The lipopolysaccharide outer core transferase genes pcgD and hptE contribute differently to the virulence of Pasteurella multocida in ducks

Molecular Detection and Antibiogram Profiling of Pasteurella multocida Isolated From Breeder Chickens Suspected of Fowl Cholera in Gondar City, Ethiopia

Fowl cholera is a highly infectious bacterial disease in poultry production. It is caused by Pasteurella multocida (P. multocida) and leads to significant health risks and financial losses. Therefore, this study is aimed at isolating, molecularly detecting, and analyzing the antibiogram of P. multocida from breeder chickens in Gondar City. A cross-sectional study design with purposive sampling was employed to collect a total of 130 tracheal swab samples from breeder chickens showing clinical signs of fowl cholera between January 2023 and December 2023, based on case availability. Bacterial isolation was performed using bacteriological and biochemical tests. The isolated P. multocida was confirmed through conventional polymerase chain reaction (PCR) using a capsular serotype-specific primer (capA). The antibiogram assessment of P. multocida against 10 antimicrobial agents was conducted using the Kirby-Bauer disk diffusion method. Descriptive statistics were used to analyze the isolation rate of the bacterium. Of the 130 sampled swabs, 10 (7.69%) tested positive for P. multocida in the phenotypic assay, and 3 (30%) of those isolates were positive for the hyaD/hyaC virulence gene. The study found that all three isolates were 100% sensitive to penicillin, ampicillin, norfloxacin, and florfenicol, while showing 100% intermediate sensitivity to streptomycin and 66.7% intermediate sensitivity to gentamycin, amoxicillin, tetracycline, trimethoprim/sulphamethoxazole, and kanamycin. The study confirms that P. multocida, the causative agent of fowl cholera in breeder chickens, is circulating in the area and exhibits varying antimicrobial sensitivity profiles.

Hemorrhagic septicemia: A major threat to livestock health

Hemorrhagic septicemia (HS) is an acute septicemic disease that primarily affects cattle and buffalo. This illness is caused by a specific serotype of Gram-negative coccobacillus, Pasteurella multocida. The frequency and distribution of HS epidemics involving various animal species vary according to the agroclimatic zone. HS has significant economic implications, particularly in Asia and, to a lesser extent, Africa. The transmission of HS can occur through direct contact, ingestion, or inhalation of contaminated feed or water. The virulence factors of P. multocida include a number of defense mechanisms or components that help the pathogen be detected by the host immune system. A number of components contribute to the pathogenicity of P. multocida, particularly its toxins and capsules. The primary clinical signs and peracute or acute pathological alterations in other HS cases include septic pneumonia, petechial hemorrhages, ecchymoses in the serous membranes, adrenal glands, and abomasum with severe bleeding, as well as widespread head and neck edema. Affected animals exhibit fever, sadness, and other vague clinical symptoms (such as reduced milk production), which are quickly followed by copious serous nasal discharge and excessive salivation. HS-causing P. multocida strains may not be found in previously obtained samples, but they can be cultivated from blood during the later stages of the illness. Antibiotics of several types have been used to treat HS. Effective control of various HS diseases will be aided by hygienic planning, immunoprophylaxis, chemotherapy, and fundamental management practices, including feeding and maintenance.

Immunoprotective efficacy of Escherichia coli-derived outer membrane vesicles displaying PlpE protein of Pasteurella multocida

Pasteurella multocida (P. multocida), a pathogenic bacterium known to induce duck cholera, stands as a significant contributor to bacterial diseases afflicting the duck industry, causing substantial annual economic losses on a global scale. In this study, the genes encoding the lipoproteins PlpE of P. multocida strain PMWSG-4 was cloned, inserted into the pBAD-ClyA vector, and the recombinant outer membrane vesicles (OMVs) fused with PlpE antigen of P. multocida was expressed by Escherichia coli (E. coli). Ducks immunized with OMV-PlpE had significantly (P < 0.001) increased production of antigen-specific antibodies. Moreover, at 28 days post-immunization, the expression of genes associated with immune response, including interleukin (IL)-2, IL-4, IL-10, and interferon (IFN)-γ in the spleen tissue of immunized ducks were significantly (P < 0.001) up-regulated compared to unimmunized ducks in the control group. And the active serum had significant bactericidal effects against the PMWSG-4 strain (P < 0.001). The protective efficacy of the vaccines was evaluated by leg muscle challenge with 20 LD50 doses of P. multocida, with the recombinant OMV-PlpE conferring 100 % protection. Histopathological examination and tissue bacterial load detection revealed that OMV-PlpE mitigated tissue damage and bacterial colonization to a statistically significant extent (P < 0.001). These findings serve as a valuable reference for the development of vaccines against P. multocida.

