Objective. To study the prevalence and mechanisms of antibiotic resistance, including carbapenemase production, in clinical isolates of Klebsiella pneumoniae and Escherichia coli isolated in different regions of Russia as part of the sentinel multicenter surveillance study in 2020–2021, and to explore the population structure of K. pneumoniae and the impact of “high-risk clones” on antibiotic resistance. Materials and Methods. Consecutive, non-duplicate isolates of K. pneumoniae (n = 2503) and E. coli (n = 2055) isolated from various specimens (blood, cerebrospinal fluid, respiratory samples, urine, wound secretions, etc.) of hospitalized patients with clinical signs of infection in 55 hospitals of 29 cities of Russia were studied. Species identification of isolates was performed by matrix-assisted laser desorption/ ionization time-of-flight mass spectrometry (MALDI-TOF MS). Antibiotic susceptibilities were determined by serial broth microdilution or, in the case of fosfomycin, by agar dilution method, and results were interpreted according to EUCAST v13 MIC breakpoints. Carbapenemase production was determined phenotypically by carbapenem inactivation method (CIM), the presence of genes of the most common serine carbapenemases (KPC, OXA-48) and metallo-β-lactamases (VIM, IMP, NDM) was determined by real-time PCR. K. pneumoniae clinical isolates were genotyped and assigned to the known clonal complexes (CC) and sequence types (ST) using SNP typing and multilocus sequencing typing (MLST) methods. K- and O-serotypes, acquired resistance and virulence genes, and plasmids carrying these genes were characterized using whole-genome sequencing of selected isolates (n = 215). Results. The resistance rates of nosocomial/community-acquired isolates of K. pneumoniae were as follows: amoxicillin-clavulanate – 88.63⁄57.99%, piperacillin-tazobactam – 82.92⁄45.49%, cefotaxime – 87.74⁄56.97%, ceftazidime – 84.76⁄53.07%, cefepime – 81.43⁄49.18%, aztreonam – 1.63⁄53.28%, ceftazidime-avibactam – 30, 88⁄9.22%, ceftolozan-tazobactam – 70.06/31.35%, ertapenem – 72.10⁄28.69%, meropenem – 49.60⁄15.16%, imipenem – 44.54⁄13.73%, gentamicin – 60.82⁄30.33%, amikacin – 42.06/17.21%, ciprofloxacin – 85.10⁄49.39%; trimethoprimsulfamethoxazole – 74.38⁄48.16%, colistin – 5.96⁄2.25%. The resistance of nosocomial/outpatient isolates of E. coli were: ampicillin – 84.93⁄67.67%, amoxicillin-clavulanate – 57.37⁄39.73%, piperacillin-tazobactam – 19.48⁄8.70%, cefotaxime – 63.83⁄34.19%, ceftazidime – 45.32⁄20.34%, cefepime – 35.95⁄16.61%, aztreonam – 51.78⁄26.11%, ceftazidime-avibactam – 5.71⁄0.80%, ceftolozane-tazobactam – 11, 95⁄2.22%, ertapenem – 8.18⁄1.42%, meropenem – 5.17⁄0.53%, imipenem – 4.95⁄0.36%, gentamicin – 24.54⁄13.68%, amikacin – 5.49⁄1.42%, ciprofloxacin – 54, 14⁄32.50%, trimethoprim-sulfamethoxazole – 52.21⁄38.54%, fosfomycin – 2.48⁄1.43%, colistin – 1.60⁄1.07%, tigecycline – 6.35⁄3.11%. The frequency of carbapenemase production among K. pneumoniae nosocomial isolates was 65.32% (OXA-48 – 40.75%, NDM – 30.28%, KPC – 8.74%, OXA-48 + NDM – 10.62%, OXA-48 + KPC – 2.98%, NDM + KPC – 0.45%, OXA-48 + NDM + KPC – 0.20%). More than 70% of nosocomial isolates of K. pneumoniae belonged to only 7 major genetic lineages known as “high-risk international clones”: CC395 – 37.40%, CC23 – 9.59%, CC307 – 8.64%, CC147 – 7.61%, CC15 – 2.95%, CC258 – 2.92%, and CC11 – 2.41%. The population of community-acquired K. pneumoniae was characterized by significantly greater genetic diversity (Simpson diversity index: D = 0.919; 95% CI: 0.904 to 0.933) compared with the population of nosocomial strains (Simpson diversity index: D = 0.815; 95% CI: 0.802 to 0.827). Strains of the “hypervirulent” genetic lineage of K. pneumoniae CC23 were more common in community-acquired infections. Conclusions. The extremely high frequency of resistance to cephalosporins in K. pneumoniae (> 80%) and E. coli (> 60%), as well as the high frequency of combined resistance to aminoglycosides and fluoroquinolones precludes their empirical use for the treatment of serious nosocomial infections caused by these pathogens. K. pneumoniae shows a rapid increase in resistance to carbapenems, mainly due to the spread of carbapenemases of three major groups: OXA-48, NDM and KPC. The overall increase in the frequency of carbapenemase production is accompanied by the growing diversity of carbapenemases, the increasing prevalence of strains producing NDM and KPC enzymes and those co-producing multiple carbapenemases simultaneously. In community-acquired infections, the high prevalence of resistance to cephalosporins in E. coli (> 30%) and K. pneumoniae (> 50%) remains the most important problem.

