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July 7, 2019

Complete genetic analysis of a Salmonella enterica serovar Indiana isolate accompanying four plasmids carrying mcr-1, ESBL and other resistance genes in China

One mcr-1-carrying Salmonella enterica serovar Indiana strain D90, was identified from 1320 Salmonella enterica isolates from poultry slaughterhouse in 2012 in China. The objective of this study was to verify the transferability of the mcr-1 gene and also completely characterize the sequence of the strain at the whole-genome level. Broth matting assays were carried out to detect the transferability and whole-genome sequencing (WGS) of S. enterica serovar Indiana D90 was performed using the PacBio RS II system. Open reading frames were assigned using Rapid Annotation using Subsystem Technology (RAST) and analysed by BLASTn and BLASTp. Salmonella Pathogenisity Islands (SPIs) were annotated by SPIFinder platform. The complete genome sequence of S. enterica serovar Indiana D90 contained a circular 4,779,514-bp chromosome and four plasmids. Genome analysis and sequencing revealed that 24 multi-drug resistance (MDR) genes were located on plasmids. The largest plasmid pD90-1, was found to be of an IncHI2/HI2A/Q1/N type that encoded a blaCTX-M-65 gene along with 20 additional antimicrobial resistance genes. A 60.5-kbp IncI2 plasmid pD90-2 contained a nikA-nikB-mcr-1 genetic structure, that can be successfully transferred to E. coli and S. enterica serovar Typhimurium at low transfer rates. Interestingly, comparative sequence analysis revealed the plasmids pD90-1 and pD90-2 showed considerable nucleotide similarity to pHNSHP45-2 and pHNSHP45, respectively. Moreover, the genome and the plasmid pD90-2 also showed high similarity to one carbapenem resistant S. enterica serovar Indiana strain, C629 and its plasmid pC629, respectively. This is the first report of the complete nucleotide sequence of one mcr-1-carrying MDR S. enterica serovar Indiana strain.

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July 7, 2019

Heat resistance mediated by pLM58 plasmid-borne ClpL in Listeria monocytogenes.

Listeria monocytogenes is one of the most heat-resistant non-spore-forming food-borne pathogens and poses a notable risk to food safety, particularly when mild heat treatments are used in food processing and preparation. While general heat stress properties and response mechanisms of L. monocytogenes have been described, accessory mechanisms providing particular L. monocytogenes strains with the advantage of enhanced heat resistance are unknown. Here, we report plasmid-mediated heat resistance of L. monocytogenes for the first time. This resistance is mediated by the ATP-dependent protease ClpL. We tested the survival of two wild-type L. monocytogenes strains-both of serotype 1/2c, sequence type ST9, and high sequence identity-at high temperatures and compared their genome composition in order to identify genetic mechanisms involved in their heat survival phenotype. L. monocytogenes AT3E was more heat resistant (0.0 CFU/ml log10 reduction) than strain AL4E (1.4 CFU/ml log10 reduction) after heating at 55°C for 40 min. A prominent difference in the genome compositions of the two strains was a 58-kb plasmid (pLM58) harbored by the heat-resistant AT3E strain, suggesting plasmid-mediated heat resistance. Indeed, plasmid curing resulted in significantly decreased heat resistance (1.1 CFU/ml log10 reduction) at 55°C. pLM58 harbored a 2,115-bp open reading frame annotated as an ATP-dependent protease (ClpL)-encoding clpL gene. Introducing the clpL gene into a natively heat-sensitive L. monocytogenes strain (1.2 CFU/ml log10 reduction) significantly increased the heat resistance of the recipient strain (0.4 CFU/ml log10 reduction) at 55°C. Plasmid-borne ClpL is thus a potential predictor of elevated heat resistance in L. monocytogenes. IMPORTANCEListeria monocytogenes is a dangerous food pathogen causing the severe illness listeriosis that has a high mortality rate in immunocompromised individuals. Although destroyed by pasteurization, L. monocytogenes is among the most heat-resistant non-spore-forming bacteria. This poses a risk to food safety, as listeriosis is commonly associated with ready-to-eat foods that are consumed without thorough heating. However, L. monocytogenes strains differ in their ability to survive high temperatures, and comprehensive understanding of the genetic mechanisms underlying these differences is still limited. Whole-genome-sequence analysis and phenotypic characterization allowed us to identify a novel plasmid, designated pLM58, and a plasmid-borne ATP-dependent protease (ClpL), which mediated heat resistance in L. monocytogenes. As the first report on plasmid-mediated heat resistance in L. monocytogenes, our study sheds light on the accessory genetic mechanisms rendering certain L. monocytogenes strains particularly capable of surviving high temperatures-with plasmid-borne ClpL being a potential predictor of elevated heat resistance.

