Use of amoxicillin-clavulanate and resistance in Escherichia coli over a 4-year period.

OBJECTIVE: To reduce the use of amoxicillin-clavulanate after high-resistance rates in Escherichia coli were detected.

DESIGN: Intervention study; the interventions were introduced successively over a 4-year period while closely monitoring the resistance patterns.

SETTING: A 260-bed acute-care hospital in Switzerland.

INTERVENTIONS: Introduction of therapeutic guidelines for specific departments or indications, which proposed alternative antibiotics to amoxicillin-clavulanate. The perioperative prophylactic use of amoxicillin-clavulanate was eliminated completely.

RESULTS: The absolute amount of amoxicillin-clavulanate consumed decreased by 23%, from 24.8 g per 100 patient days in 1992 to 18.5 g per 100 patient days in 1995. The number of courses, a parameter that takes the prophylactic use into account, decreased by 62% from 2.3 per 100 patient days in 1992 to 0.9 per 100 patient days in 1995. The percentage of sensitive strains increased from 54.9% (n=512) in 1992 and 54.0% (n=506) in 1993 to 72.1% (n=546) in 1994 and 83.1% (n=668) in 1995. No major changes were detected for other antimicrobials, such as cotrimoxazole, tetracycline, or cefuroxime, used in this 4-year period.

CONCLUSIONS: A decrease in the use of amoxicillin-clavulanate was followed by an increase in susceptibility of E coli to it. It was not possible to prove a causative relationship. Only a temporal association was discovered. The reduction of the use of amoxicillin-clavulanate was achieved through the implementation of treatment guidelines, facilitated through a close collaboration among the clinical pharmacists, the infection control practitioner, the microbiology laboratory, and the physicians in charge of the respective departments.