Prevalent Serotypes of Pasteurella multocida Isolated from Different Animal and Avian Species in India

Molecular characterization of Pasteurella multocida from cats and antibiotic sensitivity of the isolates

BACKGROUND

Companion animals, including dogs and cats, are frequently identified as sources of Pasteurella multocida, a bacterium that can be transmitted to humans and cause infections.

OBJECTIVES

This survey defines the prevalence, antibiotic sensitivity, capsular types, lipopolysaccharide (LPS) types and virulence factors of P. multocida isolated from cats.

METHODS

A total of 100 specimens from various cat breeds were collected. P. multocida was characterized using both biochemical tests and PCR. Genotypes of isolates were determined using capsular and LPS typing methods. Additionally, virulotyping was performed by detecting the presence of 12 virulence-associated genes. Disk diffusion was used to determine the antibiotic sensitivity of the isolates.

RESULTS

The prevalence of P. multocida in cats was 29%. Among the isolates, the majority were capsular type A (96.5%) and type D (3.4%), with a predominant presence of type A. Twenty-six of the isolates (89.66%) belonged to LPS genotype L6, whereas three isolates (10.3%) belonged to genotype L3. Among the 12 virulence genes examined, sodC, oma87, ptfA, nanB and ompH showed remarkable prevalence (100%). The toxA gene was detected in four isolates (13.8%). Variations were observed in other virulence genes. The nanH gene was present in 93.1% of the isolates, whereas the pfhA gene was detected in 58.6% of the isolates. The exbD-tonB, hgbB, sodA and hgbA genes showed prevalence rates of 96.5%, 96.5%, 96.5% and 82.8%, respectively. Additionally, particular capsule and LPS types were associated with specific virulence genes. Specifically, the toxA and pfhA genes were found to be more prevalent in isolates with capsular type A and LPS genotype L6. Most isolates were resistant to ampicillin, clindamycin, lincomycin, streptomycin and penicillin.

CONCLUSIONS

According to this epidemiological and molecular data, P. multocida from cats possess several virulence-associated genes and are resistant to antimicrobial medicines commonly used in humans and animals. Thus, it is crucial to consider the public health concerns of P. multocida in humans.

In Silico Functional Characterization of a Hypothetical Protein From Pasteurella Multocida Reveals a Novel S-Adenosylmethionine-Dependent Methyltransferase Activity

Genomes may now be sequenced in a matter of weeks, leading to an influx of "hypothetical" proteins (HP) whose activities remain a mystery in GenBank. The information included inside these genes has quickly grown in prominence. Thus, we selected to look closely at the structure and function of an HP (AFF25514.1; 246 residues) from Pasteurella multocida (PM) subsp. multocida str. HN06. Possible insights into bacterial adaptation to new environments and metabolic changes might be gained by studying the functions of this protein. The PM HN06 2293 gene encodes an alkaline cytoplasmic protein with a molecular weight of 28352.60 Da, an isoelectric point (pI) of 9.18, and an overall average hydropathicity of around -0.565. One of its functional domains, tRNA (adenine (37)-N6)-methyltransferase TrmO, is a S-adenosylmethionine (SAM)-dependent methyltransferase (MTase), suggesting that it belongs to the Class VIII SAM-dependent MTase family. The tertiary structures represented by HHpred and I-TASSER models were found to be flawless. We predicted the model's active site using the Computed Atlas of Surface Topography of Proteins (CASTp) and FTSite servers, and then displayed it in 3 dimensional (3D) using PyMOL and BIOVIA Discovery Studio. Based on molecular docking (MD) results, we know that HP interacts with SAM and S-adenosylhomocysteine (SAH), 2 crucial metabolites in the tRNA methylation process, with binding affinities of 7.4 and 7.5 kcal/mol, respectively. Molecular dynamic simulations (MDS) of the docked complex, which included only modest structural adjustments, corroborated the strong binding affinity of SAM and SAH to the HP. Evidence for HP's possible role as an SAM-dependent MTase was therefore given by the findings of Multiple sequence alignment (MSA), MD, and molecular dynamic modeling. These in silico data suggest that the investigated HP might be used as a useful adjunct in the investigation of Pasteurella infections and the development of drugs to treat zoonotic pasteurellosis.

