We report linezolid-resistant coagulase-negative Staphylococcus (LRCoNS) bacteremia at a tertiary hospital. LRCoNS with linezolid and tedizolid minimum inhibitory concentrations of >32 and 4-32 mg/L, respectively, were isolated from blood cultures of seven elderly patients who died post-bacteremia detection. Linezolid was administered to six of these patients at the time of LRCoNS isolation. Linezolid-resistant S. epidermidis ST5 isolates (LRSE) harboring mecA were isolated in seven of the nine episodes. Linezolid resistance is associated with mutations in the 23S rRNA, L3 and L4 ribosomal proteins, indigenous methyltransferases RlmN, and the presence of the cfr gene. All LRSE-ST5 genomes formed a single phylogenetic cluster.

Aim of the study. Genetic analysis of Streptococcus pneumoniae serogroups 15 and 11 circulating in Russia according to the following parameters: serotype affiliation; clonal complex (CC); presence of resistance and virulence determinants; relatedness to genetic lineages circulating in the world, and justification of inclusion of the actual serotypes of serogroups 15 and 11 in the future conjugate vaccine composition. Materials and methods. The study included whole genome data of S. pneumoniae serogroups 11 and 15. Results. Genomes of serogroup 15 strains from Russia are represented mainly by serotypes 15B and 15C, the majority of which belong to CC-1025 and CC-1262. CC-1025 is characterized by a more frequent association with invasive diseases. Representatives of CC-1025 and CC-1262 contain virulence determinants unique to these genetic lineages within the studied population of serogroup 15: oligopeptide transporters, fructose-specific PTS system, unique hydrolase variants, additional iron ion transporters, the gene of zinc metalloprotease ZmpC (activating human MMP9). The genomes of serogroup 11 are represented mainly by serotype 11A, the majority belong to CC-62 and CC-1012. The virulence determinants unique to CC-62 (within the studied serogroup 11) include bacteriocins, components of oligopeptide transport, flavin reductase-like protein (adhesin, also protects bacteria from oxidative stress), fucose processing operon, PsaA (adhesin, also a component of the ATP-binding cassette transporter that imports manganese ions). Conclusion. In the Russian Federation, serogroups 15 and 11 are the most common non-vaccine serogroups. No antimicrobial resistance determinants have been identified in the genomes of representatives of these serogroups. For each of the genetic lineages prevalent in Russia and associated with serogroups 15 and 11, unique virulence determinants within the studied serogroup have been identified, which may contribute to the success of these lineages. It is advisable to include serotypes 15B and 11A in vaccines promising for the Russian Federation.

BACKGROUND: The need for microbiological monitoring of the distribution of pneumococcal serotypes is associated with changes that occur during routine immunization of children with pneumococcal vaccines. AIM: To characterize the changes in the serotype structure of Streptococcus pneumoniae obtained from healthy preschool children between 2016 and 2022. MATERIALS AND METHODS: In total, 1250 healthy children aged 6 years attending kindergartens were examined in multicenter studies (2016–2018 and 2020–2022). Nasopharyngeal pneumococcal isolates (n=265) were obtained using the culture method. S. pneumoniae serotype was determined using polymerase chain reaction. RESULTS: Between 2016 and 2018, the prevalence of pneumococcal carriage decreased from 27.3 to 17.3%, and by 2022, it increased to 25.6%. Moreover, the correspondence of S. pneumoniae serotypes to the antigenic composition of the 13-valent pneumococcal vaccine decreased from 48.8 to 9.4% and the composition of the 20-valent vaccine from 75.6 to 39.1%. The proportion of “non-vaccine” types of pneumococcus increased from 22% in 2016 to 61% in 2022. Among the “non-vaccine” serotypes/groups, 15AF, 6CD, 23A, and 35F/47F were predominant, and new variants were also discovered: 23B and 35B. The serotypes included in the 13-valent conjugate vaccine were detected among unvaccinated children and were represented by variants 19F, 6A and 6B, 23F. Throughout the observation period, pneumococci of serotypes/groups 15BC, 11AD, and 10A were detected with high frequency. CONCLUSIONS: Because of the elimination of a significant part of S. pneumoniae “vaccine” serotypes in 2016–2022, the concordance of circulating variants with the antigenic composition of pneumococcal conjugate vaccines significantly decreased. In addition, the new types detected with high frequency are not included in existing pneumococcal vaccines, which necessitates the creation of new immunobiological drugs for pneumococcal infection prevention.

