Properties of Bordetella pertussis Recently Isolated from Infants

The properties of Bordetella pertussis strains recently isolated from infants in Niigata Prefecture were studied. The K antigen type of these strains was identified as 1, 3, (6). All the strains tested showed characteristics in cultural properties and biological activities similar to those of phase I, such as heat-labile toxin, mouse body weight-decreasing toxicity, leucocytosispromoting factor, and histamine-sensitizing factor. In the mouse protection test against strain 18-323, the potency of vaccines prepared from the isolated strains was equivalent to that of Tohama phase I vaccine. The sensitivity of the isolated strains to different antibiotics, as determined by the minimum inhibitory concentration in the serial dilution method, was as follows: penicillin G, 1U/ml; aminobenzyl penicillin, 1.25μg/ml; cephaloridine, 12.5μg/ml; cephazolin, 12.5μg/ml; polymyxin B, 2U/ml; colistin, 2U/ml; streptomycin, 10μg/ml; kanamycin, 12.5μg/ml; tetracycline, 0.25μg/ml; chloramphenicol, 0.5μg/ml; and erythromycin, 0.05μg/ml.