Two Gram-negative, non-motile, non-spore-forming, coccoid bacteria (strains CCM 4915T and CCM 4916), isolated from clinical specimens of the common vole Microtus arvalis during an epizootic in the Czech Republic in 2001, were subjected to a polyphasic taxonomic study. On the basis of 16S rRNA (rrs) and recA gene sequence similarities, both isolates were allocated to the genus Brucella. Affiliation to Brucella was confirmed by DNA–DNA hybridization studies. Both strains reacted equally with Brucella M-monospecific antiserum and were lysed by the bacteriophages Tb, Wb, F1 and F25. Biochemical profiling revealed a high degree of enzyme activity and metabolic capabilities not observed in other Brucella species. The omp2a and omp2b genes of isolates CCM 4915T and CCM 4916 were indistinguishable. Whereas omp2a was identical to omp2a of brucellae from certain pinniped marine mammals, omp2b clustered with omp2b of terrestrial brucellae. Analysis of the bp26 gene downstream region identified strains CCM 4915T and CCM 4916 as Brucella of terrestrial origin. Both strains harboured five to six copies of the insertion element IS711, displaying a unique banding pattern as determined by Southern blotting. In comparative multilocus VNTR (variable-number tandem-repeat) analysis (MLVA) with 296 different genotypes, the two isolates grouped together, but formed a separate cluster within the genus Brucella. Multilocus sequence typing (MLST) analysis using nine different loci also placed the two isolates separately from other brucellae. In the IS711-based AMOS PCR, a 1900 bp fragment was generated with the Brucella ovis-specific primers, revealing that the insertion element had integrated between a putative membrane protein and cboL, encoding a methyltransferase, an integration site not observed in other brucellae. Isolates CCM 4915T and CCM 4916 could be clearly distinguished from all known Brucella species and their biovars by means of both their phenotypic and molecular properties, and therefore represent a novel species within the genus Brucella, for which the name Brucella microti sp. nov. with the type strain CCM 4915T (=BCCN 07-01T=CAPM 6434T) is proposed.

A Gram-negative, non-motile, non-spore-forming coccoid bacterium (strain BO1^T) was isolated recently from a breast implant infection of a 71-year-old female patient with clinical signs of brucellosis. Affiliation of strain BO1^T to the genus Brucella was confirmed by means of polyamine pattern, polar lipid profile, fatty acid profile, quinone system, DNA–DNA hybridization studies and by insertion sequence 711 (IS711)-specific PCR. Strain BO1^T harboured four to five copies of the Brucella-specific insertion element IS711, displaying a unique banding pattern, and exhibited a unique 16S rRNA gene sequence and also grouped separately in multilocus sequence typing analysis. Strain BO1^T reacted with Brucella M-monospecific antiserum. Incomplete lysis was detected with bacteriophages Tb (Tbilisi), F1 and F25. Biochemical profiling revealed a high degree of enzymic activity and metabolic capabilities. In multilocus VNTR (variable-number tandem-repeat) analysis, strain BO1^T showed a very distinctive profile and clustered with the other ‘exotic’ Brucella strains, including strains isolated from marine mammals, and Brucella microti, Brucella suis biovar 5 and Brucella neotomae. Comparative omp2a and omp2b gene sequence analysis revealed the most divergent omp2 sequences identified to date for a Brucella strain. The recA gene sequence of strain BO1^T differed in seven nucleotides from the Brucella recA consensus sequence. Using the Brucella species-specific multiplex PCR assay, strain BO1^T displayed a unique banding pattern not observed in other Brucella species. From the phenotypic and molecular analysis it became evident that strain BO1^T was clearly different from all other Brucella species, and therefore represents a novel species within the genus Brucella. Because of its unexpected isolation, the name Brucella inopinata with the type strain BO1^T (=BCCN 09-01^T=CPAM 6436^T) is proposed.

