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July 7, 2019

Complete genome sequence of Serratia marcescens SmUNAM836, a nonpigmented multidrug-resistant strain isolated from a Mexican Patient with obstructive pulmonary disease.

Serratia marcescens SmUNAM836 is a multidrug-resistant clinical strain isolated in Mexico City from a patient with chronic obstructive pulmonary disease. Its complete genome sequence was determined using PacBio RS II SMRT technology, consisting of a 5.2-Mb chromosome and a 26.3-kb plasmid, encoding multiple resistance determinants and virulence factors. Copyright © 2016 Sandner-Miranda et al.


July 7, 2019

Colistin-Nonsusceptible Pseudomonas aeruginosa Sequence Type 654 with blaNDM-1 Arrives in North America.

This study describes 3 different blaNDM-1 genetic platforms in 3 different species obtained from the same patient who was directly transferred to an institution in Calgary, Alberta, Canada, following a prolonged hospital stay in India. The blaNDM-1 in the Escherichia coli isolate was located on a 176-kb IncA/C plasmid contained within an ISCR1 region. The blaNDM-1 in the Providencia rettgeri isolate was located on a 117-kb IncT plasmid contained within Tn3000, while the blaNDM-1 in the Pseudomonas aeruginosa isolate was located on the chromosome within an ISCR3 region. This report highlights the plasticity of the genetic regions and environments associated with blaNDM-1. To the best of our knowledge, this is the first report of P. aeruginosa with blaNDM-1 identified in North America and the first report of blaOXA-181 in P. rettgeri. The P. aeruginosa isolate belonged to the international high-risk sequence type 654 clone and was nonsusceptible to colistin. This case emphasizes the need for the use of appropriate infection prevention and control measures and vigilant screening for carbapenem-resistant Gram-negative bacteria in patients with a history of travel to areas of endemicity, such as the Indian subcontinent. Copyright © 2016, American Society for Microbiology. All Rights Reserved.


July 7, 2019

Rapid emergence and evolution of Staphylococcus aureus clones harbouring fusC-containing Staphylococcal cassette chromosome elements.

The prevalence of fusidic acid (FA) resistance amongst Staphylococcus aureus in New Zealand (NZ) is amongst the highest reported globally, with a recent study describing a resistance rate of approximately 28%. Three FA-resistant S. aureus clones (ST5 MRSA, ST1 MSSA and ST1 MRSA) have emerged over the past decade and now predominate in NZ, and in all three clones FA resistance is mediated by the fusC gene. In particular, ST5 MRSA has rapidly become the dominant MRSA clone in NZ, although the origin of FA-resistant ST5 MRSA has not been explored, and the genetic context of fusC in FA-resistant NZ isolates is unknown. To better understand the rapid emergence of FA-resistant S. aureus, we used population-based comparative genomics to characterise a collection of FA-resistant and FA-susceptible isolates from NZ. FA-resistant NZ ST5 MRSA displayed minimal genetic diversity, and represented a phylogenetically distinct clade within a global population model of clonal complex 5 (CC5) S. aureus. In all lineages, fusC was invariably located within staphylococcal cassette chromosome (SCC) elements, suggesting that SCC-mediated horizontal transfer is the primary mechanism of fusC dissemination. The genotypic association of fusC with mecA has important implications for the emergence of MRSA clones in populations with high usage of fusidic acid. In addition, we found that fusC was co-located with a recently described virulence factor (tirS) in dominant NZ S. aureus clones, suggesting a potential fitness advantage. This study points to the likely molecular mechanisms responsible for the successful emergence and spread of FA-resistant S. aureus. Copyright © 2016 Baines et al.


July 7, 2019

Genome analysis of three Pneumocystis species reveals adaptation mechanisms to life exclusively in mammalian hosts.