The bovine nasal fungal community and associations with bovine respiratory disease

Introduction

Effective identification and treatment of bovine respiratory disease (BRD) is an ongoing health and economic issue for the dairy and beef cattle industries. Bacteria pathogens Pasteurellamultocida, Mycoplasmabovis, Mannheimia haemolytica, and Histophilus somni and the virus Bovine herpesvirus-1 (BHV-1), Bovine parainfluenza-3 virus (BPIV-3), Bovine respiratory syncytial virus (BRSV), Bovine adenovirus 3 (BAdV3), bovine coronavirus (BoCV) and Bovine viral diarrhea virus (BVDV) have commonly been identified in BRD cattle; however, no studies have investigated the fungal community and how it may also relate to BRD.

Methods

The objective of this study was to understand if the nasal mycobiome differs between a BRD-affected (n = 56) and visually healthy (n = 73) Holstein steers. Fungal nasal community was determined by using Internal Transcribed Spacer (ITS) sequencing.

Results

The phyla, Ascomycota and Basidiomycota, and the genera, Trichosporon and Issatchenkia, were the most abundant among all animals, regardless of health status. We identified differences between healthy and BRD animals in abundance of Trichosporon and Issatchenkia orientalis at a sub-species level that could be a potential indicator of BRD. No differences were observed in the nasal fungal alpha and beta diversity between BRD and healthy animals. However, the fungal community structure was affected based on season, specifically when comparing samples collected in the summer to the winter season. We then performed a random forest model, based on the fungal community and abundance of the BRD-pathobionts (qPCR data generated from a previous study using the same animals), to classify healthy and BRD animals and determine the agreement with visual diagnosis. Classification of BRD or healthy animals using ITS sequencing was low and agreed with the visual diagnosis with an accuracy of 51.9%. A portion of the ITS-predicted BRD animals were not predicted based on the abundance of BRD pathobionts. Lastly, fungal and bacterial co-occurrence were more common in BRD animals than healthy animals.

Discussion

The results from this novel study provide a baseline understanding of the fungal diversity and composition in the nasal cavity of BRD and healthy animals, upon which future interaction studies, including other nasal microbiome members to further understand and accurately diagnose BRD, can be designed.

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.

Signal sequence contributes to the immunogenicity of Pasteurella multocida lipoprotein E

Recombinant Pasterurella multocida lipoprotein E (PlpE) has been shown to protect against fowl cholera. This study aimed to determine if the signal sequence may contribute to the antigenicity and protective efficacy of recombinant PlpE. A small antigenic domain of PlpE (termed truncated PlpE, tPlpE) was constructed with (SP-tPlpE) or without (tPlpE) the signal sequence and evaluated in vitro and in vivo. In vitro, the HEK-Bule hTLR2 Cells were used to evaluate the activation of NF-kB in the test associated with the stimulation of the SP-tPlpE and tPlpE proteins. When chickens were immunized, compared to the tPlpE vaccine group, the SP-tPlpE group showed higher antibody levels and enhanced CD4⁺ T cell response. In a challenge test, the SP-tPlpE group showed a survival rate of 87.5% (n = 8), compared to 25% for the tPlpE group. It is confirmed that the inclusion of the native signal sequence enhanced protective efficacy against fowl cholera and may act as a vaccine adjuvant. The short SP-tPlpE construct is amenable to further vaccine engineering and has potential to be developed as a fowl cholera vaccine.

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.

Virulence genes and enterobacterial repetitive intergenic consensus region (ERIC) profiling reveals highly diverse genetic population among avian strains of Pasteurella multocida

