The pathogenesis of persistent turbinate atrophy induced by toxigenic Pasteurella multocida in pigs

IFN-γ promotes PANoptosis in Pasteurella multocida toxin-induced pneumonia in mice

Interferon-γ (IFN-γ) is a pleiotropic cytokine that regulates diverse biological functions, including modulation of inflammatory response and innate and adaptive immunity. In our study, we found that IFN-γ plays an important role in the regulation of Pasteurella multocida toxin-associated pneumonia. In work described here, we demonstrated that rPMT induced a lethal pneumonia in WT mice and the severity of the pneumonia was substantially alleviated in IFN-γ-deficient mice, IFN-γ deficiency significantly elevated the survival rate and reduced the pathological lesions of the lungs after rPMT challenged. Notably, IFN-γ deficiency significantly decreased myeloperoxidase (MPO) expression abundance in the lung tissue, and the MPO was mainly expressed in the lung tissue injury region of WT mice. More importantly, IFN-γ deficiency impaired the activation of PANoptosis specific markers, including the caspase 3, GSDMD, and MLKL, and reduced the expression of IL-1β. Cumulatively, this study demonstrates that IFN-γ promotes PANoptosis in PMT induced pneumonia in mice, providing a basis for studying the pathogenic mechanism of PMT.

Noncanonical G-protein-dependent modulation of osteoclast differentiation and bone resorption mediated by Pasteurella multocida toxin

Pasteurella multocida toxin (PMT) induces atrophic rhinitis in animals, which is characterized by a degradation of nasal turbinate bones, indicating an effect of the toxin on bone cells such as osteoblasts and osteoclasts. The underlying molecular mechanism of PMT was defined as a persistent activation of heterotrimeric G proteins by deamidation of a specific glutamine residue. Here, we show that PMT acts directly on osteoclast precursor cells such as bone marrow-derived CD14⁺ monocytes and RAW246.7 cells to induce osteoclastogenesis as measured by expression of osteoclast-specific markers such as tartrate-resistant acid phosphatase and bone resorption activity. Treatment performed solely with PMT stimulates osteoclast differentiation, showing a receptor activator of nuclear factor-κB ligand (RANKL)-independent action of the toxin. The underlying signal transduction pathway was defined as activation of the heterotrimeric G proteins Gα_q/11 leading to the transactivation of Ras and the mitogen-activated protein kinase pathway. Gα_q/11 transactivates Ras via its effector phospholipase Cβ-protein kinase C (PKC) involving proline-rich tyrosine kinase 2 (Pyk2). PMT-induced activation of the mitogen-activated protein kinase pathway results in stimulation of the osteoclastogenic transcription factors AP-1, NF-κB, and NFATc1. In addition, Ca²⁺-dependent calcineurin activation of NFAT is crucial for PMT-induced osteoclastogenesis. The data not only elucidate a rationale for PMT-dependent bone loss during atrophic rhinitis but also highlight a noncanonical, G-protein-dependent pathway toward bone resorption that is distinct from the RANKL-RANK pathway but mimics it. We define heterotrimeric G proteins as as-yet-underestimated entities/players in the maturation of osteoclasts which might be of pharmacological relevance.

Pasteurella multocida toxin (PMT) induces degradation of nasal turbinate bones, leading to the syndrome of atrophic rhinitis. Recently, the molecular mechanism and substrate specificity of PMT were identified. The toxin activates heterotrimeric G proteins by a covalent modification. However, the mechanism by which PMT induces bone degradation is poorly understood. Our report demonstrates a direct effect of PMT on osteoclast precursor cells, leading to maturation of bone-degrading osteoclasts. Interestingly, PMT stimulates osteoclastogenesis independently of the cytokine RANKL, which is a key factor in induction of osteoclast differentiation. This implicates a noncanonical osteoclastogenic signaling pathway induced by PMT. The elucidated Gα_q/11-dependent osteoclastogenic signal transduction pathway ends in osteoclastogenic NFAT signaling. The noncanonical, heterotrimeric G protein-dependent osteoclast differentiation process may be of pharmacological relevance, as members of this pathway are highly druggable. In particular, modulation of G protein-coupled receptor activity in osteoclast progenitors by small molecules might be of specific interest.

