Outer membrane proteins of Pasteurella multocida

In field evaluation of impact on clinical signs of an inactivated autogenous vaccine against Pasteurella multocida in rabbits

In Italy, the use of autogenous inactivated vaccines prepared with the bacterial strains isolated from affected animals is authorized by the Ministry of Health in farms where bacterial diseases occur frequently. The autogenous vaccine performed using Pasteurella multocida is frequently used in rabbit farms, but the feedback of its application is not available. Therefore, the aim of this study is to give information about the impact on the clinical signs of a bivalent autogenous vaccine in rabbits of a genetic centre. The vaccine was prepared using two P. multocida strains belonging to serogroups A and F, equipped with virulence genes and responsible for cyclical outbreak of pasteurellosis in the farm. The vaccine was administered with a first injection, followed by another one after 15 days, then another one four months after the first injection, and then continuing with a further injection every six months to all rabbits. Clinical conditions and mortality rates were monitored for two years after the first vaccination. The improvement in clinical condition and the decrease of the mortality rate were significant especially in the first year post-vaccine. In addition, the number of animals removed due to the disease decreased greatly. Based on the finding of P. multocida strains belonging to serogroup D and serogroup A equipped with different virulence-gene patterns from those previously found, we suggest that the vaccine was unable to prevent the introduction and spreading of new strains among the rabbits.

Characterisation of Pasteurella multocida Strains from Different Lesions in Rabbits

Pasteurellosis, a disease caused by Pasteurella multocida, is responsible for economic losses in rabbit industrial farms due to rhinitis, conjunctivitis, pneumonia, metritis, mastitis, orchitis, subcutaneous abscesses, otitis, encephalitis, and septicaemic forms. Although the occurrence of the disease is conditioned by predisposing factors that affect the rabbit immune response, the strains of P. multocida involved in the infection may have a different pathogenic ability. Therefore, typing of strains spread among the rabbits is important to assess their pathogenic potential. The aim of this study is to investigate the P. multocida strains responsible for disease in rabbit industrial farms. A total of 114 strains identified from different lesions were serotyped. Additionally, the presence of virulence-associated genes was investigated using three PCR (polymerase chain reaction) protocols. Capsular type A was prevalently found in strains from respiratory lesions while types D and F in those from metritis, mastitis, and other lesions. Different associations between some virulence-associated genes and both capsular type and lesions found in rabbits were detected. The presence of 8 virulence-associated genes seems to increase the occurrence of metritis. In addition, strains belonging to capsular type A and responsible for respiratory disorders especially, were found equipped with 10 and 11 virulence-associated genes. Nevertheless, the presence of strains responsible only for rhinitis was also detected among the latter, suggesting that the pathogenic ability of the bacteria depends on the expression rather than the presence of a gene.

Dendritic cell targeting peptide plus Salmonella FliCd flagellin fused outer membrane protein H (OmpH) demonstrated increased efficacy against infections caused by different Pasteurella multocida serogroups in mouse models

As the major outer membrane protein (OMP) presents in the Pasteurella multocida envelope, OmpH was frequently expressed for laboratory assessments of its immunogenicity against P. multocida infections, but the results are not good. In this study, we modified OmpH with dendritic cell targeting peptide (Depeps) and/or Salmonella FliCd flagellin, and expressed three types of recombinant proteins with the MBP tag (rDepeps-FliC-OmpH-MBP, rDepeps-OmpH-MBP, rFliC-OmpH-MBP). Assessments in mouse models revealed that vaccination with rDepeps-FliC-OmpH-MBP, rDepeps-OmpH-MBP, or rFliC-OmpH-MBP induced significant higher level of antibodies as well as IFN-γ and IL-4 in murine sera than vaccination with rOmpH-MBP (P < 0.5). Vaccination with the three modified proteins also provided increased protection (rDepeps-FliC-OmpH-MBP, 70 %; rDepeps-OmpH-MBP, 50 %; rFliC-OmpH-MBP, 60 %) against P. multocida serotype D compared to vaccination with rOmpH-MBP (30 %). In mice vaccinated with different types of modified OmpHs, a significantly decreased bacterial strains were recovered from bloods, lungs, and spleens compared to rOmpH-MBP-vaccinated mice (P < 0.5). Notably, our assessments also demonstrated that vaccination with rDepeps-FliC-OmpH-MBP provided good protection against infections caused by a heterogeneous group of P. multocida serotypes (A, B, D). Our above findings indicate that modification with DCpep and Salmonella flagellin could be used as a promising strategy to improve vaccine effectiveness.

NLRC3 negatively regulates Pasteurella multocida-induced NF-κB signaling in rabbits

Pasteurella multocida (P. multocida) is a significant zoonotic pathogen that has the ability to infect various animals. The inflammatory response caused by P. multocida and the negative regulatory mechanism are not completely understood. NOD-like receptor family CARD-containing 3 (NLRC3), an intracellular member of the NLR family, has been reported as a negative regulator in human. In this study, we aimed to explore the role of rabbit NLRC3 (rNLRC3) in P. multocida infection. Our findings revealed a negative correlation between the expression of rNLRC3 and inflammatory cytokines during P. multocida infection. The expression of rNLRC3 was reduced at the initial stage of P. multocida infection and then recovered. Furthermore, rNLRC3 significantly inhibited the activation of NF-κB by reducing phosphorylation and nuclear import of p65 in response to P. multocida infection. Additionally, overexpression of rNLRC3 attenuated the expression of pro-inflammatory cytokines IL-1β, IL-6, IL-8, and TNF-α. Moreover, we demonstrated that rNLRC3 diminished NF-κB activation by interacting with rTRAF4 and rTRAF6. Overexpression of rNLRC3 promoted P. multocida proliferation, while P. multocida proliferation decreased after knockdown of rNLRC3. We also found that the NACHT-LRR domain is a functional domain of rNLRC3 that regulates the NF-κB pathway. Our study suggests that rNLRC3 negatively regulates P. multocida-induced NF-κB signaling in rabbits. It can serve as a checkpoint to prevent dysfunctional inflammation.

Characterization of Three New Outer Membrane Adhesion Proteins in Fusobacterium necrophorum

Fusobacterium necrophorum, an anaerobic Gram-negative pathogen, causes necrotic cattle infections, impacting livestock health and the US feedlot industry. Antibiotic administration is the mainstay for treating F. necrophorum infections, although resistance hampers their effectiveness. Vaccination, especially targeting outer membrane proteins (OMPs) due to their antigenic properties and host specificity, offers an alternative to antibiotics. This study identified high-binding-affinity adhesion proteins from F. necrophorum using binding and pull-down assays with bovine adrenal gland endothelial cells (EJG). Four OMP candidates (17.5 kDa/OmpH, 22.7 kDa/OmpA, 66.3 kDa/cell surface protein (CSP), and a previously characterized 43 kDa OMP) were expressed as recombinant proteins and purified. Rabbit polyclonal antibodies to recombinant OMPs were generated, and their ability to inhibit bacterial binding in vitro was assessed. The results show that treatment with individual polyclonal antibodies against 43 kDa significantly inhibited bacterial adhesion, while other antibodies were less potent. However, combinations of two or more antibodies showed a more prominent inhibitory effect on host-cell adhesion. Thus, our findings suggest that the identified OMPs are involved in fusobacterial attachment to host cells and may have the potential to be leveraged in combination for vaccine development. Future in vivo studies are needed to validate their roles and test the feasibility of an OMP-based subunit vaccine against fusobacterial infections.

