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September 22, 2019  |  

Discovery of the fourth mobile sulfonamide resistance gene.

Over the past 75 years, human pathogens have acquired antibiotic resistance genes (ARGs), often from environmental bacteria. Integrons play a major role in the acquisition of antibiotic resistance genes. We therefore hypothesized that focused exploration of integron gene cassettes from microbial communities could be an efficient way to find novel mobile resistance genes. DNA from polluted Indian river sediments were amplified using three sets of primers targeting class 1 integrons and sequenced by long- and short-read technologies to maintain both accuracy and context.Up to 89% of identified open reading frames encode known resistance genes, or variations thereof (>?1000). We identified putative novel ARGs to aminoglycosides, beta-lactams, trimethoprim, rifampicin, and chloramphenicol, including several novel OXA variants, providing reduced susceptibility to carbapenems. One dihydropteroate synthase gene, with less than 34% amino acid identity to the three known mobile sulfonamide resistance genes (sul1-3), provided complete resistance when expressed in Escherichia coli. The mobilized gene, here named sul4, is the first mobile sulfonamide resistance gene discovered since 2003. Analyses of adjacent DNA suggest that sul4 has been decontextualized from a set of chromosomal genes involved in folate synthesis in its original host, likely within the phylum Chloroflexi. The presence of an insertion sequence common region element could provide mobility to the entire integron. Screening of 6489 metagenomic datasets revealed that sul4 is already widespread in seven countries across Asia and Europe.Our findings show that exploring integrons from environmental communities with a history of antibiotic exposure can provide an efficient way to find novel, mobile resistance genes. The mobilization of a fourth sulfonamide resistance gene is likely to provide expanded opportunities for sulfonamide resistance to spread, with potential impacts on both human and animal health.

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September 22, 2019  |  

In vitro characterization of phenylacetate decarboxylase, a novel enzyme catalyzing toluene biosynthesis in an anaerobic microbial community.

Anaerobic bacterial biosynthesis of toluene from phenylacetate was reported more than two decades ago, but the biochemistry underlying this novel metabolism has never been elucidated. Here we report results of in vitro characterization studies of a novel phenylacetate decarboxylase from an anaerobic, sewage-derived enrichment culture that quantitatively produces toluene from phenylacetate; complementary metagenomic and metaproteomic analyses are also presented. Among the noteworthy findings is that this enzyme is not the well-characterized clostridial p-hydroxyphenylacetate decarboxylase (CsdBC). However, the toluene synthase under study appears to be able to catalyze both phenylacetate and p-hydroxyphenylacetate decarboxylation. Observations suggesting that phenylacetate and p-hydroxyphenylacetate decarboxylation in complex cell-free extracts were catalyzed by the same enzyme include the following: (i) the specific activity for both substrates was comparable in cell-free extracts, (ii) the two activities displayed identical behavior during chromatographic separation of cell-free extracts, (iii) both activities were irreversibly inactivated upon exposure to O2, and (iv) both activities were similarly inhibited by an amide analog of p-hydroxyphenylacetate. Based upon these and other data, we hypothesize that the toluene synthase reaction involves a glycyl radical decarboxylase. This first-time study of the phenylacetate decarboxylase reaction constitutes an important step in understanding and ultimately harnessing it for making bio-based toluene.

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September 22, 2019  |  

A community-based culture collection for targeting novel plant growth-promoting bacteria from the sugarcane microbiome.

The soil-plant ecosystem harbors an immense microbial diversity that challenges investigative approaches to study traits underlying plant-microbe association. Studies solely based on culture-dependent techniques have overlooked most microbial diversity. Here we describe the concomitant use of culture-dependent and -independent techniques to target plant-beneficial microbial groups from the sugarcane microbiome. The community-based culture collection (CBC) approach was used to access microbes from roots and stalks. The CBC recovered 399 unique bacteria representing 15.9% of the rhizosphere core microbiome and 61.6-65.3% of the endophytic core microbiomes of stalks. By cross-referencing the CBC (culture-dependent) with the sugarcane microbiome profile (culture-independent), we designed a synthetic community comprised of naturally occurring highly abundant bacterial groups from roots and stalks, most of which has been poorly explored so far. We then used maize as a model to probe the abundance-based synthetic inoculant. We show that when inoculated in maize plants, members of the synthetic community efficiently colonize plant organs, displace the natural microbiota and dominate at 53.9% of the rhizosphere microbial abundance. As a result, inoculated plants increased biomass by 3.4-fold as compared to uninoculated plants. The results demonstrate that abundance-based synthetic inoculants can be successfully applied to recover beneficial plant microbes from plant microbiota.

