Prevalence and prognosis of PIK3CA mutations in Bulgarian patients with metastatic breast cancer receiving endocrine therapy in first-line setting

BACKGROUND AND AIMS

In approximately 40% of patients with HER2-negative/HR-positive breast cancer tumors, the PIK3CA gene is mutated. Despite this, clinical outcomes vary between studies in this cohort. We aimed to ascertain the prevalence of PIK3CA mutations in patients with metastatic HR+/HER2- breast in Bulgaria, as well the evaluation and comparison of progression free survival (PFS) between wild-type (WT) and mutation-positive groups in the real-world setting.

METHODS

Three oncology centers in Bulgaria collected 250 tissue samples between 2016 and 2022 for this multicentric retrospective study. PIK3CA mutations were identified using Real-Time qPCR. The median follow-up period was 35 months.

RESULTS

The mean age of the mutant cohort was 57.6 ± 11.6 years, compared to 56.5 ± 12.2 years for the WT cohort (p = .52). The percentage of patients with visceral metastasis was 58.8% (n = 147). Approximately 84.3% (n = 210) of the patients had reached postmenopause. 29.2% (n = 73) of the patients had PIK3CA mutations. The predominant mutation was present in exon 20, H1047R (46.5%). We found a significant correlation only between the presence of a mutation and the metastatic diseases at diagnosis (p = .002). As first-line therapy, 67.1% of patients received endocrine therapy (ET) plus cyclin dependent kinase (CDK4/6) inhibitor, while the remainder received ET alone. The median PFS of patients in the group with the mutation was 32 months (95%, CI: 22-40) compared to 24 months in the WT cohort ((95%, CI: 21-36) (p = .45)); HR = 0.86 (95%, CI: 0.5-1.3) (p = .46). We corroborated our conclusion using propensity matching score analysis, (36 months [95% CI: 20-40] vs. 26 months [95% CI: 21-38], [p = .69]).

CONCLUSIONS

We found that the prevalence of PIK3CA mutations in our patients was comparable to what has been reported in other nations. Our results suggest that PIK3CA mutational status has no bearing to ET efficacy in first-line setting.

Conjugative Plasmid pPPUT-Tik1-1 from a Permafrost Pseudomonas putida Strain and Its Present-Day Counterparts Inhabiting Environments and Clinics

A novel group of conjugative plasmids of Pseudomonas is characterized. The prototype plasmid pPPUT-Tik1-1 (153,663 bp), isolated from a permafrost strain of P. putida Tik1, carries a defective mercury transposon, Tn501, and a streptomycin resistance transposon, Tn5393. Ten plasmids and 34 contigs with backbone regions closely related to pPPUT-Tik1-1 have been found in GenBank. Two of these plasmids from clinical strains of P. putida and P. fulva are almost identical to the ancient plasmid. A characteristic feature of this group of plasmids is the presence of two genes encoding the initiators of replication (repA1 and repA2). None of these genes have high similarity with plasmid replication genes belonging to known incompatibility groups. It has been demonstrated that while pPPUT-Tik1-1-like plasmids have homologous backbone regions, they significantly differ by the molecular structure and the predicted functions of their accessory regions. Some of the pPPUT-Tik1-1-related plasmids carry determinants of antibiotic resistance and/or heavy metal salts. Some plasmids are characterized by the ability to degrade xenobiotics. Plasmids related to pPPUT-Tik1-1 are characterized by a narrow host range and are found in various species of the Pseudomonas genus. Interestingly, we also found shorter plasmid variants containing the same replication module, but lacking conjugation genes and containing other structural changes that strongly distinguish them from plasmids related to pPPUT-Tik1-1, indicating that the structure of the replication module cannot be used as the sole criterion for classifying plasmids. Overall, the results suggest that the plasmids of the novel group can be spread using conjugation in environmental and clinical strains of Pseudomonas and may play diverse adaptive functions due to the presence of various accessory regions.

