Arcanobacterium bialowiezense sp. nov. and Arcanobacterium bonasi sp. nov., isolated from the prepuce of European bison bulls (Bison bonasus) suffering from balanoposthitis, and emended description of the genus Arcanobacterium Collins et al. 1983

Fecal and vaginal microbiota of vaccinated and non-vaccinated pregnant elk challenged with Brucella abortus

Introduction

Brucella abortus is the causative agent of brucellosis in cattle and in humans, resulting in economic losses in the agricultural sector and representing a major threat to public health. Elk populations in the American Northwest are reservoirs for this bacterium and transmit the agent to domestic cattle herds. One potential strategy to mitigate the transmission of brucellosis by elk is vaccination of elk populations against B. abortus; however, elk appear to be immunologically distinct from cattle in their responses to current vaccination strategies. The differences in host response to B. abortus between cattle and elk could be attributed to differences between the cattle and elk innate and adaptive immune responses. Because species-specific interactions between the host microbiome and the immune system are also known to affect immunity, we sought to investigate interactions between the elk microbiome and B. abortus infection and vaccination.

Methods

We analyzed the fecal and vaginal microbial communities of B. abortus-vaccinated and unvaccinated elk which were challenged with B. abortus during the periparturient period.

Results

We observed that the elk fecal and vaginal microbiota are similar to those of other ruminants, and these microbial communities were affected both by time of sampling and by vaccination status. Notably, we observed that taxa representing ruminant reproductive tract pathogens tended to increase in abundance in the elk vaginal microbiome following parturition. Furthermore, many of these taxa differed significantly in abundance depending on vaccination status, indicating that vaccination against B. abortus affects the elk vaginal microbiota with potential implications for animal reproductive health.

Discussion

This study is the first to analyze the vaginal microbiota of any species of the genus Cervus and is also the first to assess the effects of B. abortus vaccination and challenge on the vaginal microbiome.

Arcanobacterium buesumense sp. nov., isolated from an anal swab of a male harbour seal (Phoca vitulina)

A polyphasic taxonomic study was performed on an unidentified previously described Arcanobacterium -like Gram-positive strain 2701T isolated from an anal swab of a dead male harbour seal. Comparative 16S rRNA sequencing showed that the bacterium belonged to the genus Arcanobacterium in the family Arcanobacteriaceae . The genome sequence of the strain was obtained by Borowiak et al. []. The genome had a G+C content of 49 mol% and a total length of 1.94 Mb. The presence of the major menaquinone MK-9(H4) supported the affiliation of the isolate with the genus Arcanobacterium . The polar lipid profile consisted of diphosphatidylglycerol and an unidentified phospholipid as major components and two unidentified lipids, a further unidentified phospholipid, two unidentified phosphoglycolipids as well as phosphatidylglycerol. The major fatty acids were C16 : 0, C18 : 1 and C18 : 0. Biochemical and phylogenetic analyses clearly distinguished the isolate from other members of the genus Arcanobacterium and closely related other species. Based on these results, it is proposed that the unknown Arcanobacterium sp. strain 2701T should be classified as representing a novel species with the name Arcanobacterium buesumense sp. nov. The type strain is 2701T (=DSM 112952T=LMG 32446T).

Prevalence and Genetic Diversity of Trueperella pyogenes Isolated from Infections in European Bison (Bison bonasus)

Simple Summary

In the European bison, Trueperella pyogenes is associated with different suppurative infections of mainly the urogenital tract or with abscesses in various tissues. Our research showed that in the studied population of European bison in Poland, the prevalence of T. pyogenes infections is relatively high. The significant genetic diversity of isolated strains was observed. However, in a few cases, the same RAPD profile was obtained for strains isolated from individuals living in the same area. Our study indicated that different virulence factors are related to the pathogenicity of this bacterium. The results obtained in this study provide valuable data about the prevalence, pathogenicity and genetic diversity of T. pyogenes in the European bison. Thus, it improves the knowledge on treatment for the European bison’s health and proves the importance of continuous monitoring for the protection of these wild ruminants.

