A florfenicol resistance gene almost identical to floR of Salmonella enterica serovar Typhimurium DT104 was detected on 110-to 125-kb plasmids in Escherichia coli isolates of animal origin. Analysis of the floR gene flanking regions of one of the plasmids showed that they were different from those encountered in S. enterica serovar Typhimurium DT104.

Recently a chromosomal locus possibly specific for Salmonella enterica serovar Typhimurium DT104 has been reported that contains a multiple antibiotic resistance gene cluster. Evidence is provided that Salmonella enterica serovar Agona strains isolated from poultry harbor a similar gene cluster including the newly described floR gene, conferring cross-resistance to chloramphenicol and florfenicol.

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