The zoonotic Shiga toxin-producing Escherichia coli (STEC) group is unanimously regarded as exceptionally hazardous for humans. This study aimed to provide a genomic perspective on the STEC recovered sporadically from humans and have a foundation of internationally comparable data. Fifty clinical STEC isolates, representing the culture-confirmed infections reported by the STEC Reference Laboratory between 2016 and 2023, were subjected to whole-genome sequencing (WGS) analysis and sequences were interpreted using both commercial and public free bioinformatics tools. The WGS analysis revealed a genetically diverse population of STEC dominated by non-O157 serogroups commonly reported in human STEC infections in the European Union. The O26:H11 strains of ST21 lineage played a major role in the clinical disease resulting in hospitalisation and cases of paediatric HUS in Romania surpassing the O157:H7 strains. The latter were all clade 7 and mostly ST1804. Notably, among the Romanian isolates was a stx2a-harbouring cryptic clade I strain associated with a HUS case, stx2f- and stx2e-positive strains, and hybrid strains displaying a mixture of intestinal and extraintestinal virulence genes were found. As a clearer picture emerges of the STEC strains responsible for infections in Romania, further surveillance efforts are needed to uncover their prevalence, sources, and reservoirs.

Introduction: Hypervirulent Klebsiella pneumoniae (hvKp) is an emerging global pathogen that causes severe liver abscesses and metastatic infections. Despite rising concerns regarding multidrug-resistant convergence, molecular data in Romania remain limited. This study characterizes the epidemiological, clinical, and genomic profiles of hvKp liver abscesses in a tertiary hospital, aiming to describe the local virulence landscape and inform clinical management. Results: This study characterizes 15 cases of hvKp liver abscesses in a tertiary hospital. The cohort was predominantly male, with high rates of type 2 diabetes. Although clinical presentation was severe, featuring complications like endogenous endophthalmitis, the outcomes following prolonged antibiotic therapy were generally favorable. Phenotypically, 93.3% of isolates retained a wild-type susceptible profile, while a single ESBL-positive case highlighted the risk of resistance convergence. Genomic sequencing confirmed the presence of the ST23-K1 pandemic lineage carrying key virulence determinants (rmpA, iuc, and peg-344). Crucially, cgMLST analysis revealed genetic heterogeneity, suggesting sporadic community acquisition rather than a clonal nosocomial outbreak. Conclusions: These findings represent the first detailed molecular description of hvKp in Romania, confirming the local circulation of high-risk ST23 clones and underscoring the necessity for early detection and surveillance.

Invasive pneumococcal disease (IPD) results from the dissemination of Streptococcus pneumoniae to normally sterile anatomical sites such as the bloodstream or cerebrospinal fluid. One of the primary roles of pneumococcal conjugate vaccines (PCVs) used in Romania is to reduce the burden of pneumococcal disease. This single-center retrospective study provides an updated overview of IPD epidemiology in a Romanian tertiary hospital. We analyzed 67 IPD cases identified between 2017 and 2023, of which 45 isolates underwent whole-genome sequencing followed by multilocus sequence typing. Results of genome sequence analysis revealed a diverse population of pneumococci, underlining the importance of continuous genomic surveillance. Expanded-valency pneumococcal conjugate vaccines (PCVs), particularly PCV20, showed markedly improved serotype coverage compared to PCV7 and PCV13, while PCV21 showed serotype coverage comparable to that of PCV13. Antimicrobial susceptibility testing revealed sustained resistance to beta-lactams, particularly among meningitis isolates, underscoring the need for targeted antibiotic stewardship and continuous monitoring of local resistance trends. Overall, these findings highlight the evolving epidemiology of invasive pneumococcal disease in Romania, in the post-PCV era, and the need to adapt vaccination and treatment strategies accordingly.

Recurrent urinary tract infections (UTIs) are frequently associated with persistent uropathogenic Escherichia coli (UPEC) lineages that combine antimicrobial resistance with virulence traits, contributing to treatment failure. Whole-genome sequencing was performed on 199 UPEC isolates recovered from patients with recurrent or difficult-to-treat UTIs for whom autovaccine therapy was recommended. Assemblies were analysed using AMRFinderPlus, VFDB, MOB-suite, mobile genetic element detection, serotyping, and clonotype assignment tools, MLST, cgMLST and SNP-based phylogenetic analyses. Recurrent urinary tract infections (UTIs) were associated with multiple pandemic UPEC lineages, including ST131, ST69, ST10 and the emerging ST1193. Genomic analyses identified acquired antimicrobial resistance genes in nearly 80% of isolates, including extended-spectrum β -lactamase (ESBL) genes such as bla _CTX-M-15 and bla _CTX-M-27 , alongside chromosomal resistance-associated mutations linked to fluoroquinolone resistance. All ST131 and ST1193 isolates fulfilled the molecular UPEC criteria, while all but one isolate was classified as extraintestinal pathogenic E. coli (ExPEC). MOB-suite plasmid prediction analysis showed that IncF replicons were the most common and frequently associated with ESBL genes. Almost half of the plasmids were predicted to be mobilizable or conjugative, and one third indicated multireplicon structures. Phylogenetic analyses identified the predominant ST131 O25: H4/CH40-30 and O16: H5/CH40-41 lineages, while most ST1193 isolates belonged to the O75: H5/CH14-64 lineage. Mobile genetic element profiling identified lineage-associated insertion sequence repertoires, class 1 integrons and distinct bla _CTX-M -associated genetic environments. The results indicate that recurrent UTIs in Romania are largely driven by globally disseminated ExPEC clones that combine ESBL production, fluoroquinolone resistance-associated mutations and virulence-associated traits. The detection of closely related isolates recovered in different collection years is consistent with the circulation of successful UPEC lineages within the studied population.

This study aimed to identify circulating lineages of the most prevalent human-associated Salmonella serotypes identified through routine surveillance in Romania between 2023 and 2025 and assess their role in the spread of antimicrobial resistance (AMR). A total of 271 isolates (217 S. Enteritidis, 28 monophasic S. Typhimurium, and 26 S. Typhimurium) were investigated using Illumina short-read sequencing. The isolates were assigned to 9 MLST sequence types (STs) and 109 core genome MLST complex types. The predominant STs were ST11 (96% in S. Enteritidis), ST19 (77% in S. Typhimurium), and ST34 (79% in monophasic S. Typhimurium). Overall, 148 isolates carried at least one AMR determinant, including 28 acquired genes and 6 gene mutations, conferring resistance to ten antimicrobial classes. Four percent of all isolates were predicted to be multidrug-resistant, often associated with determinants conferring tolerances to biocides and/or heavy metals. The most prevalent resistance markers were GyrA_D87Y in S. Enteritidis ST11 (94/217) and bla_TEM-1 in S. Typhimurium ST19 (7/26). Among monophasic S. Typhimurium ST34 isolates, the co-occurrence of bla_TEM-1, aph(3”)-Ib, aph(6)-Id, sul2, and tet(B) genes was common (17/28). The 43 predicted AMR plasmids were not shared across serotypes, except among those carrying the qnrB19 gene. These results provide a genomic baseline for AMR surveillance in Romania and strengthen the human surveillance component of national One Health efforts to control resistant Salmonella.