Calcium phosphate nanoparticles conjugated with outer membrane vesicle of Riemerella anatipestifer for vaccine development in ducklings

Biodegradable calcium phosphate nanoparticles offer a viable substitute for traditional adjuvants such as aluminum in vaccine production. Calcium phosphate nanoparticle adjuvanted with outer membrane vesicle (OMV) of gram negative bacteria may induce efficient immune response in the host. The present study was carried out to evaluate the potential of a mucosal vaccine formulation of calcium phosphate (CAP) nanoparticle using OMV of Riemerella anatipestifer (RA) as antigen against New Duck disease in ducks. The work was initiated with isolation, identification of RA, followed by OMV production and extraction. The CAP-OMV nanoparticle was prepared and characterized. The efficacy of the vaccine formulation and toxicity were studied in ducks. The average OMV yield in terms of protein concentration was found to be 122.33 ± 3.48 mg per liter of BHI broth. In SDS-PAGE, isolated OMVs exhibited presence of 16 distinct protein bands with molecular weight ranging from 142.1 to 12.1 kDa. Seven protein bands of 74.1, 69.3, 55.5, 50.6, 45.6, 25.1 and 13.1 kDa were detected relatively more distinct. The major bands detected in our findings were 42 kDa, 37 kDa and 16 kDa that corresponds to OmpA, OmpH, P6 respectively. The mean zeta size (±SD) and potential of the nanoparticle were 246.20 ± 0.53 nm and -25.60 ± 5.97 respectively. In transmission electron microscopy (TEM), the nanoparticles exhibited an average diameter of 129.80 ± 11.10 nm and displayed spherical morphology. The median protective dose (PD50) of CAP-OMV nanoparticle was 1881.10 μg of protein. Group I ducks received 3762 μg of protein (entrapped protein in CAP-OMV nanoparticle) via intra nasal route and it showed the highest serum IgG and secretory IgA level than other immunized groups. All experimental ducks were challenged with 10 × LD50 on 35 days of post primary immunization. Group I showed 100 % survivability in the challenge study. No gross and biochemical indication of acute or chronic toxicity were recorded. In conclusion, our results suggest that CAP-OMV nanoparticle can be a safe and efficient mucosal vaccine delivery system for RA, eliciting strong immune response in the host.

First report of whole genome sequence of septicemic Pasteurella multocida serovar B:2 'Soron' strain isolated from swine

Pig pasteurellosis, caused by Pasteurella multocida, is an acute infection that also has economic implications for pig farmers. We report the complete genome sequence of a P. multocida, serovar B:2 'Soron' strain isolated from the blood of a pig that had died of pasteurellosis in India. The isolate was not found to be haemorrhagic septicaemia (HS) specific B:2 by the PCR assay. The genome of 'Soron' strain is a single circular chromosome of 2,272,124 base pairs in length and contains 2014 predicted coding regions, 4 ribosomal RNA operons, and 52 tRNAs. It has 1812 protein-coding genes that were also found in reference sequence PmP52Vac. Phylogenetic analysis revealed that Pm_P52VAc and P. multocida 'Soron' serovar B:2 were clustered in different clades. Pasteurella multocida 'Soron' serovar B:2 was found to cluster with the same ancestor of Pm70, which is of avian origin. The genome was found to contain regions that encode proteins which may confer resistance to various antibiotics including cephalosporin, which is used to treat pasteurellosis. The isolate was also found to harbour a phage region. This strain represents a novel multi-locus sequence type (MLST) that has not been previously identified, as all of the alleles used for MLST were found, but did not match any of the alleles in the database with 100% nucleotide identity. The most closely related ST was ST221. This is the first whole-genome sequence from P. multocida serovar B:2 of pig origin.

Combinations but Not a Single PlpE Epitope Induces Host Protective Immunity against Pasteurella multocida

Pasteurella multocida is the causative agent of a wide range of diseases (pasteurellosis) and a zoonotic pathogen in humans. Recombinant subunit vaccines are hot spots in recent pasteurellosis vaccine development. A chimeric vaccine is also constructed for rabbit hemorrhagic disease virus (RHDV) protective antigen VP60 chimeric with fragments of Pasteurella multocida protective antigen PlpE. The protective efficacy of the chimeric vaccine against P. multocida is not as high as that of PlpE, and the reason is not well known. In this study, we analyzed the linear B-cell epitopes of PlpE and then assessed the protective efficacy of these epitopes and their combinations. It was found that the immunodominant region of PlpE was mainly located in the region between the 21st to the 185th amino acids from the N terminus. Overlapping peptide scanning results demonstrated that this region contained six nonoverlapping epitopes, and epitope E was the predominant epitope. Chimeric protein antigens were constructed of single nonoverlapping PlpE epitopes or their combinations chimeric with the RHDV VP60 P domain. Immunization with recombinant antigen chimeric with a single PlpE epitope exhibited poor immunoprotection, whereas immunization with recombinant antigen chimeric with PlpE epitope combinations (epitopes A and E; epitopes C and E; epitopes A, C, and E; and epitopes B, D, and F) exhibited significant immunoprotection. In a word, P. multocida protective antigen PlpE contained six nonoverlapping linear B-cell epitopes, and combinations but not a single epitope induced host protective immunity. Our work will give help for future chimeric vaccine design.

First study on capsular serotypes and virulence factors of Pasteurella multocida isolates from Phan Rang sheep in Vietnam

Background and Aim: Pasteurella multocida is considered as a main factor mediating pneumonic pasteurellosis in ruminants, including sheep. It is also a current threat to Phan Rang sheep in Vietnam. This study aimed to characterize P. multocida isolated from Phan Rang sheep, their antibiotic resistance profile, and the prevalence of some virulence-associated genes of these strains. Materials and Methods: Bacteria were isolated on brain heart infusion, 10% sheep blood agar plates, and screened by biochemical tests. The polymerase chain reaction technique was used with specific primers to identify P. multocida, the presence of virulence-associated genes, and serotypes of isolates. Antimicrobial susceptibility and biofilm formation of isolates were examined using the disk diffusion method and crystal violet-based method, respectively. Results: A total of 41 P. multocida strains were isolated from 485 samples from clinically sick and healthy sheep. Of the isolates, 58.53% were serotype A, 9.75% were serotype B, and 31.71% were serotype D. Healthy animals were infected with serotype D only. All 15 virulence genes were identified in all strains isolated from clinically sick sheep, while strains isolated from healthy sheep carried 11/15 virulence genes tested. Among virulence-associated genes exbB, exbD, tonB, ompA, oma87, fimA, hgbA, and nanB were detected in over 90% of isolates, whereas hgbB, nanH, tbpA and pfhA were less frequent. Interestingly, pmHAS and tadD were highly prevalent in capsular type A strains, whereas the toxA gene was detected in capsular type D strains only. All of the isolated strains were fully susceptible to enrofloxacin, ciprofloxacin, neomycin, and ofloxacin. About 92.68% were susceptible to chloramphenicol and 90.24% to amikacin, but there was high resistance to erythromycin, tetracycline, and amoxicillin. Our results reveal that 53.65% of 41 isolates could produce biofilm, whereas 46.34% could not. Conclusion: Pasteurella multocida from Phan Rang sheep possess many virulence genes and resistance to several common antibiotics such as erythromycin, tetracycline, and amoxicillin. The results are an important warning regarding antibiotic resistance of P. multocida.

Experimental pathogenicity and comparative genome analysis of high- and low-virulence strains of rabbit-origin Pasteurella multocida

Pasteurella multocida, the causative pathogen of rabbit pasteurellosis, causes significant economic losses in the commercial rabbit industry. However, the associated pathogenic mechanism of P. multocida remains unclear. The aim of this study is to compare the genomes and pathogenicity of high- and low-virulence strains of P. multocida to advance the current understanding of rabbit pasteurellosis. The high-virulence strain rapidly proliferates in the lung and spleen of infected mice within approximately 9 h, maintaining a high bacterial load until host death. Meanwhile, the low-virulence strain only proliferates in mouse organs for a short time, with the bacterial load beginning to decrease 13 h post-infection. Moreover, the expressions of inflammatory cytokines MCP-1, TNF-α, and IL-1β are upregulated in all infected mouse lung and spleen tissue, however, the high-virulence strain induced significantly higher expression than the low-virulence strain. Histopathological analysis revealed greater inflammation and tissue lesions in the lung and spleen of mice infected with the high-virulence strain. Two pathogenicity-associated regions unique to the genome of the high-virulence strain harbor approximately 199 genes, including functional genes related to virulence factors, such as lipopolysaccharide biosynthesis, iron acquisition, biosynthesis of outer membrane proteins, and adhesion. These two genomic regions are shared by three previously sequenced, highly virulent P. multocida strains in rabbits. In conclusion, the increased pathogenicity of high-virulence P. multocida may be due to the presence of virulence-associated genes in two unique genomic regions, resulting in strong proliferative activity, significant inflammation, and pathological lesions in the mouse model. These findings provide important insights regarding the pathogenic mechanism underlying rabbit pasteurellosis.

