Fusobacterium necrophorum infections: virulence factors, pathogenic mechanism and control measures

Liver microbial community and associated host transcriptome in calves with feed induced acidosis

Introduction

In the dairy industry, calves are typically fed diets rich in highly fermentable carbohydrates and low in fibrous feeds to maximize ruminal papillae and tissue development. Calves on such diets are vulnerable at developing ruminal acidosis. Prevalent in cattle, liver abscess (LA) is considered a sequela to ruminal acidosis. LAs can cause significant liver function condemnation and decreased growth and production. Currently, we know little about the liver microbiome in calves with feed-induced acidosis.

Methods

Using our established model of ruminal acidosis, where young calves were fed an acidosis-inducing (AC) or -blunting (control) diet starting at birth until 17-week of age, we investigated microbial community changes in the liver resultant from ruminal acidosis. Eight calves were randomly assigned to each diet, with four animals per treatment. Rumen epithelium and liver tissues were collected at 17 weeks of age right after euthanasia. Total RNAs were extracted and followed by whole transcriptome sequencing. Microbial RNA reads were enriched bioinformatically and used for microbial taxonomy classification using Kraken2.

Results

AC Calves showed significantly less weight gain over the course of the experiment, in addition to significantly lower ruminal pH, and rumen degradation comparison to the control group (p < 0.05). In the liver, a total of 29 genera showed a significant (p < 0.05) abundance change (> 2-fold) between the treatments at 17-week of age. Among these, Fibrobacter, Treponema, Lactobacillus, and Olsenella have been reported in abscessed liver in cattle. Concurrent abundance changes in 9 of the genera were observed in both the liver and rumen tissues collected at 17-week of age, indicating potential crosstalk between the liver and rumen epithelial microbial communities. Significant association was identified between host liver gene and its embedded microbial taxa. Aside from identifying previously reported microbial taxa in cattle abscessed liver, new repertoire of actively transcribed microbial taxa was identified in this study.

Discussion

By employing metatranscriptome sequencing, our study painted a picture of liver microbiome in young calves with or without feed induced acidosis. Our study suggested that liver microbiome may have a critical impact on host liver physiology. Novel findings of this study emphasize the need for further in-depth analysis to uncover the functional roles of liver resident microbiome in liver metabolic acidosis resultant from feed-related ruminal acidosis.

Detecting Forest Musk Deer Abscess Disease Pathogens Using 16S rRNA High-Throughput Sequencing Technology

Currently, researchers use bacterial culture and targeted PCR methods to classify, culture, and identify the pathogens causing abscess diseases. However, this method is limited by factors such as the type of culture medium and culture conditions, making it challenging to screen and proliferate many bacteria effectively. Fortunately, with the development of high-throughput sequencing technology, pathogen identification at the genetic level has become possible. Not only can this approach overcome the limitations of bacterial culture, but it can also accurately identify the types and relative abundance of pathogens. In this study, we used high-throughput sequencing of 16S rRNA to identify the pathogens in purulent fluid samples. Our results not only confirmed the presence of the main pathogen reported by previous researchers, Trueperella pyogenes, but also other obligate anaerobes, Fusobacterium necrophorum and Bacteroides fragilis as the dominant pathogens causing abscess diseases for the first time. Therefore, our findings suggest that high-throughput sequencing technology has the potential to replace traditional bacterial culture and targeted PCR methods.

Field Study on the Prevalence of Ovine Footrot, Contagious Ovine Digital Dermatitis, and Their Associated Bacterial Species in Swedish Sheep Flocks

Ovine footrot and contagious ovine digital dermatitis (CODD) cause lameness in sheep, affecting welfare and economics. Previous Swedish studies focused on individual slaughter lambs, leaving flock-wide prevalence less explored. This study examined the prevalence of footrot and CODD in Swedish sheep flocks, focusing on adult sheep. From 99 flocks, 297 swabs were analysed using real-time PCR for Dichelobacter nodosus, Fusobacterium necrophorum, and Treponema spp. Sampled feet were photographed and assessed using scoring systems for footrot and CODD. Results indicated footrot prevalences (footrot score ≥ 2) of 0.7% and 2.0% at the individual and flock levels, respectively, whereas there were no signs of CODD. The individual footrot prevalence was lower than that from a 2009 study but aligned with a 2020 study, both conducted on slaughter lambs. Dichelobacter nodosus, F. necrophorum, and Treponema spp. were found in 5.7%, 1.3%, and 65.0% of sheep, and in 9.1%, 3.0%, and 82.8% of flocks, respectively. Compared to the 2020 study, there was a notable decrease in F. necrophorum and Treponema spp., while D. nodosus was consistent. In conclusion, the findings show a low prevalence of footrot, CODD, D. nodosus, and F. necrophorum in Swedish sheep flocks. Continuous surveillance and owner education are important to maintain this favourable status.

Bioinformatic and literature assessment of toxicity and allergenicity of a CRISPR-Cas9 engineered gene drive to control Anopheles gambiae the mosquito vector of human malaria

BACKGROUND

Population suppression gene drive is currently being evaluated, including via environmental risk assessment (ERA), for malaria vector control. One such gene drive involves the dsxFCRISPRh transgene encoding (i) hCas9 endonuclease, (ii) T1 guide RNA (gRNA) targeting the doublesex locus, and (iii) DsRed fluorescent marker protein, in genetically-modified mosquitoes (GMMs). Problem formulation, the first stage of ERA, for environmental releases of dsxFCRISPRh previously identified nine potential harms to the environment or health that could occur, should expressed products of the transgene cause allergenicity or toxicity.

METHODS

Amino acid sequences of hCas9 and DsRed were interrogated against those of toxins or allergens from NCBI, UniProt, COMPARE and AllergenOnline bioinformatic databases and the gRNA was compared with microRNAs from the miRBase database for potential impacts on gene expression associated with toxicity or allergenicity. PubMed was also searched for any evidence of toxicity or allergenicity of Cas9 or DsRed, or of the donor organisms from which these products were originally derived.

RESULTS

While Cas9 nuclease activity can be toxic to some cell types in vitro and hCas9 was found to share homology with the prokaryotic toxin VapC, there was no evidence from previous studies of a risk of toxicity to humans and other animals from hCas9. Although hCas9 did contain an 8-mer epitope found in the latex allergen Hev b 9, the full amino acid sequence of hCas9 was not homologous to any known allergens. Combined with a lack of evidence in the literature of Cas9 allergenicity, this indicated negligible risk to humans of allergenicity from hCas9. No matches were found between the gRNA and microRNAs from either Anopheles or humans. Moreover, potential exposure to dsxFCRISPRh transgenic proteins from environmental releases was assessed as negligible.

CONCLUSIONS

Bioinformatic and literature assessments found no convincing evidence to suggest that transgenic products expressed from dsxFCRISPRh were allergens or toxins, indicating that environmental releases of this population suppression gene drive for malaria vector control should not result in any increased allergenicity or toxicity in humans or animals. These results should also inform evaluations of other GMMs being developed for vector control and in vivo clinical applications of CRISPR-Cas9.