Identification and characterization of biosynthetic loci of lipooligosaccharide and capsular polysaccharide in Avibacterium paragallinarum

Infectious coryza is an acute respiratory disease in chickens caused by Avibacterium paragallinarum. Lipooligosaccharides (LOSs) and capsular polysaccharides are important components of Av. paragallinarum. Herein, we identified that gene cluster L6 and two genes waaF, waaQ were associated with LOS synthesis, and two genes acbD and ccbF1 were involved in capsular synthesis. Mutant and complementary strains of these genes were generated by natural transformation. Wild-type strains produced LOS that yielded an upper and lower band. In comparison, ΔwaaQ and ΔwaaF yielded a truncated lower band and lacked the upper band, while ΔL6 did not exhibit the upper band, and the lower band was identical to that of the wild-type strain. The survival rates of wild-type strain, ΔwaaF, ΔwaaQ, and ΔL6 in chicken serum were 4.89 % ± 0.27 %, 0.0013 % ± 0.0002 %, 0.43 % ± 0.05 %, and 3.1 % ± 0.35 %, respectively. Notably, the resistances of ΔwaaF, ΔwaaQ, and ΔL6 to chicken serum were significantly lower than that of parent strain. By contrast, the survival rate of the ΔacbD strain was 55.17 % ± 0.61 %, and its resistance to chicken serum was significantly higher than that of the wild-type strain (p < 0.001). Deletion of the waaF, waaQ, L6, acbD, and ccbF1 genes resulted in enhanced formation of biofilm without altering immunogenicity in chickens. The ΔwaaF, ΔwaaQ, and ΔccbF1 strains exhibited heightened susceptibility to fowlicidin-2. Furthermore, ΔwaaF, ΔacbD, and ΔccbF1 strains shown a decrease in pathogenicity (p < 0.05). These results are valuable for advancing research on the pathogenesis of Av. paragallinarum.

Global commercialization and research of veterinary vaccines against Pasteurella multocida: 2015-2022 technological surveillance

BACKGROUND AND AIM

Pasteurella multocida can infect a multitude of wild and domesticated animals, bacterial vaccines have become a crucial tool in combating antimicrobial resistance (AMR) in animal production. The study aimed to evaluate the current status and scientific trends related to veterinary vaccines against Pasteurella multocida during the 2015-2022 period.

MATERIAL AND METHODS

The characteristics of globally marketed vaccines were investigated based on the official websites of 22 pharmaceutical companies. VOSviewer® 1.6.18 was used to visualize networks of coauthorship and cooccurrence of keywords from papers published in English and available in Scopus.

RESULTS

Current commercial vaccines are mostly inactivated (81.7%), adjuvanted in aluminum hydroxide (57.8%), and designed to immunize cattle (33.0%). Investigational vaccines prioritize the inclusion of attenuated strains, peptide fragments, recombinant proteins, DNA as antigens, aluminum compounds as adjuvants and poultry as the target species.

CONCLUSION

Despite advances in genetic engineering and biotechnology, there will be no changes in the commercial dominance of inactivated and aluminum hydroxide-adjuvanted vaccines in the short term (3-5 years). The future prospects for bacterial vaccines in animal production are promising, with advancements in vaccine formulation and genetic engineering, they have the potential to improve the sustainability of the industry. It is necessary to continue with the studies to improve the efficacy of the vaccines and their availability.

Whole genome characterization of a multidrug-resistant hypervirulent Pasteurella multocida with a new drug-resistant plasmid

Pasteurella multocida (P. multocida) is a zoonotic bacterium that can cause diseases in a variety of animals. It was divided into 5 serogroups, and serogroup A is mainly prevalent in avian hosts. We isolated a virulent and multidrug-resistant P. multocida strain from Guangdong duck liver and named it PMWSG-4 (GenBank accession no. CP077723.1). To understand the pathogenicity of this strain, the pathogenicity test was carried out with mice and ducks. The results showed that PMSWG-4 was highly pathogenic to ducks and mice, and the LD50 is 4.5 and 73 CFU, respectively. In order to study its genetic characteristics, pathogenicity, and relationship with the host, we performed a whole genome sequencing. The genome size of the isolated PMWSG-4 was 2.38 Mbp, with a G+C content of 40.3%, and coding 2,313 Coding DNA Sequence (CDS). The genome carries 162 potential virulence-associated genes, 32 different drug resistance phenotypes, 102 genes possibly involved in pathogen-host interaction, 2 gene island groups, and 4 prophages. In addition, we also found a new drug-resistant plasmid from strain PMWSG-4, named pXL001 (GenBank accession no. CP077724.1). After verified, the plasmid is a new plasmid carrying the floR florfenicol resistance gene. The whole genome is of great significance for further studying the pathogenesis and genetic characteristics of duck-derived P. multocida.

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.