Ubiquitous Conjugative Mega-Plasmids of Acinetobacter Species and Their Role in Horizontal Transfer of Multi-Drug Resistance

Conjugative mega-plasmids play a special role in adaptation since they carry a huge number of accessory genes, often allowing the host to develop in new niches. In addition, due to conjugation they are able to effectively spread themselves and participate in the transfer of small mobilizable plasmids. In this work, we present a detailed characterization of a recently discovered family of multiple-drug resistance mega-plasmids of Acinetobacter species, termed group III-4a. We describe the structure of the plasmid backbone region, identify the rep gene and the origin of plasmid replication, and show that plasmids from this group are able not only to move between different Acinetobacter species but also to efficiently mobilize small plasmids containing different mob genes. Furthermore, we show that the population of natural Acinetobacter strains contains a significant number of mega-plasmids and reveal a clear correlation between the living conditions of Acinetobacter strains and the structure of their mega-plasmids. In particular, comparison of the plasmids from environmental and clinical strains shows that the genes for resistance to heavy metals were eliminated in the latter, with the simultaneous accumulation of antibiotic resistance genes by incorporation of transposons and integrons carrying these genes. The results demonstrate that this group of mega-plasmids plays a key role in the dissemination of multi-drug resistance among Acinetobacter species.

Genome Analysis of Acinetobacter lwoffii Strains Isolated from Permafrost Soils Aged from 15 Thousand to 1.8 Million Years Revealed Their Close Relationships with Present-Day Environmental and Clinical Isolates

Microbial life can be supported at subzero temperatures in permafrost up to several million years old. Genome analysis of strains isolated from permafrost provides a unique opportunity to study microorganisms that have not previously come into contact with the human population. Acinetobacter lwoffii is a typical soil bacterium that has been increasingly reported as hospital pathogens associated with bacteremia. In order to identify the specific genetic characteristics of ancient permafrost-conserved strains of A. lwoffii and their differences from present-day clinical isolates, we carried out a genome-wide analysis of five strains of A. lwoffii isolated from permafrost aged from 15 thousand to 1.8 million years. Surprisingly, we did not identify chromosomal genetic determinants that distinguish permafrost strains from clinical A. lwoffii isolates and strains from other natural habitats. Phylogenetic analysis based on whole genome sequences showed that permafrost strains do not form a separate cluster and some of them are most closely related to clinical isolates. The genomes of clinical and permafrost strains contain similar mobile elements and prophages, which indicates an intense horizontal transfer of genetic material. Comparison of plasmids of modern and permafrost strains showed that plasmids from the modern strains are enriched with antibiotic resistance genes, while the content of genes for resistance to heavy metals and arsenic is nearly the same. The thawing of permafrost caused by global warming could release new potentially pathogenic strains of Acinetobacter.

AB0636 ASYMPTOMATIC HYPERURICEMIA IN INFLAMMATORY RHEUMATIC DISEASES

Background:

Uric acid (UA) is well-known biomarker of cardiovascular risk and inflammation. However, the data about interrelations between asymptomatic hyperuricemia (AHU) and rheumatic diseases (RD) are limited and contradictory [1].

Objectives:

to identify the occurrence of AHU in pts with different RD and to evaluate the interrelations between the AHU and clinical features of the RD.

Methods:

The study included data from 822 pts with AHU and RD involved in the Saint-Petersburg Register of Pts with AHU in period from the 01jan2000 to the 01apr2020. The AHU was defined as the serum level of uric acid (UA) that exceeded 360 μmol/l without signs of gouty arthritis. Pts with the secondary reasons of AHU (an oncologic diseases, late stages of chronic kidney disease, ets), and inflammatory diseases another than RD were excluded from the study.

Patient’s demographical characteristics, duration of AHU, level of UA, activity of RD, ESR, CRP, urate-lowering therapy (ULT) were analyzed. The study was approved by local ethic committee. Statistics was performed with SPSS17.

