Clinical consequences of increased ciprofloxacin and gentamicin resistance in patients with Escherichia coli bacteraemia in the Netherlands

Background: Escherichia coli is a common cause of bacteraemia and is increasingly resistant to ciprofloxacin and gentamicin. The primary objective of this study was to investigate how often this leads to inadequate initial antimicrobial treatment. Secondary goals were to determine factors associated with inadequate empirical therapy and to assess its impact on mortality and length of stay. Methods: All patients with an E. coli bacteraemia hospitalized in 2008 were identified retrospectively. Initial antimicrobial therapy and clinical outcomes of all patients with an isolate resistant to gentamicin and/or ciprofloxacin (cases) were compared to those of a group of randomly selected patients in whom a gentamicin and ciprofloxacin susceptible E. coli was isolated (controls). Results: One hundred and thirty-six unique patients had E. coli bacteraemia. Of these, 34 patients were identified as cases and were compared to 34 controls. Among the cases, 97% of the E. coli was resistant to ciprofloxacin and 44% to gentamicin. Resistance to amoxicillin was high in both cases (94%) and controls (65%). In 41% of the cases initial antimicrobial therapy was inadequate, compared to only 3% in the controls. The majority of inadequately treated cases had a biliary focus (64%). Infections in cases were more often healthcare-associated than infections in controls (62% vs 26%). E. coli with the same resistance pattern had been isolated before in adequately treated cases more often than in inadequately treated cases. Mortality did not differ significantly between cases and controls. Conclusions: Neither ciprofloxacin nor amoxicillin should be used as empirical therapy in patients with a presumed E. coli bacteraemia.