Swine atrophic rhinitis caused by pasteurella multocida toxin and bordetella dermonecrotic toxin

Atrophic rhinitis is a widespread and economically important swine disease caused by Pasteurella multocida and Bordetella bronchiseptica. The disease is characterized by atrophy of the nasal turbinate bones, which results in a shortened and deformed snout in severe cases. P. multocida toxin and B. bronchiseptica dermonecrotic toxin have been considered to independently or cooperatively disturb the osteogenesis of the turbinate bone by inhibiting osteoblastic differentiation and/or stimulating bone resorption by osteoclasts. Recently, the intracellular targets and molecular actions of both toxins have been clarified, enabling speculation on the intracellular signals leading to the inhibition of osteogenesis.

Cellular and molecular action of the mitogenic protein-deamidating toxin from Pasteurella multocida

The mitogenic toxin from Pasteurella multocida (PMT) is a member of the dermonecrotic toxin family, which includes toxins from Bordetella, Escherichia coli and Yersinia. Members of the dermonecrotic toxin family modulate G-protein targets in host cells through selective deamidation and/or transglutamination of a critical active site Gln residue in the G-protein target, which results in the activation of intrinsic GTPase activity. Structural and biochemical data point to the uniqueness of PMT among these toxins in its structure and action. Whereas the other dermonecrotic toxins act on small Rho GTPases, PMT acts on the α subunits of heterotrimeric G(q) -, G(i) - and G(12/13) -protein families. To date, experimental evidence supports a model in which PMT potently stimulates various mitogenic and survival pathways through the activation of G(q) and G(12/13) signaling, ultimately leading to cellular proliferation, whilst strongly inhibiting pathways involved in cellular differentiation through the activation of G(i) signaling. The resulting cellular outcomes account for the global physiological effects observed during infection with toxinogenic P. multocida, and hint at potential long-term sequelae that may result from PMT exposure.

Atrophic rhinitis: the influence of the aerial environment

Infectious atrophic rhinitis is a disease of the upper respiratory tract of pigs, characterized in the live animal by deformation of the snout and conchal atrophy. However, the severity of the disease in pigs on commercial units is highly variable and air quality may be implicated as a significant factor in addition to the recognized pathogens. In this study the aerial environment was monitored in 49 pig buildings on 12 commercial farrowing-finishing units. A total of 1117 pigs from the 12 farms were examined individually at commercial slaughter weight to quantify the severity of conchal atrophy, using snout scoring and morphometric techniques.

A number of significant relationships were shown between environmental variables in the farrowing house and the severity of conchal atrophy. Mean snout score (MSS) and the percentage of snouts from each herd sample with a score of three or more (SS3) were correlated with total bacterial counts (r = 0·78 (P < 0·01) and 0-83 (P < 0·01) respectively), counts of 10 [mi to >15 urn particles (r = 0·67 (P <0·05), 0·73 (P <0·05)) and concentrations of gravimetric dust (r = 0·65 (P <0·05), 0·64 (P <0·05)). Concentrations of ammonia were correlated with SS3 (r = 0·68 (P <0·05)).

Dust in the first-stage weaner houses was again a significant component of the aerial environment associated with the severity of the disease. MSS and SS3 were correlated with counts of 10 urn to >15 μm particles (r = 0·66 (P <0·05), 0·68 (P <0·05)), concentrations of respirable dust (r = 0·67 (P <0·05), 0·63 (P <0·05)), total dust (r = 0·75 (P <0·05), 0·87 (P <0·001)), and gravimetric dust (r = 0·83 (P <0·01), 0·88 (P <0·001)). The results support the theory that the mass or number of particles present as inspirable aerosols, and the presence of large numbers of viable bacteria may compromise the local defence mechanism of the upper respiratory tract in the pig and facilitate colonization by Bordetella bronchiseptica and Pasteurella multocida. Saturation deficit in the second-stage weaner houses was correlated with both mean morphometric index and SS3 (r = 0·860 (P <0·01) and 0·683 (P <0·05) respectively), and volumetric stocking density in the finishing houses was correlated with both MSS and SS3 (r = -0·84 (P <0·01), -0·64 (P <0·05)). It is hypothesized that the severity of the disease may be lessened by reducing the concentrations of dust, microbes and ammonia which may play a significant role in the development of the disease.

