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September 22, 2019

Detection and characterization of a clinical Escherichia coli ST3204 strain coproducing NDM-16 and MCR-1.

A plasmid-mediated colistin resistance gene, mcr-1, has been reported worldwide and has caused concern regarding a major therapeutic challenge. Alarmingly, mcr-1 has spread into clinical carbapenem-resistant Enterobacteriaceae isolates, resulting in extensively drug-resistant and even pan drug-resistant isolates that can cause untreatable infections. In this study, we report isolation of an extensively drug-resistant Escherichia coli strain EC1188 that coproduces NDM-16 and MCR-1 from a urine sample taken from a patient with craniocerebral injury.E. coli strain EC1188 was identified and subjected to genotyping, susceptibility testing and conjugation experiments. The genetic locations of blaNDM-16 and mcr-1 were established with southern blot hybridization. The complete genome sequence of this strain was obtained and the genetic characteristics of the mcr-1- and blaNDM-16-harboring plasmids were analyzed. In addition, comparative genetic analyses of mcr-1 and blaNDM-16 with closely related plasmids were also carried out.Whole-genome sequencing revealed that strain EC1188 possess various resistance genes and virulence genes. S1-pulsed-field gel electrophoresis and southern blot suggested that the blaNDM-16 and mcr-1 genes were located on an ~65 kb plasmid and an ~80 kb plasmid, respectively. Moreover, the two genes could successfully transfer their resistance phenotype to E. coli strain C600. Sequence analysis showed that these two plasmids possessed high sequence similarity to previously reported blaNDM-5-harboring and mcr-1-harboring plasmids in China.To the best of our knowledge, this is the first report to isolate an E. coli strain that coproduces NDM-16 and MCR-1. In addition, we characterized the blaNDM-16-harboring plasmid for the first time. Our study further emphasizes that the co-occurrence of the two prevalent transferrable resistance plasmids in a single isolate is highly significant because infections caused by MCR-1-producing carbapenem-resistant Enterobacteriaceae isolates are increasing each year. It is imperative to perform active surveillance to prevent further dissemination of MCR-1-producing CRE isolates.

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September 22, 2019

Large scale changes in host methylation patterns induced by IncA/C plasmid transformation in Vibrio cholerae

DNA methylation is a central epigenetic modification and has diverse biological functions in eukaryotic and prokaryotic organisms alike. The IncA/C plasmid genomes are approximately 150kb in length and harbour three methylase genes, two of which demonstrate cytosine specificity. Transformation of the Vibrio cholerae strain C6706 with the IncA/C plasmid pVC211 resulted in a significant relabelling of the methylation patterns on the host chromosomes. The new methylation patterns induced by transformation with IncA/C plasmid were accepted by the restriction enzymes of the hosttextquoterights restriction modification (RM) system. These data uncover a novel mechanism by which plasmids can be compatible with a hosttextquoterights RM system and suggest a possible reason that plasmids of the IncA/C family are broad-host-range.

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September 22, 2019

Discovery of multi-drug resistant, MCR-1 and ESBL-coproducing ST117 Escherichia coli from diseased chickens in Northeast China

An endemic multi-drug resistant ST117 E. coli isolate coproducing MCR-1 and 3 ESBL loci was, for the first time, detected from diseased chicken, Liaoning Province, in Northeast China, from 2011 to 2012. Whole-genome sequencing revealed 5 unique plasmids, namely pHXH-1, pHXH-2, pHXH-3, pHXH-4 and pHXH-5). Among them, pHXH1 and pHXH4 encode ESBL, and pHXH-5 mediates MCR-1 colistin resistance. The results indicate that the potentially-national dissemination of MCR-1-positive pathogens with pan-drug resistance proceeds via food chains.

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September 22, 2019

Comparative genomics reveal a flagellar system, a type VI secretion system and plant growth-promoting gene clusters unique to the endophytic bacterium Kosakonia radicincitans.