Pneumocystis jirovecii is a major cause of life-threatening pneumonia in immunosuppressed patients including transplant recipients and those with HIV/AIDS, yet surprisingly little is known about the biology of this fungal pathogen. Here we report near complete genome assemblies for three Pneumocystis species that infect humans, rats and mice. Pneumocystis genomes are highly compact relative to other fungi, with substantial reductions of ribosomal RNA genes, transporters, transcription factors and many metabolic pathways, but contain expansions of surface proteins, especially a unique and complex surface glycoprotein superfamily, as well as proteases and RNA processing proteins. Unexpectedly, the key fungal cell wall components chitin and outer chain N-mannans are absent, based on genome content and experimental validation. Our findings suggest that Pneumocystis has developed unique mechanisms of adaptation to life exclusively in mammalian hosts, including dependence on the lungs for gas and nutrients and highly efficient strategies to escape both host innate and acquired immune defenses.


July 7, 2019

Population structure and acquisition of the vanB resistance determinant in German clinical isolates of Enterococcus faecium ST192.

In the context of the global action plan to reduce the dissemination of antibiotic resistances it is of utmost importance to understand the population structure of resistant endemic bacterial lineages and to elucidate how bacteria acquire certain resistance determinants. Vancomycin resistant enterococci represent one such example of a prominent nosocomial pathogen on which nation-wide population analyses on prevalent lineages are scarce and data on how the bacteria acquire resistance, especially of the vanB genotype, are still under debate. With respect to Germany, an increased prevalence of VRE was noted in recent years. Here, invasive infections caused by sequence type ST192 VRE are often associated with the vanB-type resistance determinant. Hence, we analyzed 49 vanB-positive and vanB-negative E. faecium isolates by means of whole genome sequencing. Our studies revealed a distinct population structure and that spread of the Tn1549-vanB-type resistance involves exchange of large chromosomal fragments between vanB-positive and vanB-negative enterococci rather than independent acquisition events. In vitro filter-mating experiments support the hypothesis and suggest the presence of certain target sequences as a limiting factor for dissemination of the vanB element. Thus, the present study provides a better understanding of how enterococci emerge into successful multidrug-resistant nosocomial pathogens.


July 7, 2019

The emergence and intercontinental spread of a multidrug-resistant clade of typhoid agent Salmonella enterica serovar Typhi

Multidrug-resistant typhoid is a global health problem. Previous studies conducted in countries of Asia and Africa have identified a highly clonal, multidrug-resistant lineage of Salmonella enterica serovar Typhi (S Typhi), known as H58. However, little is known about the emergence and geographical spread of the H58 clade. In this study, we have used whole-genome sequencing of a global collection of S Typhi to investigate this highly successful lineage.


July 7, 2019

Population structure and antimicrobial resistance profiles of Streptococcus suis serotype 2 sequence type 25 strains

Strains of serotype 2 Streptococcus suis are responsible for swine and human infections. Different serotype 2 genetic backgrounds have been defined using multilocus sequence typing (MLST). However, little is known about the genetic diversity within each MLST sequence type (ST). Here, we used whole-genome sequencing to test the hypothesis that S. suis serotype 2 strains of the ST25 lineage are genetically heterogeneous. We evaluated 51 serotype 2 ST25 S. suis strains isolated from diseased pigs and humans in Canada, the United States of America, and Thailand. Whole-genome sequencing revealed numerous large-scale rearrangements in the ST25 genome, compared to the genomes of ST1 and ST28 S. suis strains, which result, among other changes, in disruption of a pilus island locus. We report that recombination and lateral gene transfer contribute to ST25 genetic diversity. Phylogenetic analysis identified two main and distinct Thai and North American clades grouping most strains investigated. These clades also possessed distinct patterns of antimicrobial resistance genes, which correlated with acquisition of different integrative and conjugative elements (ICEs). Some of these ICEs were found to be integrated at a recombination hot spot, previously identified as the site of integration of the 89K pathogenicity island in serotype 2 ST7 S. suis strains. Our results highlight the limitations of MLST for phylogenetic analysis of S. suis, and the importance of lateral gene transfer and recombination as drivers of diversity in this swine pathogen and zoonotic agent.