Abstract

Trueperella pyogenes is a Gram-positive bacterium causing purulent infections in many animal species, including the European bison. However, the data about the virulence and genetic relationships of T. pyogenes strains isolated from these wild ruminants are strongly limited. The aim of this study was to investigate the prevalence of T. pyogenes infections in the European bison, and to evaluate the genetic diversity of isolates from these animals. In the time span of 10 years, 328 European bison from 16 different locations were examined. The standard bacteriological methods were used for T. pyogenes isolation and identification from clinical specimens obtained from urogenital tract infections and abscesses of different locations. The presence of genes encoding known virulence factors was investigated by PCR, and the genetic diversity of T. pyogenes strains was examined with the RAPD-PCR method. The prevalence of T. pyogenes infections was 14.6%, and the pathogen was isolated from both female (47.9% of isolates) and male (52.1% of isolates) European bison. It should be highlighted that a considerable number of strains were isolated from the prepuce and penis infections. Therefore, the role of T. pyogenes in the pathogenesis of balanoposthitis should be seriously perceived. A total of 39 T. pyogenes strains were subjected to genetic characterization. All studied strains carried the plo gene, while the nanH (25.6%), nanP (23.1%), cbpA (7.7%), fimA (97.4%), fimC (69.2%), fimE (92.3%) and fimG (15.4%) genes were present with a variable frequency among the tested strains. The virulence genotype plo/fimA/fimC/fimE was dominant. RAPD-PCR typing showed a high level of genetic diversity among European bison T. pyogenes strains, and a total of 31 different RAPD profiles were distinguished. In a few cases, the same RAPD profile was found in strains obtained from animals living in the same area. This study provided the first data about the prevalence and genetic relationships of T. pyogenes in the Polish population of European bison. However, further epidemiological investigations are needed to understand the routes of transmission and dissemination of the pathogen in these wild animals.

Trueperella pecoris sp. nov. isolated from bovine and porcine specimens

A novel Gram-stain-positive bacterium was isolated from a purulent bovine milk sample, the bovine placenta from an abortion, the udder secretion of a heifer and the lung of a pig that had succumbed from suppurative bronchopneumonia in Switzerland from 2015 to 2019. The strains grew best under aerobic conditions with 5 % CO₂ and colonies were non-haemolytic and greyish-white. They were non-motile and negative for catalase and oxidase. The genomes of the four strains 19M2397^T, 15A0121, 15IMD0307 and 19OD0592 were obtained by sequencing. The results of phylogenetic analyses based on the 16S rRNA gene grouped them within the genus Trueperella in the family Arcanobacteriaceae. The genomes had DNA G+C contents of 61.2-62.2 mol% and showed digital DNA-DNA hybridization (dDDH) values of 21.4-22.8 % and average nucleotide identity (ANI) values of approximately 77 % to their closest relatives Trueperella pyogenes and Trueperella bernardiae. With respect to the presence in different livestock species we propose the name Trueperella pecoris sp. nov. The type strain is 19M2397^T (=CCOS 1952^T=DSM 111392^T), isolated from the udder secretion of a heifer diagnosed with summer mastitis in 2019.

Taxonogenomics description of Arcanobacterium urinimassiliense sp. nov., a new bacterial species isolated from urine sample

Strain Marseille-P3248т is a new species from the order Actinomycetales that was isolated from the urine sample of a girl aged 20 months with rotavirus gastroenteritis. It is a facultative anaerobic Gram-positive rod-shaped bacterium. Strain Marseille-P3248т exhibits 94.73% sequence similarity with Arcanobacterium pluranimalium strain M430/94/2, a phylogenetically related species with standing in nomenclature. Its genome size is 1 667 964 bp with 49.1% G + C content. Strain Marseille-P3248т (= CSURP3248) is the type strain of the new species Arcanobacterium urinimassiliense sp. nov.

Development of a novel Trueperella pyogenes-specific PCR assay

Trueperella pyogenes is an opportunistic pathogen that causes a wide variety of purulent infections. We recently isolated a T. pyogenes strain unable to be identified by the previously reported T. pyogenes pyolysin gene (plo)-specific PCR from the lung of a sheep with astasia. Sequence comparison of plo among representative strains revealed several nucleotide substitutions in the primer-annealing regions. As such substitutions were considered to be a reason for the low PCR specificity, we designed novel primers in conserved regions of plo. Under optimized conditions, the novel primers precisely identified all T. pyogenes strains tested, and no products were generated from any other bacterial strains, suggesting the usefulness of the novel PCR assay for the diagnosis of T. pyogenes infections.

