Three hundred and twenty strains of Vibrio parahaemolyticus isolated from clinical and food materials in this prefecture from 1963 to 1964, were examined their in vitro sensitivity to 11 antibiotics and 3 antibacterial compounds by the agar plate dilution method. On the other hand, that of 72 strains of Vibrio alginolyticus, , 37 strains of Vibrio comma (cholera vibrio, 13 and El Tor vibrio, 24) and 9 strains of Aeromonas hydrophila was tested and the difference in those was investigated.
Vibrio parahaemolyticus was sensitive to mitomycin C, panfuran S, chloramphenicol and tetracycline, moderately sensitive to erythromycin, novobiocin, nalidixic acid and nitrofurantoin, and much resistent to penicillin G, streptomycin, kanamycin, oleandomycin, colistin and polymyxin B. There was no difference in the sensitivity to all drugs tested between Vibrio parahaemolyticus and Vibrio alginolyticus, but Vibrio comma and Aeromonas hydrophila were distinguished from Vibrio parahaemolyticus in the sensitivity to some drugs.