Results:

Characteristics of the Patients with the RD and AHU are present in Table 1. The duration of AHU in pts with the RD was 3.4±3.4 [0.08-18] years, mean duration of follow-up 2.7±4.0 years, mean number of visits during the period of follow-up was 3,2 [min 1; max 7], ESR 26.0±14.1 mm / h, CRP 19.6±21.0 mg/l.

Table 1.

Characteristics of the Patients with the Rheumatic diseases and asymptomatic hyperuricemia.

Age, years(Mean±SD)Male, %**Serum UA, μmol/l(Mean±SD)Normalization of UA during the follow-up, n (%)RD, n=82256.7±14.540.27493.3±98.5242 (29.44) ##RA, n=32964.2±12.13.74504.8±107.5#99 (30.09) ##PsA, n= 14956.6±12.953.69531.5±94.9#32 (21.48) ##SpA, n= 10745.6±15.1*33.43520.8±86.5#18 (16.82)##SLE, n=13750.3±14.1*20.44451.6±91.457 (41.61)SSc, n= 5761.0±12.422.81456.2±99.520 (35.09)SD, n= 4362.0±10.716.28442.4±107.516 (37.21)

RD – rheumatic disease; RA –– rheumatoid arthritis; PsA –– psoriatic arthritis; SpA –– spondyloarthritis; SLE –– systemic lupus erythematosus; SSc –– systemic sclerosis; SD –– Sjogren’s disease; * –– p<0.001 for the differences with RD, RA, PsA, SSc, SD; ** –– p < 0.01 for all intergroup differences; # –– p < 0.01 for the differences with RD, RA, SSc, SD; ##–– p < 0.01 for the differences with RA, SSc, SD.

Were revealed the interrelations between the level of UA and ESR (Spearmen’s R=0.1, p=0.01), and UA and CRP (Spearmen’s R =0.12, p=0.001).

The level of UA in male pts was 507.0 [361-940], in female pts 450.0 [361-1010] μmol /l (p<0.0001), in SLE pts with elevated anti-nuclear factor (ANF) UA was 429 [361-940] and with normal 494 [361-973] (p<0.0001). In pts with high and low RD activity UA was 490 [361-940] and 454 [363-1010]) μmol /l respectively, (p<0.0001). The higher UA level was found in any RD as compared with UA in low activity of the same RD (p<0.0001 for all the differences).

Normalization of UA was found in 243 (29.6 %) pts, lack of normalization of UA in 434 (52.8 %) of cases, n = 677, Table 1. ULT received 219 (26.6 %) pts. Normalization of UA without ULT was registered in 16 (1.9 %) of the pts.

Conclusion:

UA level is higher and normalize less often in patients with SpA and PsA as compered with RA, SLA, SSc and SD pts. In any of analyzed rheumatic diseases the level of UA is higher in male pts and in pts with high disease activity.

References:

[1]K.Bosmansky, M. Ondrasik. Ter Arkh.1987;59(4):22-5.

Disclosure of Interests:

None declared.

Acinetobacter Plasmids: Diversity and Development of Classification Strategies

Bacteria of the genus Acinetobacter, with their numerous species common in various habitats, play a significant role as pathogens. Their ability to adapt to different living conditions is largely due to the presence of numerous plasmids containing the necessary adaptive genes. At the same time the diversity of Acinetobacter plasmids and their evolutionary dynamics have not been sufficiently studied. Here, we characterized 44 plasmids isolated from five permafrost Acinetobacter lwoffii strains, examined their relationship with plasmids of modern Acinetobacter strains and identified groups of related plasmids. For this purpose, we have developed a combined approach for classifying all known Acinetobacter plasmids. The classification took into account the size of plasmids, the presence and structure of the rep and mob genes, as well as the structure of their backbone and accessory regions. Based on the analysis, 19 major groups (lineages) of plasmids were identified, of which more than half were small plasmids. The plasmids of each group have common features of the organization of the backbone region with a DNA identity level of at least 80%. In addition, plasmids of the same group have similarities in the organization of accessory regions. We also described a number of plasmids with a unique structure. The presence of plasmids in clinical strains that are closely related to those of environmental permafrost strains provides evidence of the origin of the former from the latter.