Comparative genome analysis of Pasteurella multocida serogroup B:2 strains causing haemorrhagic septicaemia (HS) in bovines

Pasteurella multocida, a Gram-negative bacterium with ubiquitous nature, is known to affect wide range of host species worldwide with varied clinical manifestations including haemorrhagic septicaemia (HS) in bovines. Although, HS causing P. multocida strains were identified and characterized by conventional tools and PCR assays, diverse strains are indistinguishable by these tools in the face of disease outbreaks. In this study, draft genomes of three virulent P. multocida serotype B:2 strains (NIVEDIPm32, NIVEDIPm34 and NIVEDIPm35) were analyzed following whole genome sequencing, assembly, annotation and compared them with existing global genomes (n = 43) of bovine origin in the database. Three draft genomes of NIVEDIPm strains consisted of 40-52 contigs with GC content of ∼40.4%. The genome size and predicted genes content was ∼2.3 Mb and 2181-2189, respectively. Besides, the presence of various mobile genetic elements, antimicrobial resistance genes and biofilm related genes suggested their vital roles in virulence; further, adaptation to the host immune system as well as host pathogen interaction. Multi locus sequence analysis based on RIRDC scheme showed the presence of ST122 in all the three strains. wgMLST based phylogenic analysis suggested that HS causing Indian virulent field strains differed geographically and showed diversity from existing HS vaccine strain P52. The phylogenetic tree revealed that North Indian strains share high similarity with strains of Pakistan than South Indian Strain. Notably, a high divergence of SNPs between the HS causing circulating virulent strains of India and current HS vaccine strain P52 suggested an imminent need for relook in to HS vaccination strategy for livestock in India.

Immunogenicity and protection of a Pasteurella multocida strain with a truncated lipopolysaccharide outer core in ducks

Pasteurella multocida infection frequently causes fowl cholera outbreaks, leading to huge economic losses to the poultry industry worldwide. This study developed a novel live attenuated P. multocida vaccine strain for ducks named PMZ2 with deletion of the gatA gene and first four bases of the hptE gene, both of which are required for the synthesis of the lipopolysaccharide (LPS) outer core. PMZ2 produced a truncated LPS phenotype and was highly attenuated in ducks with a > 10⁵-fold higher LD₅₀ than the wild-type strain. PMZ2 colonized the blood and organs, including the spleen, liver and lung, at remarkably reduced levels, and its high dose of oral infection did not cause adverse effects on body temperatures and body weights in ducks. To evaluate the vaccine efficacy of the mutant, ducklings were inoculated orally or intranasally with PMZ2 or PBS twice and subsequently subjected to a lethal challenge. Compared with the PBS control, PMZ2 immunization stimulated significantly elevated serum IgG, bile IgA and tracheal IgA responses, especially after the boost immunization in both the oral and intranasal groups, and the induced serum had significant bactericidal effects against the wild-type strain. Furthermore, the two PMZ2 immunization groups exhibited alleviated tissue lesions and significantly decreased bacterial loads in the blood and organs compared with the PBS group post-challenge. All the ducks in the PMZ2 oral and intranasal groups survived the challenge, while 70% of ducks in the PBS group succumbed to the challenge. Thus, the P. multocida mutant with mutation of the gatA gene and part of the hptE gene proved to be an effective live attenuated vaccine candidate for prevention of fowl cholera in ducks.

Characterization of Pasteurella multocida isolated from ducks in China from 2017 to 2019

Pasteurella multocida, an important gram-negative pathogen that mainly inhibits the upper respiratory tracts of domestic and wild animals such as chicken, duck, cattle and pig, which can cause cholera fowl, haemorrhagic septicaemia and infectious pneumonia. Currently, the prevalence and infection of P.multocida is still one of the most serious threats to the poultry industry in China, but studies on its characteristics are still insufficient. Here, this study was conducted to isolate and identify P.multocida in infected ducks and determined the leading serotypes and epidemiology of the diseases this pathogen causes. Results indicated that all the isolates were positive for KMT1 gene and the PCR amplified products were approximately 460 bp, demonstrating that these strains were all P.multocida. Moreover, all the isolated strains were identified as capsular type A and lipopolysaccharide type L1. Virulence factor identification results revealed that all strains possessed genes related to pili, adhesin, iron metabolism and uptake. In contrast, toxin coding gene (toxA) and sialidase encodes genes (nan B and nan H) were not detected in any isolates. The drug susceptibility results indicated that all the isolates were resistant to Lincomycin, Chloramphenicol, Clindamycin and Oxacillin but were sensitive to Ceftriaxone and Cefalotin. The animal experiments were also performed to further determine the pathogenicity of these isolated strains. Animal experiment revealed that the liver, kidney, and heart of infected ducks were swollen and had bleeding spots. We also observed hepatocyte hypertrophy, hepatic sinus congestion and single-cell infiltration in infected ducks through H&E staining. In summary, this study demonstrated that all the isolated strains belong to capsular A and lipopolysaccharide type L1 P.multocida, but their virulence factors, drug resistance and pathogenicity were different.