Time trends in odds ratios of antimicrobial susceptibility in nosocomial and non-nosocomial Gram-negative infections in Israel

Abstract number: 1733_1151

Zalounina A., Paul M., Andreassen S., Leibovici L.

Objectives: To study the changes in difference between antimicrobial susceptibilities in hospital environment and community over time.

Methods: Clinically significant, patient and episode unique, bloodstream isolates (n = 5,790) were collected prospectively from adults between 1988–2004 at Rabin Medical Center, Israel. Bacteraemia was defined as nosocomial if it occurred 48 h or more following hospital admission. We analysed in-vitro susceptibilities of Escherichia coli, Klebsiella spp., Pseudomonas spp. and Acinetobacter spp. For each pathogen and antibiotic we calculated the Odds Ratios (OR) with 95% confidence intervals (CI) for susceptibility comparing non-nosocomial vs. nosocomial isolates. ORs were plotted in blocks of 3 years. Heterogeneity of the ORs across time was assessed by the Breslow-Day test.

Results: Nosocomial infections comprised 47% of all cases. The results for the most prevalent pathogen E. coli (44%) and 5 antibiotics are shown in the chart below. The highest OR for non-nosocomial E. coli being more susceptible than nosocomial was obtained for ceftazidime during 1997–1999 (9.9, CI: 3.4–29.0). We observed 2 main patterns of ORs changes over time. In the first, ORs increased over time followed by a decrease (observed for E. coli and all antibiotics except quinolones; Acinetobacter and amikacin; Klebsiella spp. and ceftriaxone or aminoglycosides). In the second pattern, ORs decreased with time (observed for Pseudomonas and piperacillin; Acinetobacter and imipenem). ORs for quinolones fluctuated over time. The test on heterogeneity disclosed significant changes in ORs over time for E. coli with ceftazidime and ceftriaxone, Pseudomonas spp. and ciprofloxacin (p < 0.05).

Conclusion: For the majority of the pathogen/antibiotic combinations the OR starts relatively low, indicating low resistance both in community and in the hospital, then rises due to the appearance of resistance in the hospital and finally descends again, indicating diffusion of resistance from the hospital to the community.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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