Assessment of infectious organisms associated with chronic rhinosinusitis in cats

OBJECTIVE

To determine detection rates for feline herpesvirus type 1 (FHV-1), Mycoplasma spp, fungi, and bacteria in flush samples and biopsy specimens from the nasal cavities of cats with and without chronic rhinosinusitis (CRS).

DESIGN

Prospective study.

ANIMALS

10 CRS-affected cats and 7 cats without signs of respiratory tract disease.

PROCEDURES

Nasal flush samples and biopsy specimens were collected from all cats for bacterial (aerobic and anaerobic), fungal, and mycoplasmal cultures; additional biopsy specimens were collected for virus isolation and polymerase chain reaction (PCR) assay (to detect FHV-1 DNA).

RESULTS

Aerobic bacteria were detected in flush samples from 5 of 7 control cats; culture of flush samples from CRS-affected cats yielded aerobic bacteria (9/10 cats), anaerobic bacteria (3/10), and Mycoplasma spp (2/10). No fungal organisms were isolated from any cat. Potential pathogens were isolated significantly more often from CRS-affected cats than from control cats. Bacterial culture of biopsy specimens yielded aerobic bacteria (2/7 control cats and 4/10 CRS-affected cats) and anaerobic bacteria (2/10 CRS-affected cats). Although FHV-1 was not detected in nasal biopsy specimens from control or CRS-affected cats, FHV-1 DNA was detected via PCR assay in specimens from 4 of 7 control cats and 3 of 10 CRS-affected cats.

CONCLUSIONS AND CLINICAL RELEVANCE

Compared with findings in control cats, anaerobic bacteria, Mycoplasma spp, and a variety of potentially pathogenic organisms were detected more commonly in samples from cats with CRS. In both groups, FHV-1 was detected via PCR assay as a nonviable organism or in noncultivable amounts.

Pasteurella multocida toxin type D serological assay as an alternative to the toxin neutralisation lethality test in mice

The objective of this work was to develop an enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies against Pasteurella multocida toxin type D, that correlated to a mouse lethality test. Currently, the mouse lethality test is one of several tests used world-wide to evaluate serological responses in animals immunised with vaccines containing toxoids. The mouse lethality test involves injecting mice with a mixture of toxin and test serum sample (from animals that have been vaccinated with a toxoid), and then determining antibody titre of the test serum from the number of mice that survive. Thus, the titre calculated is based on the neutralising activity of the test serum. The mouse lethality test requires large numbers of animals and causes severe distress to the animals. Organisations world-wide are working towards alternatives to animals in the development and control of biological products for human and veterinary use. Additionally, the mouse lethality test is labour-intensive, costly and lacks robustness and may be difficult to reproduce between different technicians. We have developed a double sandwich ELISA to measure anti- P. multocida toxoid type D antibodies in swine serum. Sera from swine immunised with vaccines containing type D toxoid showed good correlation to the mouse lethality assay (Spearman analysis=0.94 and Pearson analysis=0.84). When compared to the mouse lethality test, titres obtained using the ELISA format had higher correlation with protective immunity (i.e., lower turbinate atrophy) following challenge with virulent P. multocida. The ELISA assay is more robust, reproducible and costs less than the mouse lethality assay; and it complements efforts to reduce the use of animals in testing.

