Salmonella typhi resistant to chloramphenicol, streptomycin sulfate, tetracycline, and sulfonamides were isolated from blood and fecal specimens of a patient who had recently travelled to Mexico. Such multiple drug resistances are characteristic of S typhi epidemic in Mexico and are identical with patterns in strains of Shigella species also prevalent in Latin America; episomal transfer of resistance has been postulated.
By incubation of mixed cultures, multiple drug resistance was transferred from our patient's S typhi culture to a susceptible strain of Escherichia coli, and then to another susceptible strain of S typhi, and to S typhimurium. Awareness of the occurrence of such resistant strains of S typhi is important because chloramphenicol, the usual drug of choice, will be ineffective. Moreover, the case of transfer of resistance among typhoidal, other salmonellal and coliform bacilli in vitro should alert physicians to the possibility of spread of such resistance.
Lawrence RM, Goldstein E, Hoeprich PD. Typhoid Fever Caused by Chloramphenicol-Resistant Organisms. JAMA. 1973;224(6):861–863. doi:10.1001/jama.1973.03220200029008