DNA targeting and interference by a bacterial Argonaute nuclease

Members of the conserved Argonaute protein family use small RNA guides to locate their mRNA targets and regulate gene expression and suppress mobile genetic elements in eukaryotes^1,2. Argonautes are also present in many bacterial and archaeal species^3-5. Unlike eukaryotic proteins, several prokaryotic Argonaute proteins use small DNA guides to cleave DNA, a process known as DNA interference^6-10. However, the natural functions and targets of DNA interference are poorly understood, and the mechanisms of DNA guide generation and target discrimination remain unknown. Here we analyse the activity of a bacterial Argonaute nuclease from Clostridium butyricum (CbAgo) in vivo. We show that CbAgo targets multicopy genetic elements and suppresses the propagation of plasmids and infection by phages. CbAgo induces DNA interference between homologous sequences and triggers DNA degradation at double-strand breaks in the target DNA. The loading of CbAgo with locus-specific small DNA guides depends on both its intrinsic endonuclease activity and the cellular double-strand break repair machinery. A similar interaction was reported for the acquisition of new spacers during CRISPR adaptation, and prokaryotic genomes that encode Ago nucleases are enriched in CRISPR-Cas systems. These results identify molecular mechanisms that generate guides for DNA interference and suggest that the recognition of foreign nucleic acids by prokaryotic defence systems involves common principles.

Drug usage analysis in pregnant women

BACKGROUND

Drug usage in pregnant women is associated with a problem of possible negative influence on prenatal development. It is always necessary to judge the need for drug administration during pregnancy.

OBJECTIVE

The aim of presented study was to analyse data about pregnant women hospitalized in the postpartum period.

METHODS

The study was designed as a retrospective observational study including 300 women hospitalized at the 2nd Department of Gynaecology and Obstetrics, University Hospital, Bratislava. Data were obtained through questionnaires in form of an interview.

RESULTS

The average age of women was 30.79 ± 4.40 years. Risk pregnancy occured in 20.59 % of women. Chronic disorders before pregnancy required regular pharmacotherapy in 29.24 %. Drug usage analysis: I. trimester, 31 % used at least one drug, 52 % nutritional supplements, 63.3 % drug and/or nutritional supplement; II. trimester, 23 % used at least one drug, 45 % nutritional supplements, 58.3 % drug and/or nutritional supplement; III. trimester, 32 % used at least one drug, 67 % nutritional supplements, 75.3 % drug and/or nutritional supplement.

CONCLUSION

Drug usage during pregnancy requires great precaution at choosing pharmacotherapy. The benefit of pharmacotherapy should always outweight the potential risk of administered drug (Tab. 3, Fig. 3, Ref. 37).

Chromium resistance genetic element flanked by XerC/XerD recombination sites and its distribution in environmental and clinical Acinetobacter strains

A novel mobile genetic element has been identified in small plasmids isolated from permafrost strains of Acinetobacter lwoffii. This element, designated the chrAB dif module, contains the chromium resistance genes chrA and chrB, functionally active both in the original host strains and after transfer into Acinetobacter baylyi. The 3011 bp chrAB dif module is flanked by XerC/XerD recombination sites highly homologous to those of the site-specific recombination system dif/Xer. Analysis of public databases revealed almost identical variants of the chrAB dif module in different plasmids in strains of various Acinetobacter species predominantly inhabiting the environment (A. lwoffii, Acinetobacter indicus, Acinetobacter idrijaensis, Acinetobacter shindleri and Acinetobacter nosocomialis). Together with previously described Acinetobacter antibiotic resistance elements, the chrAB dif module defines a new group of mobile elements that rely on the dif/Xer system for their mobility. Our observations suggest an ancient origin of the mobile elements flanked by dif sites and their participation in the mobilization of plasmid genes bearing adaptive functions.

