Streptococcus suis is an emerging zoonotic pathogen that causes septicemia, meningitis, arthritis, and pneumonia in swine and humans. The present study aimed to characterize the genetic diversity of S. suis serotype 2 isolated from pigs showing signs of illness in Brazil using pulsed-field gel electrophoresis (PFGE), single-enzyme amplified fragment length polymorphism (SE-AFLP), and profiling of virulence-associated markers. A total of 110 isolates were studied, 62.7% of which were isolated from the central nervous system and 19.1% from the respiratory tract. Eight genotypes were obtained from the combination of virulence genes, with 43.6% and 5.5% frequencies for the mrp (+) /epf (+) /sly (+) and mrp (-) /epf (-) /sly (-) genotypes, respectively. The presence of isolates with epf gene variation with higher molecular weight also appears to be a characteristic of Brazilian S. suis serotype 2. The PFGE and SE-AFLP were able to type all isolates and, although they presented a slight tendency to cluster according to state and year of isolation, it was also evident the grouping of different herds in the same PFGE subtype and the existence of isolates originated from the same herd classified into distinct subtypes. No further correlation between the isolation sites and mrp/epf/sly genotypes was observed.

Mannheimia haemolytica is an important cause of pneumonia in feedlot cattle. Nuclear factor erythroid-2-related factor 2 (Nrf2) is a redox-sensitive transcription factor responsible for the induction of antioxidant enzymes, such as heme oxygenase 1 (HO-1), within the lung. The expression of Nrf2 and HO-1 was immunohistochemically evaluated in 4 calves 24 h after experimental infection with M. haemolytica. Calves receiving normal saline served as controls. In the infected lungs, cytoplasmic Nrf2 expression was high in macrophages and bronchioles and low in alveolar epithelium, whereas nuclear expression was high in endothelial cells, macrophages, and bronchioles and lowest in alveolar epithelium. Normal lung samples displayed only faint Nrf2 cytoplasmic staining within bronchiolar epithelium. Expression of HO-1 was detected within the cytoplasm of macrophages and bronchiolar epithelial cells in all infected lung samples, whereas normal lungs displayed only weak cytoplasmic staining in bronchiolar epithelial cells. These findings suggest that bronchiolar epithelial cells and macrophages up-regulate Nrf2 expression early in the course of infection, which results in increased expression of HO-1 within these cells.

Objective—To determine the efficacy of a multivalent modified-live virus (MLV) vaccine containing a Mannheimia haemolytica toxoid to reduce pneumonia and mortality rate when administered to calves challenge exposed with virulent Bibersteinia trehalosi. Animals—74 Holstein calves. Procedures—Calves were assigned to 2 treatment groups. Calves in the control group (n = 36) were vaccinated by SC administration of 2 mL of a commercial 5-way MLV vaccine, and calves in the other group (38) were vaccinated by SC administration of a 2-mL dose of a 5-way MLV vaccine containing M haemolytica toxoid (day 0). On day 21, calves were transtracheally administered B trehalosi. Serum was obtained for analysis of antibody titers against M haemolytica leukotoxin. Nasopharyngeal swab specimens were collected from calves 1 day before vaccination (day −1) and challenge exposure (day 20) and cultured to detect bacterial respiratory pathogens. Clinical scores, rectal temperature, and death attributable to the challenge-exposure organism were recorded for 6 days after challenge exposure. Remaining calves were euthanized at the end of the study. Necropsy was performed on all calves, and lung lesion scores were recorded. Results—Calves vaccinated with the MLV vaccine containing M haemolytica toxoid had significantly lower lung lesion scores, mortality rate, and clinical scores for respiratory disease, compared with results for control calves. Conclusions and Clinical Relevance—Administration of a multivalent MLV vaccine containing M haemolytica toxoid protected calves against challenge exposure with virulent B trehalosi by reducing the mortality rate, lung lesion scores, and clinical scores for respiratory disease.

Hemorrhagic pneumonia is an acute and fatal disease of farmed mink caused by Pseudomonas aeruginosa. The pathogenesis of this disease has not yet been resolved. Mink are the only animals known to be susceptible to acute, contagious, and fatal lung infections caused by P. aeruginosa. The purpose of this study was to investigate the correlation between dose-response and season of infection and to clarify whether Danish mink are carriers of P. aeruginosa on their nasal mucosa during the season for hemorrhagic pneumonia. To elucidate the pathogenesis of the disease, an infectious dose-response trial was carried out on adult mink and mink kits, both in the season for hemorrhagic pneumonia (November) as well as out of season (July). It proved difficult to infect mink via the intra-nasal route. Only 4 out of 60 infected mink developed clinical disease and were euthanized, all of them in November, illustrating that predisposing factors in the mink itself and not infectious dose might be crucial for disease development. We were able to culture P. aeruginosa from the nasal cavity of the clinically healthy experimental mink 8 d after inoculation. This indicated that the mink can carry P. aeruginosa on their nasal mucosa without developing the disease. It was not possible, however, to culture P. aeruginosa from the nasal cavity of clinically healthy mink obtained from farms in November, which indicates that the organism is not a normal part of the nasal mucosal flora of mink.

