[Isolation, selection and characteristics of Pasteurella multocida].

Bacteriophages of 2 and AV signature were isolated from lysogenic P. multocida strains. spontaneous mutation of bacteriophage 32 of various indicator Pasteurella strains led to the isolation of 6 new bacteriophages with signature of the indicator strain 10, 55, 168, 895, 994. Bacteriophages 3,4, and 115 served to isolate bacteriophages with signature 3/10, 4/10, and 115/10 of a phage-resistant 3/10 strain. Phages TH and VL were selected from AV phage, and phage 1 was selected from phage 10. A total of 14 new P. multocida bacteriophages were obtained in all, which were reproduced on one and the same indicator strain No 10. The newly isolated phages 1, 2, 10, 895, 3/10, 4/10, 115/10, AY, VL, and TH were neutralized by antisera 2, 10, 4/10, AY, and TH in 99 to 100 per cent, and belong to a common serologic group (IVth group). Bacteriophages 55, 168, 994, and 995 were not neutralized by these sera. By the effect of chemicals and sodium citrate the AY and VL phages were found to be stable to inactivation, while tetracycline inactivated 50 per cent of them. Bacteriophages 10, and 3/10 survived at pH 9 and 11. By these indices the mentioned 10 bacteriophages were referred to the new P. multocida IVth group phages. Spontaneous mutations in the P. multocida phage populations are likely to occur. Such mutations could belong to various phage types. The genetic changes in the phage populations appear as a base in the production of P. multocida bacteriophages of various types which could be used in the phage typing of the P. multocida species.