Mannheimia bovis sp. nov., Isolated from a Dead Cow with Hemorrhagic Pneumonia

Strain ZY190616^T was isolated from lung of a dead cow with hemorrhagic pneumonia in Yunnan Province, China. The strain was Gram-stain-negative, facultatively anaerobic bacterium. Phylogenetic analysis based on 16S rRNA gene sequence indicated that the strain was closely related to species of the genus Mannheimia and formed an independent clade with M.varigena CCUG 38462 ^T (97.0% similarity). Phylogenetic analysis based on recN gene indicated that the strain formed a clade with M.caviae CCUG 59995 ^T (87.8% similarity). Phylogenetic analysis based on rpoB gene indicated that the strain formed a clade with M.varigena CCUG 38462 ^T (94.7% similarity). The genomic OrthoANI values between strain ZY190616^T and M. ovis, M.haemolytica and M.granulomatis were 84.5%, 82.7% and 81.9%, respectively. The genomic G + C content was 39.8 mol%. The predominant fatty acids (> 5%) of the strain were C_16:0, C_14:0, C_18:1ω7c, summed feature 3 (C_16:1 ω7c and/ or C_16:1ω6c) and summed feature 2 (C14:0 3OH/ C16:1 Iso). The major polar lipids were phosphatidylglycerol (PG), phosphatidylethanolamine (PE), monophosphatidylglycerol (MGDG), triacylglycerol (TAG) and diphosphatidylglycerol (DLCL). The sole respiratory quinone was CoQ-7. Based on evidence from the taxonomic study, strain ZY190616^T represents a novel species of the genus Mannheimia, for which the name Mannheimia bovis sp. nov. is proposed. The type strain is ZY190616^T (= CCTCC AB 2020168 ^T = KCTC 25018 ^T).

Mannheimia ovis sp. nov., Isolated from Dead Sheep with Hemorrhagic Pneumonia

Two Gram-stain-negative, facultatively anaerobic bacteria, designated ZY170218^T and ZY180512, were isolated from lungs of dead sheep with hemorrhagic pneumonia in Yunnan Province, China and their taxonomic positions were studied by a polyphasic approach. The two isolates grew optimally at 37 °C, pH 9.0 and 1.0% NaCl (w/v), and showed identical 16S rRNA, recN and rpoB gene sequences. Phylogenetic analysis based on 16S rRNA gene sequence showed that the two strains fell within the cluster of species in the genus Mannheimia and formed a separated lineage with comparatively low similarity to the closest related species M. granulomatis (96.5%). Phylogenetic analysis based on rpoB gene indicated that the strains formed a monophyletic evolutionary lineage, with low sequence similarity ≤ 89.0% to the species of the genus Mannheimia. The genomic OrthoANI values between strain ZY170218^T and M. granulomatis and M. haemolytica were 80.4% and 83.1%, respectively. The genomic G + C content of strain ZY170218^T was 39.1 mol%. The predominant fatty acids (> 5%) of the two strains were C_16:0, C_14:0, C_18:1ω7c, summed feature 3 (C_16:1 ω7c and/ or C_16:1ω6c) and summed feature 2 (C_14:0 3OH/ C_16:1 Iso). The major polar lipids of strain ZY170218^T were phosphatidylglycerol, phosphatidylcholine, monogalactosyldiacylglycerol, bis(monoacylglycero)phosphate and diacylglycerols. The sole respiratory quinone of the two strains was CoQ-7. On the basis of phylogenetic, phenotypic and chemotaxonomic features, strain ZY170218^T and ZY180512 clearly represents a novel species of the genus Mannheimia, for which the name Mannheimia ovis sp. nov. is proposed. The type strain is ZY170218^T (= CGMCC 1.13620 ^T = KCTC 15731 ^T).

Granulomatous Inflammation of the Muzzle in White-Tailed Deer (Odocoileus virginianus) and Mule Deer (Odocoileus hemionus) Associated With Mannheimia granulomatis

Since 2002, reports of deer with swollen muzzles from throughout the United States have resulted in significant interest by wildlife biologists and wildlife enthusiasts. The condition was identified in 25 white-tailed deer (Odocoileus virginianus) and 2 mule deer (O. hemionus). Microscopic lesions consisted of severe, granulomatous or pyogranulomatous inflammation of the muzzle, nasal planum, and upper lip, as well as similar but less severe inflammation of the hard palate. Lymphadenitis of regional lymph nodes was common and granulomatous pneumonia was present in one individual. Splendore-Hoeppli material was typical in the center of inflammatory foci. Other than the single instance of pneumonia, systemic disease was not evident. Various bacterial species were isolated in culture, most of which were not morphologically consistent with the colonies of small, gram-negative bacteria observed in the center of the granulomas. Amplification and sequencing of the bacterial 16S rRNA gene from tissues of affected deer resulted in the identification of Mannheimia granulomatis. Laser capture microdissection was used to confirm that the colonies in the inflammatory foci were M. granulomatis. The cases described here are reminiscent of a bovine disease in Brazil and Argentina, locally called lechiguana. Although the inflammation of lechiguana is mostly truncal, the microscopic lesions are very similar and are also attributed to M. granulomatis. It is unclear if this is an emerging infectious disease of deer, or if it is a sporadic, uncommon condition that has only recently been recognized.

