Detection of antibodies against Pasteurella multocida using immunohistochemical staining in an outbreak of rabbit pasteurellosis

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.

Pasteurella multocida capsular: lipopolysaccharide types D:L6 and A:L3 remain to be the main epidemic genotypes of pigs in China

Pasteurella multocida is a leading cause of respiratory disorders in pigs. This study was designed to understand the genotypical and antimicrobial resistant characteristics of P. multocida from pigs in China. To achieve this, we briefly investigated 158 P. multocida isolates from pigs with respiratory disorders in China between 2019 and 2020. Genotyping through multiplex PCR assays assigned these 158 isolates into capsular genotypes A (60.13%, 95/158), D (35.44%, 56/158), F (4.43%, 7/158), and/or lipopolysaccharide (LPS) genotypes L3 (28.48%, 45/158) and L6 (66.46%, 105/158). In addition, eight isolates (5.06%, 8/158) were found to be nontypable using the LPS genotyping method. When combining the capsular genotypes and the LPS genotypes, D: L6 (34.81%, 55/158) and A: L6 (31.65%, 50/158) were the predominant genotypes, followed by A: L3 (24.05%, 38/158). PCR detection of virulence factor-encoding genes showed that over 80% of the isolates were positive for exbB, tonB, exbD, ompH, ptfA, fimA, sodA, sodC, fur, ompA, oma87, plpB, hsf-2, nanH and hgbB, suggesting the presence of these genes were broad characteristics of P. multocida. We also found approximately 63.92% (101/158), 51.27% (81/158), 8.86% (14/158), 7.59% (12/158), 3.16% (5/158), 0.63% (1/158), and 0.63% (1/158) of the isolates grew well in media with the presence of colistin (4 μg/mL), tetracycline (16 μg/mL), tigecycline (1 μg/mL), ampicillin (32 μg/mL), chloramphenicol (32 μg/mL), cefepime (16 μg/mL), and ciprofloxacin (1 μg/mL), respectively. This study contributes to the understanding of genotypes and antimicrobial resistance profile of P. multocida currently circulation in pigs of China.

Biomarkers, immune responses and cellular changes in vaccinated and non-vaccinated goats during experimental infection of M. haemolytica A2 under tropical conditions

BACKGROUND

We investigated the biomarkers, immune responses and cellular changes in vaccinated and non-vaccinated goats experimentally challenged with M. haemolytica serotype A2 under rainy and hot tropical conditions. A total of twenty-four clinically healthy, non-pregnant, female goats randomly allocated to 2 groups of 12 goats each were used for the study. The 12 goats in each season were subdivided into three groups (n = 4), which served as the control (G-NEG), non-vaccinated (G-POS), and vaccinated (G-VACC). In week-1, the G-VACC received 2 mL of alum-precipitated pasteurellosis vaccine while G-POS and G-NEG received 2 ml of sterile PBS. In week 2, the G-POS and G-VACC received 1 mL intranasal spray containing 10⁵ CFU of M. haemolytica serotype A2. Inoculation was followed by daily monitoring and weekly bleeding for eight weeks to collect data and serum for biomarkers and immune responses using commercial ELISA test kits. The goats were humanely euthanised at the end of the experiments to collect lungs and the submandibular lymph nodes tissue samples for gross and histopathological examinations.

RESULTS

Regardless of the season, we have observed a significant (p < 0.05) increase in serum concentrations of acute-phase proteins (haptoglobin, serum amyloid A), proinflammatory cytokines (interleukine-1β, interleukin-6), antibodies (immunoglobulin M, immunoglobulin G), and stress markers (cortisol and heat shock protein 70) in the G-POS goats compared to G-VACC and G-NEG. With regards to seasons, there was a significantly (p < 0.05) higher serum concentration with 1.5, 2 and 1-folds increase in the serum interleukin (IL)-1β, cortisol, and heat shock protein (HSP)-70 in the G-POS during rainy compared to the hot season. Histopathology of the lungs in G-POS goats revealed inflammatory cell infiltration, degeneration, haemorrhage/congestion, and pulmonary oedema in the alveoli spaces; thickening of the interstitium, and desquamation of bronchiolar epithelium. Cellular changes in the lymph node were characterized by a marked hypercellularity in G-POS goats.