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July 7, 2019

Complete genome sequence of Clostridium perfringens LLY_N11, a necrotic enteritis-inducing strain isolated from a healthy chicken intestine.

Clostridium perfringens strain LLY_N11, a commensal bacterium, which previously induced necrotic enteritis in an experimental study, was isolated from the intestine of a young healthy chicken. Here, we present the complete genome sequence of this strain, which may provide a better understanding of the molecular mechanisms involved in necrotic enteritis pathogenesis.

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July 7, 2019

Genomic variation and evolution of Vibrio parahaemolyticus ST36 over the course of a transcontinental epidemic expansion.

Vibrio parahaemolyticus is the leading cause of seafood-related infections with illnesses undergoing a geographic expansion. In this process of expansion, the most fundamental change has been the transition from infections caused by local strains to the surge of pandemic clonal types. Pandemic clone sequence type 3 (ST3) was the only example of transcontinental spreading until 2012, when ST36 was detected outside the region where it is endemic in the U.S. Pacific Northwest causing infections along the U.S. northeast coast and Spain. Here, we used genome-wide analyses to reconstruct the evolutionary history of the V. parahaemolyticus ST36 clone over the course of its geographic expansion during the previous 25 years. The origin of this lineage was estimated to be in ~1985. By 1995, a new variant emerged in the region and quickly replaced the old clone, which has not been detected since 2000. The new Pacific Northwest (PNW) lineage was responsible for the first cases associated with this clone outside the Pacific Northwest region. After several introductions into the northeast coast, the new PNW clone differentiated into a highly dynamic group that continues to cause illness on the northeast coast of the United States. Surprisingly, the strains detected in Europe in 2012 diverged from this ancestral group around 2000 and have conserved genetic features present only in the old PNW lineage. Recombination was identified as the major driver of diversification, with some preliminary observations suggesting a trend toward a more specialized lifestyle, which may represent a critical element in the expansion of epidemics under scenarios of coastal warming.IMPORTANCEVibrio parahaemolyticus and Vibrio cholerae represent the only two instances of pandemic expansions of human pathogens originating in the marine environment. However, while the current pandemic of V. cholerae emerged more than 50 years ago, the global expansion of V. parahaemolyticus is a recent phenomenon. These modern expansions provide an exceptional opportunity to study the evolutionary process of these pathogens at first hand and gain an understanding of the mechanisms shaping the epidemic dynamics of these diseases, in particular, the emergence, dispersal, and successful introduction in new regions facilitating global spreading of infections. In this study, we used genomic analysis to examine the evolutionary divergence that has occurred over the course of the most recent transcontinental expansion of a pathogenic Vibrio, the spreading of the V. parahaemolyticus sequence type 36 clone from the region where it is endemic on the Pacific coast of North America to the east coast of the United States and finally to the west coast of Europe.

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July 7, 2019

Complete genomic sequences of two Salmonella enterica subsp. enterica serogroup C2 (O:6,8) strains from Central California.

Salmonella enterica subsp. enterica strains RM11060, serotype 6,8:d:-, and RM11065, serotype 6,8:-:e,n,z15, were isolated from environmental samples collected in central California in 2009. We report the complete genome sequences of these two strains. These genomic sequences are distinct and will provide additional data to our understanding of S. enterica genomics.