Pasteurella multocida is a multispecies pathogen with certain host specific capsular types but interspecies transmission cannot be overlooked. Knowing the diversity of P. multocida in a geographical location is essential to formulate a vaccination programme. Diversity among the P. multocida isolates from different avian species recovered in the state of Tamil Nadu, India was studied using enterobacterial repetitive intergenic consensus region (ERIC)-PCR and virulence gene profiling (VP). Capsular typing revealed that 44 (97.78%) strains belonged to capsular type A while only one (2.22%) strain belonged to capsular type B. ERIC-PCR analysis showed eight different clusters and four individual strains. The index of discrimination (D value) was found to be 0.8899. Virulence profiling showed that genes fimA, pfhA, hsf-2 and pmHAS were found in 100% of the strains while ompH, omp87, ompA, plpB, sodA, sodC, ptfA, hsf-1, exbB, fur, hgbA and hgbB were found in ≥90% of the strains. Dermonecrotoxin gene toxA was present only in 4.44% of the strains, while nanH in 68.89% and nanB in 88.89% of the strains. One strain each from turkey and Guinea fowl had toxA gene. Correlation analysis revealed a positive correlation between ptfA and hgbA gene, exbB and fur gene, ptfA and sodC gene, exbB and hsf-1 gene, ompA and ompH gene. Majority of duck strains clustered together both in ERIC and virulence gene profiles. Turkey strains were highly diverse with different VPs and ERIC-PCR patterns.

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.

Managing Disease Outbreaks in Captive Herds of Exotic Companion Mammals

Management of epizootics of exotic companion mammal herds relies on careful observance of animals, proper management and husbandry, adequate nutrition, and stress reduction. Many diseases occur because of the stress of weaning so anticipating this and maximizing sanitation and ventilation, minimizing overcrowding and concurrent disease, and providing enough fiber for herbivores is prudent. Antimicrobial therapy must be carefully considered in the route of administration and the likely risk of enterotoxemia development. Separation of affected animals, rapid diagnostic testing, and implementation of treatment and supportive care minimizes losses during epizootics. Knowledge of potential zoonotic pathogens is important for veterinarians and staff.

Toxigenic and non-toxigenic Pasteurella multocida genotypes, based on capsular, LPS, and virulence profile typing, associated with pneumonic pasteurellosis in Iran

Pasteurella multocida is an important cause of pneumonic pasteurellosis in small ruminants. Its prevalence was investigated in 349 pneumonic lungs from sheep (n = 197) and goats (n = 152), and genotypes of isolates were determined by capsular and lipopolysaccharide (LPS) typing as well as by virulotyping based on the detection of 12 virulence-associated genes. P. multocida was isolated from 29.4 % of sheep lungs and 13.8 % of goat lungs. A (78.5 %) and D (21.5 %) capsular types, as well as L3 (41.8 %) and L6 (57.0 %) LPS genotypes, were detected, with the A:L6 genotype being the most prevalent in both sheep (59.6 %) and goat (52.4 %) isolates. A total of 19 virulence profiles (VP) were detected, seven non-toxigenic and 12 toxigenic, which correlated with the capsular-LPS genotype. All isolates of each VP belonged to the same LPS and capsular genotype, except for one isolate of VP1. The diversity in VP was higher among toxigenic (0.29) than non-toxigenic (0.18) isolates. Moreover, the toxigenic VPs showed more diversity in their capsular-LPS genotypes, with the two main toxigenic VPs belonging to genotypes D:L3 (VP2) and A:L3 (VP3). Therefore, the abundance of toxigenic isolates among sheep and goat isolates does not seem to correspond to the expansion of a more virulent lineage associated with pneumonic pasteurellosis in small ruminants. The most prevalent genotypes among sheep isolates were the non-toxigenic VP1:A:L6 (41.4 %) and the toxigenic VP3:A:L3 (17.2 %) genotypes, whereas the most prevalent among goat isolates were the toxigenic VP2:D:L3 (33.3 %) and the non-toxigenic VP1:A:L6 (14.3 %) and VP4:A:L6 (14.3 %) genotypes. These prevalent toxigenic and non-toxigenic genotypes seem to be epidemiologically relevant in pneumonic pasteurellosis of small ruminants.

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.