The recent worldwide discovery of plant growth-promoting (PGP) Kosakonia radicincitans in a large variety of crop plants suggests that this species confers significant influence on plants, both in terms of yield increase and product quality improvement. We provide a comparative genome analysis which helps to unravel the genetic basis for K. radicincitans’ motility, competitiveness and plant growth-promoting capacities. We discovered that K. radicincitans carries multiple copies of complex gene clusters, among them two flagellar systems and three type VI secretion systems (T6SSs). We speculate that host invasion may be facilitated by different flagella, and bacterial competitor suppression by effector proteins ejected via T6SSs. We found a large plasmid in K. radicincitans DSM 16656T, the species type strain, that confers the potential to exploit plant-derived carbon sources. We propose that multiple copies of complex gene clusters in K. radicincitans are metabolically expensive but provide competitive advantage over other bacterial strains in nutrient-rich environments. The comparison of the DSM 16656T genome to genomes of other genera of enteric plant growth-promoting bacteria (PGPB) exhibits traits unique to DSM 16656T and K. radicincitans, respectively, and traits shared between genera. We used the output of the in silico analysis for predicting the purpose of genomic features unique to K. radicincitans and performed microarray, PhyloChip, and microscopical analyses to gain deeper insight into the interaction of DSM 16656T, plants and associated microbiota. The comparative genome analysis will facilitate the future search for promising candidates of PGPB for sustainable crop production.

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September 22, 2019

Comparison of highly and weakly virulent Dickeya solani strains, with a view on the pangenome and panregulon of this species.

Bacteria belonging to the genera Dickeya and Pectobacterium are responsible for significant economic losses in a wide variety of crops and ornamentals. During last years, increasing losses in potato production have been attributed to the appearance of Dickeya solani. The D. solani strains investigated so far share genetic homogeneity, although different virulence levels were observed among strains of various origins. The purpose of this study was to investigate the genetic traits possibly related to the diverse virulence levels by means of comparative genomics. First, we developed a new genome assembly pipeline which allowed us to complete the D. solani genomes. Four de novo sequenced and ten publicly available genomes were used to identify the structure of the D. solani pangenome, in which 74.8 and 25.2% of genes were grouped into the core and dispensable genome, respectively. For D. solani panregulon analysis, we performed a binding site prediction for four transcription factors, namely CRP, KdgR, PecS and Fur, to detect the regulons of these virulence regulators. Most of the D. solani potential virulence factors were predicted to belong to the accessory regulons of CRP, KdgR, and PecS. Thus, some differences in gene expression could exist between D. solani strains. The comparison between a highly and a low virulent strain, IFB0099 and IFB0223, respectively, disclosed only small differences between their genomes but significant differences in the production of virulence factors like pectinases, cellulases and proteases, and in their mobility. The D. solani strains also diverge in the number and size of prophages present in their genomes. Another relevant difference is the disruption of the adhesin gene fhaB2 in the highly virulent strain. Strain IFB0223, which has a complete adhesin gene, is less mobile and less aggressive than IFB0099. This suggests that in this case, mobility rather than adherence is needed in order to trigger disease symptoms. This study highlights the utility of comparative genomics in predicting D. solani traits involved in the aggressiveness of this emerging plant pathogen.

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September 22, 2019

Genomic analysis for heavy metal resistance in S. maltophilia

Stenotrophomonas maltophilia is highly resistant to heavy metals, but the genetic knowledge of metal resistance in S. maltophilia is poorly understood. In this study, the genome of S. maltophilia Pho isolated from the contaminated soil near a metalwork factory was sequenced using PacBio RS II. Its genome is composed of a single chromosome with a GC content of 66.4% and 4434 protein-encoding genes. Comparative analysis revealed high syntney between S. maltophilia Pho and the model strain, S. maltophilia K279a. Then, the type and number of mechanisms of heavy metal uptake were analyzed firstly. Results showed that 7 unspecific ion transporter genes and 13 specific ion transporter genes, most of which were involved in iron transport. But the sulfate permeases belonging to the family of SulT/CysP that can uptake chromate and the high affinity ZnuABC/SitABCD were absent. Secondly, the putative genes controlling metal efflux were analyzed. Results showed that this bacterium encoded 5 CDFs, 1 copper exporting ATPase and 4 RND systems, including 2 CzcABC efflux pumps. Moreover, the putative metal transformation genes including arsenate and mercury detoxification genes were also identified. This study may provide useful information on the metal resistance mechanisms of S. maltophilia.

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September 22, 2019

Variant O89 O-antigen of E. coli is associated with group 1 capsule loci and multidrug resistance.

