Pathology, Tissue Metalloproteinase Transcription and Haptoglobin Responses in Mice after Experimental Challenge with Different Isolates of Pasteurella multocida Obtained from Cases of Porcine Pneumonia

Pasteurella multocida causes liver injury in ducks by mediating inflammatory, apoptotic and autophagic pathways

Pasteurella multocida.(PM) infection is a major cause of avian cholera, but the pathogenesis of the disease is unknown. The purpose of this study was to further understand the host response to infection by using a duck model of PM, 20 female ducks were divided into two groups (n = 10). One group was infected with PM, while the other served as an uninfected control group. The ducks were observed after infection and samples were collected for testing. In this study, we report the mechanism of PM-induced inflammation to further mediate apoptosis and autophagic signaling pathways in liver cells. Our results demonstrated that PM infection initially induces hemorrhagic and necrotic lesions in the liver tissue of duck, promoting inflammasome assembly and release, triggering inflammation. The TLR4/NF-κB axis activated and interacted with multiple inflammation-related proteins, including TNF-α and IL-1β, which affected apoptosis and autophagy. Tumor necrosis factor induced hepatocyte apoptosis was implicated in a wide range of liver diseases; the release of TNF-α and activation with NF-κB further incite apoptotic pathways,such as Bax/BCL2/caspase to promote apoptotic genes APAF1, Bax, Caspase3, BCL-2, p53, and Cytc expression. Finally, PM-induced autophagy suppressed liver injury by promoting the Beclin-1, LC3B, p62, and mTOR. Thus, liver injury caused by PM via promoting autophagy was induced. In conclusion, we analyzed the liver injury of ducks infected with PM, and confirmed that inflammation appeared in the liver; this was followed by the intricate interplay between inflammation, apoptosis, and autophagy signaling pathways. The observed results provided a reference basis for studying pathogenic mechanisms of PM-host interactions.

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.

Receptor-interacting serine/threonine kinase 1- and 3-dependent inflammation induced in lungs of chicken infected with Pasteurella multocida

Fowl cholera is a serious, highly contagious disease caused by the bacterium Pasteurella multocida (P. multocida) in a range of avian species and is characterized by an acute form of septicaemia. The pathogenic mechanism of chicken lung injury caused by the bacterium is unclear. Therefore, P. multocida Q (a reference standard strain isolated from chicken) and 1G1 (a clinic isolated strain from duck) were selected to infect chickens, establishing fowl cholera-induced laying hen models. Several important proteins involved in the process of lung injury were identified and quantified using immunohistochemistry and WB. The results showed that chicken lungs infected with bacteria for 24 h showed congestion and edema. The inflammatory factors HMGB1 and IL-6, intercellular matrix MMP, the cell apoptosis-associated caspase-3 and necrotic apoptosis signal molecules RIPK1 and RIPK3 were widely expressed in the lungs of group Q and were significantly different compared with those of 1G1 group and uninfected group (P < 0.05). The results indicated that RIPK1 and RIPK3 are involved in the injury process of chicken lungs after infection with P. multocida, and the mechanisms of lung injury induced by different strains are different.

The Role of Necroptosis, Apoptosis, and Inflammation in Fowl Cholera-Associated Liver Injury in a Chicken Model

Fowl cholera resulting from infection with Pasteurella multocida causes huge economic losses in the poultry industry. Necrotic hepatitis is reported to be a significant lesion associated with fowl cholera in chickens. Clarifying the underlying molecular mechanism of hepatic injury caused by P. multocida infection is needed to develop new strategies to control fowl cholera. Pasteurella multocida Q (the standard reference strain) and P. multocida 1G1 (a clinical strain) were used to infect healthy laying hens. Clinical signs were observed and gross lesions in livers were observed postmortem. Histologic lesions and the localization and expression of protein molecules associated with necroptosis, apoptosis, and inflammation in hepatic tissues were examined by hematoxylin and eosin staining and immunohistochemistry. Western blot analysis was used to determine the expression of liver injury-related genes. Necroptotic molecules such as RIPK1 (receptor interaction protein kinases 1), RIPK3 (receptor interaction protein kinases 3), and MLKL (mixed lineage kinase domain-like protein) were observed by immunostaining primarily in the cytoplasm of hepatocytes within or around necrotic foci, and inflammatory mediators HMGB1 (high-mobility group box 1) and IL-6 (interleukin-6) were found in the cytoplasm of heterophils, monocytes/macrophages, and hepatic sinusoids. In addition, MMP9 (matrix metalloproteinase 9) and TIMP1 (tissue inhibitor of metalloproteinase 1) were observed in hepatic parenchymal cells, inflammatory cells, and interstitial spaces, whereas the apoptotic effector molecule caspase-3 (cysteine-containing aspartic proteolytic enzymes 3) was mainly found in hepatocytes. The expression of RIPK1, RIPK3, and MLKL was significantly higher in the infected chickens than in the controls. HMGB1 and IL-6 protein levels were also increased in infected chickens relative to those in controls. Both MMP9 and TIMP1 were highly expressed in infected chickens. In addition, caspase-3 protein levels were significantly elevated in infected chickens. Necroptosis, apoptosis, and inflammation played a significant role in hepatic injury caused by P. multocida.