The outer membrane protein of Fusobacterium necrophorum, 43K OMP, stimulates inflammatory cytokine production through nuclear factor kappa B activation

OBJECTIVE

Fusobacterium necrophorum causes bovine hepatic abscess, foot rot, mastitis, and endometritis. The 43 kDa outer membrane protein (43 K OMP) of F. necrophorum is a porin protein that plays an important role in infections by this bacterium, but the biological function and the pathogenesis of this protein are largely unknown.

METHODS

In this study, we investigated the role of the 43 K OMP in bacterial infection of bovine mammary epithelial cells (MAC-T cells) by Tandem Mass Tag proteomic analysis. The RAW264.7 cells were incubated with recombinant 43 K OMP (12.5 μg/mL) for 2 h, 4 h, 6 h, and 12 h, and then the inflammatory related protein and inflammatory cytokine production were measured by Western blot analysis and ELISA, the mRNA expression levels of inflammatory cytokine were measured by Real-Time PCR.

RESULTS

Proteomic analysis results demonstrated there were 224 differentially expressed proteins in the MAC-T cells stimulated with the 43 K OMP compared with control, and 118 proteins were upregulated and 106 proteins were downregulated. These differentially expressed proteins were mainly involved in NF-kappa B signaling, bacterial invasion of epithelial cells, cell adhesion, complement and coagulation cascades. The top six differentially expressed proteins were; MMP9, PLAU, STOM, PSMD13, PLAUR, and ITGAV, which were involved in a protein-protein interaction network. Furthermore, TLR/MyD88/NF-κB pathway related proteins and inflammatory cytokines (IL-6, TNF-α, and IL-1β) were assessed by Western blot analysis and ELISA. Results showed the 43 K OMP to enhance the expression of TLR4 protein at 2 h (P < 0.01) and the MyD88 protein at 4 h (P < 0.05) post-stimulation, and to decrease IκBα expression at 4 h, 6 h and 12 h (P < 0.05) post-infection, as well as induce phosphorylation at Ser536 (P < 0.01). Levels of IL-6, IL-1β, and TNF-α in the supernatants of mouse macrophages were increased (P < 0.05), as were mRNA expression levels of IL-6, IL-1β, and TNF-α (P < 0.05), while IL-4 mRNA expression was decreased (P < 0.05).

CONCLUSIONS

Taken together, these results suggested the important role for 43 K OMP in F. necrophorum infection, promoting the production of pro-inflammatory cytokines (IL-6 and TNF-α) by activation of the TLR/MyD88/NF-κB pathway. These findings provided a theoretical basis for a better understanding of the pathogenesis of F. necrophorum infection.

A genome-led study on the pathogenesis of Fusobacterium necrophorum infections

Fusobacterium necrophorum causes a range of mild to life threatening infections and there is uncertainty in terms of diagnosis and treatment due to the lack of knowledge on their pathogenic mechanisms. This study characterised genomes of F. necrophorum to compare their virulence factors and investigate potential infection markers. 27 isolates of F. necrophorum from patients with pharyngotonsillitis were subjected to whole genome sequencing and compared with 42 genomes published in the NCBI database. Phylogenomics, pangemome, pan-GWAS and virulome were analysed to study strain variations with reference to virulence factors. Core genome based phylogenomic tree exhibited three clades of which Clade A belonged to F. necrophorum subsp necrophorum, clades B and C were F. necrophorum subsp funduliforme. Pan-GWAS and Pan-Virulome suggest some marker genes associated with clinical sources of isolation that needs further validation. Our study highlights some interesting features of the pathogenesis of F. necrophorum infections. Although the animal isolate genomes had some marker genes, the genomes of human isolates did not exhibit clear correlation to their clinical sources of isolation. This prompts to think of other mechanisms such as co-infections or host factors that can be involved in the pathogenesis.

Fusobacterium necrophorum Promotes Apoptosis and Inflammatory Cytokine Production Through the Activation of NF-κB and Death Receptor Signaling Pathways

Fusobacterium necrophorum can cause liver abscess, foot rot in ruminants, and Lemire syndrome in humans, Also, its virulence factors can induce the apoptosis of macrophages and neutrophils. However, the detailed mechanism has not been fully clarified. This study investigated the mechanisms of apoptosis and inflammatory factor production in F. necrophorum–induced neutrophils and macrophages (RAW246.7). After infection of macrophages with F. necrophorum, 5-ethynyl-2’-deoxyuridine labeling assays indicated that F. necrophorum inhibited macrophage proliferation in a time- and dose-dependent manner. Hoechst staining and DNA ladder assays showed significant condensation of the nucleus and fragmentation of genomic DNA in F. necrophorum–infected macrophages, Annexin V (FITC) and propidium iodide (PI) assay confirmed the emergence of apoptosis in the macrophages and sheep neutrophils with F. necrophorum compared with the control. The group with significant apoptosis was subjected to RNA sequencing (RNA-Seq), and the sequencing results revealed 2581 up– and 2907 downregulated genes. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis of the differentially expressed genes showed that F. necrophorum drove apoptosis and production of inflammatory factors by activating genes related to the Nuclear Factor-κB (NF-κB) and death receptor pathways. Meanwhile, quantitative reverse transcription PCR and Western blot validation results were consistent with the results of transcriptome sequencing analysis. In conclusion, F. necrophorum induced apoptosis and production of pro-inflammatory factors through the NF-κB and death receptor signaling pathway, providing a theoretical basis for further mechanistic studies on the prevention and control of F. necrophorum disease treatment.

Not All Liver Abscesses Are Created Equal: The Impact of Tylosin and Antibiotic Alternatives on Bovine Liver Abscess Microbial Communities and a First Look at Bacteroidetes-Dominated Communities

Liver abscesses (LAs) are extremely prevalent in cattle and result in significant economic losses due to liver condemnation, decreased growth and production, and lower carcass quality. LAs are commonly attributed to the transition to diets high in rapidly fermentable starch which results in rumen epithelial inflammation that allows pathogenic bacteria to gain entry to liver through transport via the hepatic portal vein. The most common intervention for LAs is the inclusion of antibiotics in feedlot diets, under the supervision of a veterinarian; this treatment is associated with reduced occurrence of LAs in this and other studies. Here, through the largest LA 16S rRNA gene sequencing study to date, we demonstrate that the inclusion of tylosin and antibiotic alternatives (the essential oil limonene and Saccharomyces cerevisiae fermentation product) had little impact on LA microbial community composition. Importantly, members of Bacteroidetes (Bacteroides spp. and Porphyromonas spp.) were identified as the dominant taxa in conjunction with low proportions of Fusobacteria in nearly a quarter (61/259) of all LA communities analyzed in this study. The relative abundances of the phyla Fusobacteria and Bacteroidetes had a strongly negative correlation, and LA microbial communities rarely contained high abundances of both of these dominant phyla. Further, based on the presence of taxa discriminant of Bacteroidetes-dominated LAs within over 400 bovine gut communities, we provide evidence suggestive of Bacteroidetes-dominated abscess communities originating in more distal portions of the bovine gut. Together, these findings suggest that some LA microbial communities may originate from portions of the gut other than the rumen.