Bacterial surface polysaccharides play significant roles in fitness and virulence. In Gram-negative bacteria such as Escherichia coli, major surface polysaccharides are lipopolysaccharide (LPS) and capsule, representing O- and K-antigens, respectively. There are multiple combinations of O:K types, many of which are well-characterized and can be related to ecotype or pathotype. In this investigation, we have identified a novel O:K permutation resulting through a process of major genome reorganization in a clade of E. coli. A multidrug-resistant, extended-spectrum ß-lactamase (ESBL)-producing strain – E. coli 26561 – represented a prototype of strains combining a locus variant of O89 and group 1 capsular polysaccharide. Specifically, the variant O89 locus in this strain was truncated at gnd, flanked by insertion sequences and located between nfsB and ybdK and we apply the term O89m for this variant. The prototype lacked colanic acid and O-antigen loci between yegH and hisI with this tandem polysaccharide locus being replaced with a group 1 capsule (G1C) which, rather than being a recognized E. coli capsule type, this locus matched to Klebsiella K10 capsule type. A genomic survey identified more than 200 E. coli strains which possessed the O89m locus variant with one of a variety of G1C types. Isolates from our collection with the combination of O89m and G1C all displayed a mucoid phenotype and E. coli 26561 was unusual in exhibiting a mucoviscous phenotype more recognized as a characteristic among Klebsiella strains. Despite the locus truncation and novel location, all O89m:G1C strains examined showed a ladder pattern typifying smooth LPS and also showed high molecular weight, alcian blue-staining polysaccharide in cellular and/or extra-cellular fractions. Expression of both O-antigen and capsule biosynthesis loci were confirmed in prototype strain 26561 through quantitative proteome analysis. Further in silico exploration of more than 200 E. coli strains possessing the O89m:G1C combination identified a very high prevalence of multidrug resistance (MDR) – 85% possessed resistance to three or more antibiotic classes and a high proportion (58%) of these carried ESBL and/or carbapenemase. The increasing isolation of O89m:G1C isolates from extra-intestinal infection sites suggests that these represents an emergent clade of invasive, MDR E. coli.

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September 22, 2019

Changes in the genetic requirements for microbial interactions with increasing community complexity.

Microbial community structure and function rely on complex interactions whose underlying molecular mechanisms are poorly understood. To investigate these interactions in a simple microbiome, we introduced E. coli into an experimental community based on a cheese rind and identified the differences in E. coli’s genetic requirements for growth in interactive and non-interactive contexts using Random Barcode Transposon Sequencing (RB-TnSeq) and RNASeq. Genetic requirements varied among pairwise growth conditions and between pairwise and community conditions. Our analysis points to mechanisms by which growth conditions change as a result of increasing community complexity and suggests that growth within a community relies on a combination of pairwise and higher-order interactions. Our work provides a framework for using the model organism E. coli as a readout to investigate microbial interactions regardless of the genetic tractability of members of the studied ecosystem.© 2018, Morin et al.

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September 22, 2019

A novel bacteriocin BMP11 and its antibacterial mechanism on cell envelope of Listeria monocytogenes and Cronobacter sakazakii

Listeria monocytogenes and Cronobacter sakazakii are notorious pathogens involved in numerous foodborne outbreaks after ingested contaminated food. Bacteriocins are natural food preservatives, some of which have antimicrobial activity comparable with antibiotics. In this study, a plasmid encoded novel bacteriocin BMP11 produced by Lactobacillus crustorum MN047 was innovatively identified by combining complete genome and LC-MS/MS. The BMP11 was found to have rich a-helix conformation after prediction. Moreover, the antimicrobial activity of BMP11 was verified after its heterologous expression in E. coli with 1280 and 640 AU/mL against L. monocytogenes and C. sakazakii, respectively. After purification by anion-exchange chromatography and HPLC, BMP11 had MIC values of 0.3–38.4?µg/mL against tested foodborne pathogens. Further, it was found that BMP11 had bactericidal action mode with concomitant cell lysis to pathogens by growth curve and time-kill kinetics. The results of scanning electron microscope (SEM) and transmission electron microscope (TEM) indicated that BMP11 destroyed the integrity of cell envelope of pathogens with cell wall perforation and cell membrane permeabilization. The destruction of cell envelope integrity was further verified by propidium iodide (PI) uptake and lactic dehydrogenase (LDH) release. BMP11 increased inner-membrane permeability of C. sakazakii in a concentration-dependent manner. Meanwhile, BMP11 exhibited antibiofilm formation activity. In addition, BMP11 inhibited the growth of L. monocytogenes in milk. Therefore, BMP11 had promising potential as antimicrobial to control foodborne pathogens in dairy products.

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September 22, 2019

Involvement of Burkholderiaceae and sulfurous volatiles in disease-suppressive soils.