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July 7, 2019

Complete genome sequence of Salmonella enterica subsp. enterica serovar Minnesota strain

Mango has been implicated as food vehicle in several Salmonella-causing foodborne outbreaks. Here, Salmonella enterica subsp. enterica serovar Minnesota was isolated from fresh mango fruit imported from Mexico in 2014. The complete genome sequence of S. Minnesota CFSAN017963 was sequenced using single-molecule real-time DNA sequencing. Distinct prophage regions, Salmonella pathogenicity islands, and fimbrial gene clusters were observed in comparative genomic analysis on S. Minnesota CFSAN017963 with other phylogenetically closely related Salmonella serovars. Core genome multilocus sequencing typing analysis of all the S. Minnesota isolates in the Genbank and Enterobase also revealed a high genomic diversity among the genomes analyzed.

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July 7, 2019

Characterization of oqxAB in Escherichia coli isolates from animals, retail meat, and human patients in Guangzhou, China.

The purpose of this study was to investigate the prevalence and genetic elements of oqxAB among Escherichia coli isolates from animals, retail meat, and humans (patients with infection or colonization) in Guangzhou, China. A total of 1,354 E. coli isolates were screened for oqxAB by PCR. Fifty oqxAB-positive isolates were further characterized by pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), S1-PFGE, genetic environment analysis, plasmid replicon typing, and plasmid sequencing. oqxAB was detected in 172 (33.79%), 60 (17.34%), and 90 (18.07%) E. coli isolates from animal, food, and human, respectively. High clonal diversity was observed among oqxAB-positive isolates. In 21 oqxAB-containing transformants, oqxAB was flanked by two IS26 elements in the same orientation, formed a composite transposon Tn6010 in 19 transformants, and was located on plasmids (33.3~500 kb) belonging to IncN1-F33:A-:B- (n = 3), IncHI2/ST3 (n = 3), F-:A18:B- (n = 2), F-:A-:B54 (n = 2), or others. Additionally, oqxAB was co-located with multiple resistance genes on the same plasmid, such as aac(6′)-Ib-cr and/or qnrS, which were identified in two F-:A18:B- plasmids from pigs, and blaCTX-M-55, rmtB, fosA3, and floR, which were detected in two N1-F33:A-:B- plasmids from patients. The two IncHI2/ST3 oqxAB-bearing plasmids, pHNLDF400 and pHNYJC8, which were isolated from human patient and chicken meat, respectively, contained a typical IncHI2-type backbone, and were similar to each other with 2-bp difference, and also showed 99% identity to the Salmonella Typhimurium oqxAB-carrying plasmids pHXY0908 (chicken) and pHK0653 (human patient). Horizontal transfer mediated by mobile elements may be the primary mechanism underlying oqxAB spread in E. coli isolates obtained from various sources in Guangzhou, China. The transmission of identical oqxAB-carrying IncHI2 plasmids between food products and humans might pose a serious threat to public health.

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July 7, 2019

Widespread distribution of mcr-1-bearing bacteria in the ecosystem, 2015 to 2016.

The recently discovered colistin resistance-encoding element, mcr-1, adds to the list of mobile resistance genes whose products rapidly erode the antimicrobial efficacy of not only the commonly used antibiotics, but also the last line agents of carbapenems and colistin. The relative prevalence of mcr-1-bearing strains in various ecological niches including 1,371 food samples, 480 animal faecal samples, 150 human faecal samples and 34 water samples was surveyed using a novel in-house method. Bacteria bearing mcr-1 were commonly detected in water (71% of samples), animal faeces (51%), food products (36%), and exhibited stable carriage in 28% of human subjects surveyed. Such strains, which exhibited variable antibiotic susceptibility profiles, belonged to various Enterobacteriaceae species, with Escherichia coli being the most dominant in each specimen type. The mcr-1 gene was detectable in the chromosome as well as plasmids of various sizes. Among these, two conjugative plasmids of sizes ca?33 and ca?60 kb were found to be the key vectors that mediated mcr-1 transmission in organisms residing in various ecological niches. The high mcr-1 carriage rate in humans found in this study highlights the importance of continued vigilance, careful antibiotic stewardship, and the development of new antimicrobials.

