Further occurrence of extended-spectrum β-lactamase-producing Salmonella enteritidis

We describe the further occurrence of Salmonella enteritidis producing an extended spectrum beta-lactamase (ESBL) and transferring cefotaxime, ceftazidime and aztreonam resistance. In a previous communication we describe the isolation of a strain of S. enteritidis (No. 35) from a septic neonate with high-level resistance to cefuroxime, cefotaxime, ceftazidime and aztreonam. Six weeks later, a second neonate was found, in the same Pediatric University Hospital, to be infected with apparently the same strain of S. enteritidis (No. 100) which was isolated from blood with similar properties as the strain No. 35. In this strain we were able to study, in more detail, the transferability of its resistance to 3rd generation cephalosporins and its ESBL production. In this report we describe results of transfer experiments, relative rates of hydrolysis (Vmax) and ESBL tests which indicate that the capacity to produce ESBL was transferred from the multiply-resistant strain of S. enteritidis No. 100 to S. typhimurium LT-2 rif+str+.