MICE VIRULENCE ASSAY OF Pasteurella muttocida STRAINS ISOLATED FROM PIGS
Abstract
Virulence of 24 strains of Pasteurella multocida, 13 isolated from pleuritic and pneumonic pig lungs, and 11 from pig lungs obtained from abattoirs was studied. P multocida was cultured in BHI medium incubated at 37° C for 18 h and the number of colony forming units (C FU/ml) determined by inoculation of decimal dilutions on blood agar plates. Dilutions from 10 4 to 10.13 (8,3 x 10 15 to 1 CFU) were inoculated intraperitoneally in mice and the number of deaths for each dilution determined over a 7-day period. Each inoculated strain was recovered from at least two mice. LD50 were determined by the Spearman- Kãrber method. It was observed a wide variation in LD50, ranging from <1 to 10 10.2 CFU. There was no difference in virulence among strains from clinical cases or from abattoir lungs.
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