CONCLUSION

Host responses to pneumonic mannheimiosis based on increased serum levels of biomarkers (cortisol, HSP70, IL-1β and IL-6) and severe cellular changes seen in the lungs and lymph nodes of G-POS goats compared to vaccinated goats and control group are influenced by the high environmental humidity recorded in the rainy season. Increased relative humidity in the rainy season is a significant stress factor for the higher susceptibility and severity of pneumonic mannheimiosis of goats in the tropics. Vaccination of goats using the alum precipitated Pasteurella multocida vaccine before the onset of the rainy season is recommended to minimise mortality due to potential outbreaks of pneumonia during the rainy season.

Efficacy of grape seed hydro-alcoholic extract in the treatment of experimentally Pasteurella multocida infected rabbits

Pasteurellosis is one of the rabbit's most bacterial severe diseases and leads to considerable financial damages in large production systems worldwide. Antibiotic use in animals may lead to antibiotic residues in animal products, including meat. Therefore, this study was designed to evaluate the potential role of grape seed extract (GSE) in treating Pasteurella multocida infection in rabbits. For this purpose, 45 weaned male New Zealand rabbits were divided into three groups; control, infected and infected-GSE treated. Experimental P. multocida infection in rabbits induced a remarkable decrease in body weight, body weight gain, as well as microcytic hypochromic anaemia, leucocytosis, neutrophilia and lymphocytopenia. Also, a significant increase in the hepatic and renal injury biomarkers, in interleukin-6, total globulin, α, β and γ globulins, as well as a marked reduction in total protein and albumin, were recorded in the P. multocida-infected rabbits. Treatment of infected rabbits with GSE modulated most of these altered parameters. This study endorses the administration of GSE for the treatment of Pasteurellosis in rabbits. Further studies are required to identify the possible additional effects, appropriate doses and duration of the GSE therapy in rabbits Pasteurellosis.

Immunohistochemical and molecular analysis of Pasteurella multocida in a rabbit with suppurative pleuropneumonia

A 1-month-old rabbit, imported as a pet by a distributor, died suddenly in the quarantine period in Japan due to suppurative pleuropneumonia. A bacterial isolate from its right lung was identified as Pasteurella multocida serotype A: 11. The isolate was classified as ST204 using the RIRDC scheme of multilocus sequence typing, suggesting that the isolate was genetically related to European isolates of the same sequence type listed in the PubMLST database and not to four other isolates that originated from past imported rabbits. In the immunohistochemical assay, an antiserum recognizing the somatic serotype 11 antigen generated from chicken could specifically detect P. multocida, indicating that the antiserum for somatic serotyping was useful for immunohistochemical diagnosis of rabbit pasteurellosis.

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.

Assessment of Pasteurella multocida A Lipopolysaccharide, as an Adhesin in an In Vitro Model of Rabbit Respiratory Epithelium

The role of the P. multocida lipopolysaccharide (LPS) as a putative adhesin during the early stages of infection with this bacterium in the respiratory epithelium of rabbits was investigated. By light microscopy and double enzyme labeling of nasal septa tissues, the amount of bacteria attached to the respiratory epithelium and the amount of LPS present in goblet cells at different experimental times were estimated. Transmission electron microscopy (TEM) and LPS labeling with colloidal gold particles were also used to determine the exact location of LPS in the cells. Septa that were challenged with LPS of P. multocida and 30 minutes later with P. multocida showed more adherent bacteria and more severe lesions than the other treatments. Free LPS was observed in the lumen of the nasal septum, forming bilamellar structures and adhering to the cilia, microvilli, cytoplasmic membrane, and cytoplasm of epithelial ciliated and goblet cells. The above findings suggest that P. multocida LPS plays an important role in the process of bacterial adhesion and that it has the ability of being internalized into host cells.

