Escherichia coli (E. coli) is a ubiquitous microorganism with pathogenic and saprophytic clones. The objective of this study was to evaluate the presence, virulence, antibiotic resistance and biofilm formation of E. coli in three industrial farms in Bulgaria, as well as their adjacent sites related to the utilization of manure (feces, wastewater in a separator, lagoons, means of transport, and soils). The isolation of single bacterial cultures was performed via standard procedures with modifications, and E. coli isolates were identified via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and polymerase chain reaction (PCR). The disk diffusion method was used to assess antimicrobial resistance, and PCR was used to detect genes for antibiotic resistance (GAR) (qnr, aac(3), ampC, blaSHV/blaTEM and erm) and virulence genes (stx, stx2all, LT, STa, F4 and eae). The protocol of Stepanović was utilized to measure the biofilm formation of the isolates. A total of 84 isolates from different samples (n = 53) were identified as E. coli. Almost all demonstrated antimicrobial resistance, and most of them demonstrated resistance to multiple antibiotics from different classes. No virulence genes coding the Shiga toxin or enterotoxins or those associated with enteropathogenicity were detected. No GAR from those tested for quinolones, aminoglycosides and macrolides were found. However, all isolates that were resistant to a penicillin-class antibiotic (56) had β-lactamase-producing plasmid genes. All of them had ampC, and 34 of them had blaTEM. A total of 14 isolates formed strongly adherent biofilms. These results in a country where the use of antibiotics for growth promotion and prophylaxis in farms is highly restricted corroborate that the global implemented policy on antibiotics in human medicine and in animal husbandry needs revision.

Lactococcosis caused by Lactococcus garvieae is a bacterial infection affecting fish with a considerable economic impact. Recently, L. garvieae has established itself as an opportunistic pathogen in humans. The aim of the current study was to test classical and molecular-biological methods for the identification of L. garvieae and examine antimicrobial susceptibility and capsule production, an important virulence factor. Additionally, tests for differentiation from closely related species, as well as epidemiological typing, were performed. In a period of 18 years (2002–2019), 24 isolates presumptively identified as L. garvieae were collected from Oncorhynchus mykiss and Salmo salar fish obtained either from retail stores or fish farms. In order to confirm the species, optimized PCR-based protocols were used. As a result, 21 of the tested strains were proved to be L. garvieae (n = 21). The remaining three isolates were Lactococcus lactis, Streptococcus iniae, and Enterococcus faecalis. Epidemiological typing by randomly amplified polymorphic DNA was performed. Except for a single KG+ isolate, all other strains belonged to the European capsular serotype KG−. All L. garvieae isolates showed susceptibility to all tested antibiotics with the exception of clindamycin, which was a diagnostic sign. A thorough optimization of diagnostic methods is essential to determining the etiology of specific infections affecting the personnel at risk in fish farms, the food industry, or within the broader community.

Climate change exerts an increasing impact on the health and resilience of honey bees through a combination of rising temperatures, altered precipitation patterns, and intensified parasitic and infectious pressure. The present study aims to analyze climatic conditions in Bulgaria for the period 2021–2024 and to evaluate the results of a national survey conducted among beekeepers, focusing on winter colony losses during the 2023/2024 season and the feeding strategies applied. The survey was carried out in 2024 among 70 beekeepers from 20 administrative regions of the country, managing a total of 8935 bee colonies. The data were analyzed using descriptive statistics and stratified by region. The reported average winter mortality was 2.22% (198 colonies), with pronounced territorial variability. The most frequently indicated self-reported probable cause of losses was bee diseases, with varroosis identified as the dominant factor. Analysis of management practices revealed widespread application of combined feeding schemes based on plant-derived supplementary feeds, primarily administered in spring (March–April) and late summer (August–September). The obtained results differ from published national data for 2024, according to which total colony losses reached 16.3%, while losses associated with mortality or severe demographic collapse accounted for 11.6%. Despite the limitations inherent to the survey-based approach and self-reported data, the results suggest that integrated management combining parasite control with targeted nutritional support through the use of Bulgarian herbal supplementary feeds may coincide with the winter survival patterns reported within the surveyed sample.

Urban areas and suburbs are facing many environmental problems, one of which is the increasing pollution due to the accumulation of cellulosic waste. This article presents a laboratory study on the microbial biodegradation processes of paper as a cellulosic substrate under anaerobic and mesophilic cultivation conditions. A bacterial consortium with cellulose-degrading activity, as well as 4 individual strains originating from a methanogenic anaerobic bioreactor (BRA), was isolated, identified, and characterized. The results demonstrated that the consortium degraded 57.14% of the cellulose matrix within 20 days. Among the individual colonies, colonies 1 and 2 (identified as Clostridium tertium and Agromyces rhizospherae) exhibited lower activities (35.37% and 34.79%, respectively), while colony 3 (Clostridium paraputrificum) displayed the highest activity (83.74%). The mixture of all four colonies achieved lower degradation (21.22%). The performed metagenomic analysis of the microbial consortium revealed a wide variety of different bacterial genera, among which Clostridium, Bacteroides, and Ruminiclostridium dominate, and the species Bacteroides oleiciplenus, Clostridium butyricum, and Ruminiclostridium papyrosolvens. Scanning electron microscopy visualized the adhesion and morphological features of the degrading microbial population. Additional experiments on the development of a laboratory model for the anaerobic biodegradation of cellulose were carried out in BRAs by using different working volumes. A maximal level of cellulose decomposition was achieved in the BRA with a working volume of 1 L, reaching 71.0% cellulose decomposition on day 20. Long-term storage studies confirmed the survival and well-preserved activity of the consortium and individual isolates, demonstrating their potential for the development of bioconversion technologies.