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July 7, 2019

Complete genome sequence of Lactobacillus plantarum LZ206, a potential probiotic strain with antimicrobial activity against food-borne pathogenic microorganisms.

Lactobacilli strains have been considered as important candidates for manufacturing “natural food”, due to their antimicrobial properties and generally regarded as safe (GRAS) status. Lactobacillus plantarum LZ206 is a potential probiotic strain isolated from raw cow milk, with antimicrobial activity against various pathogens, including Gram-positive bacteria (Staphylococcus aureus and Listeria monocytogenes), Gram-negtive bacteria (Escherichia coli and Salmonella enterica), and fungus Candida albicans. To better understand molecular base for its antimicrobial activity, entire genome of LZ206 was sequenced. It was revealed that genome of LZ206 contained a circular 3,212,951-bp chromosome, two circular plasmids and one predicted linear plasmid. A plantaricin gene cluster, which is responsible for bacteriocins biosynthesis and could be associated with its broad-spectrum antimicrobial activity, was identified based on comparative genomic analysis. Whole genome sequencing of L. plantarum LZ206 might facilitate its applications to protect food products from pathogens’ contamination in the dairy industry. Copyright © 2016 Elsevier B.V. All rights reserved.

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July 7, 2019

IncHI2 plasmids are the key vectors responsible for oqxAB transmission among Salmonella species.

This study reported and analysed the complete sequences of two oqxAB-bearing IncHI2 plasmids harboured by a clinical S. Typhimurium strain and an S. Indiana strain of animal origin, respectively. Particularly, pA3T recovered from S. Indiana comprised the resistance determinants oqxAB, aac(6′)Ib-cr, fosA3 and blaCTX-M-14 Further genetic screening of 63 oqxAB-positive Salmonella spp. isolates revealed that the majority carried IncHI2 plasmids, confirming that such plasmids play a pivotal role in dissemination of oqxAB in Salmonella spp.. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

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July 7, 2019

Genomic insights into Campylobacter jejuni virulence and population genetics

Campylobacter jejuni has long been recognized as a main food-borne pathogen in many parts of the world. Natural reservoirs include a wide variety of domestic and wild birds and mammals, whose intestines offer a suitable biological niche for the survival and dissemination of the organism. Understanding the genetic basis of the biology and pathogenicity of C. jejuni is vital to prevent and control Campylobacter-associated infections. The recent progress in sequencing techniques has allowed for a rapid increase in our knowledge of the molecular biology and the genetic structures of Campylobacter. Single-molecule realtime (SMRT) sequencing, which goes beyond four-base sequencing, revealed the role of DNA methylation in modulating the biology and virulence of C. jejuni at the level of epigenetics. In this review, we will provide an up-to-date review on recent advances in understanding C. jejuni genomics, including structural features of genomes, genetic traits of virulence, population genetics, and epigenetics.

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July 7, 2019

Complete sequence of a F33:A-:B- conjugative plasmid carrying the oqxAB, fosA3, and blaCTX-M-55 elements from a foodborne Escherichia coli strain.

This study reports the complete sequence of pE80, a conjugative IncFII plasmid recovered from an Escherichia coli strain isolated from chicken meat. This plasmid harbors multiple resistance determinants including oqxAB, fosA3, blaCTX-M-55, and blaTEM-1, and is a close variant of the recently reported p42-2 element, which was recovered from E. coli of veterinary source. Recovery of pE80 constitutes evidence that evolution or genetic re-arrangement of IncFII type plasmids residing in animal-borne organisms is an active event, which involves acquisition and integration of foreign resistance elements into the plasmid backbone. Dissemination of these plasmids may further compromise the effectiveness of current antimicrobial strategies.

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July 7, 2019

Complete genome of Vibrio parahaemolyticus FORC014 isolated from the toothfish.

Foodborne illness can occur due to various pathogenic bacteria such as Staphylococcus aureus, Escherichia coli and Vibrio parahaemolyticus, and can cause severe gastroenteritis symptoms. In this study, we completed the genome sequence of a foodborne pathogen V. parahaemolyticus FORC_014, which was isolated from suspected contaminated toothfish from South Korea. Additionally, we extended our knowledge of genomic characteristics of the FORC_014 strain through comparative analysis using the complete sequences of other V. parahaemolyticus strains whose complete genomes have previously been reported.The complete genome sequence of V. parahaemolyticus FORC_014 was generated using the PacBio RS platform with single molecule, real-time (SMRT) sequencing. The FORC_014 strain consists of two circular chromosomes (3,241,330 bp for chromosome 1 and 1,997,247 bp for chromosome 2), one plasmid (51,383 bp), and one putative phage sequence (96,896 bp). The genome contains a total of 4274 putative protein coding sequences, 126 tRNA genes and 34 rRNA genes. Furthermore, we found 33 type III secretion system 1 (T3SS1) related proteins and 15 type III secretion system 2 (T3SS2) related proteins on chromosome 1. This is the first reported result of Type III secretion system 2 located on chromosome 1 of V. parahaemolyticus without thermostable direct hemolysin (tdh) and thermostable direct hemolysin-related hemolysin (trh).Through investigation of the complete genome sequence of V. parahaemolyticus FORC_014, which differs from previously reported strains, we revealed two type III secretion systems (T3SS1, T3SS2) located on chromosome 1 which do not include tdh and trh genes. We also identified several virulence factors carried by our strain, including iron uptake system, hemolysin and secretion system. This result suggests that the FORC_014 strain may be one pathogen responsible for foodborne illness outbreak. Our results provide significant genomic clues which will assist in future understanding of virulence at the genomic level and help distinguish between clinical and non-clinical isolates.