Disease-suppressive soils are ecosystems in which plants suffer less from root infections due to the activities of specific microbial consortia. The characteristics of soils suppressive to specific fungal root pathogens are comparable to those of adaptive immunity in animals, as reported by Raaijmakers and Mazzola (Science 352:1392-3, 2016), but the mechanisms and microbial species involved in the soil suppressiveness are largely unknown. Previous taxonomic and metatranscriptome analyses of a soil suppressive to the fungal root pathogen Rhizoctonia solani revealed that members of the Burkholderiaceae family were more abundant and more active in suppressive than in non-suppressive soils. Here, isolation, phylogeny, and soil bioassays revealed a significant disease-suppressive activity for representative isolates of Burkholderia pyrrocinia, Paraburkholderia caledonica, P. graminis, P. hospita, and P. terricola. In vitro antifungal activity was only observed for P. graminis. Comparative genomics and metabolite profiling further showed that the antifungal activity of P. graminis PHS1 was associated with the production of sulfurous volatile compounds encoded by genes not found in the other four genera. Site-directed mutagenesis of two of these genes, encoding a dimethyl sulfoxide reductase and a cysteine desulfurase, resulted in a loss of antifungal activity both in vitro and in situ. These results indicate that specific members of the Burkholderiaceae family contribute to soil suppressiveness via the production of sulfurous volatile compounds.

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September 22, 2019

Genomic analysis of multidrug-resistant Escherichia coli ST58 causing urosepsis.

Sequence type 58 (ST58) phylogroup B1 Escherichia coli have been isolated from a wide variety of mammalian and avian hosts but are not noted for their ability to cause serious disease in humans or animals. Here we determined the genome sequences of two multidrug-resistant E. coli ST58 strains from urine and blood of one patient using a combination of Illumina and Single Molecule, Real-Time (SMRT) sequencing. Both ST58 strains were clonal and were characterised as serotype O8:H25, phylogroup B1 and carried a complex resistance locus/loci (CRL) that featured an atypical class 1 integron with a dfrA5 (trimethoprim resistance) gene cassette followed by only 24 bp of the 3′-CS. CRL that carry this particular integron have been described previously in E. coli from cattle, pigs and humans in Australia. The integron abuts a copy of Tn6029, an IS26-flanked composite transposon encoding blaTEM, sul2 and strAB genes that confer resistance to ampicillin, sulfathiazole and streptomycin, respectively. The CRL resides within a novel Tn2610-like hybrid Tn1721/Tn21 transposon on an IncF, ColV plasmid (pSDJ2009-52F) of 138 553 bp that encodes virulence associated genes implicated in life-threatening extraintestinal pathogenic E. coli (ExPEC) infections. Notably, pSDJ2009-52F shares high sequence identity with pSF-088-1, a plasmid reported in an E. coli ST95 strain from a patient with blood sepsis from a hospital in San Francisco. These data suggest that extraintestinal infections caused by E. coli carrying ColV-like plasmids, irrespective of their phylogroup or ST, may pose a potential threat to human health, particularly to the elderly and immunocompromised. Copyright © 2018. Published by Elsevier B.V.

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September 22, 2019

Characterization of a novel SXT/R391 Integrative and Conjugative Element carrying cfr, blaCTX-M-65, fosA3 and aac(6′)-Ib-cr in Proteus mirabilis.

A novel 139,487-bp SXT/R391 integrative and conjugative element, ICEPmiChnBCP11, was characterized in Proteus mirabilis of swine origin in China. ICEPmiChnBCP11 harbors 20 different antimicrobial resistance genes, including the clinically important rRNA methyltransferase gene cfr, the extended-spectrum ß-lactamase gene blaCTX-M-65, fosfomycin resistance gene fosA3, and fluoroquinolone resistance gene aac(6′)-Ib-cr An ISPpu12-mediated composite transposon containing various resistance genes and 10 copies of IS26 is inserted in hot spot 4. ICEPmiChnBCP11 was successfully transferred to Escherichia coli. Copyright © 2018 American Society for Microbiology.

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September 22, 2019

Long-term colonization dynamics of Enterococcus faecalis in implanted devices in research macaques.