Dose-intensive cytostatic therapy and antibiotic treatment in allogeneic hematopoietic stem cell transplantation (allo-HSCT) cause severe abnormalities in a composition of gut microbiota as well as the emergence of antibiotic resistance. The data on the longitudinal recovery of major bacterial phyla and the expansion of genes associated with antibiotic resistance are limited. We collected regular stool samples during the first year after allo-HSCT from 12 adult patients with oncohematological disorders after allo-HSCT and performed 16SrRNA sequencing, multiplex PCR, conventional bacteriology and CHROMagar testing. We observed a decline in Shannon microbiota diversity index as early as day 0 of allo-HSCT (p = 0.034) before any administration of antibiotics, which persisted up to 1 year after transplantation, when the Shannon index returned to pre-transplant levels (p = 0.91). The study confirmed the previously shown decline in Bacillota (Firmicutes) genera and the expansion of E. coli/Shigella, Klebsiella and Enterococci. The recovery of Firmicutes was slower than that of other phyla and occurred only a year post-transplant. A positive correlation was observed between the expansion of E. coli/Shigella genera and blaKPC, blaCTX-M-1 and blaTEM (p < 0.001), Klebsiella spp. and blaOXA-48-like, blaNDM, blaCTX-M-1, blaTEM, and blaSHV (p < 0.001), Pseudomonas spp. and blaNDM (p = 0.002), Enterococcus spp. and blaOXA-48-like, blaNDM, blaCTX-M-1, blaSHV (p < 0.01). The correlation was observed between the expansion of Enterobacterales and and carbapenemase-positive CHROMagar samples (p < 0.001). Samples positive for carbapenem-resitant bacteria were at their maximum levels on day +30, and were gradually diminishing one year after allo-HSCT. From day +30 to +60, all isolated K. pneumoniae strains in fecal samples proved to be resistant to the main antibiotic groups (carbapenems, aminoglycosides, fluoroquinolones, third-generation cephalosporins). One year after HSCT, we documented the spontaneous decolonization of K. pneumoniae. The sensitivity of molecular biology techniques in the search for total and antibiotic-resistant Klebsiella seems to be superior to common bacteriological cultures. Future studies should be focused on searching for novel approaches to the efficient reconstitution and/or maintenance of strictly anaerobic microbiota in oncological patients.

This study was aimed at understanding the distributions of the MICs (minimum inhibitory concentrations) of aztreonam-avibactam, ceftazidime-avibactam and meropenem with respect to Klebsiella pneumoniae isolates producing different types of carbapenemases and their combinations. K. pneumoniae isolates were collected between 2019 and 2022 from 37 hospitals. PCR was used to screen for bla(KPC)-, bla(NDM)- and bla(OXA-48)-like genes. MICs were determined by the broth microdilution method for meropenem, aztreonam-avibactam and ceftazidime-avibactam at a constant avibactam concentration of 4 mg l(-1). MIC distributions were analyzed for groups of isolates based on the identified carbapenemases including their combinations. The AZT/AVI MIC50 and MIC90 for all NDM-positive isolates were 0.25 and 0.5, respectively, and for serine-carbapenemase-only producers, they were 0.25 and 1 mg l(-1), respectively. The CZD/AVI MIC50 and MIC90 values for serine-carbapenemase-only producers were 1 and 4 mg l(-1), respectively. The AZT/AVI MIC50 and MIC90 values for co-producers and single carbapenemase producers were the same (i.e., 0.25 and 1 mg l(-1), respectively). The total proportion of meropenem-susceptible isolates (<= 8 mg l(-1)) among all the carbapenemase producers was 25.1% (31.1% among single-carbapenemase producers and 9.2% among co-producers). The results support the use of aztreonam-avibactam for the empirical treatment of infections caused by any carbapenemase producers.

