Typhoid fever imported from Mexico to Switzerland. Studies on R factor mediated chloramphenicol resistance.

A case of typhoid fever caused by Salmonella typhi occurred in Geneva. The patient was probably infected in Mexico City. The strain isolated from this patient corresponds with the description of the Mexican S. typhi strain, since it is a degraded Vi-strain resistant to chloramphenicol, streptomycin, sulphonamides and tetracyclines. It carried an fi(-) transferable R factor with a CSSuT resistance pattern. It can be accepted that this case forms part of the Mexican outbreak of chloramphenicol-resistant typhoid fever which has already been observed in visitors to Mexico from England and the United States.