Teodora Vremera

Salmonella is a major foodborne pathogen, representing a significant public health concern across the European Union (EU), accounting for 39% of foodborne illness-related hospitalizations in 2022, with the highest rates observed in Romania, Cyprus, Greece, and Lithuania. This pilot study aimed to enhance the surveillance and characterization of Salmonella by implementing both phenotypic and genotypic methods for strain typing, as well as for the detection and confirmation of resistance to ciprofloxacin. Materials and methods: A total of 109 Salmonella strains from acute diarrheal cases in North-Eastern Romania were collected (January–August 2024). From these, 19 representative isolates were selected for molecular characterization, including Multi-Locus Sequence Typing (MLST) and the detection of ciprofloxacin resistance determinants. Whole-Genome Sequencing (WGS) was subsequently performed to confirm serotype identity and resistance markers. Results: The 19 isolates underwent Multi-Locus Sequence Typing (MLST) and ciprofloxacin resistance profiling, with Whole-Genome Sequencing (WGS) for confirmation. MLST identified S. Enteritidis (42.1%) as the predominant serotype, followed by S. Typhimurium, S. Livingstone, and S. Infantis. WGS confirmed serotypes in 15 isolates; 2 showed discrepancies with phenotypic results. Phenotypic resistance to ciprofloxacin was detected in 12/19 (63.2%) of the isolates, 6/12 presenting gyrA mutations (S83Y, D87G), and 2/12 strains presenting the plasmid-mediated qnrB19 gene.

The continuous variability of SARS-CoV-2 and the rapid waning of specific antibodies threatens the efficacy of COVID-19 vaccines. We aimed to evaluate antibody kinetics one year after SARS-CoV-2 vaccination with an mRNA vaccine in healthcare workers (HCW), with or without a booster. A marked decline in anti-Spike(S)/Receptor Binding Domain (RBD) antibody levels was registered during the first eight months post-vaccination, followed by a transitory increase after the booster. At three months post-booster an increased antibody level was maintained only in HCW vaccinated after a prior infection, who also developed a higher and long-lasting level of anti-S IgA antibodies. Still, IgG anti-nucleocapsid (NCP) fades five months post-SARS-CoV-2 infection. Despite the decline in antibodies one-year post-vaccination, 68.2% of HCW preserved the neutralization capacity against the ancestral variant, with a decrease of only 17.08% in the neutralizing capacity against the Omicron variant. Nevertheless, breakthrough infections were present in 6.65% of all participants, without any correlation with the previous level of anti-S/RBD IgG. Protection against the ancestral and Omicron variants is maintained at least three months after a booster in HCW, possibly reflecting a continuous antigenic stimulation in the professional setting.

This study investigated the evolution and epidemiology of the community-associated and multidrug-resistant Staphylococcus aureus clone European CC1-MRSA-IV. Whole-genome sequences were obtained for 194 European CC1-MRSA-IV isolates (189 of human and 5 of animal origin) from 12 countries, and 10 meticillin-susceptible precursors (from North-Eastern Romania; all of human origin) of the clone. Phylogenetic analysis was performed using a maximum-likelihood approach, a time-measured phylogeny was reconstructed using Bayesian analysis, and in silico microarray genotyping was performed to identify resistance, virulence-associated and SCCmec (staphylococcal cassette chromosome mec) genes. Isolates were typically sequence type 1 (190/204) and spa type t127 (183/204). Bayesian analysis indicated that European CC1-MRSA-IV emerged in approximately 1995 before undergoing rapid expansion in the late 1990s and 2000s, while spreading throughout Europe and into the Middle East. Phylogenetic analysis revealed an unstructured meticillin-resistant S. aureus (MRSA) population, lacking significant geographical or temporal clusters. The MRSA were genotypically multidrug-resistant, consistently encoded seh, and intermittently (34/194) encoded an undisrupted hlb gene with concomitant absence of the lysogenic phage-encoded genes sak and scn. All MRSA also harboured a characteristic ~5350 nt insertion in SCCmec adjacent to orfX. Detailed demographic data from Denmark showed that there, the clone is typically (25/35) found in the community, and often (10/35) among individuals with links to South-Eastern Europe. This study elucidated the evolution and epidemiology of European CC1-MRSA-IV, which emerged from a meticillin-susceptible lineage prevalent in North-Eastern Romania before disseminating rapidly throughout Europe.