Epidemiological analysis of Trueperella abortisuis isolated from cases of pig abortion of a single farm

The present study was designed to characterize six Trueperella (T.) abortisuis strains, cultured over a period of 5 months from fetus and abortion material of six pigs of a single farm in Mecklenburg-West Pomerania federal state, Germany. It was of interest to investigate the epidemiological relationships of the six strains among each other and whether a single bacterial clone was responsible for the abortion situation of the single farm. All six strains were identified phenotypically, by MALDI-TOF MS analysis and by phylogenetic analysis based on 16S rRNA gene and gap (encoding the glyceraldehyde 3-phosphate dehydrogenase) and tuf (encoding elongation factor tu) gene sequencing. Further genotypic comparison was performed using different genomic DNA fingerprint methods including BOX-PCR, (GTG)₅-PCR, and three RAPD-PCRs. The sequence analysis of the genes gap and tuf and the genomic DNA fingerprinting results revealed, as noval findings, that the six T. abortisuis strains cultured from a single farm represent six different bacterial clones showing a genetic variability of this bacterial species in the pig population. All six T. abortisuis strains were isolated in mixed culture with several other bacterial species. However, the T. abortisuis strain, generally found in high numbers, seemed to be responsible for the abortion situation in the farm.

Fudania jinshanensis gen. nov., sp. nov., isolated from faeces of the Tibetan antelope (Pantholops hodgsonii) in China

Two hitherto unknown bacteria (strains 313^T and 352) were recovered from the faeces of Tibetan antelopes on the Tibet-Qinghai Plateau, PR China. Cells were rod-shaped and Gram-stain-positive. The optimal growth conditions were at 37 °C and pH 7. The isolates were closely related to Actinotignum sanguinis (92.6 % 16S rRNA gene sequence similarity), Arcanobacterium haemolyticum (92.5 %), Actinotignum schaalii (92.4 %), Actinobaculum massiliense (92.2 %) and Flaviflexus huanghaiensis (91.6 %). Phylogenetic analyses showed that strains 313^T and 352 clustered independently in the vicinity of the genera Actinotignum, Actinobaculum and Flaviflexus, but could not be classified clearly as a member of any of these genera. Phylogenomic analysis also indicated that strains 313^T and 352 formed an independent branch in the family Actinomycetaceae. The major cellular fatty acids of the strains were C_16 : 0 and C_18 : 1ω9c. The polar lipids comprised diphosphatidylglycerol, phosphatidylinositol mannoside, phosphatidylglycerol, phosphatidylinositol and five unidentified components. The peptidoglycan contained lysine, alanine and glutamic acid. The respiratory quinone was absent. The whole-cell sugars included glucose and rhamnose. The DNA G+C content of strain 313^T was 60.6 mol%. Based on the low 16S rRNA gene sequence similarities, its taxonomic position in the phylogenetic and phylogenomic trees and its unique lipid pattern, we propose that strains 313^T and 352 represent members of a novel species in a new genus, for which the name Fudania jinshanensis gen. nov., sp. nov. is proposed. The type strain is 313^T (=CGMCC 4.7453^T=DSM 106216^T).

