The use of all-trans retinoic acid (ATRA) drastically improved the results of therapy for acute promyelocytic leukeimia (APL). The high efficiency of the Russian protocol APL-93—98 applied to 62 children and adolescents with APL (event-free and overall survival (EFS and OS) were 84±5% respectively with a relapse rate of 7%) was achieved, by administering the high cumulative dose of daunoruicin (495 mg/m2) and single doses of АТRА (45 mg/m2). In this connection, the APL-2003 protocol attempted to reduce both acute and chronic toxicity of the therapy, by decreasing the cumulative dose of daunorubicin to 405 mg/m2 and the single dose of АТRА to 25 mg/m2 under regular control of minimal residual disease via molecular monitoring of the specific transcript PML/RARα. Analysis of the results of treatment in 61 patients aged 1.3 to 17 years (median 11.3) showed that despite of the reduced protocol intensity, the efficiency of therapy did not generally reduce — EFS and OS were 79±6 and 93±3%, respectively. The likelihood of the development of a relapse was significantly affected by molecular resistance, i.e. the retention of the transcript PML/RARα before a phase of maintenance therapy: the recurrence risk in this group was 57% whereas there were no differences in all cure rates between the patients depending on baseline leukocytosis. All 6 patients with relapses were treated with arsenic trioxide, resulting in not only clinical and hematological, but also molecular remissions; thereafter the patients received myeloablative therapy and autologous hemopoietic stem cell transplantation. The second remission lasted 3 to 24 months. Thus, reducing the cumulative dose of anthracyclines and the dose of АТRА did not make the results of the therapy for APL worse. The monitoring of minimal residual disease before and during maintenance therapy is a mandatory component of successful treatment in APL patients. Arsenic trioxide is an effective agent for the treatment of APL relapses.

A capsular polysaccharide was isolated from cells of opportunistic bacterial pathogen Acinetobacter baumannii strain MAR 55–66. According to carbohydrate analysis and 1H and 13C NMR spectroscopy, it is composed of heptasaccharide repeating units, which include five l-rhamnose (Rha) residues and one residue each of d-glucuronic acid (GlcA) and N-acetyl-d-glucosamine (GlcNAc). For structural analysis of this polysaccharide, the Smith degradation, depolymerization with a recombinant endo-glycosidase from a specific bacteriophage, and selective solvolysis with CF3CO2H were applied. The two last methods resulted in formation of the same linear heptasaccharide, which was subjected to the following chemical modifications: borohydride reduction, β-elimination with alkali, and partial acid hydrolysis. The resulting oligosaccharides were isolated by gel-permeation chromatography, and their structures were established by 1H and 13C NMR spectroscopy including 2D 1H-1H and 1H-13C NMR correlation experiments, as well as high-resolution electrospray ionization mass spectrometry. Based on the data obtained, the structure of the branched heptasaccharide repeating unit containing three Rha residues and one GlcNAc residue in the main chain along with two Rha residues and one GlcA residue in the side chain was established. The polysaccharide studied belongs to a group of structurally similar capsular polysaccharides of A. baumannii, which are built up of branched oligosaccharide repeating units that include four or five l-Rha residues and one residue each of d-GlcA and d-GlcNAc.

Mul'tirezistentnye shtammy Klebsiella pneumoniae yavlyayutsya odnoj iz samyh ser'eznyh prichin vnutribol'nichnyh infekcij, vyzvannyh bakteriyami, ustojchivymi k antibiotikam. Sushchestvuyut razlichnye varianty bor'by s etoj ugrozoj, odin iz nih — klinicheskoe ispol'zovanie bakteriofagov. Cel'yu raboty bylo vydelit' i detal'no oharakterizovat' virulentnyj baktriofag, imeyushchij potencial dlya terapevticheskogo primeneniya. Ispol'zovali standartnye metody fagovoj biologii, bioinformatiki, vklyuchaya sovremennye sposoby predskazaniya belkovyh struktur (programma AlphaFold), elektronnuyu mikroskopiyu. Iz obrazcov stochnyh vod byl vydelen virulentnyj podovirus KPPK108.1, otnosyashchijsya k rodu Drulisvirus, specifichno inficiruyushchij shtammy K. pneumoniae, imeyushchie kapsulyarnyj polisaharid tipa KL108, opredelena posledovatel'nost' ego genoma, issledovany ego biologicheskie svojstva i dana geneticheskaya harakteristika.

