Comparative analysis of the outer membrane protein profiles of isolates of the Pasteurella multocida (B:2) associated with haemorrhagic septicaemia.

Outer membrane proteins (OMP) of P. multocida (serotype B:2) field isolates (n = 6) and a vaccine strain (P-52) were extracted by a sarkosyl method and characterized using SDS-PAGE and immunoblotting. About 20 polypeptide bands were observed in the profile of the vaccine strain with MW ranging from 16 to 90 kDa and, based on band thickness and intensity of staining, three polypeptides of MW 31, 33 and 37 kDa were considered to be the major OMPs. The profiles of the field isolates showed minor differences when compared with that of the vaccine strain. The OMP of 33 kDa was only expressed by the vaccine strain. Four field isolates expressed an OMP of 39 kDa, which did not appear in the profiles of the remaining two field isolates and the P-52 strain. Similarly, an OMP of 25 kDa was exclusively seen in the profile of a single isolate. By immunoblotting studies, using anti-P. multocida (P-52) whole-cell hyperimmune serum raised in rabbits as well as buffalo immune sera, it became evident that the polypeptide of 37 kDa was the most antigenic OMP in the profiles of all the isolates, including the P-52 strain. Other polypeptides were either weakly antigenic or visible in the profile of only a few of the isolates. The study thus identified the major OMP of P. multocida (B:2) and suggested that this highly antigenic 37 kDa OMP has potential for further protective and immunodiagnostic studies.

Experimental salmonellosis in guinea-pigs: haematological and biochemical studies.

Some haematological and biochemical parameters were studied in guinea-pigs infected intraperitoneally with Salmonella dublin 493 at 1 x 10(6) viable cells per animal. The infected animals showed a rise in temperature within 24 h, followed by depression and loss of body weight. On the 15th day post infection, haematological studies revealed a significant increase in the total leukocyte count due to both lymphocytosis and neutrophilia, and a decrease in the total erythrocyte count and haemoglobin concentration. There was also a significantly higher mean corpuscular volume and lower mean corpuscular haemoglobin concentration, indicating a macrocytic hypochromic anaemia. The infection caused a significant increase in alanine aminotransferase activity and creatinine, blood urea nitrogen and globulin concentrations, and a decrease in albumin and triiodothyronine. There was no significant effect on serum total protein or on thyroxine, or in the activity of aspartate aminotransferase in the serum.

Cellular and humoral immune responses in calves experimentally infected with Salmonella dublin.

Both humoral and cellular immune responses have been found to be operative in calves surviving smooth Salmonella dublin infection. Such calves showed rises in agglutinin titre and serum immunoglobulin as compared to uninfected controls. These calves at 3 weeks post infection showed a 3-4 fold increase of initial skin thickness at 5 h post antigen inoculation - an indication of immediate type of skin hypersensitivity reaction. The maximum increase in skin thickness of 2-3 fold was observed at 48 h post antigen inoculation - a criterion of delayed type of hypersensitivity reaction. There was a moderate increase, 28.1 per cent in the migration inhibition of peripheral leucocytes during the first week and a sharp increase, 45.7 and 66.6 per cent during the second and third week post infection, respectively. Passively immunized calves on challenge exhibited delayed clinical symptoms and mortality as compared to control animals, though the calves could not be protected against challenge. The serum immunoglobulin levels in passively immunized calves decreased moderately during the first week and markedly during the second week post challenge while in the control calves the levels dropped abruptly in the first week followed by death in both groups.