Genome-Based Taxonomic Classification of the Phylum Actinobacteria

The application of phylogenetic taxonomic procedures led to improvements in the classification of bacteria assigned to the phylum Actinobacteria but even so there remains a need to further clarify relationships within a taxon that encompasses organisms of agricultural, biotechnological, clinical, and ecological importance. Classification of the morphologically diverse bacteria belonging to this large phylum based on a limited number of features has proved to be difficult, not least when taxonomic decisions rested heavily on interpretation of poorly resolved 16S rRNA gene trees. Here, draft genome sequences of a large collection of actinobacterial type strains were used to infer phylogenetic trees from genome-scale data using principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families, and genera, as well as many species and a few subspecies were shown to be in need of revision leading to proposals for the recognition of 2 orders, 10 families, and 17 genera, as well as the transfer of over 100 species to other genera. In addition, emended descriptions are given for many species mainly involving the addition of data on genome size and DNA G+C content, the former can be considered to be a valuable taxonomic marker in actinobacterial systematics. Many of the incongruities detected when the results of the present study were compared with existing classifications had been recognized from 16S rRNA gene trees though whole-genome phylogenies proved to be much better resolved. The few significant incongruities found between 16S/23S rRNA and whole genome trees underline the pitfalls inherent in phylogenies based upon single gene sequences. Similarly good congruence was found between the discontinuous distribution of phenotypic properties and taxa delineated in the phylogenetic trees though diverse non-monophyletic taxa appeared to be based on the use of plesiomorphic character states as diagnostic features.

Modulation of the immune system during postpartum uterine inflammation

Postpartum uterine inflammation (endometritis) in the dairy cow is associated with lower fertility at both the time of infection and after the inflammation has resolved. We hypothesized that aberrant DNA methylation may be involved in the subfertility associated with uterine inflammation. The objective of this study was to characterize genome-wide DNA methylation and gene expression in the endometrium of dairy cows with subclinical endometritis (SCE). Endometrial tissues were obtained at 29 days postpartum ( n = 12), and microarrays were used to characterize transcription and DNA methylation. Analyses revealed 1,856 probes differentially expressed in animals with SCE ( n = 6) compared with controls (CON, n = 6, P < 0.05, Storey Multiple testing correction) and 2,976 probes with significant correlation between gene expression and bacteriology score. No significant associations among DNA methylation and gene expression were detected. Analysis of transcription data using the Database for Annotation, Visualization, and Integrated Discovery and Gene Set Enrichment Analysis identified several pathways and processes enriched in SCE cows, with the majority related to the immune response. Furthermore, the top ontology terms enriched in genes that had expression data correlated to bacteriology score were: Defense response, inflammatory response, and innate immune response. Gene expression profiles in cows with subclinical endometritis in this study indicate that the immune response is activated, potentially resulting in a local proinflammatory environment in the uterus. If this period of inflammation is prolonged it could result in tissue damage or failure to complete involution of the uterus, which may create a suboptimal environment for future pregnancy.

Flaviflexus huanghaiensis gen. nov., sp. nov., an actinobacterium of the family Actinomycetaceae

Strain H5T was isolated from a sediment sample collected from the coastal area of Qingdao, China. The cells were Gram-stain-positive, non-motile, straight or curved rods. The temperature range for growth was 20–37 °C and the pH for growth ranged from 6.5 to 9.0, with optimum growth occurring in the temperature range 28–30 °C and pH range 7.5–8.0. Growth occurred in the presence of 0–6 % (w/v) NaCl (optimum, 0–2 %). Strain H5T had MK-9, MK-9(H2) and MK-9(H4) as the major menaquinones and C18 : 1ω9c, C16 : 0, C14 : 0, C18 : 0 and C16 : 1ω9c as major fatty acids. The cell-wall peptidoglycan type was A5α l-Lys-l-Ala-l-Lys-d-Glu. The major polar lipids were phosphatidylglycerol (PG), an unknown phospholipid (PL1) and two unknown phosphoglycolipids (PGL1, PGL2). An unknown phospholipid (PL2) and two unknown glycolipids (GL1, GL2) were present in moderate to minor amounts in the polar lipid profile. The genomic DNA G+C content was 61.8 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain H5T represents a novel lineage in the family Actinomycetaceae . On the basis of phenotypic, physiological and molecular characteristics, it is proposed that the novel isolate should be classified as a novel species in a new genus: Flaviflexus huanghaiensis gen. nov., sp. nov., with strain H5T ( = DSM 24315T = CICC 10486T) as the type strain of the type species.