The ESC ACCA EAPCI EORP acute coronary syndrome ST-elevation myocardial infarction registry

Aims 

The Acute Cardiac Care Association (ACCA)–European Association of Percutaneous Coronary Intervention (EAPCI) Registry on ST-elevation myocardial infarction (STEMI) of the EurObservational programme (EORP) of the European Society of Cardiology (ESC) registry aimed to determine the current state of the use of reperfusion therapy in ESC member and ESC affiliated countries and the adherence to ESC STEMI guidelines in patients with STEMI.

Methods and results 

Between 1 January 2015 and 31 March 2018, a total of 11 462 patients admitted with an initial diagnosis of STEMI according to the 2012 ESC STEMI guidelines were enrolled. Individual patient data were collected across 196 centres and 29 countries. Among the centres, there were 136 percutaneous coronary intervention centres and 91 with cardiac surgery on-site. The majority of centres (129/196) were part of a STEMI network. The main objective of this study was to describe the demographic, clinical, and angiographic characteristics of patients with STEMI. Other objectives include to assess management patterns and in particular the current use of reperfusion therapies and to evaluate how recommendations of most recent STEMI European guidelines regarding reperfusion therapies and adjunctive pharmacological and non-pharmacological treatments are adopted in clinical practice and how their application can impact on patients’ outcomes. Patients will be followed for 1 year after admission.

Conclusion 

The ESC ACCA-EAPCI EORP ACS STEMI registry is an international registry of care and outcomes of patients hospitalized with STEMI. It will provide insights into the contemporary patient profile, management patterns, and 1-year outcome of patients with STEMI.

Adaptive dif Modules in Permafrost Strains of Acinetobacter lwoffii and Their Distribution and Abundance Among Present Day Acinetobacter Strains

The dif/Xer system of site-specific recombination allows resolution of chromosomal dimers during bacterial DNA replication. Recently, it was also shown to be involved in horizontal transfer of a few known Xer-dependent mobile elements. Here, we show that plasmids of various Acinetobacter species, including clinically important strains, often contain multiple pdif sites that are mainly located within their accessory regions. Chromosomes of Acinetobacter strains may also contain additional dif sites, and their similarity with plasmid pdif sites is higher than with the main chromosomal site dif1. We further identify putative mobile genetic elements containing pdif sites on both flanks of adaptive genes and analyze their distribution in Acinetobacter species. In total, we describe seven mobile elements containing genes with various adaptive functions from permafrost strains of A. lwoffii group. All of them are also spread in modern plasmids of different Acinetobacter species including A. baumannii. We could not detect pdif sites and corresponding mobile elements in closely related bacterial genera, including Psychrobacter and Moraxella. Thus, the widespread distribution of dif modules is a characteristic feature of Acinetobacter species and may contribute to their high adaptability both in the environment and in the clinic.

Correction to 'Intramolecular hydrogen bonds in 1,4-dihydropyridine derivatives'

[This corrects the article DOI: 10.1098/rsos.180088.].

Intramolecular hydrogen bonds in 1,4-dihydropyridine derivatives

1,4-Dihydropyridine (1,4-DHP) derivatives have been synthesized and characterized by 1H, 13C, 15N nuclear magnetic resonance (NMR) spectroscopy, secondary proton/deuterium 13C isotope shifts, variable temperature 1H NMR experiments and quantum-chemical calculation. The intramolecular hydrogen bonds NH⋯O=C and CH⋯O=C in these compounds were established by NMR and quantum-chemical studies The downfield shift of the NH proton, accompanied by the upfield shift of the 15N nuclear magnetic resonance signals, the shift to the higher wavenumbers of the NH stretching vibration in the infrared spectra and the increase of the 1J(15N,1H) values may indicate the shortening of the N-H bond length upon intramolecular NH⋯O=C hydrogen bond formation.