Objective. To assess the in vitro activity of ceftazidime-avibactam against clinical Enterobacterales and Pseudomonas aeruginosa isolates in various regions of Russia based on results of local susceptibility testing by disk diffusion method. Materials and Methods. Overall, 160 laboratories located in 61 Russian cities participated in this surveillance during 2018-2020. All consecutive clinical isolates of Enterobacterales and Pseudomonas aeruginosa in each participating laboratory were included in the study. Ceftazidime-avibactam susceptibility testing was done by disc-diffusion method in accordance with current EUCAST recommendations. Susceptibility data for carbapenems and III-IV generation cephalosporins, as well as results of carbapenemases detection, were also reported, if available. All the data were recorded in electronic case report form developed on the OpenClinica online platform (www.openclinica.com). Data analysis and reporting were done using AMRcloud online platform (https://amrcloud.net/). Results. In total, we received information on antimicrobial susceptibility of 22,121 isolates, including 17,456 (78.9%) Enterobacterales and 4,665 (21.1%) P. aeruginosa. Less than 9% of Enterobacterales isolates were resistant to ceftazidime-avibactam. At the same time rates of resistance to ceftazidime, cefotaxime, cefepime, ertapenem, imipenem, and meropenem were 54.1%, 58.9%, 59.4%, 41.4%, 23.9%, and 21.3%. Among Enterobacterales the highest level of resistance to ceftazidime-avibactam was detected in K. pneumoniae (16.5%), lowest – in E. coli (2.1%). Some increase of resistance to ceftazidimeavibactam was noted during the study – from 7.8% in 2018-2019 to 9.6% in 2020 (p = 0.0001). Rate of resistance to ceftazidime-avibactam in P. aeruginosa was 33.1%. At the same time rates of resistance to ceftazidime, cefepime, imipenem, and meropenem were 51.1%, 54.5%, 50%, and 47.3%. During the study there was statistically significant decrease in resistance to ceftazidime-avibactam in P. aeruginosa (p = 0.0001). Resistance rates for all beta-lactams for both Enterobacterales and P. aeruginosa were higher in nosocomial isolates than in community-acquired isolates. Conclusions. Ceftazidime-avibactam demonstrated significantly higher in vitro activity against Enterobacterales and P. aeruginosa Russian clinical isolates comparing with commonly used carbapenems and extended spectrum cephalosporins. Access for all study data available at the AMRcloud online platform (https://amrcloud.net/ru/project/cazavi-1-2/).