July 7, 2019

Global phylogeography and evolutionary history of Shigella dysenteriae type 1

Together with plague, smallpox and typhus, epidemics of dysentery have been a major scourge of human populations for centuries1. A previous genomic study concluded that Shigella dysenteriae type 1 (Sd1), the epidemic dysentery bacillus, emerged and spread worldwide after the First World War, with no clear pattern of transmission2. This is not consistent with the massive cyclic dysentery epidemics reported in Europe during the eighteenth and nineteenth centuries1,3,4 and the first isolation of Sd1 in Japan in 18975. Here, we report a whole-genome analysis of 331 Sd1 isolates from around the world, collected between 1915 and 2011, providing us with unprecedented insight into the historical spread of this pathogen. We show here that Sd1 has existed since at least the eighteenth century and that it swept the globe at the end of the nineteenth century, diversifying into distinct lineages associated with the First World War, Second World War and various conflicts or natural disasters across Africa, Asia and Central America. We also provide a unique historical perspective on the evolution of antibiotic resistance over a 100-year period, beginning decades before the antibiotic era, and identify a prevalent multiple antibiotic-resistant lineage in South Asia that was transmitted in several waves to Africa, where it caused severe outbreaks of disease.


July 7, 2019

Genome sequence of Shimia str. SK013, a representative of the Roseobacter group isolated from marine sediment.

Shimia strain SK013 is an aerobic, Gram-negative, rod shaped alphaproteobacterium affiliated with the Roseobacter group within the family Rhodobacteraceae. The strain was isolated from surface sediment (0-1 cm) of the Skagerrak at 114 m below sea level. The 4,049,808 bp genome of Shimia str. SK013 comprises 3,981 protein-coding genes and 47 RNA genes. It contains one chromosome and no extrachromosomal elements. The genome analysis revealed the presence of genes for a dimethylsulfoniopropionate lyase, demethylase and the trimethylamine methyltransferase (mttB) as well as genes for nitrate, nitrite and dimethyl sulfoxide reduction. This indicates that Shimia str. SK013 is able to switch from aerobic to anaerobic metabolism and thus is capable of aerobic and anaerobic sulfur cycling at the seafloor. Among the ability to convert other sulfur compounds it has the genetic capacity to produce climatically active dimethyl sulfide. Growth on glutamate as a sole carbon source results in formation of cell-connecting filaments, a putative phenotypic adaptation of the surface-associated strain to the environmental conditions at the seafloor. Genome analysis revealed the presence of a flagellum (fla1) and a type IV pilus biogenesis, which is speculated to be a prerequisite for biofilm formation. This is also related to genes responsible for signalling such as N-acyl homoserine lactones, as well as quip-genes responsible for quorum quenching and antibiotic biosynthesis. Pairwise similarities of 16S rRNA genes (98.56 % sequence similarity to the next relative S. haliotis) and the in silico DNA-DNA hybridization (21.20 % sequence similarity to S. haliotis) indicated Shimia str. SK013 to be considered as a new species. The genome analysis of Shimia str. SK013 offered first insights into specific physiological and phenotypic adaptation mechanisms of Roseobacter-affiliated bacteria to the benthic environment.


July 7, 2019

Complete genome sequence analysis of Pandoraea pnomenusa type strain DSM 16536(T) isolated from a cystic fibrosis patient.