Potential for Natural Attenuation of Domestic and Agricultural Pollution in Karst Groundwater Environments

In karst areas, anthropogenic contaminants reach the subsurface with detrimental effects on the groundwater ecosystem and downstream springs, which often serve as drinking water sources for the local human communities. We analyzed the water chemistry and microbial community composition in upstream and downstream locations of five hydrokarst systems (HKS) during four seasons. Conductivity and nitrates were higher in the downstream springs than in the pre-karst waters, whereas the concentration of organic matter, considered here as a pollution indicator, was lower. The microbial community composition varied largely between upstream and downstream locations, with multiple species of potentially pathogenic bacteria decreasing in the HKS. Bacteria indicative of pollution decreased as well when passing through the HKS, but potential biodegraders increased. This suggests that the HKS can filter out part of the polluting organic matter and, with it, part of the associated microorganisms. Nevertheless, the water quality, including the presence of pathogens in downstream springs, must be further monitored to control whether the water is appropriate for consumption. In parallel, the human populations located upstream must be advised of the risks resulting from their daily activities, improper stocking of their various wastes and dumping of their refuse in surface streams.

Prevalence of bacterial species associated with ovine footrot and contagious ovine digital dermatitis in Swedish slaughter lambs

Background

Ovine footrot and contagious ovine digital dermatitis (CODD) are contagious mixed bacterial infections with major impacts on animal health and production. In Sweden, ovine footrot and CODD were first detected in 2004 and 2019, respectively. In 2009, a voluntary control programme for footrot was established, and a prevalence study in slaughter lambs was conducted, however, the distribution of footrot and CODD-associated bacteria is still unknown. This study examined the prevalence of Dichelobacter nodosus, Fusobacterium necrophorum and Treponema spp., as well as the current prevalence of footrot and CODD, in Swedish slaughter lambs.

Results

A total of 2048 feet, from 512 slaughter lambs, were collected from eight slaughterhouses throughout Sweden in autumn 2020. All feet were visually examined for lesions of footrot and CODD and sampled for subsequent real-time polymerase chain reaction (PCR) analysis. Nine lambs (1.8%) had at least one foot affected with footrot (footrot score ≥ 2). A CODD grade 1 lesion was detected in a single lamb (0.2%). The prevalence of D. nodosus, F. necrophorum and Treponema spp. was 6.1%, 7.6% and 90.6%, respectively. The D. nodosus detected were benign strains.

Conclusions

The prevalence of footrot in Swedish slaughter lambs has been significantly reduced, from 5.8 to 1.8%, during the past 11 years. This indicates that preventive measures, such as the national control programme and elimination of footrot from affected flocks, have been effective. A single lamb (0.2%) was found with a CODD lesion (grade 1). In Sweden, benign rather than virulent strains of D. nodosus seem to be the most common. Neither D. nodosus nor F. necrophorum were widespread among Swedish slaughter lambs, but both were more likely to be found in lambs with footrot. Treponema spp. was very commonly found in lambs with and without footrot, but there is a lack of information on the individual Treponema spp. present in Swedish slaughter lambs and their potential pathogenicity.

Standardization of loop-mediated isothermal amplification for detection of D. nodosus and F. necrophorum causing footrot in sheep and goats

The loop-mediated isothermal amplification (LAMP) was standardized for rapid detection of Dichelobacter nodosus and Fusobacterium necrophorum. A total of 250 foot swabs were screened from sheep (200) and goats (50) from different districts of Rayalaseema, viz., Chittoor, Nellore, Kadapa, and Anantapur. Out of 250 samples 75 (30.0%) and 85 (34.0%) were positive for D. nodosus and F. necrophorum, respectively. All the 250 samples were screened individually for both the organisms by LAMP. Among them, 104 (41.6%) were found to be positive for D. nodosus and 120 (48.0%) were positive for F. necrophorum. The efficacy of LAMP in terms of sample DNA detection limit was compared with the PCR by using standard dilutions of DNA extracted from D. nodosus and F. necrophorum cultures. The detection limit was found to be higher than PCR for both the organisms. The sensitivity of LAMP is compared with PCR by targeting 16S rRNA gene of D. nodosus and lktA gene of F. necrophorum. In case of D. nodosus, out of 250 samples, 75 (30.0%) were positive by PCR and 104 (41.6%) were positive by LAMP. Among 250 samples, 85 (34.0%) were positive by PCR and 120 (48.0%) were positive by LAMP in case of F. necrophorum. The LAMP was found to be more sensitive than PCR in detecting the organisms with high statistical significance.

Evaluation of Immunoprotective Effects of Fusobacterium necrophorum Outer Membrane Proteins 43K OMP, Leukotoxin and Hemolysin Multi-Component Recombinant Subunit Vaccine in Mice

We evaluated the efficacy of three vaccine formulations containing different combinations of proteins (43K OMP, leukotoxin recombinant protein PL4 and hemolysin recombinant protein H2) and killed whole cell Fusobacterium necrophorum in preventing liver abscess. Four subcutaneous vaccines were formulated: vaccine 1 (43K OMP), vaccine 2 (PL4 and H2), vaccine 3 (43K OMP, PL4 and H2), and vaccine 4 (killed whole bacterial cell). 43K OMP, PL4, and H2 proteins were produced by using recombinant protein expression. To evaluate vaccine efficacy, we randomly allocated 50 BALB/c female mice to one of five different treatment groups: PBS control group, vaccine 1, vaccine 2, vaccine 3, and vaccine 4. Mice were vaccinated three times, with 14 days between each immunization. After immunization, the mice were challenged with F. necrophorum. The three key findings of this study are as follows: (1) Vaccine 3 has enabled mice to produce higher antibody titer following bacterial challenge, (2) in the liver pathology of mice, the vaccine 3 liver showed the least pathology, and (3) all four vaccines produced high levels of antibodies and cytokines in mice, but the level of vaccine 3 was the highest. Based on our results, it has been demonstrated that a mixture of F. necrophorum 43K OMP, PL4, and H2 proteins inoculated with mice can achieve protection against liver abscess in mice. Our research may therefore provide the basis for the development of a vaccine against F. necrophorum bovine infections.

Not always as simple as a UTI: An atypical case of Lemierre's syndrome, the forgotten disease

A 65-year-old man, who was previously fit and well with no known medical comorbidities, was admitted with symptoms of dysuria, urinary frequency, pyrexia, chills and lethargy. His vitals showed that he was hypotensive, tachycardic and pyrexial. Urine dip was heavily positive for leukocytes and nitrites and had markedly elevated inflammatory markers and mild acute kidney injury. He was commenced on piperacillin/tazobactam. He went on to develop severe left-sided neck swelling and erythema. Ultrasound of the neck with subsequent computed tomography revealed extensive internal jugular vein thrombosis with abscess collection around the vein. Microbiology grew Gram-negative bacilli, later identified as Fusobacterium necrophorum A diagnosis of Lemierre's syndrome was made. The patient was continued on intravenous piperacillin/tazobactam and metronidazole as per sensitivities and later switched to oral metronidazole. He was initiated on warfarin anticoagulation. He made a remarkable recovery and was discharged with outpatient ear, nose and throat and haematology follow-up.

