18), various types of fresh seafood (n ؍ 18), frozen shrimp (n ؍ 16), fresh-farmed shrimp tissue (n ؍ 18), and shrimp farm water (n ؍ 16). Phylogenetic analysis revealed a high degree of genetic diversity within the V. parahaemolyticus population, although isolates recovered from clinical samples and from farmed shrimp and water samples represented distinct clusters. The tight clustering of the clinical isolates suggests that disease-causing isolates are not a random sample of the environmental reservoir, although the source of infection remains unclear. Extensive serotypic diversity occurred among isolates representing the same sequence types and recovered from the same source at the same time. These findings suggest that the O-and K-antigen-encoding loci are subject to exceptionally high rates of recombination. There was also strong evidence of interspecies horizontal gene transfer and intragenic recombination involving the recA locus in a large proportion of isolates. As the majority of the intragenic recombinational exchanges involving recA occurred among clinical and carrier isolates, it is possible that the human intestinal tract serves as a potential reservoir of donor and recipient strains that is promoting horizontal DNA transfer, driving evolutionary change, and leading to the emergence of new, potentially pathogenic strains. Vibrio parahaemolyticus is a seafood-borne pathogenic bacterium and is the leading cause of traveler's diarrhea and gastroenteritis worldwide due to the consumption of undercooked contaminated seafood, particularly shellfish. The organism possesses a number of virulence factors, including a thermostable direct hemolysin (TDH) (1), a thermostable direct hemolysinrelated hemolysin (TRH) (2), and type 3 secretion system 1 (TTSS1) and TTSS2 (3). Strains that possess tdh, trh, and TTSS2-encoding genes are generally pathogenic and responsible for the vast majority of clinical cases. While such strains account for only 1 to 2% of isolates sampled from water and different marine species (4-6), they are known to have a widespread global distribution, having been reported from cases of infection in Japan, India, Thailand, Malaysia, China, Indonesia, the United Kingdom, Italy, and the East and Gulf Coasts of the United States (7-19).The public health and commercial burdens associated with V. parahaemolyticus contamination are very high in Thailand due to the wide consumption of seafood. Although undercooked seafood has been identified as a source of V. parahaemolyticus infection (20, 21), the relative likelihood of contamination from differ...
Although K parahaemolyticus does not generally produce urease, several studies have reported urease-positive K parahaemolyticus isolates from clinical sources. Recently, studies have shown a complete coincidence between the urease-producing phenotype of K parahaemolyticus strains and the possession of the thermostable direct haemolysin (TDH)-related haemolysin (TRH) gene (trh). TRH, like TDH, is considered to be an important virulence factor in the pathogenesis of K parahuemolyticus gastroenteritis. The present study attempted to identify the gene ure encoding urease in K parahaemolyticus to clarify the relationship between urease production and possession of trh. The polymerase chain reaction with mixed oligonucleotide primers targeted for conserved sequences of reported ure genes from other species was used to prepare a DNA probe to detect the K parahuemolyticus ure gene. Colony hybridisation with this ure probe demonstrated that all the ure-positive strains produced urease. Considering the coincidence between production of urease and possession of trh in K parahaemolyticus, it was concluded that the presence or absence of the ure gene is completely coincident with that of the trh gene in K parahuemolyticus strains. Furthermore, the relative location of ure and trh on K parahaemolyticus chromosomal DNA was analysed by pulsed-field gel electrophoresis. The results showed that, in all the strains examined, ure and trh were detected on the same Not1 fragment, showing that the two genes localise within a relatively small portion of the chromosome DNA. These results suggest that the ure and trh genes are genetically linked in
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.