Experimental Study of the Pathogenicity of Pasteurella multocida Capsular Type B in Rabbits

The increased frequency of isolation of Pasteurella multocida capsular type B from rabbitries in north-western India prompted this investigation into the role of this organism in inducing disease in rabbits. Ten rabbits were divided into two groups of five animals. Group I rabbits were infected intranasally (IN) with 1 ml of inoculum containing 2 × 10(5) colony forming units/ml, while rabbits in group II were given 1 ml phosphate buffered saline IN. The rabbits in group I developed respiratory distress, increased rectal temperature and severe dyspnoea, with death occurring 24-48 h post infection. The main pathological findings were severe congestion and haemorrhage in the trachea, fibrinopurulent pneumonia, bacteraemia and septicaemia. The nasal secretions of all group I animals contained P. multocida. These observations indicate that in addition to P. multocida capsular types A and D, P. multocida capsular type B can also be highly pathogenic for rabbits.

Experimental study of pathogenicity of Pasteurella multocida serogroup F in rabbits

The role of Pasteurella multocida serogroup F in inducing disease in rabbits was investigated in this study. Three groups of 12 Pasteurella-free rabbits each were intranasally (i.n.), subcutaneously (s.c.), and perorally (p.o.) challenged, respectively. Six rabbits of each group were immunosuppressed using dexamethasone. Eight rabbits (four of them immunosuppressed) inoculated i.n. showed symptoms of respiratory distress resulting in respiratory failure and died or were euthanized in the terminal stage of the disease 3-6 days post-infection (p.i.). The main pathological findings were fibrinopurulent pleuropneumonia (immunocompetent rabbits) or diffuse haemorrhagic pneumonia (immunosuppressed rabbits). Septicemic syndrome ending with shock occurred in 11 rabbits (6 of them immunosuppressed) inoculated s.c., which died or were euthanized in the terminal stage of the disease 2-3 days p.i. The most significant pathological findings were extensive cutaneous and subcutaneous lesions. All of the p.o. inoculated rabbits survived the challenge showing no clinical signs of the disease and no macroscopic lesions. The observations in this study indicate that in addition to serogroups A and D of P. multocida, serogroup F also can be highly pathogenic for rabbits and therefore might be a cause of considerable economic loss in commercial rabbit production.

Diagnostic and typing options for investigating diseases associated with Pasteurella multocida

Pasteurella multocida is responsible for major animal diseases of economic significance in both developed and developing countries whereas human infections related to this bacterium are infrequent. Significantly, development of a carrier status or latent infections plays a critical role in the epidemiology of these diseases. Aiming at increased knowledge of these infections, we examine potential diagnostic and selected typing systems for investigating diseases caused by P. multocida. Detection of P. multocida from clinical specimen by; (i) isolation and identification, (ii) polymerase chain reaction (PCR), iii) specific hybridisation probes, (iv) serological tests and (v) other alternative methods is critically evaluated. These detection systems provide a wide spectrum of options for rapid diagnosis and for detecting and understanding of latent infections in herd/flock health control programmes, though PCR methods for detecting P. multocida in clinical specimen appear increasingly preferred. For establishing the clonality of outbreak strains, we select to discuss macromolecular profiling, serotyping, biotyping, restriction enzyme analysis, ribotyping and multiplex PCR typing. Although P. multocida infections can be rapidly diagnosed with molecular and serological tests, isolation and accurate species identification are central to epidemiological tracing of outbreak strains. Our review brings together comprehensive and essential information that may be adapted for confirming diagnosis and determining the molecular epidemiology of diseases associated with P. multocida.

Identification of Pasteurella multocida Serogroup F isolates in rabbits

A total of 24 Pasteurella multocida rabbit isolates obtained from 24 rabbit flocks in the Czech Republic during the period of between 2001 and 2004 were analysed by capsular PCR typing. Apart from isolates identified as serogroups A (n = 14, 58.4%) and D (n = 2, 8.3%), eight isolates (33.3%) were identified as members of serogroup F. This serogroup had been predominantly associated with poultry infections so far. The rabbit serogroup F isolates were characterized in detail by ribotyping with restriction to endonuclease MspI revealing two distinct ribotypes. Seven serogroup F isolates were assigned to ribotype 1 and one isolate was assigned to ribotype 2.