Implications for dosing regimen of enrofloxacin administered concurrently with dexamethasone in febrile buffalo calves

The objective of the study was to determine the influence of dexamethasone (DXM) on pharmacokinetics (PK) and pharmacodynamics (PD) of enrofloxacin (ENR) for dosage optimization following concurrent administration of ENR and DXM in febrile buffalo calves. A 2 μg/kg intravenous dosage of lipopolysaccharide derived from Escherichia coli was used to induce fever in calves. After inducing fever, ENR was administered at the dose rate of 12 mg/kg, IM followed by IM injection of DXM (0.05 mg/kg) in calves. Minor alterations in PK of ENR were observed following the administration of ENR + DXM. The PK parameters were t_1/2K₁₀ = 6.34 h, Cl/F = 0.729 L/kg/h, and MRT_0-∞ = 10.5 h. Antibacterial activity (MIC, MBC, ex vivo time-kill kinetics) of ENR for P. multocida was not affected by DXM. But MPC of ENR against P. multocida was lessened in presence of DXM. Using PK-PD-modeled AUC_0-24h/MIC values for bactericidal effect against P. multocida, daily dosages of ENR administered in combination with DXM were 4.02 mg/kg and 16.1 mg/kg, respectively, for MIC_90s of 0.125 μg/ml and 0.50 μg/ml. A dose of 5.38 mg/kg was determined for ENR for frequently occurring P. multocida infections having ≤ MIC₉₀ of 0.125 μg/ml and PK-PD modeled dose was comparable with the recommended ENR dose of 5 mg/kg for bovines for mild infections. It is suggested that a recommended dosage of 5-12.5 mg/kg of ENR can be used effectively in combination with DXM to treat P. multocida associated infections in buffalo calves without any risk of resistance amplification.

Seroprevalence of hemorrhagic septicemia in dairy cows in Assam, India

Hemorrhagic septicemia (HS) is a highly fatal disease caused by Pasteurella multocida that often cause outbreaks in buffalo and cattle in India, and thus is a major cause of production losses. It is one of the livestock diseases with the highest mortality, and despite available vaccines, outbreaks still occur. To assess the seroprevalence in the state of Assam, Northeast India, 346 serum samples from cows from 224 randomly selected households, from both urban and rural areas of three districts, were tested with a commercial ELISA. In total 88 cows were seropositive (25.4%), and indigenous cattle were significantly more seropositive (33.5%) compared to the crossbred cattle (18.5%) (p = 0.002). Herd prevalence was 35.7%, and more rural farms (47.4%) were positive compared to the urban farms (23.6%) (p < 0.001). No other risk factors were identified in this study. Only one farm had vaccinated against HS, but there were no seropositive animals detected in that herd. This study shows that HS is highly prevalent in Assam. Considering the importance of dairy production in India, and the dependence of the rural Assam population on farming and livestock keeping, more extensive vaccination campaigns would be important.

Comparison of two indirect ELISA coating antigens for the detection of dairy cow antibodies against Pasteurella multocida

The ELISA is recognized as an efficient diagnostic tool for antibody detection, but there is no standard ELISA assay for detection of antibodies against hemorrhagic septicemia (HS) in cattle. The present study reports on an indirect ELISA assay for antibody detection of HS in dairy cows, and evaluates the sensitivity (Se) and specificity (Sp) of the method using a Bayesian approach. An indirect ELISA was developed with two types of heat extract antigens, Pasteurella multocida strains P-1256 and M-1404, as coating antigens. A checkerboard titration was employed using dairy cow sera immunized with P. multocida bacterin and colostrum-deprived calf sera. The concentrations of heat extract antigen (160μg/mL), sample serum (1:100) and goat anti-bovine immunoglobulin G labeled with horseradish peroxidase (1:2000) were optimal for the assay. The cut-off values were 0.147 and 0.128 for P-1256 and M-1404 coating antigens, and there were no differences in the results of tests with positive and negative sera (p<0.05). The characteristics of three diagnostic tests were evaluated using a one-population Bayesian model, assuming conditional dependence between two types of coating antigen-based ELISAs and indirect hemagglutination assay (IHA). A total of 415 sera samples from dairy cows without HS vaccination and no history of disease were tested. The Se and Sp of the P-1256 and M-1404 ELISAs were higher than those of the IHA. The Se and Sp of the P-1256 ELISA were 90.3% and 90.1%, while the Se and Sp of the M-1404 ELISA were 92.1% and 71.9%. The median values of Se and Sp from the IHA were 36.0% and 58.2%.

