The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has brought about significant challenges worldwide. In this study, we present a comprehensive analysis of the genomic epidemiology and lineage dynamics of SARS-CoV-2 in Bulgaria over a three-year period. Through extensive genomic sequencing and data analysis, we investigated the evolution of the virus, the emergence of variants of concern (VOCs), and their impact on the country’s pandemic trajectory. We also assessed the relationship between viral diversity and COVID-19 morbidity and mortality in Bulgaria. Our findings shed light on the temporal and spatial distribution of SARS-CoV-2 lineages and provide crucial insights into the dynamics of the pandemic in the country. The interplay between international travel and viral transmission plays a significant role in the emergence and dissemination of different SARS-CoV-2 variants. The observed proportions of exportation to various continents provide insights into the potential pathways through which these lineages spread globally. Understanding the genomic epidemiology of SARS-CoV-2 in Bulgaria is essential for formulating targeted public health strategies, enhancing vaccination efforts, and effectively managing future outbreaks.

Bloodstream infections (BSIs) are associated with substantial morbidity, mortality, and healthcare costs. Conventional diagnostics are limited by delayed results, often postponing appropriate antimicrobial therapy. This review aimed to evaluate the clinical and economic value of rapid microbiological diagnostics in BSI management. A state-of-the-art evidence synthesis was conducted using structured searches of PubMed/MEDLINE, Scopus, Web of Science, EconLit, and Google Scholar (2013–2025). Eligible studies included economic evaluations and clinical studies reporting downstream economic or resource-use outcomes. Screening and data extraction were performed by two reviewers, and findings were narratively synthesized. Fifty-nine studies were included. Rapid diagnostics consistently reduced time to pathogen identification and targeted therapy compared to conventional methods. Molecular platforms provided results within hours, while MALDI-TOF enabled identification within 30–60 min after culture positivity. Clinical benefits included earlier therapy optimization, reduced mortality, and shorter hospital stays, particularly when combined with antimicrobial stewardship programs (ASPs). Economic evaluations demonstrated improved cost-effectiveness, including reduced hospitalization, ICU utilization, and antimicrobial costs. MALDI-TOF with stewardship showed notable cost savings and improved outcomes. However, results varied depending on implementation context, infrastructure, and workflow integration. Rapid microbiological diagnostics offer significant clinical and economic benefits in BSI management, particularly when integrated with stewardship programs. Context-specific implementation is essential to maximize their value across healthcare systems.

Introduction: An effective vaccination strategy requires monitoring serotype changes by geography and age. This study analyzed Streptococcus pneumoniae serotypes in healthy children under 6 years of age vaccinated with PCV10 in Bulgaria from October 2021 to May 2025. Methods: A total of 569 children were screened for the lytA and cpsA genes viareal-time polymerase chain reaction (real-time PCR). Positive samples were typed using relevant kits, and 76 serotypes/serogroups of S. pneumoniae were identified. Results: Nasopharyngeal swabs from 232 children (40.8%) were found to carry S. pneumoniae, and a total of 255 serotypes were detected, with 19B/19C (17.2%), 6C (10.7%), and 15B/15C (9.8%) being the most prevalent. Of these, 91 serotypes (15.9%) were included in at least one vaccine, while the remaining 164 serotypes (25.4%) were not. The carriage rate reduced to 22% in 2023 but increased to 47% in 2024. Overall, younger children had lower carriage rates (p < 0.05), with serotype 6C being more common in children under 12 months of age (25%). Approximately 9.1% of pneumococcal carriage cases involved co-detected serotypes, with significantly higher co-detection rates for 19B/19C, 15B/15C, 10B, 10F/C, 23B, 7C/40, 23A, and 24A compared with mono-detection rates (p < 0.05). Conclusions: 19B/19C, 6C, 15B/15C, and 19A were identified as the main serotypes. Children over 3 years of age were also more likely to carry multiple pneumococci. These findings emphasize the need to reassess childhood vaccination strategies to curb the spread of antibiotic-resistant serotypes.

The first recombinant SARS-CoV-2 variants were identified in 2022, causing public health concerns. The importance of recombinant variants has increased especially since the WHO designated the recombinant variant XBB and its lineages as subvariants that require monitoring on 20 November 2022. In this study, we provide the first insights into the new SARS-CoV-2 variant named XAN, a recombinant composed of Omicron sub-lineages BA.2 and BA.5. To our knowledge, this is the first report on the recombinant SARS-CoV-2 XAN variant identified in Bulgaria.

Rapid diagnostic tests enable earlier pathogen identification in bloodstream infections compared with conventional culture-based methods and may improve clinical and economic outcomes, particularly when integrated with antimicrobial stewardship programs. Evidence suggests that while mortality benefits are context-dependent, rapid diagnostics can optimize antibiotic use and hospital resource allocation. The present study aimed to evaluate the clinical and economic impact of rapid diagnostic approaches compared with conventional microbiological culture in patients with confirmed bacteremia or fungemia hospitalized in a tertiary care setting in Bulgaria. A retrospective observational study was conducted between January 2015 and August 2020 at University Hospital “St. George,” Plovdiv. A total of 115 patients with confirmed bacteremia or fungemia were included and allocated to either a rapid diagnostic testing group (n = 77) or a standard culture group (n = 38). Mortality rates were comparable between groups (54.5% vs. 55.3%; OR 0.97, 95% CI 0.45–2.12; p = 0.942). Median length of stay was 20 days (12–35) in the rapid-test group versus 16 days (10–31) in the culture group (p = 0.505). Targeted antibiotic therapy duration was longer in the rapid-test group (median 12 vs. 6 days; p = 0.070). Median direct hospital costs were BGN 2319.40 versus BGN 1855.52, and indirect costs were BGN 19,388.80 versus BGN 15,511.04 (both p = 0.505). Diagnostic costs were significantly higher in the rapid-testing group (BGN 55.00 vs. BGN 38.00; p = 0.002). Rapid diagnostic testing produced clinical outcomes comparable to standard culture while demonstrating context-dependent economic differences in hospital resource utilization. Conclusions: Rapid diagnostic testing for bloodstream infections provides clinical outcomes comparable to standard culture-based methods while offering potential economic differences associated with the diagnostic strategy. When combined with antimicrobial stewardship interventions, rapid diagnostics support optimized antibiotic use and more efficient hospital resource utilization in critically ill patients.

Background: Rapid diagnostic tests (RDTs) for bloodstream infections (BSIs) reduce time to pathogen identification, yet evidence on their real-world economic and clinical value remains inconsistent. This study aimed to compare clinical outcomes, antibiotic utilization, and hospital costs associated with different rapid microbiological identification methods versus standard culture. Methods: A retrospective observational study was conducted in a tertiary university hospital including 115 hospitalized patients with suspected or confirmed BSIs. Multiplex PCR (mPCR), fluorescence in situ hybridization (FISH), and MALDI-TOF MS were compared with conventional culture. Outcomes included mortality, length of stay, antibiotic-days, and direct and indirect hospital costs. Nonparametric and exploratory adjusted analyses were performed. Results: No significant differences were observed across diagnostic groups for age, sex, mortality, or length of stay. Patients tested with mPCR showed higher empirical and total antibiotic-days and increased antibiotic-related costs (p < 0.05). Median direct and indirect hospital costs were numerically lower with FISH and mPCR but did not reach statistical significance. Adjusted analyses confirmed that diagnostic modality was not independently associated with mortality or costs. Conclusions: Rapid diagnostics accelerate identification but demonstrate heterogeneous downstream clinical and economic effects. Their value appears to depend more on local implementation and antimicrobial stewardship integration than on diagnostic speed alone.