Antimicrobial Stewardship in the Microbiology Laboratory: Impact of Selective Susceptibility Reporting on Ciprofloxacin Utilization and Susceptibility of Gram-Negative Isolates to Ciprofloxacin in a Hospital Setting

The objective of this study was to determine the impact of selective susceptibility reporting on ciprofloxacin utilization and Gram-negative susceptibility to ciprofloxacin in a hospital setting. Historically at our institution, the microbiology laboratory practice was to report ciprofloxacin susceptibility for all Enterobacteriaceae regardless of susceptibility to other agents. A selective reporting policy was implemented which involved the suppression of ciprofloxacin susceptibility to Enterobacteriaceae when there was lack of resistance to the antibiotics on the Gram-negative panel. Ciprofloxacin utilization (measured in defined daily doses [DDD] per 1,000 patient days) was collected before and after the intervention and compared to moxifloxacin, trimethoprim-sulfamethoxazole, nitrofurantoin, and amoxicillin-clavulanate. Monthly susceptibility of Pseudomonas aeruginosa and Escherichia coli to ciprofloxacin was tabulated. An interrupted time series analysis using segmented regression was performed. The mean monthly ciprofloxacin utilization decreased from 87 (95% CI, 83.7 to 91.2) to 39 (95% CI, 35.0 to 44.0) DDD per 1,000 patient days before and after the implementation of selective reporting, respectively. There was an immediate and sustained reduction in ciprofloxacin usage at 1, 3, 6, 12, and 24 months postintervention (P < 0.001). A compensatory increase in amoxicillin-clavulanate use was noted starting at 6 months postintervention and persisted for the study period (P < 0.027). Susceptibility of E. coli, but not that of P. aeruginosa, to ciprofloxacin was higher than predicted starting 12 months after the intervention (P < 0.05). In conclusion, selective reporting of ciprofloxacin susceptibly may be a useful intervention to reduce targeted antimicrobial utilization and improve Gram-negative susceptibility to ciprofloxacin. This approach should be considered as part of a broader multimodal antimicrobial stewardship program.