Two novel cross‑protective antigens for bovine Pasteurella multocida

Pasteurella multocida is an important pathogen that leads to a range of diseases that have severe economic consequences on cattle production. In order to develop an effective cross-protective component vaccine, an immunoproteomics approach was used to analyze outer membrane proteins (OMPs) of the P. multocida serotype A, B and F strains. Candidate antigen molecules from the whole genome were screened via linear trap quadrupole mass spectrometry and bioinformatics analysis, and the reactogenicity of the candidate antigen molecules was analyzed via cloning, expression, and ELISA or protein immunoblotting, and the vaccine efficacy of the candidate molecules was determined in infective animal models and cross-protective antigens may be obtained. rPmCQ2_2g0128, rPmCQ2_1g0327 and rPmCQ2_1g0020 proteins were selected. Their protective rates were 40/30/20% (rPmCQ2_2g0128), 50/40/0% (rPmCQ2_1g0327) and 0/40/30% (rPmCQ2_1g0020) against ten-fold median lethal dose (10LD₅₀) of the P. multocida serotypes A, B and F in a mouse model, respectively. The results suggested that the two proteins rPmCQ2_2g0128 and rPmCQ2_1g0327 may be used as vaccine candidates against bovine P. multocida serotypes A, B. To the best of our knowledge, the present study was the first to identify cross-protective antigens, extracted OMPs from bovine P. multocida.

Immunogenicity of recombinant Omp16 protein of Pasteurella multocida B:2 in mouse model

Bacterial peptidoglycan-associated lipoproteins (PAL) are potential targets for the development of diagnostics/subunit vaccines for infectious diseases. Most commonly prevalent Omp16 lipoprotein is absolutely conserved among Pasteurella multocida strains, which are involved in multiple infectious diseases of livestock worldwide. In the present study, we cloned omp16 gene encoding for mature Omp16 of P. multocida B:2 strain P52 and overexpressed as a fusion protein in Escherichia coli. Mice immunized with purified recombinant non-lipidated Omp16 fusion protein (~32 kDa) resulted in elicitation of significant antigen specific serum antibody titres (total IgG and subtypes). A more pronounced increase in Th2 response (IgG1) was noticed. The study indicated the potential possibilities to use lipidated recombinant Omp16 protein in developing a composite subunit vaccine along with suitable adjuvant for haemorrhagic septicaemia/ pasteurellosis in livestock.

Recombinant transferrin binding protein A (rTbpA) fragments of Pasteurella multocida serogroup B:2 provide variable protection following homologous challenge in mouse model

Transferrin binding protein A (TbpA), an iron acquisition surface protein that also acts as virulence factor, is widely distributed among strains of Pasteurella multocida. In the present study, a total of seven clones of TbpA fragments (39D to F777; 39D to Q697; 188V to F777; 188V to Q697; 39D to P377; 188V to P377 and 39D to F187) belonging to P. multocida B:2 were constructed, over-expressed and purified as recombinant fusion proteins from Escherichia coli using affinity chromatography. Immunization of mice with rTbpA fragments resulted in a significant (p < 0.05) rise in antigen specific serum total IgG and subtypes (IgG1 and IgG2a) tires. All immunized mice challenged with 8 LD50 of P. multocida B:2 resulted in a variable protective efficacy up to 50%. The study indicated the potential possibilities to incorporate full length TbpA in subunit vaccine formulation composed of synergistic subunit antigens against haemorrhagic septicaemia (HS) in cattle and buffalo.

Molecular Epidemiology of Pasteurella multocida Circulating in India by Multilocus Sequence Typing

Multilocus sequence typing (MLST), a sequence-based typing method for bacterial pathogens, is currently the best method for long-term epidemiological study and to understand the population structure of the bacteria. This investigation was carried out to study the diversity of Pasteurella multocida isolates circulating in India. Ten different sequence types (ST) identified in this study are ST 122 from cattle, goat, mithun and pig; ST 50 from pig; ST 9 from cattle and sheep; ST 229 from cattle and goat; ST 71 and ST 277 from cattle; and ST 129, ST 280, ST 281 and ST 282 from avian species. Of these, ST 277, ST 280, ST 281 and ST 282 were identified for the first time. The analysis of results provides novel epidemiological information on the circulation of multiple STs across India. The majority of STs or their variants identified in this study have already been reported from different parts of the globe. This suggests that probably transboundary spread of strains across countries and continents has occurred across evolutionary time and is still happening. The isolation of ST 122 from small ruminants and pigs suggests that these species may be included in the preventive vaccination policy for effective control of haemorrhagic septicaemia in India.