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September 22, 2019  |  

Resistance to ceftazidime-avibactam in Klebsiella pneumoniae due to porin mutations and the increased expression of KPC-3.

We reported the first clinical case of a ceftazidime-avibactam resistant KPC-3-producing Klebsiella pneumoniae (1), from a patient with no history of ceftazidime-avibactam therapy. We now present data documenting mechanisms of ceftazidime-avibactam resistance in this isolate. Whole-genome sequencing (WGS) was performed on two isolates: KP1245 (ceftazidime-avibactam MIC, 4 µg/ml; from blood on hospital day 1; referred to as isolate 1 in our previous report [1]) and KP1244 (ceftazidime-avibactam MIC, 32 µg/ml; from blood on hospital day 2; referred to as isolate 2 in our previous report [2]), using MiSeq (Illumina, San Diego, CA) and PacBio RSII (Menlo Park, CA) systems (2). The in silico multilocus sequence type (ST) was ST258. Single nucleotide polymorphism (SNP) analysis revealed 17 SNPs between KP1245 and KP1244, indicating that the isolates were related but that significant diversity existed in this patient (2). Nonsynonymous mutations are shown in Table 1; the most striking of these is in the OmpK36 porin gene. KP1244 contained a missense mutation predicted to encode a T333N mutation. Both isolates also harbored a mutation predicted to encode R191L in OmpK36 and had a nonfunctional OmpK35, due to a frameshift mutation that truncated the protein at amino acid 42, common to K. pneumoniae ST258 (3). Association between mutations in ompK36 and elevated ceftazidime-avibactam MICs has been shown previously (4). However, T333N, found in one of the ß-sheet domains of the OmpK36 subunit, has not been described in K. pneumoniae; as such, further validation is required to confirm the role of the OmpK36 mutation in this isolate’s ceftazidime-avibactam resistance phenotype.

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September 22, 2019  |  

Interaction between the microbiome and TP53 in human lung cancer.

Lung cancer is the leading cancer diagnosis worldwide and the number one cause of cancer deaths. Exposure to cigarette smoke, the primary risk factor in lung cancer, reduces epithelial barrier integrity and increases susceptibility to infections. Herein, we hypothesize that somatic mutations together with cigarette smoke generate a dysbiotic microbiota that is associated with lung carcinogenesis. Using lung tissue from 33 controls and 143 cancer cases, we conduct 16S ribosomal RNA (rRNA) bacterial gene sequencing, with RNA-sequencing data from lung cancer cases in The Cancer Genome Atlas serving as the validation cohort.Overall, we demonstrate a lower alpha diversity in normal lung as compared to non-tumor adjacent or tumor tissue. In squamous cell carcinoma specifically, a separate group of taxa are identified, in which Acidovorax is enriched in smokers. Acidovorax temporans is identified within tumor sections by fluorescent in situ hybridization and confirmed by two separate 16S rRNA strategies. Further, these taxa, including Acidovorax, exhibit higher abundance among the subset of squamous cell carcinoma cases with TP53 mutations, an association not seen in adenocarcinomas.The results of this comprehensive study show both microbiome-gene and microbiome-exposure interactions in squamous cell carcinoma lung cancer tissue. Specifically, tumors harboring TP53 mutations, which can impair epithelial function, have a unique bacterial consortium that is higher in relative abundance in smoking-associated tumors of this type. Given the significant need for clinical diagnostic tools in lung cancer, this study may provide novel biomarkers for early detection.

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September 22, 2019  |  

Role of clinicogenomics in infectious disease diagnostics and public health microbiology.

Clinicogenomics is the exploitation of genome sequence data for diagnostic, therapeutic, and public health purposes. Central to this field is the high-throughput DNA sequencing of genomes and metagenomes. The role of clinicogenomics in infectious disease diagnostics and public health microbiology was the topic of discussion during a recent symposium (session 161) presented at the 115th general meeting of the American Society for Microbiology that was held in New Orleans, LA. What follows is a collection of the most salient and promising aspects from each presentation at the symposium. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

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September 22, 2019  |  

Genomics and host specialization of honey bee and bumble bee gut symbionts.

