In vivo acquisition of extended-spectrum beta-lactamase in Salmonella enteritidis during antimicrobial therapy.

The recovery of a Salmonella enteritidis strain that acquired resistance to beta-lactams (including cefotaxime), to aminoglycosides and to chloramphenicol subsequent to cefotaxime therapy is reported. This resistance pattern to beta-lactams was due to the presence of an extended-spectrum beta-lactamase. The isoelectric point of this extended-spectrum beta-lactamase was 6.3. The resistance genes were located on a transferable high-molecular-weight plasmid.