Identification of novel drug targets in bovine respiratory disease: an essential step in applying biotechnologic techniques to develop more effective therapeutic treatments

BACKGROUND

Bovine Respiratory Disease (BRD) is a major problem in cattle production which causes substantial economic loss. BRD has multifactorial aetiologies, is multi-microbial, and several of the causative pathogens are unknown. Consequently, primary management practices such as metaphylactic antimicrobial injections for BRD prevention are used to reduce the incidence of BRD in feedlot cattle. However, this poses a serious threat in the form of development of antimicrobial resistance and demands an urgent need to find novel interventions that could reduce the effects of BRD drastically and also delay/prevent bacterial resistance.

MATERIALS AND METHODS

We have employed a subtractive genomics approach that helps delineate essential, host-specific, and druggable targets in pathogens responsible for BRD. We also proposed antimicrobials from FDA green and orange book that could be repositioned for BRD.

RESULTS

We have identified 107 putative targets that are essential, selective and druggable. We have also confirmed the susceptibility of two BRD pathogens to one of the proposed antimicrobials - oxytetracycline.

CONCLUSION

This approach allows for repositioning drugs known for other infections to BRD, predicting novel druggable targets for BRD infection, and providing a new direction in developing more effective therapeutic treatments for BRD.

Comparison of the immune responses associated with experimental bovine mastitis caused by different strains of Escherichia coli

We studied the mammary immune response to different mammary pathogenic Escherichia coli (MPEC) strains in cows, hypothesising that the dynamics of response would differ. E. coli is a major aetiologic agent of acute clinical bovine mastitis of various degrees of severity with specific strains being associated with persistent infections. We compared challenge with three distinct pathogenic MPEC strains (VL2874, VL2732 and P4), isolated from different forms of mastitis (per-acute, persistent and acute, respectively). A secondary objective was to verify the lack of mammary pathogenicity of an environmental isolate (K71) that is used for comparison against MPEC in genomic and phenotypic studies. Twelve cows were challenged by intra-mammary infusion with one of the strains. Cellular and chemokine responses and bacterial culture follow-up were performed for 35 d. All cows challenged by any of the MPEC strains developed clinical mastitis. Differences were found in the intensity and duration of response, in somatic cell count, secreted cytokines (TNF-α, IL-6 and IL-17) and levels of milk leucocyte membrane Toll-like receptor 4 (TLR4). A sharp decrease of TLR4 on leucocytes was observed concomitantly to peak bacterial counts in milk. Intra-mammary infusion of strain K71 did not elicit inflammation and bacteria were not recovered from milk. Results suggest some differences in the mammary immune response to distinct MPEC strains that could be correlated to their previously observed pathogenic traits. This is also the first report of an E. coli strain that is non-pathogenic to the bovine mammary gland.

Bronchopneumonia associated with Mannheimia granulomatis infection in a Belgian hare (Lepus europaeus)

Mannheimia granulomatis was first isolated from pneumonic European hares in the 1980s and has since been reported sporadically in pneumonic Swedish roe deer and Australian cattle. Although the pneumonic lesions caused by M. haemolytica in livestock have been extensively studied and reported, little is published with regard to the pneumonic lesions associated with M. granulomatis infection in any species. We describe the histopathology of purulent bronchopneumonia associated with M. granulomatis in a Belgian hare ( Lepus europaeus) resident in British Columbia, Canada, and compare the lesions with those caused by M. haemolytica in livestock.

Eosinophilic granuloma with Splendore-Hoeppli material caused by Mannheimia granulomatis in a calf

A large subcutaneous mass, formed on the left lower jaw of a 4-month-old Japanese Black male calf, was partially excised for histological and bacteriological examinations. Antibiotic treatment resulted in a good prognosis. Bacteria isolated from the excised material were characterized by weak hemolysis and positive reactions for catalase and oxidase, and were 99% identical to Mannheimia granulomatis strains. The presence of the leukotoxin gene product was demonstrated by polymerase chain reaction amplification. Histological examination showed that the excised material was composed of dense fibrous connective tissue with sparsely distributed eosinophilic granulomas or abscesses. These foci frequently contained Splendore-Hoeppli material with rod-shaped Gram-negative bacteria. Except for the absence of lymphangitis and the presence of basophils and mast cells, the histology of this lesion resembled that of lechiguana associated with coinfection of M. granulomatis and Dermatobia hominis. Leukotoxin was demonstrated by immunohistochemistry within Splendore-Hoeppli material and was judged to be responsible for its formation.

Visualizing the indefinable: three-dimensional complexity of 'infectious diseases'

BACKGROUND

The words 'infection' and 'inflammation' lack specific definitions. Here, such words are not defined. Instead, the ability to visualize host-microbial interactions was explored.

