Rapid identification of Bacillus anthracis by real-time PCR with dual hybridization probes in environmental swabs

Spanish Outbreak Isolates Bridge Phylogenies of European and American Bacillus anthracis

The geographical origin of a major present-day phylogenetic group (A branch WNA; A.Br.WNA) of American Bacillus anthracis is controversial. One hypothesis postulated that the anthrax pathogen reached North America via a then-existing land bridge from northeastern Asia thousands of years ago. A competing hypothesis suggested that B. anthracis was introduced to America a couple of hundred years ago, related to European colonization. The latter view is strongly supported by genomic analysis of a group of French B. anthracis isolates that are phylogenetically closely related to the North American strains of the A branch A.Br.WNA clade. In addition, three West African strains also belong to this relationship group. Recently, we have added a Spanish strain to these close relatives of the WNA lineage of American B. anthracis. Nevertheless, the diversity of Spanish B. anthracis remains largely unexplored, and phylogenetic links to European or American relatives are not well resolved. Here, we genome sequenced and characterized 29 new B. anthracis isolates (yielding 18 unique genotypes) from outbreaks in west central and central Spain in 2021. Applying comparative chromosomal analysis, we placed the chromosomes of these isolates within the established phylogeny of the A.Br.008/009 (A.Br.TEA) canonical SNP group. From this analysis, a new sub-clade, named A.Br.11/ESPc, emerged that constitutes a sister group of American A.Br.WNA.

Real-Time Polymerase Chain Reaction: Current Techniques, Applications, and Role in COVID-19 Diagnosis

Successful detection of the first SARS-CoV-2 cases using the real-time polymerase chain reaction (real-time PCR) method reflects the power and usefulness of this technique. Real-time PCR is a variation of the PCR assay to allow monitoring of the PCR progress in actual time. PCR itself is a molecular process used to enzymatically synthesize copies in multiple amounts of a selected DNA region for various purposes. Real-time PCR is currently one of the most powerful molecular approaches and is widely used in biological sciences and medicine because it is quantitative, accurate, sensitive, and rapid. Current applications of real-time PCR include gene expression analysis, mutation detection, detection and quantification of pathogens, detection of genetically modified organisms, detection of allergens, monitoring of microbial degradation, species identification, and determination of parasite fitness. The technique has been used as a gold standard for COVID-19 diagnosis. Modifications of the standard real-time PCR methods have also been developed for particular applications. This review aims to provide an overview of the current applications of the real-time PCR technique, including its role in detecting emerging viruses such as SARS-CoV-2.

Phylogenetic Placement of Isolates Within the Trans-Eurasian Clade A.Br.008/009 of Bacillus anthracis

The largest phylogenetic lineage known to date of the anthrax pathogen Bacillus anthracis is the wide-spread, so-called Trans-Eurasian clade systematically categorized as the A.Br.008/009 group sharing two defining canonical single-nucleotide polymorphisms (canSNP). In this study, we genome-sequenced a collection of 35 B. anthracis strains of this clade, derived from human infections, animal outbreaks or soil, mostly from European countries isolated between 1936 and 2008. The new data were subjected to comparative chromosomal analysis, together with 75 B. anthracis genomes available in public databases, and the relative placements of these isolates were determined within the global phylogeny of the A.Br.008/009 canSNP group. From this analysis, we have detected 3754 chromosomal SNPs, allowing the assignation of the new chromosomal sequences to established sub-clades, to define new sub-clades, such as two new Spanish, one Bulgarian or one German group(s), or to introduce orphan lineages. SNP-based results were compared with that of a multilocus variable number of tandem repeat analysis (MLVA). This analysis indicated that MLVA typing might provide additional information in cases when genomics yields identical genotypes or shows only minor differences. Introducing the delayed mismatch amplification assay (DMAA) PCR-analysis, we developed a cost-effective method to interrogate for a set of ten phylogenetically informative SNPs within genomes of A.Br.008/009 canSNP clade strains of B. anthracis. By this approach, additional 32 strains could be assigned to five of ten defined clades.