Enterococcus faecalis is a common opportunistic pathogen that colonizes cephalic recording chambers (CRCs) of macaques used in cognitive neuroscience research. We previously characterized 15 E. faecalis strains isolated from macaques at the Massachusetts Institute of Technology (MIT) in 2011. The goal of this study was to examine how a 2014 protocol change prohibiting the use of antimicrobials within CRCs affected colonizing E. faecalis strains. We collected 20 E. faecalis isolates from 10 macaques between 2013 and 2017 for comparison to 4 isolates previously characterized in 2011 with respect to the sequence type (ST) distribution, antimicrobial resistance, biofilm formation, and changes in genes that might confer a survival advantage. ST4 and ST55 were predominant among the isolates characterized in 2011, whereas the less antimicrobial-resistant lineage ST48 emerged to dominance after 2013. Two macaques remained colonized by ST4 and ST55 strains for 5 and 4 years, respectively. While the antimicrobial resistance and virulence factors identified in these ST4 and ST55 strains remained relatively stable, we detected an increase in biofilm formation ability over time in both isolates. We also found that ST48 strains were typically robust biofilm formers, which could explain why this ST increased in prevalence. Finally, we identified mutations in the DNA mismatch repair genes mutS and mutL in separate ST55 and ST4 strains and confirmed that strains bearing these mutations displayed a hypermutator phenotype. The presence of a hypermutator phenotype may complicate future antimicrobial treatment for clinically relevant E. faecalis infections in macaques.IMPORTANCEEnterococcus faecalis is a common cause of health care-associated infections in humans, largely due to its ability to persist in the hospital environment, colonize patients, acquire antimicrobial resistance, and form biofilms. Understanding how enterococci evolve in health care settings provides insight into factors affecting enterococcal survival and persistence. Macaques used in neuroscience research have long-term cranial implants that, despite best practices, often become colonized by E. faecalis This provides a unique opportunity to noninvasively examine the evolution of enterococci on a long-term indwelling device. We collected E. faecalis strains from cephalic implants over a 7-year period and characterized the sequence type, antimicrobial resistance, virulence factors, biofilm production, and hypermutator phenotypes. Improved antimicrobial stewardship allowed a less-antimicrobial-resistant E. faecalis strain to predominate at the implant interface, potentially improving antimicrobial treatment outcomes if future clinical infections occur. Biofilm formation appears to play an important role in the persistence of the E. faecalis strains associated with these implants. Copyright © 2018 American Society for Microbiology.

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September 22, 2019

Isolation, development, and genomic analysis of Bacillus megaterium SR7 for growth and metabolite production under supercritical carbon dioxide

Supercritical carbon dioxide (scCO2) is an attractive substitute for conventional organic solvents due to its unique transport and thermodynamic properties, its renewability and labile nature, and its high solubility for compounds such as alcohols, ketones, and aldehydes. However, biological systems that use scCO2 are mainly limited to in vitro processes due to its strong inhibition of cell viability and growth. To solve this problem, we used a bioprospecting approach to isolate a microbial strain with the natural ability to grow while exposed to scCO2. Enrichment culture and serial passaging of deep subsurface fluids from the McElmo Dome scCO2 reservoir in aqueous media under scCO2 headspace enabled the isolation of spore-forming strain Bacillus megaterium SR7. Sequencing and analysis of the complete 5.51 Mbp genome and physiological characterization revealed the capacity for facultative anaerobic metabolism, including fermentative growth on a diverse range of organic substrates. Supplementation of growth medium with L-alanine for chemical induction of spore germination significantly improved growth frequencies and biomass accumulation under scCO2 headspace. Detection of endogenous fermentative compounds in cultures grown under scCO2 represents the first observation of bioproduct generation and accumulation under this condition. Culturing development and metabolic characterization of B. megaterium SR7 represent initial advancements in the effort toward enabling exploitation of scCO2 as a sustainable solvent for in vivo bioprocessing.

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September 22, 2019

A model for the evolution of prokaryotic DNA restriction-modification systems based upon the structural malleability of Type I restriction-modification enzymes.

Restriction Modification (RM) systems prevent the invasion of foreign genetic material into bacterial cells by restriction and protect the host’s genetic material by methylation. They are therefore important in maintaining the integrity of the host genome. RM systems are currently classified into four types (I to IV) on the basis of differences in composition, target recognition, cofactors and the manner in which they cleave DNA. Comparing the structures of the different types, similarities can be observed suggesting an evolutionary link between these different types. This work describes the ‘deconstruction’ of a large Type I RM enzyme into forms structurally similar to smaller Type II RM enzymes in an effort to elucidate the pathway taken by Nature to form these different RM enzymes. Based upon the ability to engineer new enzymes from the Type I ‘scaffold’, an evolutionary pathway and the evolutionary pressures required to move along the pathway from Type I RM systems to Type II RM systems are proposed. Experiments to test the evolutionary model are discussed.

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