Actinomyces weissii sp. nov., isolated from dogs

Two Gram-positive, rod-shaped, non-spore-forming bacteria were isolated from the oral cavities of two dogs. On the basis of 16S rRNA gene sequence similarities both strains were shown to belong to the genus Actinomyces and were most closely related to Actinomyces bovis (97.3 % and 97.5 %, respectively). The polyamine profile of the two isolates and Actinomyces bovis DSM 43014T was composed of spermidine and spermine as the major components. Menaquinone MK-9 was the major compound in the quinone system of the two strains and Actinomyces bovis . The polar lipid profiles of strains 2298T and 4321 were almost identical, containing diphosphatidylglycerol as the major compound, and moderate to trace amounts of phosphatidylcholine, phosphatidylinositol, phosphatidylinositol-mannoside, phosphatidylglycerol and several unidentified lipids. A highly similar polar lipid profile was detected in Actinomyces bovis DSM 43014T supporting the affiliation of strains 2298T and 4321 to the genus Actinomyces . The typical major fatty acids were C16 : 0, C18 : 0 and C18 : 1ω9c. Fatty acids C14 : 0 and C18 : 2ω6,9c were found in minor amounts. The results of physiological and biochemical analyses revealed clear differences between both strains and the most closely related species of the genus Actinomyces . Thus, strains 2298T and 4321 represent a novel species, for which the name Actinomyces weissii sp. nov., is proposed, with strain 2298T ( = CIP 110333T = LMG 26472T = CCM 7951T = CCUG 61299T) as the type strain.

Phenotypic characteristics and virulence genotypes of Trueperella (Arcanobacterium) pyogenes strains isolated from European bison (Bison bonasus)

Trueperella (Arcanobacterium) pyogenes is an opportunistic animal pathogen, which in European bison is associated with different suppurative infections mainly of the urogenital tract. Little is known about the virulence of this bacterium and about the pathogenesis of infections. The main objective of this study was to determine phenotypic properties and virulence genotypes of the twenty-five T. pyogenes strains isolated from lesions in various tissues of free-living European bison. Classical bacteriological methods were used for phenotypic characterization. Genes encoding seven known and putative virulence factors of T. pyogenes were detected by PCR technique. Analysis of 16S rDNA partial sequences was performed to establish phylogenetic relationships of the isolated strains. All isolates showed typical morphological features of T. pyogenes and variable biochemical activity. Most of them displayed a strong positive effect in synergistic CAMP test. For all isolates the 16S rRNA gene partial sequence was identical to that of the T. pyogenes reference strain. All isolates carried the plo and fimA genes, while the nanH, nanP, cbpA, fimC and fimG genes were present in 40, 44, 12, 88 and 24% of the isolates, respectively. The T. pyogenes strains isolated from European bison represented various phenotypes and virulence genotypes, but there was no association between the investigated properties of the bacteria and the type of anatomopathological lesions from which they were isolated. These results indicate that the studied virulence factors of T. pyogenes are not significant determinants of the localization and type of infection caused by this bacterium.

Evaluation of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for species identification of bacteria of genera Arcanobacterium and Trueperella

In the present study matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) was evaluated for species identification of 98 bacteria previously classified phenotypically and genotypically to genera Arcanobacterium and Trueperella. Species identification was carried out by comparing the main spectra of each strain with the main spectra of reference strains of both genera and 3740 database entries included in the MALDI Biotyper 2.0 software package (Bruker Daltonik GmbH, Bremen, Germany). MALDI-TOF MS correctly identified (log (score) values ≥ 2.0) all investigated strains of the species A. (T.) bialowiezense (n=3), A. (T.) bonasi (n=7), A. haemolyticum (n=10), A. pluranimalium (n=1) and A. (T.) pyogenes (n=77). According to the present results MALDI-TOF MS had a comparable discriminating power than previously conducted tests on DNA level. Further studies with strains isolated from human infections would show the robustness of MALDI-TOF MS for identification of bacteria of these genera.

Distribution of Arcanobacterium pluranimalium in animals examined in veterinary laboratories in the United Kingdom

Arcanobacterium pluranimalium was first reported in 2001 for 2 isolates, from a harbor porpoise ( Phocoena phocoena) and a fallow deer ( Dama dama). The same organism was subsequently reported from ovine material. A review of material submitted to veterinary laboratories in the United Kingdom from a range of domestic and wild animals during the following years revealed that A. pluranimalium had been recovered from ovine specimens on 33 occasions. Twenty ovine isolates came from abortion material, 5 from semen samples, 3 from abscesses, 3 from viscera, and 1 case each of navel ill and peritonitis. The only other A. pluranimalium isolate recovered during the period was from a milk sample collected from a cow with mastitis. The findings of the current study suggest that sheep were the host most frequently affected by infection with A. pluranimalium with recovery most commonly made from abortion material.

