Multidrug-resistant human and animal Salmonella typhimurium isolates in France belong predominantly to a DT104 clone with the chromosome- and integron-encoded beta-lactamase PSE-1

Epidemiologic relationships were investigated in 187 ampicillin-resistant S almonella typhimurium strains (86 human, 101 animal) from >2000 strains iso lated in 1994, Of 23 resistance patterns, the most frequent (ampicillin [Am ], chloramphenicol [Cm], tetracycline [Tc], streptomycin and spectinomycin [Sm], and sulfonamides [Su]) was found in 69.5% of human and 64.8% of anima l isolates. Four beta-lactamase genes were identified, bla(TEM) (24%), bla( PSE-1) (78%), and bla(SHV) and oxa-2 (each <3%). bla(PSE-1) and the integra se gene, intI1, but not bla(TEM),bla(SHV) or era-a, were chromosomeborne an d found almost exclusively in the AmCmTcSmSu strains. In these, polymerase chain reaction mapping revealed two distinct integrons carrying bla(PSE-1) or aadA2. Lysotypes, plasmid profiles, and restriction fragment length poly morphisms (IS200) were determined for 50 representative isolates and for 3 DT104 strains from the United Kingdom (UK), The phage type of the PSE-l-pro ducing AmCmTcSmSu strains was 12 atypic, indistinguishable from that of the DT104 strains, The combined data indicate that the same multiresistant clo ne has spread through human and animal ecosystems in the UK and France.