Search

Today, MALDI-ToF MS is an established technique to characterize and identify pathogenic bacteria. The technique is increasingly applied by clinical microbiological laboratories that use commercially available complete solutions, including spectra databases covering clinically relevant bacteria. Such databases are validated for clinical, or research applications, but are often less comprehensive concerning highly pathogenic bacteria (HPB). To improve MALDI-ToF MS diagnostics of HPB we initiated a program to develop protocols for reliable and MALDI-compatible microbial inactivation and to acquire mass spectra thereof many years ago. As a result of this project, databases covering HPB, closely related bacteria, and bacteria of clinical relevance have been made publicly available on platforms such as ZENODO. This publication in detail describes the most recent version of this database. The dataset contains a total of 11,055 spectra from altogether 1,601 microbial strains and 264 species and is primarily intended to improve the diagnosis of HPB. We hope that our MALDI-ToF MS data may also be a valuable resource for developing machine learning-based bacterial identification and classification methods. [ABSTRACT FROM AUTHOR]

Bacillus cereus is a ubiquitous spore-forming bacterium causing food spoilage. In this study, seventeen B. cereus were isolated from dairy processing equipment in Algeria and characterized. The pathogenic potential genes encoding hemolysin, nonhaemolytic enterotoxin, cytotoxin K and emetic toxin were investigated by PCR. Phylogeny and genetic markers for antimicrobial resistance and virulence were analyzed using whole-genome sequencing data using the Illumina MiSeq® technology. The identity of the isolated strains was confirmed as B. cereus sensu lato and the sequencing of the panC gene clustered 64.7% of them in phylogenetic group III and 35.3% in group IV. The results of PFGE showed that 8 (47.1%), 4 (23.5%), 3 (17.6%) and 2 (11.8%) were differentiated into four groups A, B, C and D, respectively. Each of the two panC phylogenetic groups contains two different types of isolates corresponding to PFGE group (A and C) and (B and D) for phylogenetic groups III and IV, respectively. None of the 14 isolates carried the emetic toxin (ces) gene, whereas other toxin genes were variably detected. Genotyping assigned all isolates to three different sequence types (ST 2226, ST1018 and ST1431) while one clonal complex (CC-142) was identified in three isolates. Hierarchical clustering with a threshold of 500 core genome single nucleotide polymorphism (cgSNPs) differences grouped the strains into three clusters while two strains were less than 20 SNPs different. Three B. cereus (25%) contained three enterotoxic HBL complex-encoding genes hblA/C/D. Enterotoxic NHE complex-encoding genes (nheA/B/C) and the ctyK1 gene were detected in all isolates. The overall results highlight the risk due to toxins produced by the B. cereus group in the food safety and dairy industries in Algeria. This study emphasized the potential of whole-genome sequencing for genotyping and predicting the virulence-associated genes and antimicrobial resistance. The present study will help to better assess the health and spoilage risk associated with B. cereus in dairy processing plants and to incorporate adequate preventive measures. [ABSTRACT FROM AUTHOR]

Francisella tularensis, a category A bioterrorism agent, causes tularemia in many animal species. F. tularensis subspecies tularensis (type A) and holarctica (type B) are mainly responsible for human tularemia. The high mortality rate of 30–60 % caused by F. tularensis subspecies tularensis if left untreated and the aerosol dispersal renders this pathogen a dangerous bioagent. While a live attenuated vaccine strain (LVS) of F. tularensis type B does not provide sufficient protection against all forms of tularemia infections, a significant level of protection against F. tularensis has been observed for both passive and active immunization of mice with isolated O‐antigen capsular polysaccharide. Well‐defined, synthetic oligosaccharides offer an alternative approach towards the development of glycoconjugate vaccines. To identify diagnostics and therapeutics leads against tularemia, a collection of F. tularensis strain 15 O‐antigen capsular polysaccharide epitopes were chemically synthesized. Glycan microarrays containing synthetic glycans were used to analyze the sera of tularemia‐infected and non‐infected animals and revealed the presence of IgG antibodies against the glycans. Two disaccharide (13 and 18), both bearing a unique formamido moiety, were identified as minimal glycan epitopes for antibody binding. These epitopes are the starting point for the development of diagnostics and therapeutics against tularemia. [ABSTRACT FROM AUTHOR]

Introduction. Streptococcus uberis is a common cause of mastitis in cattle, leading to significant economic losses. The widespread use of antimicrobials has contributed to the emergence of resistance, which poses a severe challenge in controlling S. uberis infection. Aim. The objective of this study was to gain insights into the antimicrobial resistance (AMR) and epidemiological typing of S. uberis isolated from milk collected from bovine mastitis on dairy farms in Thuringia. Methodology. In this study, 84 S. uberis isolates were obtained from cattle with clinical mastitis in Thuringia, their phenotypic and genotypic AMR were analyzed and their phylogenetic relationship was explored using whole-genome sequencing. Results. Genetically heterogeneous strains were found on the farms, but clusters of highly similar strains also circulated within the same farms. All isolates were sensitive to ampicillin, penicillin, ceftiofur, and vancomycin. However, 42.9%, 42.9%, 22.6%, 19.0%, and 13.0% were resistant to tetracycline, doxycycline, clindamycin, pirlimycin, and erythromycin, respectively. Thirty-nine strains were phenotypically resistant to two or more tested antibiotics. We identified a plasmid associated with macrolide and lincosamide resistance in 12% of the strains. Conclusion. The emergence of S. uberis strains resistant to multiple antibiotics highlights the importance of S. uberis surveillance and the prudent use of antimicrobials.