Blackleg and soft rot of potato (Solanum tuberosum) were monitored in the Central European part of Russia within a period of 2012- 2019. Symptoms included decay of tubers, blackening of stem vascular bundles, and partial yellowing of leaves. The disease causes serious potato yield losses in the field and storage. Pectobacterium parmentieri, P. brasiliense, P. versatile (syn. Ca. Pectobacterium maceratum), P. carotovorum, P. atrosepticum, Dickeya dianthicola, and D. solani are considered as main causal agents of soft rot and blackleg disease in Russia (Voronina et al. 2019, Ngoc Ha et al., 2019, Shirshikov et al. 2018, Kornev et al. 2012). Potato plant samples collected in commercial fields in routine plant health assay were used for bacteria isolation on crystal violet pectate agar (CVP) (Helias et al. 2012) as described previously (Voronina et al. 2019). Bacterial colonies producing pitting on CVP were re-isolated and purified on nutrient broth yeast extract medium. DNA of bacterial isolates was extracted, and polymerase chain reaction (PCR) amplifications were performed using gapA primers (Cigna et al. 2017) followed by sequencing. DNA sequence alignment showed that the isolates F099, F100, F106, F109, and F118 were identical (deposited as part of NCBI Ref.Seq. for F109 NZ_RRYS01000004.1, locus KHDHEBDM_RS06360) and grouped together with the type strain Pectobacterium polaris NIBIO1006T (CP017481), a new species described as a potato pathogen (Dees et al. 2017). These strains were negative in diagnostic PCR assays using specific primers Y45/Y46 for the detection of P. atrosepticum, Br1f and L1r for P. brasiliense (Duarte et al. 2004), and ADE1/ADE2 for Dickeya sp. (Nassar et al. 1996). To further validate the identification, strain F109 of P. polaris was selected for genome sequencing. The genome of P. polaris strain F109, (NCBI Reference Sequence NZ_RRYS00000000.1) reveals >99% sequence similarity with type strain P. polaris IPO_1606 (GenBank accession GCA_902143345.1). The strain F109 was deposited to All-Russian Collection of Microorganisms under number VKM V-3420. Thus, the characterization of five isolates provided evidence that a previously unreported pathogen was present in the surveyed fields. The isolates were uniform in genetic and physiological properties; they were gram negative, facultative anaerobes with pectinolytic activity, negative for oxidase, urease, indole production, gelatin liquefaction. All isolates were catalase positive, produced acid from lactose, rhamnose, saccharose, xylose, and trehalose, and were tolerant to 5% NaCl, unable to utilize malonate and citrate. All the isolates grew at 37°C. All isolates caused soft rot symptoms on 10 inoculated potato tubers. They produced typical black leg rot symptoms in young potato plants inoculated with 107 CFU/ml of the pathogen by stem injection and incubated at 25°C for 48 h. The bacteria were re-isolated successfully from symptomatic potato and pathogen confirmed by gapA sequencing to complete Koch's postulates. To our knowledge, this is the first report of blackleg and soft rot caused by P. polaris on potato in the Russian Federation. According to the data of commercial diagnostic laboratory "PhytoEngineering" (Moscow region), P. polaris occurred in 5% potato seed stocks harvested in 2017-2019 in the Moscow region. This finding may indicate that new Pectobacterium strains have adapted to a diverse environment, which is consistent with widespread distribution of commercial seed potatoes. The author(s) declare no conflict of interest. Funding: This work was supported by Russian Science Foundation grant #16-16-00073.

Multidrug-resistant Klebsiella pneumoniae strains are one of the major causes of nosocomial infections caused by the antibiotic-resistant bacteria. There are different options for dealing with this threat, among which is the clinical application of bacteriophages. The study was aimed to isolate and describe a virulent bactriophage, having the potential for therapeutic use. The standard phage biology and bioinformatic methods were used, which included the advanced techniques for protein structure prediction (AlphaFold software), and electron microscopy. The virulent podovirus KPPK108.1, being the member of genus Drulisvirus, which is able to specifically infect the K. pneumoniae strains with the KL108 type capsular polysaccharide, has been isolated from the wastewater. The sequence of the bactriophage genome has been defined, the biological properties have been investigated, and the genetic features have been described.

Capsular polysaccharide (CPS), isolated from Acinetobacter baumannii LUH5549 carrying the KL32 capsule biosynthesis gene cluster, was studied by sugar analysis, Smith degradation, and one- and two-dimensional 1 H and 13 C NMR spectroscopy. The K32 CPS was found to be composed of branched pentasaccharide repeats (K units) containing two residues of β-D-Gal p NAc and one residue of β-D-Glc p A (β-D-glucuronic acid) in the main chain and one residue each of β-D-Glc p and α-D-Glc p NAc in the disaccharide side chain. Consistent with the established CPS structure, the KL32 gene cluster includes genes for a UDP-glucose 6-dehydrogenase (Ugd3) responsible for D-GlcA synthesis and four glyco- syltransferases that were assigned to specific linkages. Genes encoding an acetyltransferase and an unknown protein prod- uct were not involved in CPS biosynthesis. Whilst the KL32 gene cluster has previously been found in the global clone 2 (GC2) lineage, LUH5549 belongs to the sequence type ST354, thus demonstrating horizontal gene transfer between these lineages.

Aerobic gram-negative bacterium Acinetobacter baumannii has recently become one of the most relevant pathogens associated with hospital-acquired infections worldwide. A. baumannii produces a capsule around the cell, which represents a thick viscous layer of structurally variable capsular polysaccharide (CPS). The capsule protects the bacteria against unfavorable environmental factors and biological systems, including bacteriophages and host immune system. Many A. baumannii phages have structural depolymerases (tailspikes) that specifically recognize and digest bacterial CPS. In this work, we studied the interaction of tailspike proteins of four lytic depolymerase-carrying phages with A. baumannii CPS. Depolymerases of three bacteriophages (Fri1, AS12, and BS46) were identified as specific glycosidases that cleave the CPS of A. baumannii strains 28, 1432, and B05, respectively, by the hydrolytic mechanism. The gp54 depolymerase from bacteriophage AP22 was characterized as a polysaccharide lyase that cleaves the CPS of A. baumannii strain 1053 by β-elimination at hexuronic acid (ManNAcA) residues.

Phages of the phytopathogenic Pectobacteriaceae species causing black leg and soft rot of potato were investigated. These phages are promising as biocontrol agents to prevent the loss of seed and ware potato tubers. The present work characterizes a new podovirus PP16, infecting a broad range of Pectobacterium carotovorum strains. Based on its genomic composition, phage PP16 was assigned to a separate phylogenetic branch of the genus Phimunavirus, subfamily Autographivirinae . Bacteriophage PP16 efficiently inhibited development of bacterial infection both in vitro and in planta . The field experiment demonstrated a substantial increase of plant germination after the treatment of seed potato with phage PP16.