Immunogenicity and protective efficacy of the recombinant Pasteurella multocida lipoproteins VacJ and PlpE, and outer membrane protein H from P. multocida A:1 in ducks

Duck cholera (duck hemorrhagic septicemia) is a highly contagious disease caused by Pasteurella multocida, and is one of the major bacterial diseases currently affecting the duck industry. Type A is the predominant pathogenic serotype. In this study, the genes encoding the lipoproteins VacJ, PlpE, and the outer membrane protein OmpH of P. multocida strain PMWSG-4 were cloned and expressed as proteins in E. coli. The recombinant VacJ (84.4 kDa), PlpE (94.8 kDa), and OmpH (96.7 kDa) proteins were purified, and subunit vaccines were formulated with a single water-in-oil adjuvant, while killed vaccines were prepared using a single oil-coated adjuvant. Antibody responses in ducks vaccinated with recombinant VacJ, PlpE, and OmpH proteins formulated with adjuvants were significantly antigenic (p<0.005). Protectivity of the vaccines was evaluated via the intraperitoneal challenge of ducks with 20 LD50 doses of P. multocida A: 1. The vaccine formulation consisting of rVacJ, rPlpE, rOmpH, and adjuvant provided 33.3%, 83.33%, and 83.33% protection, respectively, the vaccine formulation consisting of three recombinant proteins, rVacJ, rPlpE, rOmpH and adjuvant, was 100% protective, and the killed vaccine was 50% protective. In addition, it was shown through histopathological examination and tissue bacterial load detection that all vaccines could reduce tissue damage and bacterial colonization to varying (p<0.001). These findings indicated that recombinant PlpE or OmpH fusion proteins formulated with oil adjuvants have the potential to be used as vaccine candidates against duck cholera subunits.

Mannheimia haemolytica OmpH binds fibrinogen and fibronectin and participates in biofilm formation

Mannheimia haemolytica is the causal agent of the shipping fever in bovines and produces high economic losses worldwide. This bacterium possesses different virulence attributes to achieve a successful infection. One of the main virulence factors expressed by a pathogen is through adhesion molecules; however, the components participating in this process are not totally known. The present work identified a M. haemolytica 41 kDa outer membrane protein (Omp) that participates in bacterial adhesion. This protein showed 100% identity with the OmpH from M. haemolytica as determined by mass spectrometry and it interacts with sheep fibrinogen. The 41 kDa M. haemolytica OmpH interacts with bovine monocytes; a previous incubation of M. haemolytica with a rabbit hyperimmune serum against this Omp diminished 45% cell adhesion. The OmpH was recognized by serum from bovines affected by acute or chronic pneumonia, indicating its in vivo expression; moreover, it showed immune cross-reaction with the serum of rabbit infected with Pasteurella multocida. The OmpH is present in biofilms and previous incubation of M. haemolytca with rabbit serum against this protein diminished biofilm, indicating this protein's participation in biofilm formation. M. haemolytica OmpH is proposed as a relevant immunogen in bovine pneumonia protection.

Spreading of Pasteurella multocida Infection in a Pet Rabbit Breeding and Possible Implications on Healed Bunnies

The number of pets such as dogs, cats, rabbits, and parrots has increased in European families. Social benefits to owners such as decreasing feelings of loneliness and anxiety are provided by pets which are also used in Animal-assisted Therapy (AAT). Nevertheless, human-animal interactions are also associated with health problems including allergies, asthma, and zoonosis. Rabbits may carry potential pathogens for humans. One of the most common bacteria that colonizes the oro-pharynx and the upper respiratory tract of rabbits is Pasteurella (P.) multocida. Transmission of the infection to humans results from scratches, licks, and bites but it also can occur from the inhalation of air particles containing the microorganism. Immunocompromised people or persons with pulmonary disorders are particularly susceptible to the infection. Infected rabbits may carry P. multocida with or without clinical signs. In this paper, the sensitivity to antibiotics and the invasiveness ability of P. multocida identified in a farm of pet rabbits affected by severe pasteurellosis were investigated. The strain was P. multocida belonging to capsular type A which is the type most often detected in humans. The identified strain was susceptible to the tested antibiotics, but it appeared equipped with several virulence genes which are responsible for fimbriae production, adhesion processes to host cells, enzyme production, and are involved in iron acquisition processes. These findings are of particular interest because rabbits recovered from pasteurellosis very often become carriers of the bacteria. Therefore, we suggest considering P. multocida screening in the routine medical checks of rabbits, especially if they are meant to be companion animals for children and elder people, given that the transmission of the pathogen cannot be excluded.

Screening and purification of NanB sialidase from Pasteurella multocida with activity in hydrolyzing sialic acid Neu5Acα(2–6)Gal and Neu5Acα(2–3)Gal

Study on sialidases as antiviral agents has been widely performed, but many types of sialidase have not been tested for their antiviral activity. Pasteurella multocida NanB sialidase is one such sialidase that has never been isolated for further research. In this study, the activity of NanB sialidase was investigated in silico by docking the NanB sialidase of Pasteurella multocida to the Neu5Acα(2–6)Gal and Neu5Acα(2–3)Gal ligands. Additionally, some local isolates of Pasteurella multocida, which had the NanB gene were screened, and the proteins were isolated for further testing regarding their activity in hydrolyzing Neu5Acα(2–6)Gal and Neu5Acα(2–3)Gal. Silico studies showed that the NanB sialidase possesses an exceptional affinity towards forming a protein–ligand complex with Neu5Acα(2–6)Gal and Neu5Acα(2–3)Gal. NanB sialidase of Pasteurella multocida B018 at 0.129 U/mL and 0.258 U/mL doses can hydrolyze Neu5Acα(2–6)Gal and Neu5Acα(2–3)Gal better than other doses. In addition, those doses can inhibit effectively H9N2 viral binding to red blood cells. This study suggested that the NanB sialidase of Pasteurella multocida B018 has a potent antiviral activity because can hydrolyze sialic acid on red blood cells surface and inhibit the H9N2 viral binding to the cells.

Molecular Insight into Gene Response of Diorcinol- and Rubrolide-Treated Biofilms of the Emerging Pathogen Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is a multidrug-resistant human opportunistic pathogen. S. maltophilia contributes to disease progression in cystic fibrosis patients and is found in wounds and infected tissues and on catheter surfaces. Due to its well-known multidrug resistance, it is difficult to treat S. maltophilia infections. Strain-specific susceptibility to antimicrobials has also been reported in several studies. Recently, three fungal diorcinols and 14 rubrolides were shown to reduce S. maltophilia K279a biofilm formation. Based on these initial findings, we were interested to extend this approach by testing a larger number of diorcinols and rubrolides and to understand the molecular mechanisms behind the observed antibiofilm effects. Of 52 tested compounds, 30 were able to significantly reduce the biofilm thickness by up to 85% ± 15% and had strong effects on mature biofilms. All compounds with antibiofilm activity also significantly affected the biofilm architecture. Additional RNA-sequencing data of diorcinol- and rubrolide-treated biofilm cells of two clinical isolates (454 and K279) identified a small set of shared genes that were affected by these potent antibiofilm compounds. Among these, genes for iron transport, general metabolism, and membrane biosynthesis were most strongly and differentially regulated. A further hierarchical clustering and detailed structural inspection of the diorcinols and rubrolides implied that a prenyl group as side chain of one of the phenyl groups of the diorcinols and an increasing degree of bromination of chlorinated rubrolides were possibly the cause of the strong antibiofilm effects. This study gives a deep insight into the effects of rubrolides and diorcinols on biofilms formed by the important global pathogen S. maltophilia.