Comparative chemotaxonomic and phylogenetic studies on the genus Arcanobacterium Collins et al. 1982 emend. Lehnen et al. 2006: proposal for Trueperella gen. nov. and emended description of the genus Arcanobacterium

The results of a study comparing the chemotaxonomic characteristics and phylogenetic positions of members of the genus Arcanobacterium indicated that the genus was not monophyletic and, therefore, was in need of taxonomic revision. Phylogenetically, the genus Arcanobacterium consisted of two distinct lines; a group comprising the species Arcanobacterium haemolyticum (the type species of the genus), A. hippocoleae, A. phocae and A. pluranimalium and a robust group consisting of the species A. abortisuis, A. bernardiae, A. bialowiezense, A. bonasi and A. pyogenes. On the basis of 16S rRNA signature nucleotide comparisons and menaquinone and phospholipid compositions, it is proposed that of these nine species only four, A. haemolyticum, A. hippocoleae, A. phocae and A. pluranimalium, should be affiliated with the genus Arcanobacterium and the species A. abortisuis, A. bernardiae, A. bialowiezense, A. bonasi and A. pyogenes should be reclassified as members of a new genus, Trueperella, as Trueperella abortisuis comb. nov., Trueperella bernardiae comb. nov., Trueperella bialowiezensis comb. nov., Trueperella bonasi comb. nov. and Trueperella pyogenes comb. nov. Positive results in Christie–Atkins–Munch-Petersen (CAMP) tests on A. haemolyticum, A. hippocoleae, A. phocae and A. pluranimalium also supported the rearrangement of the nine species in to separate genera. As such, an emended description of the genus Arcanobacterium is provided.

Core gene set as the basis of multilocus sequence analysis of the subclass Actinobacteridae

Comparative genomic sequencing is shedding new light on bacterial identification, taxonomy and phylogeny. An in silico assessment of a core gene set necessary for cellular functioning was made to determine a consensus set of genes that would be useful for the identification, taxonomy and phylogeny of the species belonging to the subclass Actinobacteridae which contained two orders Actinomycetales and Bifidobacteriales. The subclass Actinobacteridae comprised about 85% of the actinobacteria families. The following recommended criteria were used to establish a comprehensive gene set; the gene should (i) be long enough to contain phylogenetically useful information, (ii) not be subject to horizontal gene transfer, (iii) be a single copy (iv) have at least two regions sufficiently conserved that allow the design of amplification and sequencing primers and (v) predict whole-genome relationships. We applied these constraints to 50 different Actinobacteridae genomes and made 1,224 pairwise comparisons of the genome conserved regions and gene fragments obtained by using Sequence VARiability Analysis Program (SVARAP), which allow designing the primers. Following a comparative statistical modeling phase, 3 gene fragments were selected, ychF, rpoB, and secY with R²>0.85. Selected sets of broad range primers were tested from the 3 gene fragments and were demonstrated to be useful for amplification and sequencing of 25 species belonging to 9 genera of Actinobacteridae. The intraspecies similarities were 96.3–100% for ychF, 97.8–100% for rpoB and 96.9–100% for secY among 73 strains belonging to 15 species of the subclass Actinobacteridae compare to 99.4–100% for 16S rRNA. The phylogenetic topology obtained from the combined datasets ychF+rpoB+secY was globally similar to that inferred from the 16S rRNA but with higher confidence. It was concluded that multi-locus sequence analysis using core gene set might represent the first consensus and valid approach for investigating the bacterial identification, phylogeny and taxonomy.