Nasal epithelial changes induced in piglets by acetic acid and by Bordetella bronchiseptica

Research on atrophic rhinitis of pigs has shown that both Bordetella bronchiseptica infection and experimental treatment with acetic acid predispose the nasal mucosa to colonization with Pasteurella multocida. Gnotobiotic piglets aged 3 days were dosed intranasally with either B. bronchiseptica (n = 6) or acetic acid 1 per cent (n = 10) and killed at intervals up to the 4th day after treatment. Samples of the ventral turbinates were examined by light microscopy and scanning and transmission electron microscopy. Within 12 h acetic acid induced loss of cilia, oedema, focal cell exfoliations, mitochondrial swelling and inflammatory cell infiltration. Bordetella bronchiseptica induced only a limited oedema and loss of cilia. Colonization of cilia by the bacteria was observed 96 h after infection. We conclude that, although acetic acid and B. bronchiseptica do not induce the same modifications of the nasal respiratory epithelium, their action causes stagnation of nasal mucus, which results in a nasal environment favourable to colonization by Pasteurella multocida.

A siderophore production mutant of Bordetella bronchiseptica cannot use lactoferrin as an iron source

Bordetella bronchiseptica secreted a hydroxamate siderophore when grown in Fe-depleted medium. A Tn5lac insertion mutant of B. bronchiseptica, DBB22, did not produce this hydroxamate siderophore and was incapable of using lactoferrin as an Fe source. Our data suggest that B. bronchiseptica uses a siderophore for removal of Fe from lactoferrin and transferrin rather than relying upon a receptor for these host Fe-binding proteins.

Effects of Pasteurella multocida toxin on the osteoclast population of the rat

Pasteurella multocida type D toxin is a peptide shown to induce severe atrophic rhinitis in the pig as the result of an increased osteoclastic resorption of the ventral nasal turbinates. In the present study, the effects of the toxin on the histological, cytochemical and ultrastructural features of the osteoclast population of the rat were examined. Pasteurella multocida toxin induced atrophy of the ventral and dorsal nasal turbinates and thinning of the nasal bones. The number and size of the long bone metaphyseal osteoclasts were significantly increased, but not the number of nuclei per cell. Osteoclasts of toxin-treated rats had more developed clear zones and ruffled borders than those of the controls and their cytoplasmic vacuoles were more abundant and larger. We concluded that P. multocida toxin stimulates bone resorption by osteoclasts in the rat by increasing resorption activity and by increasing their number. Its action is not limited to the nasal turbinates but occurs also in the other bones, such as the long bones.

Effect of Pasteurella multocida toxin on bone resorption in vitro

Pasteurella multocida toxin (PMT), which is the primary etiologic factor in the pathogenesis of progressive atrophic rhinitis in pigs, was found to stimulate bone resorption in vitro. This stimulation was observed both in cultures of murine calvaria by measuring the release of calcium and of the lysosomal enzyme beta-glucuronidase and in murine long bone cultures by measuring the release of calcium. Both systems showed the same dose response curve, with the maximal effect at a concentration of 5 ng/ml. The effect on calvaria was studied in more detail. PMT increased bone resorption 24 h after its addition and always had to be present to express an effect. Calcitonin was able to inhibit this increase of resorption completely, and inhibitors of prostaglandin synthesis suppressed it partially. Although the data show an effect of PMT on bone tissue, the results do not exclude an action on cells in the nasal cavity, which could indirectly stimulate bone resorption.

Osteogenesis and growth of the nasal ventral conchae of the piglet

The present study investigated the osteogenesis and growth of the nasal ventral conchae of piglets aged from 1 to 28 days. Serial transverse sections of paraffin wax-embedded noses were stained and examined by light microscopy. Bone formation occurred in a rostrocaudal direction in the ventral scroll, dorsal scroll, connecting zone, transverse lamina and articular lamina, successively, and occurred by two ossification processes: endochondral ossification and intramembranous bone apposition. Endochondral ossification was responsible for the longitudinally, rostrally directed growth. Rapid transverse bone growth and modelling were centrifugally directed and occurred by intramembranous bone apposition at the eccentric side of the scrolls and resorption at the concentric scroll side. Elongation of the distal scroll extremities took place by intramembranous bone apposition.