IMPORTANCE Combating Stenotrophomonasmaltophilia biofilms in clinical and industrial settings has proven to be challenging. S. maltophilia is multidrug resistant, and occurrence of resistance to commonly used drugs as well as to antibiotic combinations, such as trimethoprim-sulfamethoxazole, is now frequently reported. It is therefore now necessary to look beyond conventional and already existing antimicrobial drugs when battling S. maltophilia biofilms. Our study contains comprehensive and detailed data sets for diorcinol and rubrolide-treated S. maltophilia biofilms. The study defines genes and pathways affected by treatment with these different compounds. These results, together with the identified structural elements that may be crucial for their antibiofilm activity, build a strong backbone for further research on diorcinols and rubrolides as novel and potent antibiofilm compounds.

Spatial, Temporal, and Demographic Patterns in the Prevalence of Hemorrhagic Septicemia in 41 Countries in 2005–2019: A Systematic Analysis with Special Focus on the Potential Development of a New-Generation Vaccine

Hemorrhagic septicemia (HS) caused by Pasteurella multocida B:2 and E:2 is among the fatal bacterial diseases in cattle and buffaloes that are economically valuable in Asian and African countries. The current work aims to study the prevalence of HS among buffaloes, cattle, sheep, and goats in 41 countries in 2005–2019. The data analysis revealed that 74.4% of the total infection rate in the world was distributed among cattle, followed by buffaloes (13.1%). The mortality of HS among cattle and buffaloes increased in 2017–2019 compared to the period between 2014 and 2016. The best measure to control the disease is through vaccination programs. Current commercial vaccines, including live-attenuated vaccines and inactivated vaccines, have some shortcomings and undesirable effects. Virus-like particles (VLPs) have more potential as a vaccine platform due to their unique properties to enhance immune response and the ability to use them as a platform for foreign antigens against infectious diseases. VLPs-based vaccines are among the new-generation subunit vaccine approaches that have been licensed for the human and veterinary fields. However, most studies are still in the late stages of vaccine evaluation.

Outer Membrane Protein F Is Involved in Biofilm Formation, Virulence and Antibiotic Resistance in Cronobacter sakazakii

In some Gram-negative bacteria, ompF encodes outer membrane protein F (OmpF), which is a cation-selective porin and is responsible for the passive transport of small molecules across the outer membrane. However, there are few reports about the functions of this gene in Cronobacter sakazakii. To investigate the role of ompF in detail, an ompF disruption strain (ΔompF) and a complementation strain (cpompF) were successfully obtained. We find that OmpF can affect the ability of biofilm formation in C. sakazakii. In addition, the variations in biofilm composition of C. sakazakii were examined using Raman spectroscopy analyses caused by knocking out ompF, and the result indicated that the levels of certain biofilm components, including lipopolysaccharide (LPS), were significantly decreased in the mutant (ΔompF). Then, SDS-PAGE was used to further analyze the LPS content, and the result showed that the LPS levels were significantly reduced in the absence of ompF. Therefore, we conclude that OmpF affects biofilm formation in C. sakazakii by reducing the amount of LPS. Furthermore, the ΔompF mutant showed decreased (2.7-fold) adhesion to and invasion of HCT-8 cells. In an antibiotic susceptibility analysis, the ΔompF mutant showed significantly smaller inhibition zones than the WT, indicating that OmpF had a positive effect on the influx of antibiotics into the cells. In summary, ompF plays a positive regulatory role in the biofilm formation and adhesion/invasion, which is achieved by regulating the amount of LPS, but is a negative regulator of antibiotic resistance in C. sakazakii.

Conservation of ptfA gene encoded Type IV fimbrial protein among circulating Pasteurella multocida serogroup A strains causing pneumonia in sheep

Respiratory infections are most common in small ruminants. Differentiation of homogenous bacterial strains originated from similar clinical forms (acute or chronic) of infections in a particular or diverse host origin and regions posses a greater challenge for rapid epidemiological studies. Pasteurella multocida, being a multi-host pathogen with wide range of infections among small ruminants especially sheep, is of greater economical concern among small and marginal farmers. In our study, we report ptfA gene sequence based analysis of circulating P. multocida strains recovered from clinically ailing sheep either with pneumonia or septicaemia belonging to different geographical regions of Karnataka. All the 29 P. multocida strains were characterized by conventional methods as well as molecular methods which indicated homogeneity as they belonged to serogroup A and possessed highly conserved ptfA gene by phylogenetic analysis. The study highlighted the conservation of ptfA gene/fimbrial protein among P. multocida strains from identical/diverse clinical conditions and could be employed in rapid epidemiological studies in routine surveillance of circulating pathogenic bacterial strains as well as pasteurellosis outbreak investigations among animals and birds.

Putative Riemerella anatipestifer Outer Membrane Protein H Affects Virulence

Riemerella anatipestifer causes serious contagious disease in ducks, geese, and other fowl. However, as a harmful pathogen causing significant economic losses in the poultry industry, R. anatipestifer is still poorly understood for its pathogenesis mechanisms. In a previous study, we developed an indirect ELISA method for detecting R. anatipestifer infection using B739_0832 protein, a putative outer membrane protein H (OmpH) that is conserved among different serotypes of R. anatipestifer. Although OmpH in some pathogenic bacteria, such as Pasteurella, has been reported as a virulence factor, it is still not clear whether B739_0832 protein contributes to the virulence of R. anatipestifer. In this study, we confirmed that B739_0832 protein in R. anatipestifer localizes to the outer membrane. We constructed a B739_0832 deletion mutant strain (ΔB739_0832) and assayed various effects from the deletion of B739_0832. ΔB739_0832 strain had a similar growth rate to wild-type R. anatipestifer CH-1. However, the survival rate of ducklings in 10 days after infection from ΔB739_0832 strain was 50%, whereas no ducklings survived from wild-type R. anatipestifer infection. Furthermore, the median lethal dose (LD₅₀) of the ΔB739_0832 strain was approximately 150 times higher than that of the wild-type strain. Pathology examinations on infected ducklings found that, at 36 h after infection, bacterial loads in blood, liver, and brain tissues from ΔB739_0832-infected ducklings were considerably lower than those from wild-type infected ducklings. These results demonstrate that the B739_0832 protein contributes to the virulence of R. anatipestifer CH-1.

A bite difficult to heal: Pasteurella multocida induced decompensated hepatic cirrhosis

Pasteurella multocida is a gram-negative bacterium that colonizes domestic animals. It is commonly implicated in bite and scratch wounds, potentially resulting in cellulitis, superficial abscesses, osteomyelitis, or peritonitis. Rarely, it can lead to bacteremia and septic shock in high-risk patients. We present an atypical presentation of Pasteurella multocida bacteremia and sepsis in a patient with stage 4 decompensated cirrhosis. The patient presented with melena and altered mental status with CT imaging showing a heterogeneous nodular liver along with an enlarged portal vein, gastric varices, and ascites consistent with decompensated cirrhosis. The patient was initially managed with intravenous (IV) octreotide and pantoprazole, blood and platelet transfusions, and broad-spectrum antibiotics. Upper endoscopy showed diffuse non-bleeding esophageal and gastric varices, which required band ligation and continued IV octreotide therapy. The infection resolved after a 7-day course of IV ceftriaxone.

The effect of carbohydrates on the adherence of Pasteurella multocida to the nasal respiratory epithelium

Pasteurella multocida subsp. multocida is responsible for different diseases that generate great economic losses in farm animal. The effectiveness of immunization against those bacteria are variable and the use of antibiotics is questioned; for that reason, we investigated the potential inhibitory effect of different carbohydrates on the adherence in vivo of P. multocida to the rabbit respiratory epithelium as an alternative for the prevention of respiratory infections. Rabbits were intranasally and intratracheally inoculated with a solution containing 200 µl of 1x107 CFU of P. multocida that was previously mixed with 250 µg /200 µl of N-acetylglucosamine, alphamethylglucoside, alphamethylmannoside, N-acetylgalactosamine or sialic acid. The animals that received N-acetylglucosamine, alphamethylglucoside or alphamethylmannoside individually or a mixture of these three carbohydrates plus the bacterium, showed a significant decrease (P <0.05) of the clinical symptoms, microscopic and macroscopic lesions in the nasal septa and in the lungs; also, the number of adhered bacteria to the nasal epithelium were also significantly reduced. This research demonstrates for the first time that such an approach could convert into a method for prevention of P. multocida infection in rabbits that is ecologically and economically safe and effective.