Professional burnout in European young oncologists: results of the European Society for Medical Oncology (ESMO) Young Oncologists Committee Burnout Survey

Background

Burnout in health care professionals could have serious negative consequences on quality of patient care, professional satisfaction and personal life. Our aim was to investigate the burnout prevalence, work and lifestyle factors potentially affecting burnout amongst European oncologists ≤40 (YOs).

Methods

A survey was conducted using the validated Maslach Burnout Inventory (MBI) and additional questions exploring work/lifestyle factors. Statistical analyses were carried out to identify factors associated with burnout.

Results

Total of 737 surveys (all ages) were collected from 41 European countries. Countries were divided into six regions. Results from 595 (81%) YOs were included (81% medical oncologists; 52% trainees, 62% women). Seventy-one percent of YOs showed evidence of burnout (burnout subdomains: depersonalization 50%; emotional exhaustion 45; low accomplishment 35%). Twenty-two percent requested support for burnout during training and 74% reported no hospital access to support services. Burnout rates were significantly different across Europe (P < 0.0001). Burnout was highest in central European (84%) and lowest in Northern Europe (52%). Depersonalization scores were higher in men compared with women (60% versus 45% P = 0.0001) and low accomplishment was highest in the 26-30 age group (P < 0.01). In multivariable linear regression analyses, European region, work/life balance, access to support services, living alone and inadequate vacation time remained independent burnout factors (P < 0.05).

Conclusions

This is the largest burnout survey in European Young Oncologists. Burnout is common amongst YOs and rates vary across Europe. Achieving a good work/life balance, access to support services and adequate vacation time may reduce burnout levels. Raising awareness, support and interventional research are needed.

Study of interactions of mononucleotides with 1,4-dihydropyridine vesicles using NMR and ITC techniques

The possible binding site of mononucleotides is the phosphate group with important hydrophobic interactions between the mononucleotides and the alkyl chains of DHP derivatives.

Tunable nanoporous silicon oxide templates by swift heavy ion tracks technology

Nanoporous silicon oxide templates formed by swift heavy ion tracks technology have been investigated. The influence of the heavy ion characteristics, such as type of ion, energy, stopping power and irradiation fluence on the pore properties of the silicon oxide templates, has been studied. Furthermore, the process of pore formation by chemical etching with hydrofluoric acid has been thoroughly investigated by assessing the effect of etchant concentration and etching time. The outcome of this investigation enables us to have precise control over the resulting geometry of nanopores arrays. As a result, guidelines for the creation of a-SiO2/Si templates with tunable parameters and general recommendations for their further application are presented.

The ancient small mobilizable plasmid pALWED1.8 harboring a new variant of the non-cassette streptomycin/spectinomycin resistance gene aadA27

The small mobilizable plasmid pALWED1.8 containing a novel variant of the streptomycin/spectinomycin resistance gene aadA27 was isolated from the permafrost strains of Acinetobacter lwoffii. The 4135bp plasmid carries mobА and mobC genes that mediate its mobilization by conjugative plasmids. The nucleotide sequences of mobА and mobC are similar to those of mobilization genes of the modern plasmid pRAY* and its variants, which contain aadB gene, and are widespread among the pathogenic strains of Acinetobacter baumannii. Almost identical pALWED1.8 variants were detected in modern environmental Аcinetobacter strains. A highly similar plasmid was revealed in a strain of Acinetobacter parvus isolated from mouse intestine. Furthermore, we discovered six previously unidentified variants of plasmids related to pALWED1.8 and pRAY* in public databases. In contrast to most known variants of aadA which are cassette genes associated with integrons, the aadA27 variant harbored by pALWED1.8 is a non-cassette, autonomously transcribed gene. Non-cassette aadA genes with 96% sequence identity to aadA27 were detected in the chromosomes of Acinetobacter gyllenbergii and several uncharacterized strains of Аcinetobacter sp. Moreover, we revealed that the autonomous aadA-like genes are present in the chromosomes of many gram-positive and gram-negative bacteria. The phylogenetic analysis of amino acid sequences of all identified AadA proteins showed the following: (i) cassette aadA genes form a separate monophyletic group and mainly reside on plasmids and (ii) chromosomal non-cassette aadA genes are extremely diverse and can be inherited both vertical and via horizontal gene transfer.

