April 21, 2020  |  

Detection of VIM-1-Producing Enterobacter cloacae and Salmonella enterica Serovars Infantis and Goldcoast at a Breeding Pig Farm in Germany in 2017 and Their Molecular Relationship to Former VIM-1-Producing S. Infantis Isolates in German Livestock Production.

In 2011, VIM-1-producing Salmonella enterica serovar Infantis and Escherichia coli were isolated for the first time in four German livestock farms. In 2015/2016, highly related isolates were identified in German pig production. This raised the issue of potential reservoirs for these isolates, the relation of their mobile genetic elements, and potential links between the different affected farms/facilities. In a piglet-producing farm suspicious for being linked to some blaVIM-1 findings in Germany, fecal and environmental samples were examined for the presence of carbapenemase-producing Enterobacteriaceae and Salmonella spp. Newly discovered isolates were subjected to Illumina whole-genome sequencing (WGS) and S1 pulsed-field gel electrophoresis (PFGE) hybridization experiments. WGS data of these isolates were compared with those for the previously isolated VIM-1-producing Salmonella Infantis isolates from pigs and poultry. Among 103 samples, one Salmonella Goldcoast isolate, one Salmonella Infantis isolate, and one Enterobacter cloacae isolate carrying the blaVIM-1 gene were detected. Comparative WGS analysis revealed that the blaVIM-1 gene was part of a particular Tn21-like transposable element in all isolates. It was located on IncHI2 (ST1) plasmids of ~290 to 300?kb with a backbone highly similar (98 to 100%) to that of reference pSE15-SA01028. SNP analysis revealed a close relationship of all VIM-1-positive S Infantis isolates described since 2011. The findings of this study demonstrate that the occurrence of the blaVIM-1 gene in German livestock is restricted neither to a certain bacterial species nor to a certain Salmonella serovar but is linked to a particular Tn21-like transposable element located on transferable pSE15-SA01028-like IncHI2 (ST1) plasmids, being present in all of the investigated isolates from 2011 to 2017.IMPORTANCE Carbapenems are considered one of few remaining treatment options against multidrug-resistant Gram-negative pathogens in human clinical settings. The occurrence of carbapenemase-producing Enterobacteriaceae in livestock and food is a major public health concern. Particularly the occurrence of VIM-1-producing Salmonella Infantis in livestock farms is worrisome, as this zoonotic pathogen is one of the main causes for human salmonellosis in Europe. Investigations on the epidemiology of those carbapenemase-producing isolates and associated mobile genetic elements through an in-depth molecular characterization are indispensable to understand the transmission of carbapenemase-producing Enterobacteriaceae along the food chain and between different populations to develop strategies to prevent their further spread.Copyright © 2019 Roschanski et al.


April 21, 2020  |  

High-throughput amplicon sequencing of the full-length 16S rRNA gene with single-nucleotide resolution.

Targeted PCR amplification and high-throughput sequencing (amplicon sequencing) of 16S rRNA gene fragments is widely used to profile microbial communities. New long-read sequencing technologies can sequence the entire 16S rRNA gene, but higher error rates have limited their attractiveness when accuracy is important. Here we present a high-throughput amplicon sequencing methodology based on PacBio circular consensus sequencing and the DADA2 sample inference method that measures the full-length 16S rRNA gene with single-nucleotide resolution and a near-zero error rate. In two artificial communities of known composition, our method recovered the full complement of full-length 16S sequence variants from expected community members without residual errors. The measured abundances of intra-genomic sequence variants were in the integral ratios expected from the genuine allelic variants within a genome. The full-length 16S gene sequences recovered by our approach allowed Escherichia coli strains to be correctly classified to the O157:H7 and K12 sub-species clades. In human fecal samples, our method showed strong technical replication and was able to recover the full complement of 16S rRNA alleles in several E. coli strains. There are likely many applications beyond microbial profiling for which high-throughput amplicon sequencing of complete genes with single-nucleotide resolution will be of use. © The Author(s) 2019. Published by Oxford University Press on behalf of Nucleic Acids Research.