Objective—To investigate the effect of opsonization of Rhodococcus equi with R equi-specific antibodies in plasma on bacterial viability and phagocyte activation in a cell culture model of infection. Sample—Neutrophils and monocyte-derived macrophages from 6 healthy 1-week-old foals and 1 adult horse. Procedures—Foal and adult horse phagocytes were incubated with either opsonized or nonopsonized bacteria. Opsonization was achieved by use of plasma containing high or low concentrations of R equi-specific antibodies. Phagocyte oxidative burst activity was measured by use of flow cytometry, and macrophage tumor necrosis factor (TNF)-α production was measured via an ELISA. Extracellular and intracellular bacterial viability was measured with a novel R equi-luciferase construct that used a luminometer. Results—Opsonized bacteria increased oxidative burst activity in adult horse phagocytes, and neutrophil activity was dependent on the concentration of specific antibody. Secretion of TNF-α was higher in macrophages infected with opsonized bacteria. Opsonization had no significant effect on bacterial viability in macrophages; however, extracellular bacterial viability was decreased in broth containing plasma with R equi-specific antibodies, compared with viability in broth alone. Conclusions and Clinical Relevance—The use of plasma enriched with specific antibodies for the opsonization of R equi increased the activation of phagocytes and decreased bacterial viability in the extracellular space. Although opsonized R equi increased TNF-α secretion and oxidative burst in macrophages, additional factors may be necessary for effective intracellular bacterial killing. These data have suggested a possible role of plasma antibody in protection of foals from R equi pneumonia.

The purpose of this study was to develop a percutaneous lung biopsy technique to be used on steers in a commercial feedlot setting. Thirty-four crossbred steer and heifer calves from a commercial feedlot in southern Alberta were used in this study. The calves originated from the auction market and all were chronically affected with bovine respiratory disease (BRD). A technique was developed to obtain a lung sample from the right cranioventral lung lobe, intercostal space (ICS) 2, using a manual or an automatic biopsy instrument with a 14- or 12-gauge (ga) biopsy needle. Overall, lung parenchyma was successfully harvested in 55.9% of experimental animals and in 55.0% of lung biopsy trials. Compared with postmortem diagnosis, the biopsy resulted in the same pathologic diagnosis for 75% of biopsy samples when evaluated using standardized criteria by the same veterinary pathologist. The success rate was 61.5% and 42.9% in a hospital or field setting, respectively. With an automatic instrument, lung was recovered from 57.9% and 37.5% of samples obtained using a 12- or 14-ga biopsy needle, respectively. One experimental animal or 2.9% of the total had fatal complications from the procedure. In a commercial feedlot setting, the procedure took 20 min for each animal. Percutaneous lung biopsy of the right cranioventral lung lobe may be a viable technique when used on feedlot steers affected with chronic pneumonia. These findings suggest that using an automatic instrument with either a 14- or 12-ga biopsy needle may yield lung samples that are suitable for histopathological evaluation. However, this technique needs to be further evaluated in a field setting.

The interaction of Bordetella bronchiseptica, toxigenic Pasteurella multocida serotype D, and the mycotoxin fumonisin B1 (FB1) was studied. On day 0 of the experiment, 28 artificially reared 3-day-old piglets were divided into 4 groups (n = 7 each): a control group (A), a group fed FB1 toxin (B), a group infected with the 2 pathogens (C), and a group infected with the 2 pathogens and fed FB1 toxin (D). The B. bronchiseptica infection [with 106 colony-forming units (CFU)/mL] was performed on day 4 and the P. multocida infection (with 108 CFU/mL) on day 16. From day 16 a Fusarium verticillioides fungal culture (dietary FB1 toxin content 10 mg/kg) was mixed into the feed of groups B and D. In groups C and D, clinical signs including mild serous nasal discharge, sneezing, panting, and hoarseness appeared from day 4, and then from day 16 some piglets had coughing and dyspnea as well. Computed tomography (CT) performed on day 16 demonstrated lung lesions attributable to colonization by B. bronchiseptica in the infected groups. By day 25 the number of piglets exhibiting lesions had increased, and the lesions appeared as well-circumscribed, focal changes characterized by a strong density increase in the affected areas of the lungs. The gross pathological findings confirmed the results obtained by CT. These results indicate that, when combined with dual infection by B. bronchiseptica and P. multocida, dietary exposure of pigs to FB1 toxin raises the risk of pneumonia and increases the extent and severity of the pathological changes.