Aim: demonstration of basic molecular biological, metabolic and immunological effects of fecal microbiota transplantation (FMT), on the example of a rare case of acute graft-versus-host disease (GVHD) with intestinal damage in a patient after allogeneic hematopoietic stem cell transplantation (allo-HSCT).Materials and methods. To monitor the basic effects of FMT, we performed targeted DNA sequencing of 16S rRNA gene (V3–V4) using MiSeq platform as well as multiplex real-time PCR, MS/gas chromatography technique, immunophenotyping of blood lymphocytes, histological and immunohistochemical techniques.Clinical case. A 40-year-old female patient diagnosed with myelodysplastic syndrome, with a history of two unsuccessful allo-HSCTs due to graft failure, underwent the third haploidentical HSCT (haplo-HSCT) from her father as ‘salvage’ therapy. Due to early viral/bacterial colitis post-transplant associated with a multidrug-resistant strain of K. pneumoniae and herpes virus type 6, FMT was performed on days 46 and 47 after allo-HSCT. Complete resolution of the enteropathy symptoms was noted following FMT. However, immunosuppressive therapy was canceled on D+106 after haplo-HSCT due to the detection of minimal residual disease causing development of the ‘overlap’-type GVHD with damage skin lesions grade 4, and intestinal mucous membranes grade 3. This complication required resumption and subsequent intensification of immunosuppressive therapy with complete resolution of GVHD symptoms. Following FMT treatment, the patient showed complete resolution of clinical colitis symptoms. According to results of 16S rRNA sequencing, the species-specific diversity of fecal microbiota increased significantly, along with decreased relative contents of opportunistic bacteria (Klebsiella, Enterococcus, Streptococcus genera). A significant growth was revealed for commensal Bacteroidota, and re-emergence of Faecalibacterium, Blautia, Roseburia. Acute gastrointestinal GVHD promoted by tacrolimus withdrawal was associated with repeated depletion of intestinal microbiota. Upon resolution of GVHD and resumed immunosuppression, increased microbiota diversity (Shannon index) was again recorded, and the parameters of patient’s fecal microbiota reached the donor values. The microbiota shifts at all clinical stages (before and after FMT, at the peak of acute intestinal GVHD and intensive immunosuppressive therapy) showed some relations with metabolism of bile and fatty acids in blood plasma and immune parameters.Conclusions. FMT may be a component of complex therapy aimed at early reconstitution of immune system and organic acid metabolism in patients after allo-HSCT. The composition of fecal microbiota, metabolic profile and spectrum of lymphocyte subpopulations may be markers for monitoring complex rehabilitation after allo-HSCT.

Гентамицин является одним из компонентов комбинированной терапии инфекционных эндокардитов, вызванных Staphylococcus aureus, включая метициллинорезистентные штаммы (methicillin-resistant S.aureus, MRSA). Цель исследования — анализ влияния десяти 6-часовых циклов воздействия высоких концентраций (16 мкг/мл) гентамицина in vitro на изменение фенотипа и генотипа аминогликозидочувствительных штаммов S.aureus, относящихся к четырём сиквенс-типам: ST5 (ATCC 29213), ST8, ST97 и ST22 (MRSA). Для всех штаммов, кроме ATCC 29213, после селекции отмечалось увеличение МПК гентамицина до 8–64 мкг/мл. Один штамм (SA0937) диссоциировал на три морфотипа, включая мелкоколониевый вариант (small colony variant, SCV). Вариант производного штамма SA0937 с колониями нормального размера характеризовался ассоциированной устойчивостью к даптомицину за счёт мутации P314L в MprF. Формирование устойчивости не сопровождалось изменением скорости роста, кроме морфотипа SCV. Для штамма ATCC 29213 после селекции отмечалось появление толерантности, проявляющейся в увеличении эффективного киллинга до 14 ч в 24-часовом time-killing эксперименте с концентрацией антибиотика 16 мкг/мл. У штамма ATCC 29213 выявлены мутации в пептидил т-РНК гидролазе (Pth). У трёх штаммов были обнаружены делеции в гене atpG, входящим в состав АТФ-синтазного комплекса. У остальных производных штаммов были выявлены делеции и мутации в генах метаболизма менахинона hepS, menA и трансляционном факторе элонгации G (fusA). Таким образом, использование гентамицина сопряжено с возможным быстрым формированием устойчивости и толерантности, не связанными с приобретением генов аминогликозид-модифицирующих ферментов. Выявление SCV ассоциировано с неблагоприятными клиническими исходами. При использовании комбинированной терапии необходимо учитывать, что существует возможность формирования устойчивости к даптомицину на фоне селекции гентамицином.