April 21, 2020  |  

Stout camphor tree genome fills gaps in understanding of flowering plant genome evolution.

We present reference-quality genome assembly and annotation for the stout camphor tree (Cinnamomum kanehirae (Laurales, Lauraceae)), the first sequenced member of the Magnoliidae comprising four orders (Laurales, Magnoliales, Canellales and Piperales) and over 9,000 species. Phylogenomic analysis of 13 representative seed plant genomes indicates that magnoliid and eudicot lineages share more recent common ancestry than monocots. Two whole-genome duplication events were inferred within the magnoliid lineage: one before divergence of Laurales and Magnoliales and the other within the Lauraceae. Small-scale segmental duplications and tandem duplications also contributed to innovation in the evolutionary history of Cinnamomum. For example, expansion of the terpenoid synthase gene subfamilies within the Laurales spawned the diversity of Cinnamomum monoterpenes and sesquiterpenes.


April 21, 2020  |  

Urinary tract colonization is enhanced by a plasmid that regulates uropathogenic Acinetobacter baumannii chromosomal genes.

Multidrug resistant (MDR) Acinetobacter baumannii poses a growing threat to global health. Research on Acinetobacter pathogenesis has primarily focused on pneumonia and bloodstream infections, even though one in five A. baumannii strains are isolated from urinary sites. In this study, we highlight the role of A. baumannii as a uropathogen. We develop the first A. baumannii catheter-associated urinary tract infection (CAUTI) murine model using UPAB1, a recent MDR urinary isolate. UPAB1 carries the plasmid pAB5, a member of the family of large conjugative plasmids that represses the type VI secretion system (T6SS) in multiple Acinetobacter strains. pAB5 confers niche specificity, as its carriage improves UPAB1 survival in a CAUTI model and decreases virulence in a pneumonia model. Comparative proteomic and transcriptomic analyses show that pAB5 regulates the expression of multiple chromosomally-encoded virulence factors besides T6SS. Our results demonstrate that plasmids can impact bacterial infections by controlling the expression of chromosomal genes.


April 21, 2020  |  

A Phage-Like Plasmid Carrying blaKPC-2 Gene in Carbapenem-Resistant Pseudomonas aeruginosa.

Background: Lateral gene transfer plays a central role in the dissemination of carbapenem resistance in bacterial pathogens associated with nosocomial infections, mainly Enterobacteriaceae and Pseudomonas aeruginosa. Despite their clinical significance, there is little information regarding the mobile genetic elements and mechanism of acquisition and propagation of lateral genes in P. aeruginosa, and they remain largely unknown. Objectives: The present study characterized the genetic context of blaKPC-2 in carbapenem-resistant P. aeruginosa strain BH9. Methods:Pseudomonas aeruginosa BH9 sequencing was performed using the long-read PacBio SMRT platform and the Ion Proton System. De novo assembly was carried out using the SMRT pipeline and Canu, and gene prediction and annotation were performed using Prokka and RAST. Results:Pseudomonas aeruginosa BH9 exhibited a 7.1 Mb circular chromosome. However, the blaKPC-2 gene is located in an additional contig composed by a small plasmid pBH6 from P. aeruginosa strain BH6 and several phage-related genes. Further analysis revealed that the beginning and end of the contig contain identical sequences, supporting a circular plasmid structure. This structure spans 41,087 bp, exhibiting all the Mu-like phage landmarks. In addition, 5-bp direct repeats (GGATG) flanking the pBH6 ends were found, strongly indicating integration of the Mu-like phage into the pBH6 plasmid. Mu phages are commonly found in P. aeruginosa. However, for the first time showing a potential impact in shaping the vehicles of the dissemination of antimicrobial (e.g., plasmid pBH6) resistance genes in the Pseudomonas genus. Conclusion: pBH6 captured the Mu-like Phage BH9, creating a co-integrate pBH6::Phage BH9, and this phage-plasmid complex may represent novel case of a phage-like plasmid.


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