Kim A. Brogden

Response of the ruminant respiratory tract to Mannheimia (Pasteurella) haemolytica

Pneumonia is a leading cause of loss to the sheep and cattle industry throughout the world. Mannheimia (Pasteurella) haemolytica is one of the most important respiratory pathogens of domestic ruminants and causes serious outbreaks of acute pneumonia in neonatal, weaned and growing lambs, calves, and goats. M. haemolytica is also an important cause of pneumonia in adult animals. Transportation, viral infections with agents such as infectious bovine rhinotracheitis virus, parainfluenza-3 virus or bovine respiratory syncytial virus, overcrowding, housing of neonates and weaned animals together and other stressful conditions predispose animals to M. haemolytica infection [1, 2]. This review assimilates some of the findings key to cellular and molecular responses of the lung from a pathologists perspective. It includes some of what is known and underscores areas that are not fully understood.

Binding between lipopolysaccharide and cecropin A

Cecropin A (CA), a bioactive peptide, produced significant lethality toPantoea agglomerans (PA) at low concentrations. Significant mortality occurred immediately after addition of CA. Separate preincubations of lipopolysaccharides (LPS) from the following bacteria: PA,Serratia marcescens, Escherichia coli (EC), andSalmonella typhimurium with CA were performed prior to the bioassay. CA was also preincubated with diphosphoryl lipid A (DPL-A) from EC andS. minnesota (SM), trilinolein, palmitic, lauric and myristic acids (fatty acids contained in the lipid A of PA-LPS) and bovine brain gangliosides. Spectral analyses to determine the interaction between glycosphingolipids (sphingomyelin, bovine brain gangliosides, and galactocerebrosides) and CA were performed. Results showed that all types of LPS and DPL-A as well as the gangliosides studied blocked CA lethality to PA. The level of inhibition of CA antibacterial properties was dependent on LPS and DPL-A concentration. The individual fatty acids and trilinolein did not affect CA lethality to PA. Spectral studies showed complexation between CA and PA-LPS, both types of DPL-A, and the glycosphingolipids. Biological and chemical analyses confirm that CA binds to the diphosphoryl lipid A moiety of LPS.