METHODS

Leukocyte differential counts and four bacterial species (Staphylococcus aureus, Streptococcus dysgalactiae, Staphylococcus chromogenes, and Escherichia coli) were determined or isolated in a cross-sectional and randomized study conducted with 611 bovine milk samples. Two paradigms were evaluated: (i) the classic one, which measures non-structured (count or percent) data; and (ii) a method that, using complex data structures, detects and differentiates three-dimensional (3D) interactions among lymphocytes (L), macrophages (M), and neutrophils (N).

RESULTS

Classic analyses failed to differentiate bacterial-positive (B+) from -negative (B-) observations: B- and B+ data overlapped, even when statistical significance was achieved. In contrast, the alternative approach showed distinct patterns, such as perpendicular data inflections, which discriminated microbial-negative/mononuclear cell-predominating (MCP) from microbial-positive/phagocyte-predominating (PP) subsets. Two PP subcategories were distinguished, as well as PP/culture-negative (false-negative) and MCP/culture-positive (false-positive) observations. In 3D space, MCP and PP subsets were perpendicular to one another, displaying ≥ 91% specificity or sensitivity. Findings supported five inferences: (i) disease is not always ruled out by negative bacterial tests; (ii) low total cell counts can coexist with high phagocyte percents; (iii) neither positive bacterial isolation nor high cell counts always coincide with PP profiles; (iv) statistical significance is not synonymous with discrimination; and (v) hidden relationships cannot be detected when simple (non-structured) data formats are used and statistical analyses are performed before data subsets are identified, but can be uncovered when complexity is investigated.

CONCLUSIONS

Pattern recognition-based assessments can detect host-microbial interactions usually unobserved. Such cutoff-free, confidence interval-free, gold standard-free approaches provide interpretable information on complex entities, such as 'infection' and 'inflammation', even without definitions. To investigate disease dynamics, combinations of observational and experimental longitudinal studies, on human and non-human infections, are recommended.

Characterization of bacterial community of raw milk from dairy cows during subacute ruminal acidosis challenge by high-throughput sequencing

BACKGROUND

Four cannulated primiparous Holstein dairy cows (84 ± 25 DIM) were used in a 2 × 2 crossover experimental design. The two diets contained 40% (low-concentrate diet, or control diet, LC) and 70% (high-concentrate diet, or SARA induction diet, HC) concentrate feeds respectively. Milk samples were collected on days 17, 18 and 19 of each experimental period. DNA was extracted from each milk sample, and pyrosequencing was applied to analyse the milk microbial community.

RESULTS

Regardless of diet, the bacterial community of milk was dominated by Actinobacteria, Firmicutes, Proteobacteria and Bacteroidetes. HC feeding showed a higher proportion of some mastitis-causing pathogen bacteria, such as Stenotrophomonas maltophilia, Streptococcus parauberis and Brevundimonas diminuta, as well as of psychrotrophic bacteria, such as Pseudomonas, Brevundimonas, Sphingobacterium, Alcaligenes, Enterobacter and Lactobacillus. However, the diversity of the milk bacterial microbiota (ACE, Chao, and Shannon index) was not affected by HC feeding.

CONCLUSION

To the best of our knowledge, this is the first report on the use of pyrosequencing for evaluating the impacts of nutrition on changes in the composition of milk microbiota. These findings indicate that HC feeding may increase the risk of dairy cows suffering from mastitis, decrease the organoleptic quality of raw milk and dairy products, and limit the shelf life of processed fluid milk.

Bacterial community profiling of milk samples as a means to understand culture-negative bovine clinical mastitis

Inflammation and infection of bovine mammary glands, commonly known as mastitis, imposes significant losses each year in the dairy industry worldwide. While several different bacterial species have been identified as causative agents of mastitis, many clinical mastitis cases remain culture negative, even after enrichment for bacterial growth. To understand the basis for this increasingly common phenomenon, the composition of bacterial communities from milk samples was analyzed using culture independent pyrosequencing of amplicons of 16S ribosomal RNA genes (16S rDNA). Comparisons were made of the microbial community composition of culture negative milk samples from mastitic quarters with that of non-mastitic quarters from the same animals. Genomic DNA from culture-negative clinical and healthy quarter sample pairs was isolated, and amplicon libraries were prepared using indexed primers specific to the V1–V2 region of bacterial 16S rRNA genes and sequenced using the Roche 454 GS FLX with titanium chemistry. Evaluation of the taxonomic composition of these samples revealed significant differences in the microbiota in milk from mastitic and healthy quarters. Statistical analysis identified seven bacterial genera that may be mainly responsible for the observed microbial community differences between mastitic and healthy quarters. Collectively, these results provide evidence that cases of culture negative mastitis can be associated with bacterial species that may be present below culture detection thresholds used here. The application of culture-independent bacterial community profiling represents a powerful approach to understand long-standing questions in animal health and disease.