Experimental model of atrophic rhinitis in gnotobiotic pigs

To study the pathogenesis of atrophic rhinitis, gnotobiotic pigs (n = 6) were inoculated intranasally with a sterile sonicate of a toxigenic strain of Bordetella bronchiseptica (0.16 mg of protein per ml) at 5 days of age, and they were then inoculated intranasally with 1 ml (5,250 CFU/ml) of a live, toxigenic strain of Pasteurella multocida at 7 days of age. Pigs were necropsied at 2, 5, 9, 14, 21, and 28 days postinoculation; those pigs necropsied after 5 days had developed turbinate atrophy. Other gnotobiotic pigs received the following inoculation protocols: (i) a sterile sonicate of a nontoxigenic strain of B. bronchiseptica (0.2 mg of protein per ml), followed by toxigenic P. multocida (n = 4); (ii) toxigenic P. multocida alone (n = 7); (iii) diluent (sterile tryptose broth) (n = 2); (iv) the sterile sonicate of toxigenic B. bronchiseptica alone (n = 2); or (v) the sterile sonicate of a nontoxigenic strain of B. bronchiseptica alone (n = 2). Turbinate atrophy did not occur in the latter groups except for one pig inoculated with only toxigenic P. multocida. These studies show that turbinate atrophy occurs in pigs given the toxigenic B. bronchiseptica sonicate and then given live, toxigenic P. multocida. This experimental regimen is a useful model for (i) studying the pathogenesis of atrophic rhinitis and (ii) testing vaccine strategies.

Colonization of the pharyngeal tonsil and respiratory tract of the gnotobiotic pig by a toxigenic strain of Pasteurella multocida type D

Seven-day-old gnotobiotic pigs were inoculated intranasally with Pasteurella multocida and euthanatized 2, 5, 9, and 14 days after inoculation. Tissues from the oropharynx and respiratory tract of pigs were cultured quantitatively and analyzed microscopically. Pigs remained afebrile and alert, except one that died of acute fibrinopurulent pneumonia. Pasteurella multocida was isolated in greatest numbers from the pharyngeal tonsils, but only in low numbers from turbinate, trachea, lung, spleen, and liver. Significant histologic changes were limited to the tonsil. Infected pigs developed mild tonsillitis with lymphocytic hyperplasia, and accumulation of cell debris and bacteria in crypts. Capsular antigens of P. multocida, identified on tissue sections with rabbit anti-capsular polysaccharide antibody and immunocytochemical reagents, were confined to the crypt lumen. Ultrastructurally, bacteria were free within crypt material or within phagosomes of macrophages or neutrophils. In a second experiment, 5-day-old pigs were infected with Streptococcus suis type 2, followed by toxigenic Pasteurella multocida at 7 days of age; one pig died of streptococcal septicemia. Pigs developed a mild tonsillitis, and both bacteria were cultured from the tonsillar crypts for up to 14 days after infection. These studies show that a toxigenic strain of Pasteurella multocida, which is a causative agent of atrophic rhinitis, can colonize the tonsil and respiratory tract of gnotobiotic pigs for up to 14 days. In addition, colonization can occur concurrently with Streptococcus suis type 2.

Human infections associated with Bordetella bronchiseptica

This study examines the potential of Bordetella bronchiseptica to act as a human pathogen. After encountering two patients from whom B. bronchiseptica was isolated, we searched the literature and found 23 reports in which a human infection was reported in association with B. bronchiseptica. As a basis for evaluating these cases, we summarize the literature about the current microbiological status of B. bronchiseptica, the pathology and pathogenic mechanisms associated with the microorganism, and the likelihood of it acting as a commensal or colonizer. From this review we conclude that B. bronchiseptica has been rarely isolated from humans despite their considerable exposure to animal sources. Evidence suggests that B. bronchiseptica may be rarely encountered as a commensal or colonizer of the respiratory tract of humans and rarely in association with infection. When found as a probable pathogen, most infections have been respiratory tract in origin and have occurred in severely compromised hosts.

