The aim of this study was to determine the effect of infection with hog cholera virus on the bactericidal action of swine serum against strains of E. coli. This study also was intended to broaden the present conceptions of the mechanism of bacterial complications in the course of a virus infection (6), which is in turn connected with the problem of a quantitative evaluation of the level of natural resistance by means of the bactericidal reaction.
Biochemical properties, serotype classification and drug resistance were evaluated in 41 Pasteurella multocida strains isolated from cattle suffering from haemorrhagic septicaemia (HS). The API 20E test and standard methods were used to examine selected biochemical features of the strains. The results permitted classifying the isolates as P. multocida subspecies multocida strains. All the isolates revealed both capsular antigen B (by Carter) and the somatic antigen specific to the serotype 2 (by Heddleston). A weak positive reaction with the specific serum to serotype 5 was noticed. Haemorrhagic septicaemia was serologically confirmed for the first time in Poland. The isolates examined were highly sensitive to antibiotics and chemiotherapeutics. A distinct resistance was found in the case of streptomycin; several strains were also resistant to neomycin, gentamycin, erythromycin or sulphonamides.