Pathology of experimental infection by Pasteurella multocida serotype A: 1 in buffalo calves

Pasteurella multocida serotype A:3 has been mostly implicated in pneumonic pasteurellosis in ruminants. In contrast, our previous studies have reported that both serotypes A:1 and A:3 were responsible for respiratory diseases in cattle and buffaloes. However, the pathology and pathogenesis of P. multocida serotype A:1 (Pm A:1) infection have not been studied in ruminants. In the present study, 12- to 15-week-old buffalo calves (Bubalus bubalis) infected by Pm A:1 had fibrinous and suppurative bronchopneumonia with focal areas of coagulation necrosis typical of pneumonic pasteurellosis. For the first time, this study reports the lung pathology and pathogenecity of Pm A:1 infection in calves.

Development of immunization trials against Pasteurella multocida

Pasteurellosis is one of the most important respiratory diseases facing economically valuable farm animals such as poultry, rabbit, cattle, goats and pigs. It causes severe economic loss due to its symptoms that range from primary local infection to fatal septicemia. Pasteurella multocida is the responsible pathogen for this contagious disease. Chemotherapeutic treatment of Pasteurella is expensive, lengthy, and ineffective due to the increasing antibiotics resistance of the bacterium, as well as its toxicity to human consumers. Though, biosecurity measures played a role in diminishing the spread of the pathogen, the immunization methods were always the most potent preventive measures. Since the early 1950s, several trials for constructing and formulating effective vaccines were followed. This up-to-date review classifies and documents such trials. A section is devoted to discussing each group benefits and defects.

Pasteurella multocida: from zoonosis to cellular microbiology

In a world where most emerging and reemerging infectious diseases are zoonotic in nature and our contacts with both domestic and wild animals abound, there is growing awareness of the potential for human acquisition of animal diseases. Like other Pasteurellaceae, Pasteurella species are highly prevalent among animal populations, where they are often found as part of the normal microbiota of the oral, nasopharyngeal, and upper respiratory tracts. Many Pasteurella species are opportunistic pathogens that can cause endemic disease and are associated increasingly with epizootic outbreaks. Zoonotic transmission to humans usually occurs through animal bites or contact with nasal secretions, with P. multocida being the most prevalent isolate observed in human infections. Here we review recent comparative genomics and molecular pathogenesis studies that have advanced our understanding of the multiple virulence mechanisms employed by Pasteurella species to establish acute and chronic infections. We also summarize efforts being explored to enhance our ability to rapidly and accurately identify and distinguish among clinical isolates and to control pasteurellosis by improved development of new vaccines and treatment regimens.

A review of hemorrhagic septicemia in cattle and buffalo

Hemorrhagic septicemia (HS), an acute, fatal and septicemic disease of cattle and buffaloes caused by Pasteurella multocida, is important in tropical regions of the world, especially in African and Asian countries. The prevalence of disease has been well documented with predominant isolation of P. multocida serotypes B:2 and E:2. Conventional methods of identification such as serotyping, biotyping, antibiogram determination and pathogenicity as well as molecular methods (P. multocida-specific polymerase chain reaction (PCR), a serogroup B-specific PCR assay, multiplex capsular typing system and loop-mediated isothermal amplification techniques) and characterization (restriction endonuclease analysis, randomly amplified polymorphic DNA analysis, repetitive extragenic palidromic PCR and enterobacterial repetitive intergenic consensus PCR analysis) are applied in parallel for rapid epidemiological investigations of HS outbreaks. Although several vaccine formulations including alum precipitated, oil adjuvant and multiple emulsion vaccines are commercially available, the quest for suitable broadly protective HS vaccines with long-lasting immunity is on the upsurge. Concurrently, attempts are being made to unravel the mysteries of the pathogen and its virulence factors, pathogenesis and determinants of protective immunity as well as diversity among strains of P. multocida. This review highlights the advances in these various aspects of HS.