Effects of purified Pasteurella multocida dermonecrotoxin on cartilage and bone of the nasal ventral conchae of the piglet

The effect of intramuscular injection of purified dermonecrotoxin (DNT) from Pasteurella multocida type D on the nasal ventral conchae of piglets was studied. Severe atrophy of the conchae was observed 4, 6, and 10 days after injection (p.i.d). Lesions were observed in conchae cartilage and bone. Cartilage changes observed were the absence of chondrocyte maturation and hypertrophy, hyaline cartilage invasion by fibroblast-like and multinucleated cells, and endothelium damage with haemorrhages along the cartilage. Intramembranous bone was absent on p.i.d. 4, 6, and 10. Lamellar bone trabeculae were rarefied on p.i.d. 4 and almost absent on p.i.d. 10. Trabeculae were either normal or had the aspect of a dissolved bone matrix, leaving only irregularly oriented collagen fiber bundles. The number of osteoclasts was increased, especially the subperiosteal osteoclasts at the eccentric side of the scrolls. The osteoblasts appeared normal or their cytoplasm was dilated by vacuoles. It is concluded that the macroscopic conchae atrophy results from histological alterations and subsequent loss of both cartilage and bone. Further investigation is necessary to know whether the toxic effect of DNT on cells and matrix is direct or dependent of the vascular damage.

A comparison of different challenge methods for induction of atrophic rhinitis in pigs

Transmission and development of atrophic rhinitis (AR) was studied in 5- to 15-week-old pigs (Groups 2-7) originating from a herd free of AR, and compared to unexposed healthy pigs (Group 1), and pigs from a herd with endemic AR (Group 8). At the start of the trial, pigs in Groups 2-5 were challenged intranasally twice a week for 3 weeks with pure cultures of bacteria originating from the endemic AR herd: Nontoxigenic Pasteurella multocida type A (PmA) plus Bordetella bronchiseptica phase I (Bb) (Group 2); PmA + toxigenic Pm type D (PmD) (Group 3); PmD only (Group 4); and PmD + Bb (Group 5). Group 6 pigs were challenged with nasal wash of pigs from the endemic AR herd, and Group 7 pigs were challenged by being housed together in the same pen with Group 8 pigs throughout the study. Nasal swabs of all pigs were cultured 5 times during the study. Serum was collected at 6 weeks post challenge. Average daily gain (ADG) and turbinate lesions (turbinate gross lesions by visual scoring and by Turbinate Perimeter Ratio, TPR, scoring, and histopathological lesions) were measured at the time of slaughter at 15 weeks of age. Mean TPR value for the Group 1 pigs was 1.64, which was significantly (P less than 0.05) different from the mean TPR value of 0.58 for the pigs from the endemic AR herd (Group 8), the 0.79 value for Group 6 pigs, and 1.03 value for Group 7 pigs. Of pigs challenged with pure bacterial cultures, only Group 5 (PmD + Bb) developed significant AR (mean TPR = 1.24). Only one pig in each of Groups 2 and 3, and two pigs in Group 4 showed TPR values indicative of AR (TPR less than 1.30). However, histopathological examination showed that those pigs were recovering from the infection 7 weeks post challenge. Constant exposure to certain bacteria or other factors in nasal washings, stress of crowding or poor environmental conditions might be required to experimentally produce AR in 5-week and older pigs similar to that in naturally infected pigs. There was no relationship between turbinate lesions and the isolation frequency or quantity of PmA, PmD, or Bb. Antibody levels against PmA or PmD had moderate to high correlation with TPR values (r = -0.694 and -0.503 respectively). ELISA values also corresponded well with the type of bacteria inoculated in each group of pigs and appeared to be a sensitive test for PmA, PmD, and Bb infections in pigs.(ABSTRACT TRUNCATED AT 400 WORDS)