Fusobacterium necrophorum Endocarditis with Liver Abscesses: A Case Report and Review of the Literature

Fusobacterium necrophorum is a very rare cause of endocarditis. We herein report a case of F. necrophorum endocarditis with liver abscesses in a 51-year-old woman. This is the first reported case of monomicrobial F. necrophorum endocarditis to present in a patient over 50 years old. We also reviewed 10 reported cases, including the present case. Our review indicated that anaerobic bacteria, including Gram-negative anaerobic bacilli such as F. necrophorum, should be considered in the differential diagnosis of infective endocarditis, especially in patients without preexisting organic heart disease.

Interrogating the bovine reproductive tract metagenomes using culture-independent approaches: a systematic review

Undesirable microbial infiltration into the female bovine reproductive tracts, for example during calving or mating, is likely to disturb the commensal microflora. Persistent establishment and overgrowth of certain pathogens induce reproductive diseases, render the female bovine reproductive tract unfavourable for pregnancy or can result in transmission to the foetus, leading to death and abortion or birth abnormalities. This review of culture-independent metagenomics studies revealed that normal microflora in the female bovine reproductive tract is reasonably consistently dominated by bacteria from the phyla Bacteroidetes, Firmicutes, Proteobacteria, following by Actinobacteria, Fusobacteria and Tenericutes. Reproductive disease development in the female bovine reproductive tract was demonstrated across multiple studies to be associated with high relative abundances of bacteria from the phyla Bacteroidetes and Fusobacteria. Reduced bacterial diversity in the reproductive tract microbiome in some studies of cows diagnosed with reproductive diseases also indicated an association between dysbiosis and bovine reproductive health. Nonetheless, the bovine genital tract microbiome remains underexplored, and this is especially true for the male genital tract. Future research should focus on the functional aspects of the bovine reproductive tract microbiomes, for example their contributions to cattle fertility and susceptibility towards reproductive diseases.

Gut microbiome of migratory shorebirds: Current status and future perspectives

Migratory shorebirds have many unique life history characteristics, such as long-distance travel between breeding sites, stopover sites, and wintering sites. The physiological challenges for migrant energy requirement and immunity may affect their gut microbiome community. Here, we reviewed the specific features (e.g., relatively high proportion of Corynebacterium and Fusobacterium) in the gut microbiome of 18 migratory shorebirds, and the factors (e.g., diet, migration, environment, and phylogeny) affecting the gut microbiome. We discussed possible future studies of the gut microbiome in migratory shorebirds, including the composition and function of the spatial-temporal gut microbiome, and the potential contributions made by the gut microbiome to energy requirement during migration.

TREATMENT OF ORAL DISEASE IN EIGHT CAPTIVE BENNETT'S WALLABIES (MACROPUS RUFOGRISEUS) BETWEEN 2011 AND 2019: A CASE SERIES

Oral disease, such as endodontic disease and macropod progressive periodontal disease (MPPD), which can progress to chronic alveolar osteomyelitis (CAO), have been identified as a common source of morbidity and mortality in captive macropods. This case series reviews the diagnosis and treatment of dental disease in eight captive Bennett's wallabies (Macropus rufogriseus) over the course of an 8-yr period (2011-2019) in a zoological collection. Two wallabies were treated at four separate times, for a total of 14 anesthetized dental surgical procedures. Two wallabies died after treatment for dental disease. Endodontic disease, MPPD, and CAO were all identified and treated with extraction. Cases in which disease was identified early and treated aggressively had a good outcome with no return of clinical signs in the affected area. Several cases of extensive CAO were treated successfully with extraction and extensive debridement. One wallaby developed immune-mediated anemia, a suspected adverse drug reaction associated with prolonged administration of intravenous clindamycin.

Leukotoxin production by Fusobacterium necrophorum strains in relation to severity of liver abscesses in cattle

Fusobacterium necrophorum, a Gram-negative anaerobe, is the primary etiologic agent of liver abscesses of beef cattle. The bacterium, a member of the microbial community of the rumen, travels to the liver via portal circulation to cause abscesses. The severity of liver abscesses vary from mild with one or two small abscesses to severe with medium to large multiple abscesses. Leukotoxin, a secreted protein, is the critical virulence factor involved in the infection. Our objective was to compare leukotoxin production between strains of F. necrophorum isolated from mild and severe liver abscesses collected from slaughtered cattle. The quantification of leukotoxin was based on assays to measure cytotoxicity and protein antigen concentration. One-hundred strains, 50 from mild and 50 from severe abscesses, were utilized in the study. Cell-free supernatants were prepared from cultures grown in anaerobic broth at 9 and 24 h incubations. The leukotoxic activity was quantified by measuring cytotoxicity based on the release of lactic dehydrogenase from bovine lymphocyte cells, BL3, treated with the culture supernatant. Leukotoxin protein concentration was quantified by a sandwich ELISA assay with a leukotoxin-specific monoclonal antibody as the capture antibody. The leukotoxin activity and concentration were highly variable among the strains within each severity of liver abscesses. Although the leukotoxic activity was unaffected by incubation time, leukotoxin protein concentration was consistently higher at 24 h compared to 9 h incubation. Strains from severe liver abscesses had significantly higher leukotoxic activity and higher protein concentration compared to strains from mild liver abscesses (P < 0.0001) at both 9 and 24 h culture supernatants. Across all strains, the correlation coefficients between leukotoxic activity and leukotoxin concentration at 9 and 24 h were 0.14 (P = 0.17) and 0.47 (P < 0.0001), respectively. In conclusion, strains isolated from severe liver abscesses had significantly higher leukotoxic activities and leukotoxin protein concentrations compared to strains isolated from mild liver abscesses.