The immune response and protective efficacy of a potential DNA vaccine against virulent Pasteurella multocida

Background

Pasteurella multocida is the main cause of several infections of farm animals, and the immunity gained from commercial vaccines is for the short term only and needs to be routinely administered, so work on new vaccines against virulent P. multocida is crucial.

Results

In this study, the OmpH gene was amplified from ten P. multocida strains, and the PCR products were sequenced and analyzed. The results of RFLP analysis of OmpH gene digested by MspI enzyme showed that all of ten strains examined possessed one restriction site and two fragments, 350 and 650 bp. The OmpH sequence of strain No. 10 was cloned into bacterial expression vector pUCP24, and the recombinant pUCP24-OmpH was expressed in E. coli DH5α. Serum samples obtained from the ELISA test from a group of vaccinated rats indicate that the antibodies were present at high titer in immunized rats and can be tested as a vaccine candidate with a challenge.

Conclusions

In rats infected with the DNA vaccine and inactivated vaccine, a significant increase in serum antibody levels was observed. In addition, the DNA vaccine provided the vaccinated rats with partial protection; however, the protective efficacy was greater than that offered by the live attenuated vaccine. This successful recombinant vaccine is immunogenic and may potentially be used as a vaccine in the future.

Three novel immunogenic proteins determined through 2-Dimensional electrophoresis and mass spectrometry with immune serum confer protection against challenge with porcine Pasteurella multocida in mouse models

Pasteurella multocida is an important zoonotic pathogen that causes multiple diseases in both animals and humans. Test of good immunogenic proteins is beneficial for vaccine development and disease control. In the present study, we determined four novel immunogenic proteins of P. multocida by using 2-DE MALDI-TOF MS with immune serum. These four proteins included a trimethylamine-N-oxide reductase TorA, a translation elongation factor Ts, a phosphoglyceromutase PGAM, and a peroxiredoxin PrX. Among these proteins, TorA, Prx, and PGAM were successfully expressed by using E. coli. Western-blotting assays showed that recombinant TorA, Prx, and/or PGAM displayed good reactions with infectious sera of P. multocida serogroups A, B, D and F. Immunization of either rTorA, rPrx, and/or rPGAM induced significantly high levels of antibodies as well as IFN-γ, IL-4 and IL-10 in mice (P < 0.01). Protective efficacy tests revealed that vaccination of either rTorA, rPrx, and/or rPGAM protected 60% ~ 80% of the tested mice against the challenge with P. multocida field isolate. Our results obtained from the present study suggest that these three proteins could be tested as good vaccine candidates against P. multocida infections.

Comparative genetic diversity analysis based on virulence and repetitive genes profiling of circulating Pasteurella multocida isolates from animal hosts

Virulence associated and/or housekeeping/repetitive genes either in single or multiple copies are being extensively targeted for bacterial pathogen detection and differentiation in epidemiological studies. In the present study, isolation of Pasteurella multocida from different animals and their genetic profiling based on the capsular types, virulence and repetitive elements (ERIC/REP) were carried out. A total 345 clinical samples from apparently healthy and diseased (pneumonic, septicaemia) animals (sheep, goat, pig, cattle, buffalo and rabbits) from different geographical regions of Karnataka, Uttar Pradesh, Mizoram and Assam states of India were screened. A total of 32% of the samples were found positive, of which 41 P. multocida isolates recovered. Virulence profiling of isolates indicated that omp87, ompA, ptfA, sodA, sodC, nanB, fur and exbB were present in 100% of isolates. Whereas, prevalence of other genes were; nanH (90%), ompH (71%), pfhA (63%), plpB (80%), hsf-1 (12%), hsf-2 (37%), pmHAS (78%), toxA (73%), hgbA (37%), hgbB (81%), tbpA (78%) and fimA (98%), among isolates. There was no influence of host or place on prevalence of virulence genes when assessed by fitting a Hierarchial Bayesian ordinal regression model. There was correlation (positive and negative) between broad groups of virulence genes. Both repetitive gene profiles (ERIC and REP) generated multiple amplicons (~200 to ~4000 bp). Cluster analysis with ERIC profiles revealed 5 clusters and 3 non- typable isolates with higher discriminatory power (D = 0.7991) than the REP-PCR profiles (D = 00.734) which revealed 4 clusters and 6 non- typable isolates. The results showed that a considerable level of genetic diversity exists among circulating P. multocida isolates despite belonging to the same geographical origin. The genetic diversity or clustering based on either virulence or repetitive elements among isolates could be largely driven by multiple factors acting together which lead to manifestations of particular disease symptoms.

Variability in in vitro biofilm production and antimicrobial sensitivity pattern among Pasteurella multocida strains

Biofilm production, hitherto an uncharacterized feature among circulating Pasteurella multocida strains, was studied along with the antibiotic susceptibility pattern. On the basis of biofilm formation ability, all the strains were categorized into four groups under six different culture conditions: strong biofilm-forming (22%), moderate (19%), weak (51%), and non-adherent (7%). Strains from serogroups A and B formed significant biofilms in at least one culture condition whereas strains from serogroup D were unable to form biofilms. All strains were found to be susceptible to tetracycline. In addition, the correlation between diverse factors (host, capsule type, clinical condition and the tadD gene) as well as antimicrobial susceptibility in biofilm production were analyzed by Joint distribution models, and showed that enrofloxacin and azithromycin resistant strains were positively correlated with strong biofilm production.

Pasteurella multocida Pm0442 Affects Virulence Gene Expression and Targets TLR2 to Induce Inflammatory Responses

Pasteurella multocida is an important pathogenic bacterium of domestic animals. However, the mechanisms of infection are still poorly understood. Here, we found that Pm0442 was dramatically up-regulated in infected mice among 67 predicted lipoproteins of P. multocida serotype A CQ2 strain (PmCQ2). To explore the role of Pm0442 in virulence and the potential of the mutant as a vaccine, Pm0442 mutant of PmCQ2 was successfully constructed. Then, the virulence characteristics, immune/inflammatory responses, and the survival rates of challenged mice were determined. As a result, it was found that the Pm0442 deletion of PmCQ2 significantly decreased bacterial loads and inflammatory responses of lung tissue in mice, resulting in improved survival. Mechanically, Pm0442 affects PmCQ2 capsular and lipopolysaccharide (LPS) synthesis and iron utilization-related genes expression affecting adhesion and phagocytosis. Furthermore, PM0442 bound directly to Toll-like receptor 2 (TLR2) to mediate the secretion of pro-inflammatory cytokine (IL-1β, TNF-α, IL-6, and IL-12p40) in macrophages via activation of the NF-κB, ERK1/2 and p38 signaling pathways. Notably, PmCQ2Δ0442 could provide 70-80% protection to mice challenged with 3.08 × 107 CFU of PmCQ2. Our findings demonstrate that Pm0442 is a virulence-related gene of PmCQ2, which provides new guidance for the prevention and control of Pasteurellosis.

An Intranasal Vaccination with a Recombinant Outer Membrane Protein H against Haemorrhagic Septicemia in Swamp Buffaloes

Hemorrhagic septicemia (HS) is an important infectious disease in cattle and buffaloes, caused by Pasteurella multocida B:2 and E:2. The intranasal recombinant OmpH-based vaccine was successfully used to protect dairy cattle from HS in a previous study. Thus, this study aimed to examine the protective ability of that vaccine among buffaloes. Four groups of Thai swamp buffaloes received different vaccines and were labeled as 100 or 200 μg of the rOmpH with CpG-ODN2007, commercial HS bacterin vaccine, and nonvaccinated control groups. Sera and whole blood were collected to examine the antibody levels and cellular immune response using indirect ELISA and MTT assay, respectively. Challenge exposure was performed with virulent P. multocida strain M-1404 serotype B:2 on day 72 of the experiment. The antibody titers to P. multocida among immunized buffaloes were significantly higher than in the control group (p < 0.01), especially the 200 μg of the rOmpH group. The stimulation index (SI) of the intranasally vaccinated groups revealed significantly higher levels than the nonvaccinated group (p < 0.01), but not different from the intramuscularly commercial HS vaccine. The clinical signs and high fever were observed after challenge exposure in the nonvaccinated group, while it was not observed among the 200 μg of rOmpH immunized buffaloes. The other immunized groups showed partial protection with transient fever. In conclusion, the rOmpH-based intranasal vaccine could elicit protective ability and induce antibody- and cell-mediated immune response against virulent P. multocida strain among swamp buffaloes.