Acute pericarditis is usually a self-limiting disorder that commonly occurs due to viral etiology or unexplained causes. Meningococcal pericarditis (MP) is a remarkably uncommon clinical entity that manifests as a complication during the acute or convalescent phase of meningococcal meningitis. However,its occurrence within the context of meningococcal septicemia has also been documented. We report a rare case of a previously healthy male patient who developed both acute pericarditis and uveitis as a presentation of meningococcal septicemia,with no characteristic skin rashes or meningeal signs.

Background/Objectives: Carbapenem-resistant Enterobacterales (CRE) are a global health threat due to their high morbidity and mortality rates and limited treatment options. This study examines the plasmid-mediated transmission of virulence and antibiotic resistance determinants in carbapenem-resistant Klebsiella pneumoniae (Kpn) and Escherichia coli (E. coli) isolated from Russian hospitals. Methods: We performed short- and long-read whole-genome sequencing of 53 clinical isolates (48 Kpn and 5 E. coli) attributed to 15 genetic lineages and collected from 21 hospitals across nine Russian cities between 2016 and 2022. Results: The plasmid analysis identified 18 clusters that showed high concordance with replicon typing, with all clusters having a major replicon type. The majority of plasmids in the IncHI1B(pNDM-MAR)/IncFIB(pNDM-Mar)-like cluster (79.16%) carried both antibiotic resistance genes (e.g., blaNDM-1 and blaOXA-48) and virulence factors (VFs) such as siderophore genes. We hypothesized that hybrid plasmids could play a critical role in the dissemination of antibiotic resistance genes and VFs. Comparative analyses with global plasmid databases revealed high-risk lineages of hybrid plasmids that are predominantly spread throughout Russia at present. Conclusions: Our findings underscore the importance of monitoring plasmid backbones for clinical management, surveillance, and infection control activities.

Methylphosphorylated mono-, di- and trimannosides structurally related to the lipopolysaccharide (LPS) O-antigens of Klebsiella pneumoniae of serotype O3 were synthesized and conjugated with a biotin tag. The stereo- and regioselective assembly of target carbohydrate chains was conducted using uniform monosaccharide synthetic blocks. After that, a methylphosphate group was introduced by coupling with a methyl-H-phosphonate reagent followed by oxidation and deprotection to give the target oligosaccharides. The 1H and 13C NMR spectra of the obtained compounds showed a good fit with the spectrum of the corresponding natural polysaccharide. The newly prepared biotinylated oligosaccharides along with the previously reported biotinylated glycoconjugates related to galactan I and galactan II of K. pneumoniae LPS were used for the ELISA detection of antibodies in anti-K. pneumoniae rabbit sera. Anti-O3 serum antibodies specifically recognized the synthesized oligosaccharide ligands with terminal methylphosphomannosyl residues, whereas anti-O1 serum antibodies recognized the oligosaccharide related to K. pneumoniae galactan II. The analysis of human sera from patients with confirmed Klebsiella infection also revealed the presence of antibodies against the synthesized oligosaccharides in clinical cases. Thus, the described compounds together with other Klebsiella related antigenic oligosaccharides could be potentially used as molecular probes for K. pneumoniae serological diagnostics development and strain serotyping.