A new pleuromutilin candidate with potent antibacterial activity against Pasteurella multocida

This study assessed the antimicrobial activity of 14-O-[(4,6-Diaminopyrimidine-2-yl) thioacetyl] mutilin (DPTM), a novel pleuromutilin candidate with a substituted pyrimidine moiety, against Pasteurella multocida. Minimum Inhibitory Concentration (MIC), Oxford Cup assay, and time-kill experiments were used to measure the activity of DPTM against P. multocida serotype A in vitro. We observed that DPTM was potent against Pasteurella multocida serotype A with the MIC value of 0.781 μg/mL. The mean inhibition-zone diameters of DPTM (50, 25, and 12.5 μg/mL) were 29.4, 24.2 and 20.1 mm, respectively. Time-kill experiments showed that the drug caused a rapid decline in the number of bacteria compared with the initial inoculum at 4 h and killed 94.6% of the bacteria during 24 h. Furthermore, DPTM activity was also assessed in a lung infection model challenged with 4.0 × 109 CFU/mL P. multocida serotype A. The results showed that DPTM significantly reduced mortality rate and bacterial load, and alleviated the pathological changes of lung. The antibacterial effect of DPTM found in this study suggested that it was useful in the prevention or control of pneumonia caused by P. multocida.

Identification of haptoglobin switch-on status in archived placental specimens indicates antenatal exposure to inflammation and potential participation of the fetus in triggering preterm birth

OBJECTIVE

Haptoglobin (Hp) has key immunoregulatory roles that vary with phenotype (Hp1-1, Hp2-1, Hp2-2). Cord blood Hp expression is switched-off in the normal fetus. We hypothesized that in the setting of fetal inflammation placenta becomes inundated with Hp of fetal origin that in turn modulates the output of PGE₂ and MMP-9 in a phenotype dependent manner.

METHODS

Placentas from 40 pregnancies complicated by preterm birth (PTB) (<37 weeks), without (n = 15) or with (n = 25) intra-amniotic infection and histological chorioamnionitis (HCA) were scored for intensity of Hp immunostaining. Hp mRNA levels were evaluated by PCR. Cord blood Hp levels, switch-on status and phenotypes were determined by ELISA and Western blotting. Using a villous trophoblast explant system we investigated if Hp can modulate the release of PGE₂ and MMP-9 in the presence or absence of lipopolysaccharide (LPS).

RESULTS

All cases with HCA had positive Hp immunoreactivity within fetal vascular spaces. Hp staining intensity correlated with cord blood Hp levels and IL-6. Placentas with and without HCA had similar Hp mRNA levels suggesting Hp immunostaining in the fetal spaces is of fetal rather than placental origin. Both Hp1-1 and Hp2-2 up-regulated PGE₂ release in the presence of LPS (2-fold over the LPS level, P < .05), without affecting MMP-9 concentrations.

CONCLUSIONS

Fetal Hp switch-on status, a marker of antenatal exposure to intra-amniotic infection/inflammation, can be reliably established through evaluation of archived placental specimens. In the setting of infection/inflammation, Hp enhances placental PGE₂ output thereby supporting the role of the fetus in triggering parturition.

Cytokine gene expression and pathology in experimental Pasteurella multocida infection in mice

The study was conducted to know the pathology and cytokine gene expression studies in experimental infection with Pasteurella multocida in mice. Swiss albino mice (20) were inoculated with P. multocida (200 μl of 1 × 108 cfu/ml) and control mice with sterile PBS intraperitoneally and sacrificed 4 mice at 6, 12, 18 and 24 h. Mice showed dullness, lethargy and unable to move at 18 and 24 h after inoculation. Histopathology revealed changes in liver, kidney, spleen, lung and no observable changes in heart and abdominal muscles. Liver showed septicemia condition and acute bronchopneumonia of lung at 24 h. TNF-α gene showed 20-fold increase in liver and spleen and 5-folds in kidney. There was upregulation of pro-inflammatory cytokines in liver, kidney, spleen and IL–10 gene at later periods of infection which is a new finding, needs further study. Thus, the present study indicated that increase in tissue cytokine gene expression concurred with histopathological changes were attributed to the pathogenesis of Pasteurellosis in mice.

Responses to Bacteria, Virus, and Malaria Distinguish the Etiology of Pediatric Clinical Pneumonia

RATIONALE

Plasma-detectable biomarkers that rapidly and accurately diagnose bacterial infections in children with suspected pneumonia could reduce the morbidity of respiratory disease and decrease the unnecessary use of antibiotic therapy.

OBJECTIVES

Using 56 markers measured in a multiplexed immunoassay, we sought to identify proteins and protein combinations that could discriminate bacterial from viral or malarial diagnoses.