Objective-To develop polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis for molecular typing of strains of Streptococcus zooepidemicus and to use the new typing method to analyze a collection of isolates from the respiratory tract of Thoroughbreds. Sample Population-10 strains of S zooepidemicus, 65 isolates from the respiratory tract of 9 yearlings following long distance transportation, and 89 isolates from tracheal aspirates of 20 foals with pneumonia. Procedure-Phenotypic variations in the SzP protein were detected by western immunoblot analysis. Using PCR-RFLP analysis, genotypes were obtained with primer sets from the SzP gene, followed by restriction endonuclease digestion of the amplicons. Results-Unique genotypic patterns were obtained with a primer set designed from both ends of the structural gene and the restriction endonuclease Dde I. Forty-five isolates from the lymphoid tissue within the pharyngeal recess (ie, pharyngeal tonsil) of yearlings included 10 SzP genotypes and SzP phenotypes. Isolates from the trachea of each yearling were of a single genotype that was also present among isolates from the pharyngeal tonsil of the same horses. Isolates from tracheal aspirates of foals belonged to 14 genotypes. Conclusion and Clinical Relevance-Analysis of the SzP gene by use of PCR-RFLP was effective for molecular typing of strains of S zooepidemicus in the study of respiratory tract disease in horses. Results of PCR-RFLP analysis indicate that a single strain of S zooepidemicus can migrate from the pharyngeal tonsil to the trachea at a high rate in horses undergoing long distance transportation.

Plasma and lung tissue pharmacokinetics of danofloxacin calves with naturally induced acute pneumonia were determined in 2 separate studies. A maximal pneumonic tissue concentration of 1.17 microgram/g was achieved 1.8 hours after IM injection of 1.25 mg of danofloxacin/kg of body weight. Pneumonic tissue danofloxacin concentrations were 5.5 times greater than those in plasma at 1 and 2 hours after injection. Cranioventral pneumonic tissue had significantly decreased danofloxacin concentration, compared with that of grossly normal tissue from the caudodorsal part of the lungs at 2 of 6 sample times. After IV injection, the apparent steady-state volume of distribution was 3.44 +/- 1.13 L/kg, and the elimination half-life was 6.26 2.27 hours. Maximal plasma danofloxacin concentration of 0.25 microgram/ml was detected 0.80 hour after IM injection. Bioavailability was 91%. Our findings indicated that a large percentage of danofloxacin is rapidly absorbed after IM administration to calves with acute pneumonia. Extensive tissue penetration was suggested by a high steady-state volume of distribution and was indicated by high concentrations in pneumonic tissue.

Aerosol vaccination is used effectively to immunize poultry against Newcastle disease, but to the authors' knowledge, this vaccination procedure is not well studied in other species. The efficacy of IM and aerosol vaccination of pigs against Mycoplasma hyopneumoniae infection was evaluated. Twenty-one pigs from a Mycoplasma-free herd were randomly allotted by litter and body weight into 3 groups. One group was given aerosolized phosphate-buffered saline solution (PBSS) by inhalation. The second group (AERO) was given aerosolized M hyopneumoniae vaccine by inhalation. The third group (IM) was given the same vaccine by IM injection. Vaccination by IM administration was repeated once, and aerosol vaccination was repeated twice at 2-week intervals. Two weeks after the last vaccination, all pigs were intratracheally challenge-exposed with 3 ml of broth culture containing 10(7) color-changing units (CCU) of a low-passage strain of virulent M hyopneumoniae. Pigs were observed daily for coughing. Four weeks after challenge exposure, all pigs were necropsied. Percentage of lung affected by gross pneumonia was measured, bronchioalveolar lavage fluid (BALF) cells were counted, and quantitative culture for mycoplasmas was performed on lung sections. Additionally, M hyopneumoniae-specific antibodies were measured in prevaccination, postvaccination, and postchallenge-exposure serum and BALF by use of indirect ELISA. Mean prevalence of persistent coughing in pigs of the AERO group (4.6 d/pig) was not different from that in pigs of the PBSS group (3.7 d/pig). Prevalence of coughing in IM vaccinated pigs (1.0 d/ pig) was lower (P < 0.05) than that in pigs of the PBSS group. Mean gross lung lesion scores and BALF cell counts were not different between the AERO (15% pneumonia, 5,233 cells/microliter) and PBSS (11% pneumonia, 3,022 cells/microliter) groups, but were lower (P < 0.05) in the IM group (1.5% pneumonia, 400 cells/microliter) than in the PBSS group. Mean lung mycoplasmal counts were not significantly (P < 0.05) different among the PBSS (10(5.6) CCU/g), AERO (10(5.3) CCU/g), and IM (10(3.3) CCU/g) groups. Postvaccination M hyopneumoniae-specific IgG or IgA was not detectable in BALF after either vaccination procedure. Postvaccination M hyopneumoniae-specific serum IgG concentration was not different among the 3 groups. Postchallenge exposure M hyopneumoniae-specific IgG and IgA were detectable in BALF of all pigs, but were not different among the 3 treatment groups. Postchallenge exposure-specific serum IgG concentration was not different between the PBSS (mean OD, 0.739) and AERO (mean OD, 0.672) groups, but was higher (P < 0.05) in the IM group (mean OD, 1.185) than in the PBSS group. Aerosol vaccination failed to induce local and systemic antibody responses detectable by ELISA, and failed to protect pigs against mycoplasmal pneumonia. Intramuscular vaccination failed to induce local and systemic antibody responses detectable by ELISA, but substantially reduced the clinical signs and lesions caused by challenge exposure to virulent M hyopneumoniae.