During a prospective multicenter non-interventional observational study, a comparative assessment was made of the serotype structure of pneumococci circulating among healthy children under the age of 5 years and children of the same age group with signs of respiratory infections in the periods 2016-2018 and 2020-2022. Data on the serotype structure of pneumococci in the period from 2016-2018 were obtained from our previous works. In 2020-2022 the study included 2066 healthy children and 603 children with respiratory infections. Streptococcus pneumoniae and their DNA were detected in nasopharyngeal swabs by classical culture and molecular methods. Typing was carried out by molecular methods. On the territory of the Russian Federation, pneumococci belonging to the serotypes included in the 13-valent vaccine are being forced out of circulation and replaced by non-vaccine serotypes. Before the introduction of mass antipneumococcal vaccination (until 2015), the 13-valent conjugate vaccine covered from 66.2% to 92% of pneumococci, after the start of mass anti-pneumococcal vaccination in the period 2016-2018, coverage decreased to 57.3%. Between 2020 and 2022, coverage was less than 40%. The main “non-vaccine” serotypes/serogroups circulating in the Russian Federation are 15AF, 11AD, 23A, 9LN and 16F.

The aim of this study is to describe the phenotypic and genetic properties of oxacillin-susceptible methicillin-resistant Staphylococcus aureus (OS-MRSA) isolates and their beta-lactam resistant derivatives obtained after selection with oxacillin. A collection of hospital- (HA-) and community-acquired (CA-) MRSA was screened for oxacillin susceptibility. Antibiotic susceptibility testing, population analysis profile (PAP), mecA expression analysis, and whole genome sequencing (WGS) were performed for 60 mecA-positive OS-MRSA isolates. Twelve high-level beta-lactam resistant derivatives selected during PAP were also subjected to WGS. OS-MRSA were more prevalent among CA-MRSA (49/205, 24

A high cellular level of cyclic di-adenosine monophosphate (c-di-AMP) influences the formation of resistance to antibiotics that target the cell-wall in Staphylococcus aureus . The increase in intracellular molecules of c-di-AMP is due to mutations in the DHH/DHHA1 domain of the GdpP protein. The influence of mutations in the other domains of GdpP has not been fully studied. The aim of this study was to obtain a targeted nonframeshifting deletion in the GdpP protein’s linker region between the GGDEF and DHH/DHHA1 domains. The restriction-modification deficient strain S. aureus RN4220 was used for genome editing. Two vectors with thermosensitive origins of replication were used. The first, the pCN-EF2132tet vector, contained the Enterococcus faecalis EF2132 recombinase gene; the second, the pCAS9counter vector contained the Streptococcus pyogenes RNA-directed Cas9 nuclease gene. The S. aureus RN4220 strain was transformed with the pCN-EF2132tet vector to obtain recombining competent cells and then a donor oligonucleotide was introduced simultaneously with the counterselection vector. A recombinant strain with a target deletion (90 bp) in GdpP (amino acids 308–337) was obtained after two sequential transformations. The mutant strain showed no changes in the phenotype: lag phase, growth rate, doubling time, and colony morphology did not differ from the progenitor strain. The susceptibility to cell-wall targeted antibiotics was the same as in the progenitor strain. Thus, mutations in the linker region between the GGDEF and DHH/DHHA1 domains of the GdpP do not affect susceptibility to antibiotics in S. aureus .