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July 7, 2019

Listeria monocytogenes in stone fruits linked to a multistate outbreak: enumeration of cells and whole-genome sequencing.

In 2014, the identification of stone fruits contaminated with Listeria monocytogenes led to the subsequent identification of a multistate outbreak. Simultaneous detection and enumeration of L. monocytogenes were performed on 105 fruits, each weighing 127 to 145 g, collected from 7 contaminated lots. The results showed that 53.3% of the fruits yielded L. monocytogenes (lower limit of detection, 5 CFU/fruit), and the levels ranged from 5 to 2,850 CFU/fruit, with a geometric mean of 11.3 CFU/fruit (0.1 CFU/g of fruit). Two serotypes, IVb-v1 and 1/2b, were identified by a combination of PCR- and antiserum-based serotyping among isolates from fruits and their packing environment; certain fruits contained a mixture of both serotypes. Single nucleotide polymorphism (SNP)-based whole-genome sequencing (WGS) analysis clustered isolates from two case-patients with the serotype IVb-v1 isolates and distinguished outbreak-associated isolates from pulsed-field gel electrophoresis (PFGE)-matched, but epidemiologically unrelated, clinical isolates. The outbreak-associated isolates differed by up to 42 SNPs. All but one serotype 1/2b isolate formed another WGS cluster and differed by up to 17 SNPs. Fully closed genomes of isolates from the stone fruits were used as references to maximize the resolution and to increase our confidence in prophage analysis. Putative prophages were conserved among isolates of each WGS cluster. All serotype IVb-v1 isolates belonged to singleton sequence type 382 (ST382); all but one serotype 1/2b isolate belonged to clonal complex 5.WGS proved to be an excellent tool to assist in the epidemiologic investigation of listeriosis outbreaks. The comparison at the genome level contributed to our understanding of the genetic diversity and variations among isolates involved in an outbreak or isolates associated with food and environmental samples from one facility. Fully closed genomes increased our confidence in the identification and comparison of accessory genomes. The diversity among the outbreak-associated isolates and the inclusion of PFGE-matched, but epidemiologically unrelated, isolates demonstrate the high resolution of WGS. The prevalence and enumeration data could contribute to our further understanding of the risk associated with Listeria monocytogenes contamination, especially among high-risk populations. Copyright © 2016 Chen et al.

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July 7, 2019

Genomic insights into a sustained national outbreak of Yersinia pseudotuberculosis.

In 2014, a sustained outbreak of yersiniosis due to Yersinia pseudotuberculosis occurred across all major cities in New Zealand (NZ), with a total of 220 laboratory-confirmed cases, representing one of the largest ever reported outbreaks of Y. pseudotuberculosis. Here, we performed whole genome sequencing of outbreak-associated isolates to produce the largest population analysis to date of Y. pseudotuberculosis, giving us unprecedented capacity to understand the emergence and evolution of the outbreak clone. Multivariate analysis incorporating our genomic and clinical epidemiological data strongly suggested a single point-source contamination of the food chain, with subsequent nationwide distribution of contaminated produce. We additionally uncovered significant diversity in key determinants of virulence, which we speculate may help explain the high morbidity linked to this outbreak.

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July 7, 2019

Salmonella enterica serovar Enteritidis strains recovered from human clinical cases between 1949 and 1995 in the United States.

Salmonella enterica serovar Enteritidis is one of the most commonly isolated foodborne pathogens and is transmitted primarily to humans through consumption of contaminated poultry and poultry products. We are reporting completely closed genome and plasmid sequences of historical S. Enteritidis isolates recovered from humans between 1949 and 1995 in the United States.

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July 7, 2019

High-quality complete and draft genome sequences for three Escherichia spp. and three Shigella spp. generated with Pacific Biosciences and Illumina sequencing and optical mapping.

Escherichia spp., including E. albertii and E. coli, Shigella dysenteriae, and S. flexneri are causative agents of foodborne disease. We report here reference-level whole-genome sequences of E. albertii (2014C-4356), E. coli (2011C-4315 and 2012C-4431), S. dysenteriae (BU53M1), and S. flexneri (94-3007 and 71-2783).. Copyright © 2018 Schroeder et al.

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July 7, 2019

High-quality complete genome sequences of three bovine Shiga toxin-producing Escherichia coli O177:H- (fliCH25) isolates harboring virulent stx2 and multiple plasmids.

Shiga toxin-producingEscherichia coli(STEC) bacteria are zoonotic pathogens. We report here the high-quality complete genome sequences of three STEC O177:H- (fliCH25) strains, SMN152SH1, SMN013SH2, and SMN197SH3. The assembled genomes consisted of one optical map-verified circular chromosome for each strain, plus two plasmids for SMN013SH2 and three plasmids for SMN152SH1 and SMN197SH3, respectively. Copyright © 2018 Sheng et al.

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