Gilliamella apicola and Snodgrassella alvi are dominant members of the honey bee (Apis spp.) and bumble bee (Bombus spp.) gut microbiota. We generated complete genomes of the type strains G. apicola wkB1(T) and S. alvi wkB2(T) (isolated from Apis), as well as draft genomes for four other strains from Bombus. G. apicola and S. alvi were found to occupy very different metabolic niches: The former is a saccharolytic fermenter, whereas the latter is an oxidizer of carboxylic acids. Together, they may form a syntrophic network for partitioning of metabolic resources. Both species possessed numerous genes [type 6 secretion systems, repeats in toxin (RTX) toxins, RHS proteins, adhesins, and type IV pili] that likely mediate cell-cell interactions and gut colonization. Variation in these genes could account for the host fidelity of strains observed in previous phylogenetic studies. Here, we also show the first experimental evidence, to our knowledge, for this specificity in vivo: Strains of S. alvi were able to colonize their native bee host but not bees of another genus. Consistent with specific, long-term host association, comparative genomic analysis revealed a deep divergence and little or no gene flow between Apis and Bombus gut symbionts. However, within a host type (Apis or Bombus), we detected signs of horizontal gene transfer between G. apicola and S. alvi, demonstrating the importance of the broader gut community in shaping the evolution of any one member. Our results show that host specificity is likely driven by multiple factors, including direct host-microbe interactions, microbe-microbe interactions, and social transmission.

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September 22, 2019  |  

Bacterial diversity and community structure in Chongqing radish paocai brines revealed using PacBio single-molecule real-time sequencing technology.

Traditional Chongqing radish paocai fermented with aged brine is considered to have the most intense flavor and authentic taste. Eight ‘Yanzhi’ (red, RRPB group) and ‘Chunbulao’ (white, WRPB) radish paocai brine samples were collected from Chongqing peasant households, and the diversity and community structures of bacteria present in these brines were determined using PacBio single-molecule real-time sequencing of their full-length 16S rRNA genes.In total, 30 phyla, 218 genera, and 306 species were identified from the RRPB group, with 20 phyla, 261 genera, and 420 species present in the WRPB group. Obvious differences in bacterial profiles between the RRPB and WRPB groups were found, with the bacterial diversity of the WRPB group shown to be greater than that of the RRPB group. This study revealed several characteristics of the bacteria composition, including the predominance of heterofermentative lactic acid bacteria, the species diversity of genus Pseudomonas, and the presence of three opportunistic pathogenic species.This study provides detailed information on the bacterial diversity and community structure of Chongqing radish paocai brine samples, and suggests it may be necessary to analyze paocai brine for potential sources of bacterial contamination and take appropriate measures to exclude any pathogenic species. © 2018 Society of Chemical Industry.© 2018 Society of Chemical Industry.

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September 22, 2019  |  

Different next generation sequencing platforms produce different microbial profiles and diversity in cystic fibrosis sputum.

Cystic fibrosis (CF) is an autosomal recessive disease characterized by recurrent lung infections. Studies of the lung microbiome have shown an association between decreasing diversity and progressive disease. 454 pyrosequencing has frequently been used to study the lung microbiome in CF, but will no longer be supported. We sought to identify the benefits and drawbacks of using two state-of-the-art next generation sequencing (NGS) platforms, MiSeq and PacBio RSII, to characterize the CF lung microbiome. Each has its advantages and limitations.Twelve samples of extracted bacterial DNA were sequenced on both MiSeq and PacBio NGS platforms. DNA was amplified for the V4 region of the 16S rRNA gene and libraries were sequenced on the MiSeq sequencing platform, while the full 16S rRNA gene was sequenced on the PacBio RSII sequencing platform. Raw FASTQ files generated by the MiSeq and PacBio platforms were processed in mothur v1.35.1.There was extreme discordance in alpha-diversity of the CF lung microbiome when using the two platforms. Because of its depth of coverage, sequencing of the 16S rRNA V4 gene region using MiSeq allowed for the observation of many more operational taxonomic units (OTUs) and higher Chao1 and Shannon indices than the PacBio RSII. Interestingly, several patients in our cohort had Escherichia, an unusual pathogen in CF. Also, likely because of its coverage of the complete 16S rRNA gene, only PacBio RSII was able to identify Burkholderia, an important CF pathogen.When comparing microbiome diversity in clinical samples from CF patients using 16S sequences, MiSeq and PacBio NGS platforms may generate different results in microbial community composition and structure. It may be necessary to use different platforms when trying to correctly identify dominant pathogens versus measuring alpha-diversity estimates, and it would be important to use the same platform for comparisons to minimize errors in interpretation. Copyright © 2016 Elsevier B.V. All rights reserved.

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September 22, 2019  |  

Diversified microbiota of meconium is affected by maternal diabetes status.