Objective. To characterize the genomes of oxacillin-susceptible mecA-positive Staphylococcus aureus ST59 isolated in St. Petersburg. Materials and Methods. Nine oxacillin-susceptible mecA-positive of S. aureus isolates (OS-MRSA) of ST59 were included in the study. The isolates were obtained from children who showed no clinical signs of staphylococcal infections during nasal screening of S. aureus in St. Petersburg in 2018–2019. One isolate was obtained from an adult patient with skin and soft tissue infection (SSTI). The susceptibility to antibiotics and whole genome sequencing were performed. The analysis included 242 genomes of S. aureus ST59 from open access databases. Results. By employing the broth serial dilution and VITEK, the isolates' phenotypic susceptibility to oxacillin was determined. The cefoxitin inhibition zones ranged from 17 to 22 mm. All isolates showed a penicillinclavulanate MIC ≤ 0.5 µg/mL. Isolates obtained from carriers belonged to the ST59-t1950-SCCmec Vb (seb+) genotype whereas the isolate obtained from SSTI belonged to the ST59-t437-SCCmec Vb (seb/ lukF/lukS+) genotype. Nucleotide position -33 (C/T) of mecA promoter and mutations in PBP2a (S225R + E246G) were present in all isolates. Based on phylogenetic analysis and Bayesian clustering the ST59 genomes were divided into four clusters and all Russian genomes belonged to the East Asian ST59 sublineage. The PVL toxin was present in the genomes of the first cluster of the East Asian ST59 sublineage. Pairwise comparisons of nucleotide substitutions among the genomes of Russian isolates showed a high similarity: median 13, interquartile range 8–18. All ST59 clusters were characterized by the presence of enterotoxin B, as well as mutations in PBP2a (S225R and E246G) and the promoter regions of the mecA gene (-7 G/A or -33 C/T). The genomes of the Russian isolates differed from the globally spread ST59 by specific mutations at the following loci (relative to the reference genome of S. aureus M013TW): lactose catabolism regulator RS03495 (N168D), ribosomal protein L28 (V47A), putative glyoxalase RS07825 (V42A), and the hypothetical protein RS13235 (K32E). Conclusions. Russian MRSA-ST59 isolates belong to the East Asian sublineage and are characterized by the presence of the enterotoxin B gene. Oxacillin susceptibility and borderline resistance to cefoxitin are specific characteristics of MRSA-ST59. OS-MRSA phenotypes have a risk of improper sensitivity testing leading to ineffective antibiotic treatment. Detection of mecA gene is the most accurate method for differentiating between MSSA and MRSA.

Vancomycin and daptomycin are first-line drugs for the treatment of complicated methicillin-resistant Staphylococcus aureus (MRSA) infections, including bacteremia. However, their effectiveness is limited not only by their resistance to each antibiotic but also by their associated resistance to both drugs. It is unknown whether novel lipoglycopeptides can overcome this associated resistance. Resistant derivatives from five S. aureus strains were obtained during adaptive laboratory evolution with vancomycin and daptomycin. Both parental and derivative strains were subjected to susceptibility testing, population analysis profiles, measurements of growth rate and autolytic activity, and whole-genome sequencing. Regardless of whether vancomycin or daptomycin was selected, most of the derivatives were characterized by a reduced susceptibility to daptomycin, vancomycin, telavancin, dalbavancin, and oritavancin. Resistance to induced autolysis was observed in all derivatives. Daptomycin resistance was associated with a significant reduction in growth rate. Resistance to vancomycin was mainly associated with mutations in the genes responsible for cell wall biosynthesis, and resistance to daptomycin was associated with mutations in the genes responsible for phospholipid biosynthesis and glycerol metabolism. However, mutations in walK and mprF were detected in derivatives selected for both antibiotics.

OXA-48 carbapenemases are frequently expressed by Klebsiella pneumoniae clinical isolates; they decrease the effectiveness of carbapenem therapy, particularly with meropenem. Among these isolates, meropenem-susceptible carbapenemase-producers may show decreased meropenem effectiveness. However, the probability of the emergence of resistance in susceptible carbapenemase-producing isolates and its dependence on specific K . pneumoniae meropenem MICs is not completely known. It is also not completely clear what resistance patterns will be exhibited by these bacteria exposed to meropenem, if they would follow the patterns of non-beta-lactamase-producing bacteria and other than beta-lactams antibiotics. These issues might be clarified if patterns of meropenem resistance related to the mutant selection window (MSW) hypothesis. To test the applicability of the MSW hypothesis to meropenem, OXA-48-carbapenemase-producing K . pneumoniae clinical isolates with MICs in a 64-fold range (from susceptible to resistant) were exposed to meropenem in a hollow-fiber infection model; epithelial lining fluid meropenem pharmacokinetics were simulated following administration of 2 grams every 8 hours in a 3-hour infusion. Strong bell-shaped relationships between the meropenem daily dose infused to the model as related to the specific isolate MIC and both the antimicrobial effect and the emergence of resistance were observed. The applicability of the MSW hypothesis to meropenem and carbapenemase producing K . pneumoniae was confirmed. Low meropenem efficacy indicates very careful prescribing of meropenem to treat K . pneumoniae infections when the causative isolate is confirmed as an OXA-48-carbapenemase producer.

