Salmonella typhi in vivo acquires resistance to both chloramphenicol and co-trimoxazole.

@article{Datta1981SalmonellaTI,
  title={Salmonella typhi in vivo acquires resistance to both chloramphenicol and co-trimoxazole.},
  author={Naomi Datta and Hilary Richards and C Datta},
  journal={Lancet},
  year={1981},
  volume={1 8231},
  pages={1181-3}
}
Salmonella typhi in the bowel of a patient with enteric fever treated with chloramphenicol and later co-trimoxazole acquired resistance to these drugs. Chloramphenicol and sulphonamide resistances were determined by one plasmid, of IncH, whose carriage also changed the Vi phage type. Trimethoprim resistance was determined by a transposon, Tn7, carried in another plasmid, of IncI. The same resistance genes were identified in a strain of klebsiella isolated from the patient.