Pathogenomics insights for understanding Pasteurella multocida adaptation

Pasteurella multocida is an important veterinary pathogen able to infect a wide range of animals in a broad spectrum of diseases. P. multocida is a complex microorganism in relation to its genomic flexibility, host adaptation and pathogenesis. Epidemiological analysis based on multilocus sequence typing, serotyping, genotyping, association with virulence genes and single nucleotide polymorphisms (SNPs), enables assessment of intraspecies diversity, phylogenetic and strain-specific relationships associated with host predilection or disease. A high number of sequenced genomes provides us a more accurate genomic and epidemiological interpretation to determine whether certain lineages can infect a host or produce disease. Comparative genomic analysis and pan-genomic approaches have revealed a flexible genome for hosting mobile genetic elements (MGEs) and therefore significant variation in gene content. Moreover, it was possible to find lineage-specific MGEs from the same niche, showing acquisition probably due to an evolutionary convergence event or to a genetic group with infective capacity. Furthermore, diversification selection analysis exhibits proteins exposed on the surface subject to selection pressures with an interstrain heterogeneity related to their ability to adapt. This article is the first review describing the genomic relationship to elucidate the diversity and evolution of P. multocida.

Characterization of Pasteurella multocida isolates from rabbits in China

Pasteurella multocida is the causative agent of a wide range of diseases (pasteurellosis) and is a zoonotic pathogen in humans. The molecular epidemiology of P. multocida from rabbits in some southern European countries has been characterized, and the associations of some populations with the respiratory niche or virulence factors have been suggested. However, the population structure of P. multocida from rabbits in China has not been well characterized. In this study, 30 P. multocida isolates from rabbits without epidemiological relations in China were clustered using mutilocus sequence typing (MLST). Then, the genotypes of virulence factors (capsule, lipopolysaccharides, HgbB, and PfhA) of these isolates were determined via multiplex PCR methods. Next, the virulence of the isolates in a mice model was established by determining the 50 % lethal dose. Finally, the associations between MLST types and the prevalence of genotypes, virulent strains, or clinical origins were characterized. The P. multocida isolates identified in this work included 3 major clonal complexes: CC9, CC74, and ST129. CC9 exhibited cpsA(F)L3, and was associated with a higher prevalence of rhinitis; CC74 exhibited cpsAL6, and was associated with higher prevalences of hgbB+pfhA- and pneumonia; ST129 exhibited cpsAL1, and was associated with higher prevalences of high-virulence strains and septicemia. The results provided insights into P. multocida from rabbits in China and suggested the use of strains from different populations in future P. multocida pathogenesis and vaccine studies.

Immunogenicity of recombinant outer membrane protein (OmpW) of Pasteurella multocida serogroup B:2 in mouse model

Haemorrhagic septicaemia (HS) caused by Pasteurella multocida serogroup B:2, in cattle and buffalo especially in tropical regions of Asian and African countries, is known to possess several outer membrane proteins (OMPs) as virulent factors which are being targeted to evaluate their immunogenicity and protective efficacy as candidate antigens for vaccine. In the present study, ompW gene encoding for OmpW protein of P. multocida serogroup B:2 strain P52, an Indian HS vaccine strain, has been cloned and over-expressed in recombinant Escherichia coli. The recombinant OmpW fusion protein (~37 kDa) including histidine tag was purified by affinity chromatography under denaturing condition and confirmed by Western blotting. Further, mice immunized with rOmpW (50μg/ dose) along with FCA/FIA resulted in antigen specific IgG antibodies as well as subtypes (IgG1 and IgG2a). The study indicated the potential possibilities to use the rOmpW antigen in developing subunit vaccine for HS as well as other diseases caused by members of Pasteurellaceae.

Pasteurella multocida: Genotypes and Genomics

Pasteurella multocida is a highly versatile pathogen capable of causing infections in a wide range of domestic and wild animals as well as in humans and nonhuman primates. Despite over 135 years of research, the molecular basis for the myriad manifestations of P. multocida pathogenesis and the determinants of P. multocida phylogeny remain poorly defined. The current availability of multiple P. multocida genome sequences now makes it possible to delve into the underlying genetic mechanisms of P. multocida fitness and virulence. Using whole-genome sequences, the genotypes, including the capsular genotypes, lipopolysaccharide (LPS) genotypes, and multilocus sequence types, as well as virulence factor-encoding genes of P. multocida isolates from different clinical presentations can be characterized rapidly and accurately. Putative genetic factors that contribute to virulence, fitness, host specificity, and disease predilection can also be identified through comparative genome analysis of different P. multocida isolates. However, although some knowledge about genotypes, fitness, and pathogenesis has been gained from the recent whole-genome sequencing and comparative analysis studies of P. multocida, there is still a long way to go before we fully understand the pathogenic mechanisms of this important zoonotic pathogen. The quality of several available genome sequences is low, as they are assemblies with relatively low coverage, and genomes of P. multocida isolates from some uncommon host species are still limited or lacking. Here, we review recent advances, as well as continuing knowledge gaps, in our understanding of determinants contributing to virulence, fitness, host specificity, disease predilection, and phylogeny of P. multocida.

Complete Genome Sequence Analysis and Characterization of Selected Iron Regulation Genes of Pasteurella Multocida Serotype A Strain PMTB2.1

Although more than 100 genome sequences of Pasteurella multocida are available, comprehensive and complete genome sequence analysis is limited. This study describes the analysis of complete genome sequence and pathogenomics of P. multocida strain PMTB2.1. The genome of PMTB2.1 has 2176 genes with more than 40 coding sequences associated with iron regulation and 140 virulence genes including the complete tad locus. The tad locus includes several previously uncharacterized genes such as flp2, rcpC and tadV genes. A transposable phage resembling to Mu phages was identified in P. multocida that has not been identified in any other serotype yet. The multi-locus sequence typing analysis assigned the PMTB2.1 genome sequence as type ST101, while the comparative genome analysis showed that PMTB2.1 is closely related to other P. multocida strains with the genomic distance of less than 0.13. The expression profiling of iron regulating-genes of PMTB2.1 was characterized under iron-limited environment. Results showed significant changes in the expression profiles of iron-regulating genes (p < 0.05) whereas the highest expression of fecE gene (281 fold) at 30 min suggests utilization of the outer-membrane proteins system in iron acquisition at an early stage of growth. This study showed the phylogenomic relatedness of P. multocida and improved annotation of important genes and functional characterization of iron-regulating genes of importance to the bacterial growth.

Assessment of FTA card employment for Pasteurella multocida DNA transport and detection of virulence-associated genes in strains isolated from fowl cholera in the United States

ABSTRACT Fowl Cholera (FC) is a disease caused by Pasteurella multocida. The severity of this disease is partly caused by virulence factors. Genes encoding fimbriae, capsule, sialidases and proteins for iron metabolism may be related to P. multocida’s ability to infect the host. Besides to examining DNA for the presence of virulence genes, DNA is essential for the diagnostic and FTA cards are an alternative for genetic material transport. The study aims to evaluate the viability of P. multocida DNA transport using the cards and to detect 14 virulence genes in 27 strains isolated from FC cases in the United States by multiplex-PCR. No growth was observed in any of the FTA cards, which was essential to assess the security. Furthermore, DNA detection was possible in 100% of the samples, independent of the storage period (7 to 35 days) and temperature (4°C and 37°C). ptfA, exbd-tonB, hgbA, nanB, oma87, hyaD-hyaC, sodC, hgbB, sodA, nanH and pfhA genes were detected in more than 80% of the samples. FTA cards have proven to be a viable and safe tool for DNA transport of P. multocida. A majority of genes showed a high frequency, which was similar to strains isolated from FC cases.

