Salmonella typhi strain with transmissible multiple resistance.

A case of typhoid fever caused by multiple drug resistant S typhi by R factor was clinically and bacteriologically studied. The clinical course was weakly influenced by successive chloramphenicol (21 days) and ampicillin (7 days) therapy; recovery occured after 62 days of disease including 2 relapses) as a result of the combined effect of immunization by disease and septrin administration (9 days). Two strains of S. typhi were isolated, one of them from blood culture before treatment, being Vi A degraded, sensitive to antibiotics A, C, T (strain 221) and the other from stool culture, after 4 days chloramphenicol treatment, being untypable with adapted Vi II phages, resistant to A, S, C, T (strain 552). Resistance markers were transferred within 4 conjugation systems, from strain 552 - as donor - to E. coli K12, to S. typhi A and to S. typhi 221 - as recipient-, the resistance level found was equal to that of the donor for all the determinants. The fi- character of the resistance factor was established and its possible restrictive effect in explaining the presence of two lytic patterns was discussed. The importance of the occurence of multiple drug-resistant S. typhi in certain areas, as well as chemical and epidemiological consequences, is emphasized.