Pasteurella multocida and Bordetella bronchiseptica infections in rabbits

The natural history of infection with Pasteurella multocida and Bordetella bronchiseptica in domestic rabbits was studied prospectively at a commercial rabbitry. At weaning, about 25% of rabbits had nasal infections with P. multocida and 75% had infections with B. bronchiseptica. Infection of weanling rabbits paralleled nasal infections of their dams. The proportion of rabbits with both infections increased with age. At 2 to 4 months old, about 50% of rabbits with P. multocida or P. multocida and B. bronchiseptica infections had upper respiratory disease (URD), whereas rabbits with B. bronchiseptica infection had no disease. In rabbits about 10 months old, 75% with P. multocida or P. multocida and B. bronchiseptica infections had URD, whereas virtually none with B. bronchiseptica infection had disease. Disease of the nares, paranasal sinuses, middle ears, and lungs was associated with P. multocida and not B. bronchiseptica infection. In adult rabbits with nasal P. multocida infection, with or without signs of URD, about 80% had concurrent infection of the paranasal sinuses and middle ears and 20% had infection of the bronchi and lungs. In rabbits without nasal P. multocida infection, 20 to 35% had P. multocida infection of the paranasal sinuses and middle ears. Weanling rabbits with and without P. multocida infection had similar immunoglobulin G (IgG) levels. In rabbits observed prospectively, the only antibody differences between those transiently and persistently infected with P. multocida were a diminished IgA response in nasal lavages and an earlier IgM response in sera of transiently infected rabbits. IgG levels increased with the duration of infection. There was no relationship between immunoglobulin levels and freedom from P. multocida infection.

Serum complement activity and serum enzymes in rats after a subcutaneous injection of toxin prepared from Pasteurella multocida type D

Toxin produced by Pasteurella multocida type D was investigated for its effect on serum complement and serum biochemistry in rats. Rats were given a sublethal single subcutaneous injection of D toxin equivalent to 0.2 microgram/kg of body weight. Serum obtained 1, 3, 5 and 7 days post-treatment was tested for complement activity, total bilirubin, aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP). Serum complement titers were significantly elevated (P less than 0.05) at all times after injection of toxin compared to rats injected with diluent and tested at the same intervals. Bilirubin was decreased but both control and D toxin-treated rats had low concentrations of bilirubin in their sera. The other biochemical constituents measured had no consistent pattern that would indicate liver damage in the rats.

A protein toxin from Pasteurella multocida type D causes acute and chronic hepatic toxicity in rats

Pasteurella toxin given subcutaneously to rats caused severe liver damage and growth suppression in doses as low as 15.6 ng. Toxin was lethal at and above 31.25 ng. Survival times were dose-dependent, and lesions differed with time of survival after toxin. Rats dead of acute toxicity had focal hepatic necrosis. Liver lesions were associated with diffuse endothelial damage, intravascular trapping of leukocytes, and degeneration of hepatocytes (characterized by glycogen depletion, development of vacuoles, and eosinophilic cytoplasmic inclusions). Endothelial cells, Kupffer cells, and macrophages had evidence of activation, e.g., increased cellular size with increases in Golgi vesicles, granules, and lysosomes. Rats with chronic toxicity (survival greater than 150 hr) had cirrhosis, intestinal villous atrophy, and markedly reduced body weight and fat. These data show that the rat is highly sensitive to toxins of Pasteurella multocida, and that even low doses of toxin cause liver injury and growth suppression.

Stimulation of bone resorption by inflamed nasal mucosa, dermonecrotic toxin-containing conditioned medium from Pasteurella multocida, and purified dermonecrotic toxin from P. multocida

The effects of inflamed nasal mucosa from pigs with atrophic rhinitis (AR), cell extract from Bordetella bronchiseptica, conditioned medium from Pasteurella multocida, and purified dermonecrotic toxin (DNT) from P. multocida on mouse fetal long bones in organ culture were studied. Inflamed nasal "AR mucosa" stimulated the release of 45Ca from prelabeled cultures, while histologically the formation of calcified matrix was impaired as well. B. bronchiseptica cell extract only transiently increased 45Ca release, but also impaired the formation of matrix. 45Ca release was also stimulated by DNT-containing conditioned medium from P. multocida and by purified DNT. The effect of DNT was biphasic: low doses (1 to 25 ng/ml) slightly stimulated bone resorption, higher doses were inhibitory. The stimulatory action of DNT on 45Ca release was accompanied by an increase in numbers of preosteoclasts and osteoclasts. The significance of these findings for the pathogenesis of AR is discussed.