METHODS

We selected 80 patients with clinically diagnosed pneumonia (as defined by the World Health Organization) who also met criteria for bacterial, viral, or malarial infection based on clinical, radiographic, and laboratory results. Ten healthy community control subjects were enrolled to assess marker reliability. Patients were subdivided into two sets: one for identifying potential markers and another for validating them.

MEASUREMENTS AND MAIN RESULTS

Three proteins (haptoglobin, tumor necrosis factor receptor 2 or IL-10, and tissue inhibitor of metalloproteinases 1) were identified that, when combined through a classification tree signature, accurately classified patients into bacterial, malarial, and viral etiologies and misclassified only one patient with bacterial pneumonia from the validation set. The overall sensitivity and specificity of this signature for the bacterial diagnosis were 96 and 86%, respectively. Alternative combinations of markers with comparable accuracy were selected by support vector machine and regression models and included haptoglobin, IL-10, and creatine kinase-MB.

CONCLUSIONS

Combinations of plasma proteins accurately identified children with a respiratory syndrome who were likely to have bacterial infections and who would benefit from antibiotic therapy. When used in conjunction with malaria diagnostic tests, they may improve diagnostic specificity and simplify treatment decisions for clinicians.

Disseminated intravascular coagulation in a novel porcine model of severe Staphylococcus aureus sepsis fulfills human clinical criteria

Sepsis is a common and often fatal complication in human patients in intensive care units. Relevant and well characterized animal models of sepsis may provide valuable information on pathophysiological mechanisms and be a mean of testing new therapeutic strategies. Large animal models of Staphylococcus aureus sepsis are rare, even though S. aureus increasingly affects human patients. Sepsis changes the haemostatic balance and leads to endothelial cell (EC) activation, coagulopathy and, in severe cases, disseminated intravascular coagulation (DIC). The aim of this study was to characterize the haemostatic and vascular alterations in a novel porcine model of severe S. aureus sepsis, investigating whether the changes fulfill the human clinical criteria for DIC. Five pigs were inoculated intravenously with S. aureus and two control animals were sham-inoculated. Blood samples were collected for thromboelastography (TEG) and assessment of plasma-based haemostatic parameters. Tissue was collected for histopathology and reverse transcriptase quantitative real-time polymerase chain reaction for measurement of mRNA encoding EC markers. All infected animals developed DIC; including procoagulant activation represented by hypercoagulable TEG profiles and prolonged clotting time. Histologically, numerous pulmonary thrombi were present in one pig. Inhibitor consumption was represented by decreasing antithrombin levels in infected pigs. Hyaline globules were found in three infected pigs, confirming fibrinolytic activation. EC activation was identified by expression of von Willebrand factor in small vessels together with elevated mRNA encoding activated EC markers. Severe haemostatic and vascular changes fulfilling the human criteria for DIC were therefore seen in all infected pigs. A tendency towards uncompensated DIC was seen in two animals.

Hibridização in situ fluorescente: princípios básicos e perspectivas para o diagnóstico de doenças infecciosas em medicina veterinária

Nesse manuscrito são discutidos aspectos relevantes sobre desenvolvimento da técnica de hibridização fluorescente in situ, seus princípios básicos, aplicações e perspectivas em medicina veterinária. Além disso, compara as vantagens e desvantagens em relação às outras técnicas de diagnóstico in situ. A FISH demonstra ser uma técnica com grande potencialidade de uso rotineiro, pois associa agilidade de execução, alta sensibilidade e especificidade e visualização do agente infeccioso viável no tecido.

Host-pathogen gene expression profiles during infection of primary bovine mammary epithelial cells with Escherichia coli strains associated with acute or persistent bovine mastitis

Escherichia coli intramammary infection (IMI) is often acute with local and systemic clinical manifestations that clear within 7 days. However, if not diagnosed early and treated, E. coli IMI could result in generalized systemic reaction and death. Persistent E. coli IMI is characterized by mild clinical manifestations followed by acute episodes of clinical mastitis during lactation. Factors responsible for pathogenesis of E. coli IMI and variation in clinical manifestations are not known. There are studies indicating that the outcome of E. coli IMI is mainly determined by cow factors. However, recent research demonstrated that virulence attributes of E. coli strains have significant impact on the outcome of E. coli IMI. The aims of this study were; (a) to compare gene expression profiles of PBMEC cocultured with strains of E. coli associated with acute or persistent IMI and; (b) to identify genes of E. coli induced during bacterial interaction with PBMEC. Utilizing cDNA we analyzed gene expression patterns of PBMEC cocultured with strains of E. coli using non-treated PBMEC as negative control. We evaluated also expression patterns of virulence associated genes of E. coli after co-culture with PBMEC using qRT-PCR. Our results showed that infection by both strains induced increased expression of pro-inflammatory cytokines, chemokines and innate immune response and apoptosis related genes. Our qRT-PCR results showed significant up-regulation of ler, eae, flic and iutA genes mainly in the strains of E. coli associated with persistent IMI. The pathogenesis and clinical severity of E. coli IMI may be determined by combined effects of host-pathogen factors.