Molecular heterogeneity of plpE gene in Indian isolates of Pasteurella multocida and expression of recombinant PlpE in vaccine strain of P. multocida serotype B: 2

Outer membrane proteins of Pasteurella (P.) multocida have been known to be protective immunogens. Pasteurella lipoprotein E (PlpE) has been reported to be an important cross reactive outer membrane protein in P. multocida. The gene encoding the PlpE of P. multocida serotypes A: 3, B: 2 and D: 1 was amplified from the genomic DNA. The amplified products were cloned and the nucleotide sequence was determined. Sequence analysis of the recombinant clones revealed a single open reading frame of 1,011 bp, 1,008 bp and 1,017 bp encoding a protein with a calculated molecular mass of 37.829 kDa, 37.389 kDa and 37.965 kDa for serotypes A: 3, B: 2 and D: 1 respectively. The comparison of the plpE sequence in different capsular types revealed a high degree (>90%) of homology. Furthermore, the plpE gene of Haemorhhagic septicaemia causing serotype (B: 2) was expressed in E. coli and recombinant PlpE was strongly immunostained by antiserum against whole cell antigen, indicating that the protein is expressed in vivo.

PCR analysis of Pasteurella multocida isolates from an outbreak of pasteurellosis in Indian pigs

An outbreak of pasteurellosis with high mortality was recorded in indigenous pigs in India. The presence of Pasteurella multocida in samples collected from dead pigs was detected by smear examination and isolation, and later by P. multocida specific polymerase chain reaction (PM-PCR). P. multocida was detected in all the samples collected from dead pigs, with nine strains ultimately isolated. All the isolates were positive by PM-PCR. Six isolates showed CAPA and three were of CAPD capsular types. All the isolates were negative for toxigenic gene (toxA). The isolates were sensitive to oxytetracycline, doxycycline, gentamycin, erythromycin, ampicillin, amoxycillin, chloramphenicol and enrofloxacin and resistant to sulphadiazine and cloxacillin. The PCR assays used in this study have been shown to be useful diagnostic tools for P. multocida detection and characterization.

Pasteurella multocidaand bovine respiratory disease

Pasteurella multocidais a pathogenic Gram-negative bacterium that has been classified into three subspecies, five capsular serogroups and 16 serotypes.P. multocidaserogroup A isolates are bovine nasopharyngeal commensals, bovine pathogens and common isolates from bovine respiratory disease (BRD), both enzootic calf pneumonia of young dairy calves and shipping fever of weaned, stressed beef cattle.P. multocidaA:3 is the most common serotype isolated from BRD, and these isolates have limited heterogeneity based on outer membrane protein (OMP) profiles and ribotyping. Development ofP. multocida-induced pneumonia is associated with environmental and stress factors such as shipping, co-mingling, and overcrowding as well as concurrent or predisposing viral or bacterial infections. Lung lesions consist of an acute to subacute bronchopneumonia that may or may not have an associated pleuritis. Numerous virulence or potential virulence factors have been described for bovine respiratory isolates including adherence and colonization factors, iron-regulated and acquisition proteins, extracellular enzymes such as neuraminidase, lipopolysaccharide, polysaccharide capsule and a variety of OMPs. Immunity of cattle against respiratory pasteurellosis is poorly understood; however, high serum antibodies to OMPs appear to be important for enhancing resistance to the bacterium. Currently availableP. multocidavaccines for use in cattle are predominately traditional bacterins and a live streptomycin-dependent mutant. The field efficacy of these vaccines is not well documented in the literature.