Outer Membrane Lipoprotein Lip40 Modulates Adherence, Colonization, and Virulence of Actinobacillus pleuropneumoniae

Bacterial lipoproteins are a set of membrane proteins with various functions; many of which are virulence factors of pathogenic bacteria. In the present study, we investigated the role of an outer membrane lipoprotein Lip40 in the pathogenesis of Actinobacillus pleuropneumoniae. A mutant strain (Δlip40) lacking Lip40 and a complemented strain (CΔlip40) were constructed. Δlip40 exhibited reduced adherence to the St. Jude porcine lung cells. The ability of the Δlip40 mutant to colonize the mouse lung tissues was significantly impaired compared to that of the wild type and complementation strains. Furthermore, an infection assay revealed that pigs infected with Δlip40 showed fewer clinical signs and lung lesions, indicating that Lip40 contributed to the development of porcine pleuropneumonia. Collectively, our data suggest that Lip40 is involved in the virulence of A. pleuropneumoniae.

Virulence gene profiling of porcine Pasteurella multocida isolates of Assam

Aim:

The present study was conducted to detect and identify the virulence genes in Pasteurella multocida isolates of porcine origin from Assam.

Materials and Methods:

A total of 21 porcine P. multocida isolates were subjected to capsular typing and detection of virulence-associated genes (pfhA, tbpA, hgbB, toxA, oma87, ompH, and nanB) using various polymerase chain reaction (PCR) methods reported elsewhere. Further, pathogenicity of the porcine isolates of P. multocida was studied in mice. For each strain of P. multocida selected for pathogenicity trial, the group of mice was injected intraperitoneally (i/p) with 0.1 ml of the inoculum prepared from respective field isolates, containing 10⁹ organisms per ml.

Results:

Capsular typing of the isolates by multiplex PCR showed two capsular types, type A (66.66%) and type D (33.33%). All the isolates were positive for outer membrane protein genes, oma87 and ompH genes. Iron acquisition genes, tbpA and hgbB, were detected in 14.28% and 19.04% of the isolates. The dermonecrotoxin encoding gene, toxA, was present in 23.80% of the isolates. Filamentous hemagglutinin encoding gene, pfhA, was detected in 28.57%. The virulence gene distribution pattern of the isolates indicates the important role of the genes in disease pathogenesis.

Conclusion:

From the present study, it can be concluded that toxA gene is an important marker gene for defining the pathogenic potential of P. multocida strains in swine.

In silico identification and high throughput screening of antigenic proteins as candidates for a Mannheimia haemolytica vaccine

This study examined the use of comparative genomic analysis for vaccine design against Mannheimia haemolytica, a respiratory pathogen of ruminants. A total of 2,341genes were identified in at least half of the 23 genomes. Of these, a total of 240 were identified to code for N-terminal signal peptides with diverse sub-cellular localizations (78 periplasmic, 52 outer membrane, 15 extracellular, 13 cytoplasmic membrane and 82 unknown) and were examined in an ELISA assay using a coupled-cell free transcription/translation system for protein expressionwith antisera from cattle challenged with serovars 1, 2 or 6 of M. haemolytica. In total, 186 proteins were immunoreactive to at least one sera type and of these, 105 were immunoreactive to all sera screened. The top ten antigens based on immunoreactivity were serine protease Ssa-1 (AC570_10970), an ABC dipeptid transporter substrate-binding protein (AC570_04010), a ribonucleotide reductase (AC570_10780), competence protein ComE (AC570_11510), a filamentous hemagglutinin (AC570_01600), a molybdenum ABC transporter solute-binding protein (AC570_10275), a conserved hypothetical protein (AC570_07570), a porin protein (AC569_05045), an outer membrane assembly protein YeaT (AC570_03060), and an ABC transporter maltose binding protein MalE (AC570_00140). The framework generated from this research can be further applied towards rapid vaccine design against other pathogens involved in complex respiratory infections in cattle.

Intranasal immunization with a recombinant outer membrane protein H based Haemorrhagic septicemia vaccine in dairy calves

Haemorrhagic septicemia (HS) is a contagious disease in cattle with high morbidity and mortality rates. HS vaccine in Thailand is an oil-adjuvant formulation, and is difficult to administer. The present study aimed to formulate and evaluate the protection in dairy calves conferred by immunization with an in-house intranasal HS vaccine. The intranasal vaccine was formulated in a total volume of 500 µl containing either 50 or 100 µg of the recombinant outer membrane protein H (rOmpH) of Pasteurella multocida strain M-1404 (serovar B:2), and 10 µg of Cytosine-phosphate-guanosine oligodeoxynucleotides (CpG-ODN) as a mucosal adjuvant. Intranasal immunizations were conducted three times at three-week intervals. The antibodies post-immunization were detected by indirect ELISA and demonstrated efficient in vitro activity in suppressing a P. multocida strain from the complement-mediated killing assay. An intranasal vaccine induced both the serum IgG and secretory IgA levels that were significantly higher than the level conferred by the parenteral vaccine (P<0.05). Challenge exposure was conducted with a P. multocida strain M-1404 at day 72 of the experiments. The immunized calves had reduced clinical signs after challenge exposure that would normally result in disease proliferation. We conclude that intranasal vaccination of calves with rOmpH with CpG-ODN 2007 stimulated serum and secretory antibodies to rOmpH and whole cells of P. multocida strain M-1404 antigen. Moreover, it would result in protection in calves against artificial P. multocida infection.

Evaluation of the biofilm formation capacity of Pasteurella multocida strains isolated from cases of fowl cholera and swine lungs and its relationship with pathogenicity

ABSTRACT: Pasteurella multocida is a Gram-negative bacillus that causes economic losses due to the development of respiratory diseases in several animal species. Among the mechanisms of virulence, the formation of biofilms is an important factor for bacterial survival in hostile environments. Studies of biofilm formation by P. multocida are needed because P. multocida is an important pathogen involved in respiratory infections. However, in contrast to other microorganisms, few studies of biofilm formation have examined P. multocida. Studies comparing the pathogenicity of microbial strains as a function of their biofilm production capacity are also rare. Consequently, the aim of this study was to evaluate the biofilm formation capacity of 94 P. multocida strains isolated from cases of fowl cholera and from swine lungs on polystyrene plates. The associations of the biofilm formation capacity with the pathogenicity index (PI) in vivo and with the presence of four genes (screened by PCR) of the tad locus (tadB, tadD, tadE and tadG), described as adhesion markers, were also determined. Strains from both animal origins were able to form biofilms. However, most of the specimens (52.13%) were classified as weak producers, and more than 40% of the strains of P. multocida (40.42%) did not produce biofilms. There was no significant difference (p>0.05) in the degree of biofilm production between the two sources of isolation. Of the analyzed strains, 56.52% contained all four genes (tadB, tadD, tadE and tadG). The PI arithmetic mean of the strains classified as non-biofilm producers was significantly different (p<0.05) from the PI of moderate-producer strains. The PI of specimens classified as weak biofilm producers also differed significantly (p<0.05) from that of the moderate-producer strains. The results indicate that even though the P. multocida strains isolated from cases of fowl cholera and swine lungs formed biofilms on polystyrene surfaces, adhesion was usually weak. The genes tadB, tadD, tadE and tadG were not significantly associated (p>0.05) with the production of biofilms and with the origin of a given strain. Finally, low virulence strains may suggest a higher biofilm formation capacity on polystyrene plates.

OmpA protein sequence-based typing and virulence-associated gene profiles of Pasteurella multocida isolates associated with bovine haemorrhagic septicaemia and porcine pneumonic pasteurellosis in Thailand

Background

Pasteurella multocida is a Gram-negative bacterium that causes economically significant infections of a broad range of animal species. Pneumonic and septicaemic pasteurellosis caused by this bacterium remain important problems in pigs, cattle, and water buffaloes in Thailand. The aim of this study was to characterise the virulence-associated gene profiles and to develop an OmpA molecular typing scheme for classifying 191 bovine and porcine isolates of P. multocida collected between 1989 and 2012 in Thailand using polymerase chain reactions (PCRs), nucleotide sequencing, and sequence and structural bioinformatics analyses.