Objective. To evaluate in vitro activity of biapenem and other clinically available carbapenems against Russian clinical isolates of Enterobacterales, Pseudomonas aeruginosa и Acinetobacter spp., including isolates with acquired fermentative mechanisms of resistance to β-lactams. Materials and Methods. A total of 3139 Enterobacterales isolates, 793 P. aeruginosa isolates and 634 Acinetobacter spp. isolates from hospitalized patients in 63 hospitals from 35 Russian cities were included in the study during 2018-2019. Minimal inhibitory concentrations (MIC) for biapenem and other antimicrobials were determined in accordance with ISO 20776-1:2006. Carbapenemases genes were detected by commercially available real-time PCR kits AmpliSens® MDR KPC/OXA-48-FL and AmpliSens® MDR MBL-FL (Central Research Institute of Epidemiology, Russia). Data analysis and reporting was performed using AMRcloud online platform (www.amrcloud.net). Results. For all tested Escherichia coli isolates MIC50/90 were 0.06/0.125 mg/l for biapenem, 0.125⁄0.25 mg/l for imipenem, and 0.06/0.06 mg/l for meropenem. When MIC50/90 for ertapenem (0.015/0.125 mg/l for all isolates tested) were comparable to those of biapenem, a greater number of nosocomial E. coli isolates had MIC >4 mg/l for ertapenem (3.6%) than for biapenem (2.6%). MIC50/90 of Klebsiella pneumoniae for biapenem were 0.5⁄16 mg/l, for both imipenem and meropenem – 0.5⁄32 mg/l, for ertapenem – 2⁄32 mg/l. Resistance to oxyimino-β-lactams had no significant influence on activity of biapenem against Enterobacterales isolates. For 321 carbapenemase-producing K. pneumoniae isolates (ОХА-48 – 63.9%, NDM – 27.7%) biapenem has shown no advantages over imipenem and meropenem. МПК50/90 for nosocomial and community-acquired P. aeruginosa isolates were 8⁄64 mg/l and 0,5⁄16 mg/l for biapenem, 8⁄128 mg/l and 1⁄16 mg/l – for imipenem, 16⁄64 mg/l and 0,5⁄32 mg/l – for meropenem. All carbapenems, including biapenem, had very low in vitro activity against carbapenemaseproducing P. aeruginosa isolates. МПК50/90 of Acinetobacter spp. were 64⁄128 mg/l for biapenem, 64⁄128 mg/l – for imipenem, and 128⁄128 mg/l – for meropenem. Conclusions. According to the MIC distributions and MICs50/90 values independently of the presence of fermentative mechanisms of resistance to β-lactams, in vitro activity of biapenem against Russian clinical isolates of Enterobacterales, P. aeruginosa and Acinetobacter spp. was comparable to those of imipenem and meropenem.

Objective. To evaluate in vitro activity of various macrolide antibiotics against a current collection of clinical isolates of Streptococcus pneumoniae and Streptococcus pyogenes isolated from patients with community-acquired infections in different regions of the Russian Federation. Materials and Methods. A total of 350 clinical isolates from patients with community-acquired infections, including 200 S. pneumoniae and 150 S. pyogenes, were included in the study. To further evaluate the in vitro activity of 16-member macrolides against erythromycin-resistant isolates (MIC ≥ 0.5 mg/L), a retrospective collection of 253 erythromycin-resistant S. pneumoniae and 112 S. pyogenes isolates was tested. Susceptibility to antimicrobials was determined by broth microdilution method in accordance with the recommendations of the European Committee on Antimicrobial Susceptibility Testing (EUCAST, v.14.0). Results. Resistant to 14- and 15-member macrolides erythromycin, clarithromycin, and azithromycin were 41.5%, 42% and 40.5% of S. pneumoniae isolates (MIC50/MIC90 values were 0.06/128, 0.03/128, and 0.125⁄128 mg/L, respectively). MIC50/MIC90 values for spiramycin and josamycin were 0.06/128 mg/L and 25⁄32 mg/L, respectively. When the previously used 1996 French Society for Microbiology (SFM) criteria (Ch, ≤ 1 mg/L; P, > 4 mg/L) were applied, 70.5% of S. pneumoniae isolates could be considered as susceptible to spiramycin. MIC value ≥0.5 mg/L accounted for 31.5% of isolates for spiramycin and 48% for josamycin. Among the retrospective collection of erythromycin-resistant S. pneumoniae isolates, 64.0% of isolates could be considered as resistant to spiramycin using the old SFM interpretative criteria; 74.9% of isolates had spiramycin MIC ≥ 0.5 mg/L. Among the S. pyogenes isolates, 19.3%, 22%, and 26.7% were resistant to the 14- and 15-member macrolides erythromycin, clarithromycin, and azithromycin (MIC50/MIC90 0.03/1, 0.03/2, and 0.06/8 mg/L, respectively). MIC50/MIC90 values for the 16-member macrolides spiramycin and josamycin were 0.25⁄0.5 mg/L and 0.125⁄0.5 mg/L, respectively. When the 1996 SFM criteria (S – ≤ 1 mg/L; R – > 4 mg/L) were applied, 94.7% of S. pyogenes isolates could be considered as susceptible to spiramycin; MIC values ≥ 0.5 mg/L had 15.3% of isolates for spiramycin and 16.5% for josamycin. Conclusions. The 16-member macrolide spiramycin can retain in vitro activity against a significant proportion of S. pneumoniae and S. pyogenes isolates resistant to 14- and 15-member macrolides, which should be taken into account when choosing therapy for infections caused by these microorganisms.

