Global Expansion of Linezolid-Resistant Coagulase-Negative Staphylococci.

Coagulase-negative staphylococci (CoNS) for a long time were considered avirulent constituents of the human and warm-blooded animal microbiota. However, at present, S. epidermidis, S. haemolyticus, and S. hominis are recognized as opportunistic pathogens. Although linezolid is not registered for the treatment of CoNS infections, it is widely used off-label, promoting emergence of resistance. Bioinformatic analysis based on maximum-likelihood phylogeny and Bayesian clustering of the CoNS genomes obtained in the current study and downloaded from public databases revealed the existence of international linezolid-resistant lineages, each of which probably had a common predecessor. Linezolid-resistant S. epidermidis sequence-type (ST) 2 from Russia, France, and Germany formed a compact group of closely related genomes with a median pairwise single nucleotide polymorphism (SNP) difference of fewer than 53 SNPs, and a common ancestor of this lineage appeared in 1998 (1986-2006) before introduction of linezolid in practice. Another compact group of linezolid-resistant S. epidermidis was represented by ST22 isolates from France and Russia with a median pairwise SNP difference of 40; a common ancestor of this lineage appeared in 2011 (2008-2013). Linezolid-resistant S. hominis ST2 from Russia, Germany, and Brazil also formed a group with a high-level genome identity with median 25.5 core-SNP differences; the appearance of the common progenitor dates to 2003 (1996-2012). Linezolid-resistant S. hominis isolates from Russia demonstrated associated resistance to teicoplanin. Analysis of a midpoint-rooted phylogenetic tree of the group confirmed the genetic proximity of Russian and German isolates; Brazilian isolates were phylogenetically distant. repUS5-like plasmids harboring cfr were detected in S. hominis and S. haemolyticus.

Comparative genome analysis of global and Russian strains of community-acquired methicillin-resistant Staphylococcus aureus ST22, a 'Gaza clone'.

In this study, we identified the relationship between the genetic lineage of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) sequence type 22 (ST22) from Russia and other regions. Sixty ST22 isolates from Russia were characterised through whole-genome sequencing. To evaluate the phylogenetic relationship of Russian isolates with the global ST22 population, we analysed 1283 genomes obtained from NCBI's GenBank. The phylogenetic tree of the ST22 global population consisted of three main clusters (A, B and C). The first (cluster A) was represented by EMRSA-15 isolates, the second (cluster B) by heterogeneous isolates from different regions harbouring different sets of virulence genes, and the third (cluster C) by isolates from the Middle East previously recognised as 'Gaza clone' and similar isolates from Russia. Presence of the toxic shock syndrome toxin (tsst) and elastin-binding protein S (ebpS) genes as well as the hypothetical proteins NCTC13616_00051 and NCTC13616_00047 were the most useful factors in discriminating ST22 lineages. Although the CA-MRSA 'Gaza clone' was mainly recovered from carriers, its widespread occurrence is a cause for concern. Differentiation of the 'Gaza clone' from other MRSA lineages is necessary for planning infection control measures.

The emergence of hypervirulent blaNDM-1-positive Klebsiella pneumoniae sequence type 395 in an oncology hospital.

Fifteen hypermucoviscous isolates (13 blaNDM-1-positive) obtained from 11 oncology patients were analyzed by whole genome sequencing, and selected isolates were assessed in a murine model of sepsis. ST395/K2 isolates harboring rmpA, rmpA2, peg-344, aerobactin, enterobactin, yersiniabactin, type I fimbriae, etc. displayed maximal virulence in the mouse lethality assay (LD50 = 102 CFU). ST147/K20 isolates lacking yersiniabactins were relatively less virulent (LD50 = 104 CFU), ST395/K2 isolates lacking rmpA, rmpA2, peg-344, and aerobactin, but harboring yersiniabactin demonstrated minimal virulence (LD50 = 105 CFU). Isolates represent various paths and stages of evolution directed towards convergence of multidrugresistant classical Klebsiella pneumoniae and hypervirulent K. pneumoniae.

Design of a New [PSI +]-No-More Mutation in SUP35 With Strong Inhibitory Effect on the [PSI +] Prion Propagation.

A number of [PSI +]-no-more (PNM) mutations, eliminating [PSI +] prion, were previously described in SUP35. In this study, we designed and analyzed a new PNM mutation based on the parallel in-register ß-structure of Sup35 prion fibrils suggested by the known experimental data. In such an arrangement, substitution of non-charged residues by charged ones may destabilize the fibril structure. We introduced Q33K/A34K amino acid substitutions into the Sup35 protein, corresponding allele was called sup35-M0. The mutagenized residues were chosen based on ArchCandy in silico prediction of high inhibitory effect on the amyloidogenic potential of Sup35. The experiments confirmed that Sup35-M0 leads to the elimination of [PSI +] with high efficiency. Our data suggested that the elimination of the [PSI +] prion is associated with the decreased aggregation properties of the protein. The new mutation can induce the prion with very low efficiency and is able to propagate only weak [PSI +] prion variants. We also showed that Sup35-M0 protein co-aggregates with the wild-type Sup35 in vivo. Moreover, our data confirmed the utility of the strategy of substitution of non-charged residues by charged ones to design new mutations to inhibit a prion formation.