Results

PCR screening successfully characterised the profiles of 25 virulence-associated genes in all isolates. The gene profiles separated these isolates into bovine and porcine clusters based on eight genes (hgbB, hsf1, tadD, nanH, pfhA, plpE, pmHAS, and tbpA). Phylogenetic analyses of the nucleotide and protein sequences corresponding to the ompA gene, which encodes a major outer membrane surface protein, showed two major bovine and porcine clusters. Structural prediction and analysis of the dN/dS ratio revealed four hypervariable extracellular loops of the OmpA transmembrane domains. These four loops were used to develop an OmpA typing scheme. This scheme classified 186 isolates into five major loop sequence types (LST8, LST12, LST15, LST18, and LST19), consistent with the phylogenetic results. The loop regions of the bovine isolates were predicted to be more antigenic than those of the porcine isolates. Thus, molecular evolution of the OmpA proteins could be used to classify P. multocida isolates into different capsular types, host types, and, possibly, pathogenicity levels.

Conclusions

Together with the virulence-associated gene profiles, the typing reported in this work provides a better understanding of P. multocida virulence. Effective monitoring and potential strain-specific subunit vaccines could be developed based on these loop oligopeptides.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-1157-6) contains supplementary material, which is available to authorized users.

Identification of proteome, antigen protein and antigen membrane protein from Spiroplasma eriocheiris

Spiroplasma eriocheiris, which causes tremor disease in Chinese mitten crab Eriocheir sinensis, has led to huge economic losses in aquaculture. Immunoproteomics, a new scientific technique combining proteomics and immunological analytical methods, provided the direction of our research on S. eriocheiris. The aim of our study was to identify the proteome, antigen proteins and antigen membrane proteins of S. eriocheiris. A total of 780 S. eriocheiris proteins were identified by the LC-MS/MS technique. Based on immunoproteomics, 51 proteins and 7 proteins in S. eriocheiris were identified by anti-S. eriocheiris serum and negative serum respectively (six proteins in common). Thus, 45 antigenic proteins in S. eriocheiris were identified; among them, molecular chaperone DnaK, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), ATP synthase subunit beta and enolase can be considered as immunogenic proteins. Similarly, 32 membrane proteins and 6 membrane proteins were identified by anti-S. eriocheiris serum and negative serum respectively (two proteins in common). Thus, 30 antigenic membrane proteins in S. eriocheiris were identified; three of them have been reported as surface proteins including pyruvate kinase, enolase and GAPDH. All of these proteins may play key roles in the pathogeny and can be used in the future for diagnoses and prevention.

SIGNIFICANCE AND IMPACT OF THE STUDY

Spiroplasma eriocheiris is a novel pathogen causing the tremor disease in Chinese mitten crab Eriocheir sinensis. This is the first time LC-MS/MS was used to identify the proteome, antigen protein and antigen membrane protein of S. eriocheiris. The results can certainly provide valuable information towards the identification of virulent proteins or diagnosis of pathogenic mechanisms.

Ducks as a potential reservoir for Pasteurella multocida infection detected using a new rOmpH-based ELISA

Pasteurella multocida is an important pathogen of numerous domestic poultry and wild animals and is associated with a variety of diseases including fowl cholera. The aim of this study was to develop an indirect enzyme-linked immunosorbent assay (ELISA) based on recombinant outer-membrane protein H (rOmpH) for detection of anti-P. multocida antibodies in serum to determine their prevalence in Chinese ducks. The P. multocida ompH gene was cloned into pET32a, and rOmpH was expressed in Escherichia coli BL21 (DE3). Western blotting revealed that purified rOmpH was recognized by duck antisera against P. multocida, and an indirect ELISA was established. During analysis of serum samples (n=115) from ducks, the rOmpH ELISA showed 95.0% specificity, 100% sensitivity and a 92.0% κ coefficient (95% confidence interval 0.844–0.997) as compared with a microtiter agglutination test. Among 165 randomly selected serum samples, which were collected in 2015 and originated from six duck farms across Fujian Province, China, anti-P. multocida antibodies were detected in 22.42% of apparently healthy ducks, including 25 of 90 sheldrakes (27.8%), eight of 50 Peking ducks (16.0%) and four of 25 Muscovy ducks (16%). Overall, the data suggest that rOmpH is a suitable candidate antigen for the development of an indirect ELISA for detection of P. multocida in ducks; moreover, our results showed that ducks could serve as a potential reservoir for P. multocida infection.

Cross-protection conferred by immunization with an rOmpH-based intranasal fowl cholera vaccine

A previous study demonstrated that a recombinant outer membrane protein H (rOmpH)-based intranasal fowl cholera vaccine elicited efficient homologous protection against the Pasteurella multocida strain X-73 (A:1) in chickens. The present study aimed to determine the cross-protectivity against heterologous P. multocida strains. The rOmpH was purified via electroelution and formulated with two kinds of adjuvants. The vaccine formulations in a total volume of 100 µl were 100 µg rOmpH with 3 µg of Escherichia coli enterotoxin B or 10 µg of CpG ODN2007. Chickens were assigned to three experimental groups depending on bacterial strain challenge exposure as well as three control groups. The chickens were immunized intranasally three times at three-week intervals. Challenge exposures were conducted by inoculation with homologous strain X-73 or heterologous strains P-1059 (A:3) or P-1662 (A:4) at four weeks after the final immunization. The specific antibody against rOmpH was produced in vaccinated birds. Sera IgY and secretory IgA antibody titres were significantly increased (P < 0.05) post-immunization. The stimulation index values of the vaccinated groups were significantly different from stimulation index values of the non-vaccinated groups (P < 0.05). Chicken survival rates after exposure to avian P. multocida strains ranged from 70% to 100%. There was no significant difference in protection between two kinds of adjuvants in vaccine formulations. Statistical analysis indicated no significant differences in protection among avian P. multocida strains challenge exposure. We conclude that an in-house rOmpH-based intranasal fowl cholera vaccine produced efficient cross-protectivity against heterologous strains of P. multocida.

Reproductive hormonal variations and adenohypophyseal lesions in pre-pubertal buffalo heifers inoculated with Pasteurella multocida type B: 2 and its immunogens

BACKGROUND

Hemorrhagic septicemia is a fatal disease of cattle and buffaloes caused by P. multocida. Although the pathogenesis of the bacteria has been well established in literature, there is a paucity of information on the possible role of the bacteria and its immunogens; lipopolysaccharide (LPS) and outer membrane proteins (OMPs) on the reproductive capacity of buffalo heifers.

METHODS

In this study, twenty one healthy prepubertal female buffaloes aged 8 months were divided into seven groups of 3 buffaloes each (G1-G7). Group 1 (G1) served as the negative control group and were inoculated orally with 10 mL sterile Phosphate Buffer Saline (PBS), groups 2 (G2) and 3 (G3) were inoculated orally and subcutaneously with 10 mL of 10¹² colony forming unit (cfu) of P.multocida type B: 2, while groups 4 (G4) and 5 (G5) received 10 mL of bacterial LPS orally and intravenously, respectively. Lastly, groups 6 (G6) and 7 (G7) were orally and subcutaneously inoculated with 10 mL of bacterial OMPs. Whole blood was collected in EDTA vials at stipulated time points (0, 2, 4, 6, 8, 10, 12, 24, 36, 48, 72, 120, 168, 216, 264, 312, 360, 408, 456 and 504 h), while tissue sections of the pituitary glands were collected and transported to the histopathology laboratory in 10% buffered formalin for processing and Hematoxylin and eosin staining. Plasma levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), progesterone (PG), estradiol (EST) and gonadotrophin releasing hormone (GnRH) were determined.

RESULTS

The histopathological lesions observed in the pituitary gland included hemorrhage, congestion, inflammatory cell infiltration, hydropic degeneration, necrosis and edema. These changes were higher (p < 0.05) in distribution and severity in G3, G6 and G7. Hormonal concentrations of LH, FSH, PG, EST and GnRH declined in all inoculation groups as time elapsed and were lower (p < 0.05) than that of the control group.

CONCLUSION

Based on these findings, P.multocida B: 2 and its immunogens can be said to negatively affect the hypothalamic-pituitary-gonadal axis, resulting in decreased levels of reproductive hormones which may predispose to infertility in buffalo heifers.