The inoculum effect (IE) is a well-known phenomenon with beta-lactams. At the same time, the IE has not been extensively studied with carbapenem/carbapenemase inhibitor combinations. The antibiotic-to-inhibitor concentration ratio used in susceptibility testing can influence the in vitro activity of the combination. To explore the role of these factors, imipenem/relebactam and doripenem/relebactam MICs were estimated against six Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae strains at standard inocula (SI) and high inocula (HI) by two methods: with a fixed relebactam concentration and with a fixed, pharmacokinetic-based carbapenem-to-relebactam concentration ratio. The combination MICs at HI, compared to SI, increased with most of the tested strains. However, the IE occurred with only two K. pneumoniae strains regardless of the MIC testing method. The relationship between the MICs at SI and the respective inoculum-induced MIC changes was observed when the MICs were estimated at pharmacokinetic-based carbapenem-to-relebactam concentration ratios. Thus, (1) IE was observed with both carbapenem/relebactam combinations regardless of the MIC testing method; however, IE was not observed frequently among tested K. pneumoniae strains. (2) At HI, carbapenem/relebactam combination MICs increased to levels associated with carbapenem resistance. (3) Combination MICs determined at pharmacokinetic-based carbapenem-to-inhibitor concentration ratios predict susceptibility elevations at HI in KPC-producing K. pneumoniae.

Escherichia coli isolates from various sources from 2018 to 2019 were included in the study. Mcr-1 genes were found in two of 105 animal strains (2%) and seven of 928 human strains (0.8%). All mcr-1-positive strains showed a low level of resistance to colistin (MIC ranged from 4 to 8 µg/ml). Both strains isolated from animals remained sensitive to betalactam antibiotics and did not contain beta-lactamase genes. Beta-lactamases were absent only in one of the strains isolated from humans. Four strains were resistant to cephalosporins with sensitivity to carbapenems and carried class A (blaCTX-M-15 or blaCTX-M-1) or class C (blaCMY-2) extended-spectrum beta-lactamases genes. One strain showed resistance to cephalosporins and meropenem and contained four beta-lactamase genes: blaNDM-1, blaCTX-M-15, blaTEM-1B, and blaCMY-6. Only one strain isolated from animals remained sensitive to ciprofloxacin, the rest showed high level of resistance, had amino acid substitutions in the DNA gyrase genes or mutations leading to overexpression of the mdfA gene. In terms of resistance to aminoglycosides, the strains varied widely and carried up to four aminoglycoside-modifying enzyme genes. One strain isolated from humans showed resistance to tigecycline, but no genes conferring resistance to this antibiotic were found. The data obtained substantiate the need for extended studies on the molecular epidemiology of associated resistance to polymyxins and beta-lactams.

The paper presents optimized methods for PCR and sequence typing of Streptococcus pneumoniae. The serotype composition of pneumococci isolated from children under 5 years of age with infections of the upper respiratory tract was analyzed using optimized methods. Between 2016 and 2021, there was a decrease in the frequency of serotypes included in the pneumococcal 13-valent conjugate vaccine (PCV13) from 94.1 to 25.8%, mainly due to the 6ABCD serogroup and the 19F serotype. The coverage of serotypes circulating in children with PCV15 and PCV20 vaccines was 28.1% and 41.6% in 2021, respectively. During the study period, the number of non-vaccine serogroups 11AD and 15AF, as well as serotypes that are not detected under this capsular PCR typing protocol, increased most significantly.