Evaluation of immunoglobulin-Y in place of tylosin phosphate in the diets fed to Holstein Steers and preliminary analysis of liver abscess duration on animal growth performance

Despite the regular use of feed-grade macrolide-antibiotics, bovine liver abscesses persist, representing a financial burden to pre- and post-mortem sectors of the beef industry. An immunoglobulin-Y (IGY) additive developed to target Fusobacterium necrophorum and Trueperella pyogenes, was evaluated for the control of liver abscesses. Research is needed for the impact of liver abscess severity as well as abscess duration on steer performance and carcass characteristics. Holstein steers (n = 64; initial body weight (BW) = 372.5 ± 2.41 kg) consuming a finishing diet for 188 d were used in a completely randomized design where treatments included: TYL (tylosin phosphate 90 mg/d; n = 32) or IGY (2.5 g/d; n = 32) and steer was the experimental unit. Feed intake was recorded daily while BW and liver ultrasound outcome (normal or abnormal) was recorded every 28 d until slaughter to estimate duration of abscess presence (DUR). Continuous variables of animal growth performance and carcass characteristics were analyzed using the MIXED procedure of SAS. Categorical quality grade and liver data were analyzed using the GLIMMIX procedure of SAS. Treatment did not affect live or carcass-adjusted growth performance (P ≥ 0.131). However, steers fed TYL had greater (P = 0.042) empty body fat (EBF) % and a greater proportion of carcasses grading premium choice than steers fed IGY (P = 0.030). Treatment did not affect prevalence of abscessed livers, abscess severity or estimated abscess duration (P ≥ 0.213) but datasets with greater experimental units are needed to substantiate this outcome. Increasing abscess severity tended (P ≤ 0.10) to linearly reduce carcass-adjusted gain to feed (G:F), fat thickness, and EBF. Carcass dressing % was only affected by severe (A+ and A+AD) abscess scores (P = 0.010). Carcass-adjusted final BW, average daily gain, G:F, and hot carcass weight was decreased only when the estimated DUR was ≥140 d (P ≤ 0.05). Carcass dressing %, however, was linearly affected by estimated liver abscess DUR (P ≤ 0.005), regardless of abscess severity. Preliminary evidence suggests that measuring the duration of liver abscess affliction during the feeding period may also give insight to the degree of performance reduction.

Lemierre's syndrome: a forgotten life-threatening entity

Lemierre's syndrome is a very rare but potentially fatal condition. It mainly affects adolescents and young adult males, and usually arises as a serious complication of pharyngitis or peritonsillar abscess. It is characterised by the triad of internal jugular vein septic thrombophlebitis, septic emboli (mostly pulmonary) and the isolation of the agent 'Fusobacterium necrophorum' in sterile fluids. In this report, it is described a case in which the nonspecific and subtle clinic made the diagnosis difficult to reach. In fact, only the dissociation between flu-like symptoms and the presence of significant changes in the blood tests (suggestive of acute bacterial infection), led to the request for imaging tests, which proved to be essential for the final diagnosis and subsequent control of the disease. This case report aims to increase the awareness among Ear, Nose and Throat (ENT) residents, paediatricians and family doctors about the existence of this entity and its potential life-threatening nature.

Targeting the Hindgut to Improve Health and Performance in Cattle

An adequate gastrointestinal barrier function is essential to preserve animal health and well-being. Suboptimal gut health results in the translocation of contents from the gastrointestinal lumen across the epithelium, inducing local and systemic inflammatory responses. Inflammation is characterized by high energetic and nutrient requirements, which diverts resources away from production. Further, barrier function defects and inflammation have been both associated with several metabolic diseases in dairy cattle and liver abscesses in feedlots. The gastrointestinal tract is sensitive to several factors intrinsic to the productive cycles of dairy and beef cattle. Among them, high grain diets, commonly fed to support lactation and growth, are potentially detrimental for rumen health due to their increased fermentability, representing the main risk factor for the development of acidosis. Furthermore, the increase in dietary starch associated with such rations frequently results in an increase in the bypass fraction reaching distal sections of the intestine. The effects of high grain diets in the hindgut are comparable to those in the rumen and, thus, hindgut acidosis likely plays a role in grain overload syndrome. However, the relative contribution of the hindgut to this syndrome remains unknown. Nutritional strategies designed to support hindgut health might represent an opportunity to sustain health and performance in bovines.

Screening of BHK-21 cellular proteins that interact with outer membrane protein 43K OMP of Fusobacterium necrophorum

Fusobacterium necrophorum is a Gram negative, spore-free, anaerobic bacterium that can cause pyogenic and necrotic infections in animals and humans. It is a major bovine pathogen and causes hepatic abscesses, foot rot, and necrotic laryngitis. The 43K OMP of F. necrophorum is an outer membrane protein with molecular weight of 43 kDa, exhibiting similarity to pore-forming proteins of other Fusobacterium species that plays an important role in bacterial infections. However, the role of 43K OMP in F. necrophorum adhesion remains unknown. In this study, we evaluated whether the 43K OMP of F. necrophorum mediates adhesion to BHK-21 cells and performed a preliminary screen of the proteins that interact with 43K OMP of F. necrophorum by immunoprecipitation-mass spectrometry. The results showed that the natural 43K OMP and recombinant 43K OMP could bind to BHK-21 cells, and preincubation of F. necrophorum with an antibody against the recombinant 43K OMP of F. necrophorum decreased binding to BHK-21 cells. Seventy differential interacting proteins were successfully screened by immunoprecipitation-mass spectrometry. Among these seventy differential interacting proteins, seven cell membrane proteins and four extracellular matrix proteins shown to be relevant to bacteria adhesion through subcellular localization and single-molecule function analysis. These data increase our understanding of the pathogenesis of F. necrophorum and provide a new theoretical basis for the design of antimicrobial drugs against F. necrophorum.

Antimicrobial Resistance in Clostridium and Brachyspira spp. and Other Anaerobes

This article describes the antimicrobial resistance to date of the most frequently encountered anaerobic bacterial pathogens of animals. The different sections show that antimicrobial resistance can vary depending on the antimicrobial, the anaerobe, and the resistance mechanism. The variability in antimicrobial resistance patterns is also associated with other factors such as geographic region and local antimicrobial usage. On occasion, the same resistance gene was observed in many anaerobes, whereas some were limited to certain anaerobes. This article focuses on antimicrobial resistance data of veterinary origin.

The Cattle Microbiota and the Immune System: An Evolving Field

New insights into the host-microbiota relationship have recently emerged with the advancement of molecular technologies such as next-generation sequencing. This article presents the current knowledge regarding the interaction between bacteria and the immune system of the gut, the uterus, and the mammary gland of cattle.

Atypical presentation of Lemierre's syndrome: case report and literature review

BACKGROUND

The classic Lemierre's syndrome refers to a septic thrombosis of the internal jugular vein, usually caused by a Fusobacterium necrophorum infection starting in the oral cavity, and typically complicated by pulmonary emboli. However, unusual forms of the disorder have been rarely reported.

CASE PRESENTATION

We describe an unusual case of a previously healthy 58-year-old male with Lemierre's syndrome, manifesting with lumbar pain and fever. A thrombosis of the iliac veins and abscesses in the right iliac and the left psoas muscles was diagnosed by a computed tomography scan, together with a right lung pneumonia complicated by pleural effusion and an L4-L5 spondylodiscitis. Blood culture and pus drainage were positive for Fusobacterium nucleatum and an atypical Lemierre's syndrome was suspected. The patient was treated with anticoagulant therapy for 12 weeks and intravenous antibiotic therapy for 6 weeks with a good evolution and resolution of the thrombosis.

CONCLUSIONS

This case illustrates the thrombogenic and thromboembolic tendency of Fusobacterium nucleatum and its potential invasiveness, regardless of the site of primary infection. The concept of an atypical Lemierre's syndrome is redefined here to take into consideration non-cervical sites.

