[Clarification of a Salmonella typhimurium epidemic in north-eastern Switzerland by means of bacteriological and serological methods].

An outbreak of Salmonella typhi murium caused by person-to-person contacts was observed in Kurhaus (NE Switzerland) in late 1973. In all, 18 patients with clinical symptoms and 8 asymptomatic carriers were registered. However, 1 1/2 months elapsed before the etiologic diagnosis could be established. The infection was then transmitted, probably by a visiting nurse, to the personnel of a neighbouring school. An outbreak followed thereafter including 31 clinically manifest patients and 10 asymptomatic carriers. Infected food was most probably responsible for the dissemination of the disease, since two asymptomatic carriers were detected among persons engaged in the preparation of food. The close correlation between the two epidemics was confirmed by phague typing of isolated Salmonella strains according to the method of GUINEE. A common Biotype I, Lysotype 650, was identified in all cases. Clinical findings revealed diarrhea in 77,6%, fever in 59,2% and vomiting in 18.4% of cases. Only two patients who were admitted to the hospital, were given chemotherapy. The excretion of Salmonellae in the stools was observed on average for about one month in clinical cases and for 12 days in asymptomatic carriers. All the strains, with one exception, were in vitro sensitive against tetracycline, Chloramphenicol and trimethoprim-sulfamethoxazole. In one case the tetracycline treatment resulted in homologous resistance. In this case the carrier state had been observed for 111 days. Serologic tests were made one month after the outbreak was detected using Widal reactions with antigens of homologous strain. In most patients with clinical symptoms antibody titers were at serum dilutions of more than 1:80, whereas only 4 of the 9 asymptomatic carriers investigated presented with titers in this range. Patients who were not excreting Salmonellae had uniform antibody titers of less than 1:80.