Molecular characterization of Avian strains of Pasteurella multocida serogroup-A:1 based on amplification of repetitive regions by PCR

Repetitive extragenic palindromic (REP)-PCR (polymerase chain reaction), enterobacterial repetitive intergenic consensus (ERIC)-PCR, and single primer PCR assays were employed to characterize 66 strains of Pasteurella multocida serogroup A:1 isolated from avian species belonging to different regions of India. REP-PCR resulted in amplification of REP sequences from the genome which were in the range of approximately 200 to approximately 3000 bp and accounted for a total of 54 distinguishing profiles (D=0.99). ERIC-PCR analysis also generated amplified products in the range of approximately 200 to approximately 3200 bp categorizing strains into a total of 50 different profiles (D=0.98). Amplification of repetitive regions using a microsatellite primer (GTG)(5), resulted in clear distinctive bands ranging from approximately 200 to approximately 2400 bp. Strains were assigned to 43 profiles (D=0.96). No correlation could be drawn between genotypic profiles and avian hosts with their geographical area of origin. Avian strains of P. multocida serogroup A:1 were found to be highly heterogeneous with diverse profiles. REP-PCR was found to be highly discriminatory and simple method for differentiation of phenotypically similar strains. The present study also indicated that PCR based amplification of repetitive regions of P. multocida is a rapid technique with good discrimination and could be employed directly for routine typing of field isolates from fowl cholera outbreaks.

Pasteurella multocida Sepsis and Meningitis in 2-Month-Old Twin Infants after Household Exposure to a Slaughtered Sheep

This article outlines 2 cases of Pasteurella multocida sepsis and meningitis in 2-month-old twins after their father was exposed to a sheep during a sacrifice celebration at home. These cases emphasize the necessity of respecting basic hygiene rules and the danger involved in animal sacrifice without suitable professional structure.

Immunization with Outer Membrane Proteins of Pasteurella multocida (6:B) Provides Protection in Mice

The immunoprotective efficacy of Pasteurella multocida (6:B) outer membrane proteins (OMPs) was examined in the mouse model. Bacterial OMPs were extracted using sarkosyl method and analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and immunoblotting. Prototype vaccines were prepared using OMPs with adjuvants including dioleoyl phosphatidyl choline-based liposome and Montanide ISA206 water-in oil-in water emulsion. Antibody response to the vaccine was monitored using indirect enzyme linked immunosorbent assay. The results of the study showed that immunized mice had high titre with both the formulations. The vaccinated mice were able to survive a live virulent bacterial challenge. Based on the findings of the study it can be inferred that OMPs are important determinants of immunoprotection hence can serve as vaccine candidates against haemorrhagic septicaemia.

Characterization of avian strains of Pasteurella multocida by restriction endonuclease and amplified fragment length polymorphism

Avian strains of Pasteurella multocida were typed by employing restriction endonuclease analysis (REA) and single enzyme-amplified fragment length polymorphism (AFLP) to evaluate their applicability for epidemiological studies of fowl cholera outbreaks. A total of 72 strains isolated from different avian species (chicken, duck, turkey, quail and goose) belonging to various geographical regions of India were characterized. REA using two different enzymes HhaI and HpaII produced 9 and 18 clusters respectively, whereas Single enzyme-AFLP recognized 32 patterns out of 72 strains typed. The study indicated that REA using HpaII is a simple and resource efficient method, however, further typing with more stringent and rapid method like Single enzyme-AFLP, could drastically enhance investigation in epidemiological studies of fowl cholera outbreaks.

Detection of multiple strains ofPasteurella multocidain fowl cholera outbreaks by polymerase chain reaction-based typing

Applicability of molecular methods for the detection and differentiation of Pasteurella multocida strains involved in two separate fowl cholera outbreaks in a single poultry farm was investigated. A total of 12 and 18 strains of P. multocida obtained from two separate outbreaks were subjected to phenotypic and genotypic characterization. Phenotypically, all strains were similar; however, DNA-based techniques by employing polymerase chain reaction (PCR) assays were found to be highly specific and sensitive for rapid detection and differentiation of strains. All 30 strains gave amplicons of approximately 460 bp and approximately 1,044 bp specific for P. multocida and capsular serogroup A in the Multiplex Capsular PCR typing system. Molecular typing techniques such as repetitive extragenic palindromic PCR, enterobacterial repetitive intergenic consensus PCR and single primer PCR differentiated all 30 strains into different profiles. However, similar patterns of genome fragments were observed among all strains following restriction endonuclease analysis using the enzyme HpaII. The current investigation revealed involvement of the same and multiple strains of P. multocida in two outbreaks. The results also indicated that molecular methods of detection and typing are rapid in comparison with conventional methods for epidemiological investigations of fowl cholera outbreaks.