Spread of Enterobacteriaceae producing broad-spectrum beta-lactamase and the development of their incidence over a 16-month period in a university hospital center

Enterobacteriaceae producing extended-spectrum beta-lactamases (ESBLE) constitute with methicillin-resistant Staphylococcus aureus the main multiresistant bacteria recovered in French hospitals. Our objectives were to evaluate these ESBLE diffusion in our teaching hospital and to follow their incidence during a 16-month period, whereas a control programme (barrier precautions) had been implemented in the beginning of 1999. This study was conducted in a teaching hospital containing 1800 beds, from February 1999 to May 2000. All ESBLE isolated in clinical or screening samples were included. Duplicates (same bacteria in the same patient) were excluded. The detection of the ESBL was performed with the double-disk diffusion test. Incidence densities were determined with their 95% confidence interval (CI95%). Their evolution by four-month period was evaluated with the chi-square test for trend. During the 16-month period, 229 ESBLE were isolated. The incidence was 0.35 per 1000 patient-days (PD) (CI95% = [0.30-0.40]) for the whole hospital. It was 0.47/1000 PD (CI95% = [0.38-0.56]) in medical wards, 0.29/1000 PD (CI95% = [0.20-0.38]) in surgical wards and 1.32/1000 PD (CI95% = [0.90-1.74]) in intensive care units. Enterobacter aerogenes strains represented more than 75% of all ESBLE, whereas Klebsiella pneumoniae stains represented only 8.6%. During the study, the incidence of ESBLE and the proportion of strains acquired in our hospital decreased significantly (p < 0.0001 and p < 0.001 respectively). Indeed, between the first eight-month period and the last one, the incidence of ESBLE acquired in our hospital decreased by 55%, whereas the incidence of imported strains increased slightly. This study shows that the diffusion of ESBLE concerns the entire hospital. The implementation of a control programme of the spread of multiresistant bacteria allowed us to reduce significantly the incidence of ESBLE. This incidence seemed to be stable for several months. The implementation of a policy which restricts antimicrobial use would allow us to complete the the efficacy of barrier precautions.