Sites of persistence of Fusobacterium necrophorum and Dichelobacter nodosus: a paradigm shift in understanding the epidemiology of footrot in sheep

Sites of persistence of bacterial pathogens contribute to disease dynamics of bacterial diseases. Footrot is a globally important bacterial disease that reduces health and productivity of sheep. It is caused by Dichelobacter nodosus, a pathogen apparently highly specialised for feet, while Fusobacterium necrophorum, a secondary pathogen in footrot is reportedly ubiquitous on pasture. Two prospective longitudinal studies were conducted to investigate the persistence of D. nodosus and F. necrophorum in sheep feet, mouths and faeces, and in soil. Molecular tools were used to detect species, strains and communities. In contrast to the existing paradigm, F. necrophorum persisted on footrot diseased feet, and in mouths and faeces; different strains were detected in feet and mouths. D. nodosus persisted in soil and on diseased, but not healthy, feet; similar strains were detected on both healthy and diseased feet of diseased sheep. We conclude that D. nodosus and F. necrophorum depend on sheep for persistence but use different strategies to persist and spread between sheep within and between flocks. Elimination of F. necrophorum would be challenging due to faecal shedding. In contrast D. nodosus could be eliminated if all footrot-affected sheep were removed and fade out of D. nodosus occurred in the environment before re-infection of a foot.

Comparative Analysis of Intestine Microbiota of Four Wild Waterbird Species

Waterbirds are ubiquitous and globally distributed. Yet, studies on wild waterbirds' gut microbiota are still rare. Our aim was to explore and compare the gut microbial community composition of wild waterbird species. Four wild waterbird species that are either wintering or all-year residents in Israel were studied: great cormorants, little egrets, black-crowned night herons and black-headed gulls. For each bird, three intestinal sections were sampled; anterior, middle and posterior. No significant differences were found among the microbiota compositions in the three intestine sections of each individual bird. Each waterbird species had a unique microbial composition. The gut microbiota of the black-headed gulls' fundamentally deviated from that of the other bird species, probably due to a very high abundance (58.8%) of the genus Catellicoccus (Firmicutes). Our results suggest a correlation between the waterbird species' phylogeny and their intestine microbial community hierarchical tree, which evinced phylosymbiosis. This recent coinage stands for eco-evolutionary patterns between the host phylogeny and its microbiota composition. We conclude that eco-evolutionary processes termed phylosymbiosis may occur between wild waterbird species and their gut microbial community composition.

Detection of Fusobacterium necrophorum and Dichelobacter nodosus from cow footrot in the Heilongjiang Province, China

Cow footrot in the Heilongjiang Province, northeast China is a problem resulting in lost production in agriculture. In this study, 200 swab samples from footrot lesions of naturally infected cows with odorous exudative inflammation and keratinous hoof separation at 10 farms were examined in the period from May 2016 to May 2017. Twenty cows from each farm were taken for sampling. The samples were examined for detectingthe presence of Dichelobacter nodosus (D. nodosus) and Fusobacterium necrophorum (F. necrophorum). Such detection was carried out using polymerase chain reaction (PCR). The PCR primers were designed to identify the lktA gene, which encodes a leukotoxin unique to F. necrophorum, and the fimA gene of D. nodosus. Of the 200 samples, 111 (55.5%) revealed the presence of F. necrophorum and 11 (5.5%) exhibited D. nodosus. The frequent finding of F. necrophorum in cow farms of Heilongjiang province, northeast China is noteworthy. The possibility of F. necrophorum and D. nodosus infection should be an important concern when controlling cow footrot in China.

Examination of the temporal and spatial dynamics of the gut microbiome in newborn piglets reveals distinct microbial communities in six intestinal segments

Intestinal microbiota plays a crucial role in immune development and disease progression in mammals from birth onwards. The gastrointestinal tract of newborn mammals is rapidly colonized by microbes with tremendous biomass and diversity. Understanding how this complex of segmental communities evolves in different gastrointestinal sites over time has great biological significance and medical implications. However, most previous reports examining intestinal microbiota have focused on fecal samples, a strategy that overlooks the spatial microbial dynamics in different intestinal segments. Using intestinal digesta from six intestinal segments (duodenum, jejunum, ileum, cecum, colon and rectum) of newborn piglets, we herein conducted a large-scale 16S rRNA gene sequencing-based study to characterize the segmental dynamics of porcine gut microbiota at eight postnatal intervals (days 1, 7, 14, 21, 28, 35, 120 and 180). A total of 4,465 OTUs were obtained and showed that the six intestinal segments could be divided into three parts; in the duodenum-jejunum section, the most abundant genera included Lactobacillus and Bacteroides; in the ileum, Fusobacterium and Escherichia; and in the cecum-rectum section, Prevotella. Although the microbial communities of the piglets were similar among the six intestinal segments on postnatal day 1, they evolved and quickly differentiated at later intervals. An examination of time-dependent alterations in the dominant microbes revealed that the microbiome in the large intestine was very different from and much more stable than that in the small intestine. The gut microbiota in newborn piglets exhibited apparent temporal and spatial variations in different intestinal segments. The database of gut microbes in piglets could be a referable resource for future studies on mammalian gut microbiome development in early host growth phases.

Bacterial species associated with interdigital phlegmon outbreaks in Finnish dairy herds

Background

Severe outbreaks of bovine interdigital phlegmon (IP) have occurred recently in several free stall dairy herds in Finland. We studied the aetiology of IP in such herds, and the association of bacterial species with the various stages of IP and herds of various morbidity of IP. Nineteen free stall dairy herds with IP outbreaks and three control herds were visited and bacteriological samples collected from cows suffering from IP (n = 106), other hoof diseases (n = 58), and control cows (n = 64). The herds were divided into high morbidity (morbidity ≥50%) and moderate morbidity groups (9–33%) based on morbidity during the first two months of the outbreak.

Results

F. necrophorum subspecies necrophorum was clearly associated with IP in general, and T. pyogenes was associated with the healing stage of IP. Six other major hoof pathogens were detected; Dichelobacter nodosus, Porphyromonas levii, Prevotella melaninogenica, Treponema spp. and Trueperella pyogenes. Most of the samples of acute IP (66.7%) harboured both F. necrophorum and D. nodosus. We found differences between moderate morbidity and high morbidity herds. D. nodosus was more common in IP lesion in high than in moderate morbidity herds.

Conclusions

Our result confirms that F. necrophorum subspecies necrophorum is the main pathogen in IP, but also T. pyogenes is associated with the healing stage of IP. Our results suggest that D. nodosus may play a role in the severity of the outbreak of IP, but further research is needed to establish other bacteriological factors behind these severe outbreaks.