This study was aimed to assess the diversity of the meconium microbiome and determine if the bacterial community is affected by maternal diabetes status.The first intestinal discharge (meconium) was collected from 23 newborns stratified by maternal diabetes status: 4 mothers had pre-gestational type 2 diabetes mellitus (DM) including one mother with dizygotic twins, 5 developed gestational diabetes mellitus (GDM) and 13 had no diabetes. The meconium microbiome was profiled using multi-barcode 16S rRNA sequencing followed by taxonomic assignment and diversity analysis.All meconium samples were not sterile and contained diversified microbiota. Compared with adult feces, the meconium showed a lower species diversity, higher sample-to-sample variation, and enrichment of Proteobacteria and reduction of Bacteroidetes. Among the meconium samples, the taxonomy analyses suggested that the overall bacterial content significantly differed by maternal diabetes status, with the microbiome of the DM group showing higher alpha-diversity than that of no-diabetes or GDM groups. No global difference was found between babies delivered vaginally versus via Cesarean-section. Regression analysis showed that the most robust predictor for the meconium microbiota composition was the maternal diabetes status that preceded pregnancy. Specifically, Bacteroidetes (phyla) and Parabacteriodes (genus) were enriched in the meconium in the DM group compared to the no-diabetes group.Our study provides evidence that meconium contains diversified microbiota and is not affected by the mode of delivery. It also suggests that the meconium microbiome of infants born to mothers with DM is enriched for the same bacterial taxa as those reported in the fecal microbiome of adult DM patients.

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September 22, 2019  |  

Resolving the complexity of human skin metagenomes using single-molecule sequencing.

Deep metagenomic shotgun sequencing has emerged as a powerful tool to interrogate composition and function of complex microbial communities. Computational approaches to assemble genome fragments have been demonstrated to be an effective tool for de novo reconstruction of genomes from these communities. However, the resultant “genomes” are typically fragmented and incomplete due to the limited ability of short-read sequence data to assemble complex or low-coverage regions. Here, we use single-molecule, real-time (SMRT) sequencing to reconstruct a high-quality, closed genome of a previously uncharacterized Corynebacterium simulans and its companion bacteriophage from a skin metagenomic sample. Considerable improvement in assembly quality occurs in hybrid approaches incorporating short-read data, with even relatively small amounts of long-read data being sufficient to improve metagenome reconstruction. Using short-read data to evaluate strain variation of this C. simulans in its skin community at single-nucleotide resolution, we observed a dominant C. simulans strain with moderate allelic heterozygosity throughout the population. We demonstrate the utility of SMRT sequencing and hybrid approaches in metagenome quantitation, reconstruction, and annotation.The species comprising a microbial community are often difficult to deconvolute due to technical limitations inherent to most short-read sequencing technologies. Here, we leverage new advances in sequencing technology, single-molecule sequencing, to significantly improve reconstruction of a complex human skin microbial community. With this long-read technology, we were able to reconstruct and annotate a closed, high-quality genome of a previously uncharacterized skin species. We demonstrate that hybrid approaches with short-read technology are sufficiently powerful to reconstruct even single-nucleotide polymorphism level variation of species in this a community. Copyright © 2016 Tsai et al.

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September 22, 2019  |  

Stalking a lethal superbug by whole-genome sequencing and phylogenetics: Influence on unraveling a major hospital outbreak of carbapenem-resistant Klebsiella pneumoniae.

From July 2010-April 2013, Leipzig University Hospital experienced the largest outbreak of a Klebsiella pneumoniae carbapenemase 2 (KPC-2)-producing Klebsiella pneumoniae (KPC-2-Kp) strain observed in Germany to date. After termination of the outbreak, we aimed to reconstruct transmission pathways by phylogenetics based on whole-genome sequencing (WGS).One hundred seventeen KPC-2-Kp isolates from 89 outbreak patients, 5 environmental KPC-2-Kp isolates, and 24 K pneumoniae strains not linked to the outbreak underwent WGS. Phylogenetic analysis was performed blinded to clinical data and based on the genomic reads.A patient from Greece was confirmed as the source of the outbreak. Transmission pathways for 11 out of 89 patients (12.4%) were plausibly explained by descriptive epidemiology, applying strict definitions. Five of these and an additional 15 (ie, 20 out of 89 patients [22.5%]) were confirmed by phylogenetics. The rate of phylogenetically confirmed transmissions increased significantly from 8 out of 66 (12.1% for the time period before) to 12 out of 23 patients (52.2% for the time period after; P?<.001) after implementation of systematic screening for KPC-2-Kp (33,623 screening investigations within 11 months). Using descriptive epidemiology, systematic screening showed no significant effect (7 out of 66 [10.6%] vs 4 out of 23 [17.4%] patients; P?=?.465). The phylogenetic analysis supported the assumption that a contaminated positioning pillow served as a reservoir for the persistence of KPC-2-Kp.Effective phylogenetic identification of transmissions requires systematic microbiologic screening. Extensive screening and phylogenetic analysis based on WGS should be started as soon as possible in a bacterial outbreak situation. Copyright © 2018 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Elsevier Inc. All rights reserved.