The genus of Pandoraea was first proposed in 2000 following the isolation from the sputum of cystic fibrosis patients (Coenye et al., 2000). Five species were initially assigned to the novel genus namely Pandoraea apista, Pandoraea pulmonicola, Pandoraea pnomenusa, Pandoraea sputorum, and Pandoraea norimbergensis but the description of four new species and another four genomospecies in the subsequent years led to a total of nine species and four genomospecies within the genus of Pandoraea (Daneshvar et al., 2001; Anandham et al., 2010; Sahin et al., 2011). The isolation of Pandoraea spp. from various environmental samples such as water, sludge, and soils have been reported, but to date, only P. pnomenusa, P. apista, P. pulmonicola, and P. sputorum were isolated from clinical specimens such as blood, sputum and bronchial fluid of patients with cystic fibrosis or chronic lung diseases (Coenye et al., 2000; Daneshvar et al., 2001; Stryjewski et al., 2003; Han-Jen et al., 2013). Members of Pandoraea tend to exhibit broad resistance to ampicillin, extended-spectrum cephalosporins, aztreonam, aminoglycosides, and meropenem but they are sensitive to imipenem (Daneshvar et al., 2001; Stryjewski et al., 2003). However, the clinical significance and prevalence of these multi-drug resistant bacteria among patients with cystic fibrosis or respiratory diseases remained unknown since Pandoraea spp. are usually misidentified as Burkholderia cepacia complex, Ralstonia pickettii, or Ralstonia paucula (Segonds et al., 2003). Ambiguity in differentiating between B. cepacia complex, Ralstonia spp. and Pandoraea spp. can be resolved by 16S ribosomal DNA-PCR (Coenye et al., 2001) and gyrB gene restriction fragment length polymorphism (Coenye and LiPuma, 2002) but the limited use of molecular typing methods in routine clinical microbiological laboratory has resulted in the underreporting of Pandoraea spp. in clinical cases.


July 7, 2019

A carbapenem-resistant Pseudomonas aeruginosa isolate harboring two copies of blaIMP-34 encoding a metallo-ß-lactamase.

A carbapenem-resistant strain of Pseudomonas aeruginosa, NCGM1984, was isolated in 2012 from a hospitalized patient in Japan. Immunochromatographic assay showed that the isolate was positive for IMP-type metallo-ß-lactamase. Complete genome sequencing revealed that NCGM1984 harbored two copies of blaIMP-34, located at different sites on the chromosome. Each blaIMP-34 was present in the same structures of the class 1 integrons, tnpA(ISPa7)-intI1-qacG-blaIMP-34-aac(6′)-Ib-qacEdelta1-sul1-orf5-tniBdelta-tniA. The isolate belonged to multilocus sequence typing ST235, one of the international high-risk clones. IMP-34, with an amino acid substitution (Glu126Gly) compared with IMP-1, hydrolyzed all ß-lactamases tested except aztreonam, and its catalytic activities were similar to IMP-1. This is the first report of a clinical isolate of an IMP-34-producing P. aeruginosa harboring two copies of blaIMP-34 on its chromosome.


July 7, 2019

Characterization of VCC-1, a novel ambler class A carbapenemase from Vibrio cholerae isolated from imported retail shrimp sold in Canada.

One of the core goals of the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS) is to monitor major meat commodities for antimicrobial resistance. Targeted studies with methodologies based on core surveillance protocols are used to examine other foods, e.g., seafood, for antimicrobial resistance to detect resistances of concern to public health. Here we report the discovery of a novel Ambler class A carbapenemase that was identified in a nontoxigenic strain of Vibrio cholerae (N14-02106) isolated from shrimp that was sold for human consumption in Canada. V. cholerae N14-02106 was resistant to penicillins, carbapenems, and monobactam antibiotics; however, PCR did not detect common ß-lactamases. Bioinformatic analysis of the whole-genome sequence of V. cholerae N14-02106 revealed on the large chromosome a novel carbapenemase (referred to here as VCC-1, for Vibrio cholerae carbapenemase 1) with sequence similarity to class A enzymes. Two copies of blaVCC-1 separated and flanked by ISVch9 (i.e., 3 copies of ISVch9) were found in an acquired 8.5-kb region inserted into a VrgG family protein gene. Cloned blaVCC-1 conferred a ß-lactam resistance profile similar to that in V. cholerae N14-02106 when it was transformed into a susceptible laboratory strain of Escherichia coli. Purified VCC-1 was found to hydrolyze penicillins, 1st-generation cephalosporins, aztreonam, and carbapenems, whereas 2nd- and 3rd-generation cephalosporins were poor substrates. Using nitrocefin as a reporter substrate, VCC-1 was moderately inhibited by clavulanic acid and tazobactam but not EDTA. In this report, we present the discovery of a novel class A carbapenemase from the food supply. Copyright © 2016, American Society for Microbiology. All Rights Reserved.


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