Complete genome sequence of Arcanobacterium haemolyticum type strain (11018)

Arcanobacterium haemolyticum (ex MacLean et al. 1946) Collins et al. 1983 is the type species of the genus Arcanobacterium, which belongs to the family Actinomycetaceae. The strain is of interest because it is an obligate parasite of the pharynx of humans and farm animal; occasionally, it causes pharyngeal or skin lesions. It is a Gram-positive, nonmotile and non-sporulating bacterium. The strain described in this study was isolated from infections amongst American soldiers of certain islands of the North and West Pacific. This is the first completed sequence of a member of the genus Arcanobacterium and the ninth type strain genome from the family Actinomycetaceae. The 1,986,154 bp long genome with its 1,821 protein-coding and 64 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project.

Phenotypic and genotypic characterization of Arcanobacterium haemolyticum isolates from infections of horses

The present study was designed to characterize phenotypically and genotypically seven Arcanobacterium haemolyticum strains obtained from infections of six horses. All seven strains showed the cultural and biochemical properties typical of A. haemolyticum and were susceptible to most of the antibiotics tested. The species identification could be confirmed by amplification and sequencing of the 16S rRNA gene and the 16S-23S rRNA intergenic spacer region and by PCR amplification of species-specific parts of the gene encoding phospholipase D in A. haemolyticum. Use of the latter could possibly improve future identification of this generally human pathogenic bacterial species which, according to the present results, seems to occur also in infections of horses.

Isolation of Arcanobacterium hippocoleae from a case of placentitis and stillbirth in a mare

Based on the scarcity of reports in veterinary medicine literature, it appears that Arcanobacterium spp. are rarely isolated from horses. Recently, a single isolate from vaginal discharge in a mare was characterized as a new species, Arcanobacterium hippocoleae. The present report describes a case of necrosuppurative placentitis and stillbirth in an American Quarterhorse mare. Numerous colonies of irregular, Gram-positive, rod-shaped bacteria were observed by histological examination within fibrin lattice associated with placental lesions. Arcanobacterium hippocoleae was isolated in large numbers from the placenta, lung, and stomach contents. To the authors' knowledge, this is the first report of placentitis associated with Arcanobacterium spp. in a horse and the third reported isolation of A. hippocoleae from a horse.

Molecular identification of Arcanobacterium bialowiezense and Arcanobacterium bonasi based on 16S-23S rRNA intergenic spacer region sequences

In the present study, the 16S-23S rDNA intergenic spacer region (ISR) of Arcanobacterium (A.) bialowiezense DSM 17162, A. bonasi DSM 17163, A. bernardiae DSM 9152, A. haemolyticum DSM 20595, A. hippocoleae DSM 15539, A. phocae DSM 10002, A. pluranimalium DSM 13483 and A. pyogenes DSM 20630 was amplified, sequenced and compared with the corresponding 16S rRNA gene sequences yielding comparable phylogenetic relationships. The ISR sequence of A. bialowiezense and A. bonasi allowed the design of species-specific oligonucleotide primers which could successfully be used for PCR-mediated identification of previously characterized A. bialowiezense and A. bonasi isolated from infections of the European bison. The presented molecular identification might help to improve a future diagnosis of both newly described bacterial pathogens.

MHC-DRB3 variation in a free-living population of the European bison, Bison bonasus

MHC genes play a crucial role in pathogen recognition and are the most polymorphic genes in vertebrates. Loss of variation in these genes in bottlenecked species is thought to put their survival at risk. We examined variation at the MHC II DRB3 locus in the European bison, Bison bonasus, a species that has undergone an extreme bottleneck: the current population originated from only 12 founders. We also tested for the association of DRB3 genes with the incidence of posthitis, a disease affecting the reproductive organs of bulls and posing a new threat to the survival of the species. We found very limited MHC diversity, with only four alleles segregating in a sample of 172 individuals from a free-ranging Białowieza population. The alleles were highly divergent and revealed the hallmark of positive selection acting on them in the past, that is, a significant excess of nonsynonymous substitutions. This excess was concentrated in putative antigen-binding sites, suggesting that selection was driven by pathogens. However, we did not observe departures from Hardy-Weinberg equilibrium, an indicator of strong ongoing selection. Neither have we found a significant association between DRB3 alleles or genotypes and susceptibility to posthitis. Alleles conferring resistance to males may have been lost during the extreme bottleneck the species had undergone.