An Advanced Understanding of Uterine Microbial Ecology Associated with Metritis in Dairy Cows

Metritis, the inflammation of the uterus caused by polymicrobial infections, is a prevalent and costly disease to the dairy industry as it decreases milk yield, survival, and the welfare of dairy cows. Although affected cows are treated with broad-spectrum antibiotics such as ceftiofur, endometrial and ovarian function are not fully recovered, which results in subfertility and infertility. According to culture-dependent studies, uterine pathogens include Escherichia coli, Trueperella pyogenes, Fusobacterium necrophorum, and Prevotella melaninogenica. Recent studies using high-throughput sequencing observed very low relative abundance of Escherichia coli, Trueperella pyogenes, and Prevotella melaninogenica in cows with metritis. Herein, we propose that metritis is associated with a dysbiosis of the uterine microbiota, which is characterized by high abundance of Bacteroides, Porphyromonas, and Fusobacterium.

The detection and prevalence of leukotoxin gene variant strains of Fusobacterium necrophorum in footrot lesions of sheep in Kashmir, India

The objective of this study was to determine the prevalence and identification of leukotoxin gene, lktA, variant strains of Fusobacterium necrophorum in the footrot lesions of sheep. The detection of F. necrophorum was carried out by PCR targeting the lktA gene fragment and identification of lktA variant strains was done by PCR-single stranded conformational polymorphism (PCR-SSCP) and gene sequencing. Of the 450 swabs collected from footrot lesions of sheep, 117 were lktA-positive for F. necrophorum. Of the 50 swabs collected from apparently asymptomatic sheep, only one was lktA-positive for F. necrophorum. The overall prevalence of F. necrophorum in footrot affected sheep in Kashmir valley was 26%, and ranged from 20 to 34.8%, respectively. PCR-SSCP of lktA gene fragment analysis revealed three lktA variants, designated as JKS-F1/F2/F3, while two samples (1.7%) showed multiple lktA variant strains of F. necrophorum in a single footrot-affected sheep hoof. This appears to be the first report on the presence of more than one lktA variant of F. necrophorum in a footrot lesion of sheep. The JKS-F3 lktA variant was the most frequent (75.4%), followed by JKS-F2 (14.4%) and JKS-F1 (8.4%), respectively. Among the three lktA variants identified, JKS-F3 was detected in 74 (86.0%) samples from severe footrot affected sheep with a lesion score of 4. The data suggest that JKS-F3 is the predominant lktA variant of F. necrophorum and is associated with severe footrot in sheep. Hence, JKS-F3 may be a significant variant contributing to the severity and duration of the disease in sheep.

Quantifying known and emerging uterine pathogens, and evaluating their association with metritis and fever in dairy cows

Metritis is caused by polymicrobial infection; however, recent metagenomic work challenges the importance of known pathogens such as Escherichia coli and Trueperella pyogenes while identifying potential new pathogens such as Bacteroides pyogenes, Porphyromonas levii and Helcococcus ovis. This study aims to quantify known and emerging uterine pathogens, and to evaluate their association with metritis and fever in dairy cows. Metritis was diagnosed at 6 ± 2 days postpartum, a uterine swab was collected and rectal temperature was measured. 39 cows were classified into three groups: Healthy (n = 14), Metritis without fever (MNoFever; n = 12), and Metritis with fever (MFever; n = 13). Absolute copy number was determined for total bacteria and for 8 potentially pathogenic bacteria using droplet digital PCR. Both MNoFever and MFever cows had higher copy number of total bacteria, Fusobacterium necrophorum, Prevotella melaninogenica, Bacteroides pyogenes, Porphyromonas levii, and Helcococcus ovis than Healthy cows. MNoFever and MFever groups were similar. There was no difference among groups in copy number of Escherichia coli, Trueperella pyogenes, and Bacteroides heparinolyticus, and they all had low copy numbers. Our work confirms the importance of some bacteria identified by culture-based studies in the pathogenesis of metritis such as Fusobacterium necrophorum and Prevotella melaninogenica; however, it challenges the importance of others such as Escherichia coli and Trueperella pyogenes at the time of metritis diagnosis. Additionally, Bacteroides pyogenes, Porphyromonas levii, and Helcococcus ovis were recognized as emerging pathogens involved in the etiology of metritis. Furthermore, fever was not associated with the total bacterial load or specific bacteria.

Characterization of Fusobacterium necrophorum subsp. necrophorum outer membrane proteins

Liver abscesses are of major economic importance to the cattle industry. These are mainly associated with the presence of Fusobacterium necrophorum, a non-spore forming and Gram-negative anaerobe. There are two main subspecies, F. necrophorum subspecies necrophorum and subsp. funduliforme, and they differ molecularly, morphologically, biochemically and in virulence. Previous studies have shown that the outer membrane proteins (OMP) of F. necrophorum subsp. necrophorum are important for its successful binding to immobilized bovine adrenal gland capillary endothelial (EJG) cells. In this study, a 42.4 kDa OMP of F. necrophorum subsp. necrophorum with the highest binding capacity to EJG cells was characterized. The gene was cloned into pFLAG-CTS vector and the proteins were subsequently expressed on the surface of E. coli BL21 DE3 cells. When E. coli carrying the recombinant plasmid (SM 2013) was induced using IPTG, there was significant enhancement in the binding to immobilized EJG cells compared to both uninduced SM 2013 and the E. coli carrying control vector only. When fixed EJG cells were incubated with purified native OMP, SM 2013 showed lowered levels of binding, compared to the uninduced SM 2013 and the E. coli carrying control vector only. Pre-incubation of induced SM 2013 with polyclonal antibodies made against the OMP reduced the binding to immobilized EJG cells to uninduced SM 2013 levels. This gain of function by recombinant E. coli confirms the ability of this protein to act as an adhesion to help binding of F. necrophorum subsp. necrophorum to host cells.

Bacterial flora of liver abscesses in crossbred beef cattle and Holstein steers fed finishing diets with or without tylosin

Holstein steers raised for beef production consistently have a higher prevalence and more severe form of liver abscesses than cattle of beef breeds. A study was conducted to compare bacterial flora of liver abscesses collected from multiple abattoirs from 4 groups of cattle, arranged in a 2 × 2 factorial design, consisting of crossbred cattle and Holstein steers, and each group fed a finishing diet supplemented with or without tylosin. A total of 383 liver abscess samples, consisting of 94 and 81 from crossbred cattle and 89 and 119 from Holstein steers fed finishing diets with or without tylosin, respectively, were subjected for anaerobic and aerobic bacterial isolations. The minimum inhibitory concentrations (MIC) of tylosin to the predominant bacterial species were determined. The likelihood chi-square test was performed to assess unadjusted differences in bacterial prevalence proportions between the 2 types of cattle (crossbred and Holstein steers) and feed type (tylosin or no tylosin). There was no interaction between cattle type and tylosin inclusion on the prevalence of any of the bacterial species isolated. Liver abscesses from Holstein steers yielded a higher total number of isolates compared to liver abscesses from crossbred cattle (1060 vs. 788). subsp. was isolated from all abscesses. The prevalence of subsp. was 19.1% and was not affected by the cattle type or tylosin. The prevalence of was higher ( < 0.01) in crossbred cattle (73.7%) compared to Holstein steers (29.8%). Also, the prevalence of was higher in abscesses from tylosin-fed (66.1%) cattle than no tylosin-fed cattle (35%). The overall prevalence of was 25.3% and was similar ( = 0.58) between cattle type, but the prevalence was lower ( < 0.01) in tylosin-fed (16.9%) compared to no tylosin-fed group (33%). Mean MIC of tylosin for and were similar across both cattle types and tylosin inclusion. Although bacterial flora of liver abscesses from Holstein steers appeared to be more diverse than that of crossbred cattle, there was no difference in the prevalence of the and and in fact, prevalence of was higher in crossbred than Holstein steers. Therefore, the difference in bacterial flora is not the likely reason for higher prevalence and severity of liver abscesses in Holstein steers than crossbred beef cattle.

