leukotoxin and Respiratory-Tract-Infections

To determine the effect of intranasal exposure to live leukotoxin (LktA)-deficient Mannheimia haemolytica (MH) at the time of feedyard arrival on nasopharyngeal colonization by wild-type MH in calves.. 200 calves.. Calves from Arkansas (AR calves; n = 100; mean body weight, 205 kg) were purchased from an order buyer barn. Calves from New Mexico (NM calves; n = 100; mean body weight, 188 kg) were obtained from a single ranch. Calves were transported to a feedyard, where half of each group was exposed intranasally with LktA-deficient MH at the time of arrival. Calves were observed daily for respiratory tract disease (RTD), and nasal swab specimens were collected periodically to determine nasopharyngeal colonization status with MH. Serum samples were assayed for antibodies to MH.. 15 AR calves had nasopharyngeal colonization by wild-type MH at the order buyer barn, whereas none of the NM calves had nasopharyngeal colonization. Intranasal exposure to LktA-deficient MH elicited an increase in serum antibody titers against MH in NM calves, but titers were less in NM calves treated for RTD. Exposure of NM calves to LktA-deficient MH offered protection from nasopharyngeal colonization by wild-type MH.. Exposure of calves to LktA-deficient MH elicited an increase in serum antibody titers against MH and decreased colonization of the nasopharynx by wild-type MH. Earlier exposure would likely allow an immune response to develop before transportation and offer protection from nasopharyngeal colonization and pneumonia caused by wild-type MH.

Topics: Animals; Antibodies, Bacterial; Arkansas; Bacterial Vaccines; Cattle; Cattle Diseases; Exotoxins; Mannheimia haemolytica; Nasal Mucosa; Nasopharynx; New Mexico; Pasteurellaceae Infections; Respiratory Tract Infections; Time Factors; Vaccination

A real-time PCR assay for the leukotoxin gene of Bibersteinia trehalosi was developed and validated to better identify this pathogen, which is a cause of respiratory disease in bighorn sheep. The specificity of the PCR primers was evaluated with DNA from 59 known isolates of the Pasteurellaceae family. For validation, 162 field samples were compared using both the new assay and an indirect method using 2 sets of published protocols. The real-time PCR assay was found to be specific for the leukotoxin gene of B. trehalosi and provides a rapid and direct approach for detecting leukotoxin-producing forms of this organism from samples containing mixed species of leukotoxin-positive Pasteurellaceae.

Topics: Animals; Bacterial Infections; Exotoxins; Gammaproteobacteria; Real-Time Polymerase Chain Reaction; Respiratory Tract Infections; Sheep, Bighorn

To assess the serologic response of calves to inactivated and modified-live (ML) Mannheimia haemolytica (MH) preparations given alone and concurrently with combination viral vaccines containing ML bovine herpesvirus type 1 (BHV-1).. 642 calves seronegative for BHV-1.. In experiment 1, 192 calves received 1 of 3 MH preparations alone or concurrently received 1 of 3 MH preparations and 1 of 4 combination viral vaccines. In experiment 2, 450 calves received 1 of 4 MH preparations alone or concurrently received 1 of 4 MH preparations and 1 of 5 combination viral vaccines. Pretreatment and posttreatment blood samples were processed to obtain serum, which was analyzed to detect concentrations of antibodies against MH leukotoxin and BHV-1.. In experiment 1, antibody titers against MH leukotoxin in calves receiving MH and ML virus vaccine appeared decreased, albeit nonsignificantly, compared with titers for calves receiving MH preparations alone. In experiment 2, all groups (except for 1) concurrently receiving an MH preparation and viral vaccine had a significant decrease in antibodies against MH leukotoxin. In both experiments, there was a significant decrease in the number of calves responding to MH leukotoxin when ML viral vaccine was coadministered.. Coadministration of ML BHV-1 and MH preparations interfered with the serologic response to MH leukotoxin in calves seronegative for BHV-1. Serologic response to MH leukotoxin may be substantially improved in seronegative calves when MH vaccination is delayed until after calves have received a dose of ML BHV-1 vaccine.

Topics: Age Factors; Animals; Antibodies, Bacterial; Antibodies, Viral; Bacterial Toxins; Bacterial Vaccines; Cattle; Cattle Diseases; Exotoxins; Female; Herpesvirus 1, Bovine; Immunization; Male; Mannheimia haemolytica; Random Allocation; Respiratory Tract Infections; Vaccines, Combined; Vaccines, Inactivated; Viral Vaccines

To evaluate the role of leukotoxin (LKT) of Mannheimia haemolytica and lipopolysaccharide (LPS) of E. coli 055:B5 in pathogenesis of bovine respiratory disease (BRD) we investigated their in vitro effects on cultured bovine neutrophils. Functional parameters of neutrophils including degranulation, generation of superoxide, and nitric oxide were distorted in response to both toxins. The most essential reaction of neutrophils was found in respect to release of elastase after addition of LKT as well as LPS at concentration of 300 microg/ml. Moreover, we observed an increased release of myeloperoxidase (MPO) and alkaline phosphatase (ALK-P) from polymorphonuclear cells (PMN) after addition of LKT and LPS. We also found enhanced superoxide generation by bovine neutrophils after exposure to different concentrations of LKT and LPS. In cultures of PMN treated with LKT, concentration of nitrite increased with growing concentrations of LKT. Lower values of nitrite were obtained in cultures exposed to LPS. Partial lysis of PMN, determined by LDH (lactate dehydrogenase) leakage, started at concentration of 300 microg/ml for both toxins, meanwhile LKT concentration above 300 microg/ml was lethal. Our study has revealed that neutrophils in response to both toxins exaggerate release of analysed substances, which participate in worsening the course of the disease and play a role in lung injury during BRD. Toxins introduced to the cultural medium stimulate release of studied constituents from neutrophils by combined activation and lysis of neutrophils.

Topics: Alkaline Phosphatase; Animals; Bacterial Toxins; Cattle; Cattle Diseases; Escherichia coli; Escherichia coli Infections; Exotoxins; Lipopolysaccharides; Mannheimia haemolytica; Neutrophils; Pasteurellosis, Pneumonic; Peroxidase; Respiratory Tract Infections