Genetic structure and biological properties of the first ancient multiresistance plasmid pKLH80 isolated from a permafrost bacterium

A novel multidrug-resistance plasmid, pKLH80, previously isolated from Psychrobacter maritimus MR29-12 found in ancient permafrost, was completely sequenced and analysed. In our previous studies, we focused on the pKLH80 plasmid region containing streptomycin and tetracycline resistance genes, and their mobilization with an upstream-located ISPpy1 insertion sequence (IS) element. Here, we present the complete sequence of pKLH80 and analysis of its backbone genetic structure, including previously unknown features of the plasmid's accessory region, notably a novel variant of the β-lactamase gene blaRTG-6. Plasmid pKLH80 was found to be a circular 14 835 bp molecule that has an overall G+C content of 40.3 mol% and encodes 20 putative ORFs. There are two distinctive functional modules within the plasmid backbone sequence: (i) the replication module consisting of repB and the oriV region; and (ii) the mobilization module consisting of mobA, mobC and oriT. All of the aforementioned genes share sequence identities with corresponding genes of different species of Psychrobacter. The plasmid accessory region contains antibiotic resistance genes and IS elements (ISPsma1 of the IS982 family, and ISPpy1 and ISAba14 of the IS3 family) found in environmental and clinical bacterial strains of different taxa. We revealed that the sequences flanking blaRTG-6 and closely related genes from clinical bacteria are nearly identical. This fact suggests that blaRTG-6 from the environmental strain of Psychrobacter is a progenitor of blaRTG genes of clinical bacteria. We also showed that pKLH80 can replicate in different strains of Acinetobacter and Psychrobacter genera. The roles of IS elements in the horizontal transfer of antibiotic resistance genes are examined and discussed.

A new subgroup of the IS3 family and properties of its representative member ISPpy1

Recently, we described a novel insertion element, ISPpy1, isolated from a permafrost strain of Psychrobacter maritimus. In this work, we demonstrated that ISPpy1 is a member of a novel subgroup of the IS3 family of insertion sequences (ISs) that was not identified and characterized previously. IS elements of this subgroup termed the ISPpy1 subgroup are broadly distributed among different taxa of Eubacteria, including Geobacteraceae, Chlorobiaceae, Desulfobacteraceae, Methylobacteriaceae, Nitrosomonadaceae and Cyanobacteria. While displaying characteristic features of the IS3-family elements, ISPpy1 subgroup elements exhibit some unusual features. In particular, most of them have longer terminal repeats with unconventional ends and frameshifting box with an atypical organization, and, unlike many other IS3-family elements, do not exhibit any distinct IS specificity. We studied the transposition and mutagenic properties of a representative member of this subgroup, ISPpy1 and showed that in contrast to the original P. maritimus host, in a heterologous host, Escherichia coli K-12, it is able to translocate with extremely high efficiency into the chromosome, either by itself or as a part of a composite transposon containing two ISPpy1 copies. The majority of transposants carry multiple chromosomal copies (up to 12) of ISPpy1. It was discovered that ISPpy1 is characterized by a marked mutagenic activity in E. coli: its chromosomal insertions generate various types of mutations, including auxotrophic, pleiotropic and rifampicin-resistance mutations. The distribution of IS elements of the novel subgroup among different bacteria, their role in the formation of composite transposons and the horizontal transfer of genes are examined and discussed.