Development and validation of a multiple locus variable number tandem repeat analysis (MLVA) scheme for Fusobacterium necrophorum

Fusobacterium necrophorum is associated with various diseases in humans and animals. Reservoirs (sites where the pathogen persists in the absence of disease) of F. necrophorum are believed to be present in healthy individuals e.g. tonsillar epithelium, or their environment e.g. soil, but for most diseases the reservoir sites are unknown. Strain typing of F. necrophorum would facilitate linking specific reservoirs with a specific disease. The aim of this study was to develop multiple locus variable number tandem repeat analysis (MLVA) as a strain typing technique for F. necrophorum, and to test the use of this scheme to analyse both isolates and mixed communities of bacteria. Seventy-three tandem repeat regions were identified in the F. necrophorum genome; three of these loci were suitable and developed as a MLVA scheme. The MLVA scheme was sensitive, specific, and discriminatory for both isolates and communities of F. necrophorum. The MLVA scheme strain typed 46/52F. necrophorum isolates including isolates of both subspecies and from different countries, host species and sample sites within host. There were 12 unique MLVA strain types that clustered by subspecies. The MLVA scheme characterised the F. necrophorum community in DNA from 32/49 foot- and 28/33 mouth swabs from sheep. There were 17 community types in total. In 31/32 foot swabs, single strains of F. necrophorum were detected while in the 28 mouth swabs there were up to a maximum of 8 strains of F. necrophorum detected. The results demonstrate the potential for this method to elucidate reservoirs of F. necrophorum.

Mixed species biofilms of Fusobacterium necrophorum and Porphyromonas levii impair the oxidative response of bovine neutrophils in vitro

Biofilms composed of anaerobic bacteria can result in persistent infections and chronic inflammation. Host immune cells have difficulties clearing biofilm-related infections and this can result in tissue damage. Neutrophils are a vital component of the innate immune system and help clear biofilms. The comparative neutrophilic response to biofilms versus planktonic bacteria remains incompletely understood, particularly in the context of mixed infections. The objective of this study was to generate mixed species anaerobic bacterial biofilms composed of two opportunistic pathogens, Fusobacterium necrophorum and Porphyromonas levii, and evaluate neutrophil responses to extracellular fractions from both biofilms and planktonic cell co-cultures of the same bacteria. Purified bovine neutrophils exposed to culture supernatants from mixed species planktonic bacteria showed elevated oxidative activity compared to neutrophils exposed to biofilms composed of the same bacteria. Bacterial lipopolysaccharide plays a significant role in the stimulation of neutrophils; biofilms produced substantially more lipopolysaccharide than planktonic bacteria under these experimental conditions. Removal of lipopolysaccharide significantly reduced neutrophil oxidative response to culture supernatants of planktonic bacteria. Oxidative responses to LPS-removed biofilm supernatants and LPS-removed planktonic cell supernatants were similar. The limited neutrophil response to biofilm bacteria observed in this study supports the reduced ability of the innate immune system to eradicate biofilm-associated infections. Lipopolysaccharide is likely important in neutrophil response; however, the presence of other extracellular, immune modifying molecules in the bacterial media also appears to be important in altering neutrophil function.

The bovine colostrum microbiome and its association with clinical mastitis

In an effort to characterize colostrum microbial diversity and its potential associations with early-lactation clinical mastitis, we used high-throughput sequencing of the 16S rRNA gene to investigate the bovine colostrum microbiome. A prospective observational study was conducted that included 70 Holstein cows; colostrum samples were collected from all 4 mammary gland quarters. Colostrum samples were categorized according to whether the quarter was diagnosed (CMC) or not diagnosed (NCMC) with clinical mastitis during the first 30 d postpartum. Colostrum samples were dominated by Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, Fusobacteria, and Tenericutes phyla, with the 6 most common taxa [order (o), family (f), and genus (g)] being g_Staphylococcus, g_Prevotella, f_Ruminococcaceae, o_Bacteroidales, o_Clostridiales, and g_Pseudomonas. The colostrum microbiota of primiparous cows was significantly richer (higher number of bacterial species) than that of multiparous cows, and differences in colostrum taxonomic structure between parities were also observed. The microbial community of NCMC samples of primiparous cows was significantly more diverse than that of CMC samples, and the relative abundances of the Tenericutes and Fusobacteria phyla as well as the Mycoplasma and Fusobacterium genera were significantly higher in NCMC than in CMC samples of primiparous cows. The colostrum core microbiome, defined as the bacterial taxa common to all colostrum samples examined, was composed of 20 taxa and included bacterial genera already known to be associated with mastitis (e.g., Staphylococcus, Mycoplasma, and Streptococcus spp.). Our results indicate that the colostrum microbiome of primiparous cows differs from that of multiparous cows, and it harbors some diversity and taxonomic markers of mammary gland health specific to primiparous cows only.

LEISHMANIA INFANTUM INFECTION IN BENNETT'S WALLABIES (MACROPUS RUFOGRISEUS RUFOGRISEUS) IN A SPANISH WILDLIFE PARK

Although dogs are the main reservoir for human Leishmania infantum infection, the disease has also been reported in other domestic and wild mammals. In 2011, a fatal case of naturally acquired leishmaniosis was described for the first time in a Bennett's wallaby (Macropus rufogriseus rufogriseus) kept in a wildlife park in Madrid (Spain). This study was designed to assess the infection status of twelve Bennett's wallabies in the same park one year after this incident. Phlebotomus perniciosus, the main vector of L. infantum in Spain, was screened for using sticky and Centers for Disease Control miniature light traps. L. infantum infection was confirmed by molecular diagnosis in four animals, but only one wallaby returned a positive serology result. The presence of the sand fly vector was also confirmed in this habitat. These results suggest that the first case of L. infantum in a wallaby in this park was not an isolated incident and stress the need for further work to determine the role of this parasite in the morbidity and mortality of these macropods. Madrid was recently the scene of an outbreak of human cutaneous and visceral leishmaniosis. Epidemiological studies have so far revealed the widespread presence of L. infantum infection in animals other than the dog. Our ongoing work suggests a risk of L. infantum infection not only among captive animals in Madrid, but also among threatened species or even species that are already extinct in the wild.