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September 22, 2019  |  

Revisiting the contribution of gene duplication of blaOXA-23 in carbapenem-resistant Acinetobacter baumannii.

Gene duplication has been discovered for many antimicrobial resistance genes in bacterial genomes and has been considered a source of elevated antimicrobial resistance.1 The gene blaOXA-23is a major determinant in the emergence of carbapenem-resistant Acinetobacter baumannii (CRAB).2–4 We have previously reported the widespread duplication of blaOXA-23by surveying 113 clinical CRAB isolates in China.5 However, in these isolates the blaOXA-23 copy number did not correlate well with the MIC of imipenem. A similar phenomenon was also reported recently by Yoon et al.6 One reasonable explanation is that, in addition to gene duplica- tions, other mechanisms might also impact on the MIC, such as the presence of specific outer membrane proteins and/ortheover-expression of resistance–nodulation–division (RND)-type efflux pumps.7 Often, these mechanisms might vary in their performance when in different genomic contexts. Instead of making comparisons between clinical isolates, in this study we cultured A. baumannii under treatment with carbapenem, thus avoiding any interference induced in different genomic contexts. If an increase in the blaOXA-23 copy number or MIC were to occur within the same strain, the contribution of gene duplication to carbapenem resistance would be acknowledged.

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September 22, 2019  |  

Complete genome sequence of Enterobacter cloacae R11 reveals multiple genes potentially associated with high-level polymyxin E resistance.

Enterobacter cloacae strain R11 is a multidrug-resistant bacterium isolated from sewage water near a swine feedlot in China. Strain R11 can survive in medium containing up to 192 µg/mL polymyxin E, indicating a tolerance for this antibiotic that is significantly higher than that reported for other gram-negative bacteria. In this study, conjugation experiments showed that partial polymyxin E resistance could be transferred from strain R11 to Escherichia coli strain 25922, revealing that some genes related to polymyxin E resistance are plasmid-based. The complete genome sequence of this strain was determined, yielding a total of 4?993?008 bp (G+C content, 53.15%) and 4908 genes for the circular chromosome and 4 circular plasmids. Genome analysis revealed a total of 73 putative antibiotic resistance genes, including several polymyxin E resistance genes and genes potentially involved in multidrug resistance. These data provide insights into the genetic basis of the polymyxin E resistance and multidrug resistance of E. cloacae.

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September 22, 2019  |  

Extensively drug-resistant Escherichia coli sequence type 1642 carrying an IncX3 plasmid containing the blaKPC-2 gene associated with transposon Tn4401a.

Extensively drug-resistant (XDR) Enterobacteriaceae carrying the bla(KPC) gene have emerged as a major global therapeutic concern. The purpose of this study was to analyze the complete sequences of plasmids from KPC-2 carbapenemase-producing XDR Escherichia coli sequence type (ST) 1642 isolates.We performed antimicrobial susceptibility testing, PCR, multilocus sequence typing (MLST), and whole-genome sequencing to characterize the plasmid-mediated KPC-2-producing E. coli clinical isolates.The isolates were resistant to most available antibiotics, including meropenem, ampicillin, ceftriaxone, gentamicin, and ciprofloxacin, but susceptible to tigecycline and colistin. The isolates were identified as the rare ST1642 by MLST. The isolates carried four plasmids: the first 69-kb conjugative IncX3 plasmid harbors bla(KPC-2) within a truncated Tn4401a transposon and bla(SHV-11) with duplicated conjugative elements. The second 142-kb plasmid with a multireplicon consisting of IncQ, IncFIA, and IncIB carries bla(TEM-1b) and two class 1 integrons. This plasmid also harbors a wide variety of additional antimicrobial resistance genes including aadA5, dfrA17, mph(A), sul1, tet(B), aac(3′)-IId, strA, strB, and sul2.The complete sequence analysis of plasmids from an XDR E. coli strain related to persistent infection showed the coexistence of a bla(KPC-2)-carrying IncX3-type plasmid and a class 1 integron-harboring multireplicon, suggesting its potential to cause outbreaks. Of additional clinical significance, the rare ST1642, identified in a cat, could constitute the source of human infection.

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