A mass incidence of mixed infection, paratyphus A (P.A.) and bacillary dysentery (D) was experienced in summer, 1956 in Yokohama city. According to the sanitary bureau, the dysentery infection from contaminated well water broke out explosively during the course of paratyphus A incidence. Ninety patients treated in this hospital consisted of 37 P. A., 8 carriers of P. A., 10 mixed infected, 20 D., and 15 carriers of D. Seventy-eight point eight percent of them were over 51 years of age.
Clinical symptoms of P.A. were relatively slight for the aged persons except for only one case with intestinal bleeding. Febrile period averaged 20.9 days with 38-39°C fever. Relapses were recorded in 21.7%. The lapse of time till relapse was on an average 20.9 days, the early being on the 6th day after the complete subsiding of fever, the latest on the 43rd day. P. A. bacilli were isolated in 61.8%. The Widal reaction reached the peak in a half of the patients in the 1st-2rd week. The chiefly used antibiotic, CM was administered in the dosis of 2.0gm a day till 3 or 4 days after the removal of fever. The fever subsided on an average in 3.6 days, so that the antibiotics were used only in 8 cases for more than 5 days. The manner of CM administration had nothing to do with the relapse. The combined nse of PVL with CM at the beginning of the disease, however, seemed to prevent the relapse and to shorten the duration of bacillary discharge with 3 exceptional cases in which the bacilli appear in the stool from time to time even now, one year after the infection.
Most of the dysentery patients likewise showed slight clinical symptoms. The bacilli were isolated in 65.7% and identified as Sh. dysenteriae II. None of 10 patients showed any aggravation as the result of mixed infection.
Isolated bacilli were confirmed as lysogenic and the lysogenicity is in a stable way transmitted to the subcolonies. The average amount of phage showed ca 240 in 35 minutes of incubation. It was completely inactivated by heating at 90°C for 10 minutes. This temperate phage demonstrated bacteriolytic specifity against 4 species of salmonella.
