Effects of аntimicrobials on <i>Pseudomonas aeruginosa</i> biofilm formation

Pseudomonas aeruginosa is one of the most problematic pathogens in medical institutions, which may be due to the ability of this microorganism to exist in a biofilm, which increases its resistance to antimicrobials, as well as its prevalence and survival ability in the external environment. This work aimed to evaluate the antimicrobial susceptibility of P. aeruginosa strains in planktonic and biofilm forms. We studied 20 strains of P. aeruginosa collected during 2018–2021 by specialists from the Laboratory of Microbiome and Microecology of the Scientific Centre for Family Health and Human Reproduction Problems. The identification of strains was carried out using test systems for differentiating gram-negative non-fermenting bacteria (NEFERMtest 24 Erba Lachema s.r.o., Czech Republic), and confirmed by mass spectrometric analysis and 16S rRNA gene sequencing. Antimicrobial activity was assessed by the degree of inhibition of cell growth in planktonic and biofilm forms (on a flat-bottomed 96-well plastic immunological plate). All clinical isolates of P. aeruginosa were biofilm formers, 47.6 % of the isolates were weak biofilm formers, and 52.4 % of the isolates were moderate biofilm formers. Planktonic cells and the forming biofilm of the tested P. aeruginosa strains were carbapenems-resistant. Biofilm formation was suppressed in more than 90 % of cases by the agents of the cephalosporin and aminoglycoside groups. Antimicrobial susceptibility of P. aeruginosa strains in the formed biofilm was significantly lower (p < 0.05). Carbapenems and cephalosporins did not affect the mature biofilms of the tested P. aeruginosa strains in more than 60 % of cases. Only non-beta-lactam antibiotics (ciprofloxacin and amikacin) suppressed the growth of planktonic cells and destroyed the mature biofilm. The revealed differences in the effect of the tested antimicrobials on the P. aeruginosa strains biofilms correlate with resistance to a number of antibiotics. To prevent biofilm formation in the hospital strains of P. aeruginosa, the use of ceftazidime may be recommended, and antimicrobials such as ciprofloxacin and amikacin may be used to affect mature biofilms of P. aeruginosa.

CRISPR Element Patterns vs. Pathoadaptability of Clinical Pseudomonas aeruginosa Isolates from a Medical Center in Moscow, Russia

Pseudomonas aeruginosa is a member of the ESKAPE opportunistic pathogen group, which includes six species of the most dangerous microbes. This pathogen is characterized by the rapid acquisition of antimicrobial resistance, thus causing major healthcare concerns. This study presents a comprehensive analysis of clinical P. aeruginosa isolates based on whole-genome sequencing data. The isolate collection studied was characterized by a variety of clonal lineages with a domination of high-risk epidemic clones and different CRISPR/Cas element patterns. This is the first report on the coexistence of two and even three different types of CRISPR/Cas systems simultaneously in Russian clinical strains of P. aeruginosa. The data include molecular typing and genotypic antibiotic resistance determination, as well as the phylogenetic analysis of the full-length cas gene and anti-CRISPR genes sequences, predicted prophage sequences, and conducted a detailed CRISPR array analysis. The differences between the isolates carrying different types and quantities of CRISPR/Cas systems were investigated. The pattern of virulence factors in P. aeruginosa isolates lacking putative CRISPR/Cas systems significantly differed from that of samples with single or multiple putative CRISPR/Cas systems. We found significant correlations between the numbers of prophage sequences, antibiotic resistance genes, and virulence genes in P. aeruginosa isolates with different patterns of CRISPR/Cas-elements. We believe that the data presented will contribute to further investigations in the field of bacterial pathoadaptability, including antimicrobial resistance and the role of CRISPR/Cas systems in the plasticity of the P. aeruginosa genome.