Yersinia pestis, the etiologic agent of the disease plague, has been implicated in three historical pandemics. These include the third pandemic of the 19^th and 20^th centuries, during which plague was spread around the world, and the second pandemic of the 14^th–17^th centuries, which included the infamous epidemic known as the Black Death. Previous studies have confirmed that Y. pestis caused these two more recent pandemics. However, a highly spirited debate still continues as to whether Y. pestis caused the so-called Justinianic Plague of the 6^th–8^th centuries AD. By analyzing ancient DNA in two independent ancient DNA laboratories, we confirmed unambiguously the presence of Y. pestis DNA in human skeletal remains from an Early Medieval cemetery. In addition, we narrowed the phylogenetic position of the responsible strain down to major branch 0 on the Y. pestis phylogeny, specifically between nodes N03 and N05. Our findings confirm that Y. pestis was responsible for the Justinianic Plague, which should end the controversy regarding the etiology of this pandemic. The first genotype of a Y. pestis strain that caused the Late Antique plague provides important information about the history of the plague bacillus and suggests that the first pandemic also originated in Asia, similar to the other two plague pandemics. Plague is a notorious and fatal human disease caused by the bacterium Yersinia pestis that is endemic in many countries around the world. Three of the most devastating pandemics in human history have been associated with plague. The second pandemic originated in central Asia and peaked in Europe between 1348 and 1350 (a period of time known as the Black Death). The third pandemic began in the Yunnan province of China in the mid-1850s and subsequently spread to Africa, the Americas, Australia, Europe, and other parts of Asia. The second and third pandemics are well documented and scientifically proven. However, the first pandemic, which began in the 6^th century and is also known as Justinianic Plague, is still a matter of controversy. Recently it has been suggested that Justinian's plague was not caused by Y. pestis. We detected Y. pestis DNA in samples obtained from multiple 6^th century skeletons from Germany. This confirms that Justinianic Plague crossed the Alps and affected local populations there, including current day Bavaria. Furthermore, we used DNA fingerprinting approaches to determine Asia as the likely geographic origin for these strains.

From the mandibular lymph nodes of wild red foxes (Vulpes vulpes) hunted in the region of Gmünd, Lower Austria, two gram-negative, oxidase- and urease-positive, coccoid rod-shaped bacteria (strains 257 and 284) were isolated. Cells were fast growing, nonmotile, and agglutinated with monospecific anti-Brucella (M) serum. Both strains were biochemically identified as Ochrobactrum anthropi by using the API 20NE test. However, sequencing of the 16S rRNA and recA genes clearly identified strains 257 and 284 as Brucella spp. Further molecular analysis by omp2a/b gene sequencing, multilocus sequence typing and multilocus variable number tandem repeats analysis revealed Brucella microti, a recently described Brucella species that has originally been isolated from diseased common voles (Microtus arvalis) in South Moravia, Czech Republic in 2000. Our findings demonstrate that B. microti is prevalent in a larger geographic area covering the region of South Moravia and parts of Lower Austria. Foxes could have become infected by ingestion of infected common voles.

The genus Brucella (Mayer and Shaw, 1920) currently consists often species with validly published names. Within most species further differentiation into biovars exists. Genetically, all Brucella species are highly related to each other, exhibiting sequence similarity values of 98% to 100% in aligned regions (core genome). The population structure is clonal. Despite this close genetic relatedness, the various species can be clearly distinguished from each other by application of high-resolution molecular typing tools, in addition to assessment of phenotype and host preference. Accurate species delineation can be achieved by conventional multiplex polymerase chain reaction (PCR), single nucleotide polymorphism (SNP) analysis and multilocus sequence typing (MLST) or multilocus sequence analysis (MLSA). The last is also suitable for phylogenetic reconstructions, owing to the highly clonal evolution of the different species. Highly discriminatory multilocus variable number of tandem repeats (VNTR) analysis (MLVA) allows both species delineation and differentiation of individual isolates and thus represents a perfect first-line toolfor molecular epidemiological studies within outbreak investigations. More recently,whole genome sequencing (WGS)and the resulting global genome-wide SNP analysis have become available. These novel approaches should help in further understanding the evolution, host specificity and pathogenicity of the genus Brucella.