Dataset Information

Identification of NDM-1 in a Putatively Novel Acinetobacter Species ("NB14") Closely Related to Acinetobacter pittii.

ABSTRACT: In this study, we describe the molecular characterization of a plasmid-located blaNDM-1 harbored by an Acinetobacter clinical isolate recovered from a patient in Turkey that putatively constitutes a novel Acinetobacter species, as shown by its distinct ARDRA (amplified 16S ribosomal DNA restriction analysis) profile and molecular sequencing techniques. blaNDM-1 was carried by a conjugative plasmid widespread among non-baumannii Acinetobacter isolates, suggesting its potential for dissemination before reaching more clinically relevant Acinetobacter species.

SUBMITTER: Espinal P

PROVIDER: S-EPMC4576105 | biostudies-literature | 2015 Oct

REPOSITORIES: biostudies-literature

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Publications

Identification of NDM-1 in a Putatively Novel Acinetobacter Species ("NB14") Closely Related to Acinetobacter pittii.

Espinal Paula P Mosqueda Noraida N Telli Murat M van der Reijden Tanny T Rolo Dora D Rolo Dora D Fernández-Orth Dietmar D Dijkshoorn Lenie L Roca Ignasi I Vila Jordi J

Antimicrobial agents and chemotherapy 20150810 10

In this study, we describe the molecular characterization of a plasmid-located blaNDM-1 harbored by an Acinetobacter clinical isolate recovered from a patient in Turkey that putatively constitutes a novel Acinetobacter species, as shown by its distinct ARDRA (amplified 16S ribosomal DNA restriction analysis) profile and molecular sequencing techniques. blaNDM-1 was carried by a conjugative plasmid widespread among non-baumannii Acinetobacter isolates, suggesting its potential for dissemination b ...[more]

PMID: 26259796

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Project description:The genus Acinetobacter comprises species with ecological significance and opportunistic pathogens and has a complicated taxonomy. Precise species identification is a foundation for understanding bacteria. In this study, we found and characterized two novel Acinetobacter species, namely, Acinetobacter tianfuensis sp. nov. and Acinetobacter rongchengensis sp. nov., based on phenotype examinations and genome analyses of the two strains WCHAc060012T and WCHAc060115T. The two strains had ≤89.69% (mean, 79.28% or 79.72%) average nucleotide identity (ANI) and ≤36.4% (mean, 20.89% or 22.19%) in silico DNA-DNA hybridization (isDDH) values compared with each other and all known Acinetobacter species. Both species can be differentiated from all hitherto known Acinetobacter species by a combination of phenotypic characteristics. We found that Acinetobacter pullorum B301T and Acinetobacter portensis AC 877T are actually the same species with 98.59% ANI and 90.4% isDDH values. We then applied the updated taxonomy to curate 3,956 Acinetobacter genomes in GenBank and found that 6% of Acinetobacter genomes (n = 234) are required to be corrected or updated. We identified 56 novel tentative Acinetobacter species, extending the number of Acinetobacter species to 144, including 68 with species names and 76 unnamed taxa. We also found that ANI and the average amino acid identity (AAI) values among type or reference strains of all Acinetobacter species and taxa are ≥76.97% and ≥66.5%, respectively, which are higher than the proposed cutoffs to define the genus boundary. This study highlights the complex taxonomy of Acinetobacter as a single genus and the paramount importance of precise species identification. The newly identified unnamed taxa warrant further studies. IMPORTANCE Acinetobacter species are widely distributed in nature and are of important ecological significance and clinical relevance. In this study, first, we significantly update the taxonomy of Acinetobacter by reporting two novel Acinetobacter species, namely, Acinetobacter tianfuensis and Acinetobacter rongchengensis, and by identifying Acinetobacter portensis as a synonym of Acinetobacter pullorum. Second, we curated Acinetobacter genome sequences deposited in GenBank (n = 3,956) using the updated taxonomy by correcting species assignations for 6% (n = 234) genomes and by assigning 94 (2.4%) to 56 previously unknown tentative species (taxa). Therefore, after curation, we further update the genus Acinetobacter to comprise 144 species, including 68 with species names and 76 unnamed taxa. Third, we addressed the question of whether such a large number of species should be divided in different genera and found that Acinetobacter is indeed a single genus. Our study significantly advanced the taxonomy of Acinetobacter, an important genus with science and health implications.

Project description:BACKGROUND:Multilocus phylogenies can be used to infer the species tree of a group of closely related species. In species trees, the nodes represent the actual separation between species, thus providing essential information about their evolutionary history. In addition, multilocus phylogenies can help in analyses of species delimitation, gene flow and genetic differentiation within species. However, few adequate markers are available for such studies. RESULTS:In order to develop nuclear markers that can be useful in multilocus studies of mammals, we analyzed the mammalian genomes of human, chimpanzee, macaque, dog and cow. Rodents were excluded due to their unusual genomic features. Introns were extracted from the mammalian genomes because of their greater genetic variability and ease of amplification from the flanking exons. To an initial set of more than 10,000 one-to-one orthologous introns we applied several filters to select introns that belong to single-copy genes, show neutral evolutionary rates and have an adequate length for their amplification. This analysis led to a final list of 224 intron markers randomly distributed along the genome. To experimentally test their validity, we amplified twelve of these introns in a panel of six mammalian species. The result was that seven of these introns gave rise to a PCR band of the expected size in all species. In addition, we sequenced these bands and analyzed the accumulation of substitutions in these introns in five pairs of closely related species. The results showed that the estimated genetic distances in the five species pairs was quite variable among introns and that this divergence cannot be directly predicted from the overall intron divergence in mammals. CONCLUSIONS:We have designed a new set of 224 nuclear introns with optimal features for the phylogeny of closely related mammalian species. A large proportion of the introns tested experimentally showed a perfect amplification and enough variability in most species, indicating that this marker set can be very helpful in multilocus phylogenetics of mammals. Due to the lower variability and stronger stochasticity of nuclear markers with respect to mitochondrial genes, studies should be designed to make use of several markers like the ones designed here.

Dataset Information

Identification of NDM-1 in a Putatively Novel Acinetobacter Species ("NB14") Closely Related to Acinetobacter pittii.

Publications

Identification of NDM-1 in a Putatively Novel Acinetobacter Species ("NB14") Closely Related to Acinetobacter pittii.

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