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July 7, 2019

Complete genome sequences of Clostridium perfringens Del1 strain isolated from chickens affected by necrotic enteritis.

Clostridium perfringens is ubiquitous in nature. It is a normal inhabitant in the intestinal tract of animals and humans. As the primary etiological agent of gas gangrene, necrosis and bacteremia, C. perfringens causes food poisoning, necrotic enteritis (NE), and even death. Epidemiology research has indicated that the increasing incidence of NE in poultry is associated with the withdrawal of in-feed antibiotic growth promoters in poultry production in response to government regulations. The recent omics studies have indicated that bacterial virulence is typically linked to highly efficient conjugative transfer of toxins, or plasmids carrying antibiotic-resistance traits. Currently, there is limited information on understanding of host-pathogen interaction in NE caused by virulent strains of C. perfringens. Elucidating such pathogenesis has practical impacts on fighting infectious diseases through adopting strategies of prophylactic or therapeutic interventions. In this report, we sequenced and analyzed the genome of C. perfringens Del1 strain using the hybrid of PacBio and Illumina sequencing technologies.Sequence analysis indicated that Del1 strain comprised a single circular chromosome with a complete 3,559,163 bp and 4 plasmids: pDel1_1 (82,596 bp), pDel1_2 (69,827 bp), pDel1_3 (49,582 bp), and pDel1_4 (49,728 bp). The genome had 3361 predicted coding DNA sequences, harbored numerous genes for pathogenesis and virulence factors, including 6 for antibiotic and antimicrobial resistance, and 3 phage-encoded genes. Phylogenetic analysis revealed that Del1 strain had similar genome and plasmid sequences to the CP4 strain.Complete chromosomal and plasmid sequences of Del1 strain are presented in this report. Since Del1 was isolated from a field disease outbreak, this strain is a good source to identify virulent genes that cause many damaging effects of Clostridial infections in chicken gut. Genome sequencing of the chicken pathogenic isolates from commercial farms provides valuable insights into the molecular pathogenesis of C. perfringens as a gastrointestinal pathogen in food animals. The detailed information on gene sequencing of this important field strain will benefit the development of novel vaccines specific for C. perfringens-induced NE in chickens.

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July 7, 2019

Complete genome sequences of two strains of the meat spoilage bacterium Brochothrix thermosphacta isolated from ground chicken.

Brochothrix thermosphacta is an important meat spoilage bacterium. Here we report the genome sequences of two strains of B. thermosphacta isolated from ground chicken. The genome sequences were determined using long-read PacBio single-molecule real-time (SMRT) technology and are the first complete genome sequences reported for B. thermosphacta.

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July 7, 2019

Complete genome sequence of Bacillus velezensis YJ11-1-4, a strain with broad-spectrum antimicrobial activity, isolated from traditional Korean fermented soybean paste.

Bacillus velezensis YJ11-1-4 is a strain that exhibits broad-spectrum antimicrobial activity against various pathogens. It was isolated from doenjang, a traditional Korean fermented soybean paste. The genome comprises a single circular chromosome of 4,006,637 bp with 46.42% G+C content without plasmids. Copyright © 2017 Lee et al.

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July 7, 2019

Closed genome sequence of Chryseobacterium piperi strain CTMT/ATCC BAA-1782, a Gram-negative bacterium with clostridial neurotoxin-like coding sequences.

Clostridial neurotoxins, including botulinum and tetanus neurotoxins, are among the deadliest known bacterial toxins. Until recently, the horizontal mobility of this toxin gene family appeared to be limited to the genusClostridiumWe report here the closed genome sequence ofChryseobacterium piperi, a Gram-negative bacterium containing coding sequences with homology to clostridial neurotoxin family proteins. Copyright © 2017 Wentz et al.

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