Simulation of bacterial biofilms and estimation of the sensitivity of healthcare-associated infection pathogens to bactericide Sekusept active

The effect of bactericide Sekusept active (B SA), a peracetic acid-based preparation, on microbial strains, isolated from patients with severe infectious diseases who were treated in a regional children's multi-specialty hospital, was studied. Based on the biochemical identification, the strains were classified as gram-negative non-fermenting bacteria (22 strains), Enterobacteriaceae family (18 strains), and bacilli - 3 strains. The biocidal activity of B SA was evaluated by the degree of inhibition of the growth of bacterial cells, existing in the planktonic form and in the form of biofilm (on a flat-bottomed plastic immunological tablet). It was shown that all the studied strains had the ability to biofilm formation, most of them (67,4%) formed moderately pronounced biofilms, and non-fermenting bacteria had a particularly pronounced coefficient of biofilm formation. The selected concentrations of B CA inhibited the growth of planktonic cells, and the ability of bactericide to prevent the formation of biofilms depended on the concentration (the most effective concentrations were 0,8 and 3,0%). Sensitivity of the strains existed in the aged biofilm to the bactericide was significantly lower, especially resistant to this effect were biofilms formed by non-fermenting bacteria and representatives of fam. Enterobacteriaceae. Our results confirm the importance of testing the effectiveness of biocides not only in accordance with standard methods developed for microorganisms in planktonic form, but also for biofilms.

Susceptibility of clinical Enterobacterales and Pseudomonas aeruginosa isolates to ceftazidimeavibactam in Russia: multicenter local laboratory databased surveillance

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/).

[The problem of global development of antibiotic resistant nosocomial pathogens]

The problem of global expansion of multidrug-resistant nosocomial infections pathogens is under special attention at the moment. Antibiotic resistance increasing give us the limited treatment options. This problem is particularly acute for transplant clinics, because of patients need lifelong immunosuppressive therapy. From the one hand this ensures stable allograft functioning, but from the other increases the risk of severe infectious complications in the postoperative period. The purpose of this article is analysis carbapenem resistance dynamics of Klebsiella spp., Acinetobacter spp., Pseudomonas spp. and Staphylococcus spp. isolated from the blood of recipients of donor organs from 2009 to 2019 in the Shumakov National Medical Research Center of Transplantology and Artificial Organs. A significant annual decrease of carbapenem-sensitive strains of Klebsiella spp. and Acinetobacter spp. are shown. The study of a distinctive pathogen resistance profile specific to each institution can help one in selecting an adequate antimicrobial strategy and is an effective predictive tool for controlling the growth of multidrug-resistant microorganisms.

[Structure of microorganisms isolated from bronhoalveolar lavage from patients in the department of reanimation and intensive therapy.]

The aim of the work was to determine and compare the structure of microorganisms isolated from bronchoalveolar lavage from patients in the ICU of Clinics in 2016 and 2019. This work presents the results of a bacteriological examination of 229 samples from 139 patients for 2016 and 387 samples from 218 patients for 2019. The predominant microorganism in 2016 was Acinetobacter baumanii - 75 (26.2%). Less common were Klebsiella pneumoniae - 55 (19.2%), Pseudomonas aeruginosa - 35 (12.2%), Escherichia coli - 19 (6.6%). In 2019, the prevailing microorganism was K.pneumoniae - 158 (19.1%). As in 2016, A.baumanii - 115 (13.9%) and P. aeruginosa - 57 (6.9%) were most often found, but unlike 2016, in 2019 there was a high incidence of such pathogens as Enterococcus faecalis - 52 (6.3%), Candida albicans - 43 (5.2%), Staphylococcus aureus and Stenotrophomonas maltophilia - 40 (4.8%). One of the features is the presence of polymicrobial associations. In 2016, microorganisms isolated in monoculture predominated (53.4%), while in 2019 the frequency of occurrence of monocultures decreased and amounted to 24.7%. At the same time, a two-component association prevailed (31.5%). Thus, in ICU it is necessary to regularly monitor nosocomial pathogens not only to make the right decision when choosing antimicrobial therapy, but also to identify new potential nosocomial pathogens.