Objective. To study the antimicrobial susceptibility profile of Moraxella catarrhalis isolates from different regions of Russia in 2010–2021. Materials and Methods. The study included 352 isolates of M. catarrhalis isolated in 11 cities of Russia (Volgograd, Irkutsk, Kazan, Kirov, Moscow, Murmansk, Perm, Seversk, Togliatti, Tomsk, and Ulan-Ude) in 2010–2021. Identification was done by MALDI-TOF mass spectrometry. Antimicrobial susceptibility testing was determined by broth microdilution method in accordance with the ISO 20776-1:2020. Interpretation of results was done in accordance with EUCAST guidelines (v.14.0). Results. Most of the isolates were isolated from respiratory specimens: 225 (63.9%) from sputum, 49 (13.9%) from nasal swabs, 41 (11.6%) from sinus aspirates, 17 (4.8%) from bronchoalveolar lavage, 8 (2.3%) from middle ear fluid, 6 (1.7%) from pharyngeal swabs, and 5 (1.4%) from conjunctival secretions. All tested isolates were susceptible to beta-lactams for which interpretive criteria have been established (amoxicillin-clavulanate, cefixime, ceftriaxone, cefuroxime). The susceptibility to clarithromycin and azithromycin was 99.7% and 100%, respectively. Ciprofloxacin, levofloxacin and moxifloxacin were active against 98.9%, 99.2% and 99.7% of isolates tested, respectively. Susceptibility to tetracycline was 99.7% and to trimethoprim-sulfamethoxazole was 99.4% (92% of isolates susceptible, 7.4% – susceptible at increased exposure). Conclusions. In the Russian Federation there is a favorable situation regarding the susceptibility of M. catarrhalis to antimicrobials. Amoxicillin-clavulanic acid, cefixime, ceftriaxone, azithromycin, clarithromycin, ciprofloxacin, levofloxacin, moxifloxacin and tetracycline retain high in vitro activity

Objective. To determine the population structure of clinical P. aeruginosa isolates recovered from hospitals in different regions of Russia and to assess the role of high-risk clones in the dissemination of carbapenemases and carbapenem resistance. Materials and Methods. The study included consecutive, non-duplicate clinical isolates of P. aeruginosa (N = 1379) obtained from 55 hospitals across 30 Russian cities over a 24-month period. Species identification was performed using MALDI-TOF mass-spectrometry. Antimicrobial susceptibility testing was carried out by broth microdilution. The presence of acquired carbapenemase genes (VIM, IMP, NDM, GES-2/-5) was determined by real-time PCR. Subspecies typing and assignment to known sequence types (STs) and clonal complexes (CCs) were performed by identifying single nucleotide polymorphisms (SNPs) in seven chromosomal loci used in the multilocus sequence typing (MLST) scheme. Whole-genome sequencing (WGS) and resistance gene annotation were performed for selected isolates representing the main high-risk clones. Results. All P. aeruginosa isolates were assigned to 264 genetic lineages, among which four clonal complexes corresponding to internationally recognized high-risk clones were predominant: CC235 (13.05%), CC244 (7.11%), CC654 (5.51%), and CC357 (4.21%). Three of these lineages – CC235, CC357, and CC654 – showed significantly higher levels of resistance to most antibiotics, including carbapenems, and were more frequently associated with nosocomial than communityacquired infections. Carbapenemase production was detected in 14.5% of isolates (VIM, 11.02%; GES-5, 2.61%; IMP, 0.44%; NDM, 0.44%), with the majority of carbapenemase-producing strains belonging to CC235 (52.0%) and CC654 (35.0%). WGS data revealed that CC235 isolates collected from different regions of Russia exhibited the greatest diversity of resistance determinants, including carbapenemase genes VIM-2, GES-5, and IMP-1. In contrast, all CC654 isolates carried the VIM-2 metallo-β-lactamase gene and shared similar genotypic and phenotypic resistance profiles to various antibiotic classes. Compared with previous surveillance data from the Russia, a decreasing trend was observed in the proportion of CC235 isolates, including carbapenemase producers, while the prevalence of other high-risk clones within the P. aeruginosa population remained stable. Conclusions. Despite a decline in carbapenemase production frequency and overall carbapenem resistance, the data show that high-risk clones continue to serve as the main reservoirs and drivers of resistance dissemination, underscoring the importance of maintaining systematic molecular surveillance and control of their circulation.