Infection Control & Hospital Epidemiology
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aeruginosa susceptibility declined from 72% to 50% (annual trend RR 0 (annual trend RRn 0.937; 95% CI, 0.923–0.951) (Tables 1 and 2).
Comparing the annual trends between the preimplementation
and postimplementation periods, overall, a decreasing annual trend of the FQ susceptibility rates was observed during 1998– 2005 (RR, 0.935; 95% CI, 0.918–0.954). Following the imple- mentation of the restriction policy, the annual trend was flat (RR, 1.000; 95% CI, 0.990–1.009), a difference that was statistically significant between the 2 periods (P < .0001) (Table 2). When examining trends by organism, a significant difference in the annual trends between the preimplementation and post- implementation periods was observed for all 5 gram-negative organisms (P < .0001 for all organisms except K. pneumoniae, which had a P = .0002). Specifically, following the imple- mentation of the restrictive policy, susceptibility increased for Acinetobacter spp (RR, 1.038; 95% CI, 1.005–1.072), E. cloacae (RR, 1.028; 95% CI, 1.013–1.044), and P. aeruginosa (RR, 1.013; 95% CI, 1.006–1.020). The annual trend of K. pneumoniae did not increase in the postimplementation period, though it did remain flat (RR, 1.002; 95% CI, 0.996–1.008), and the trend of E. coli continued to decrease though not as sharply (RR, 0.981; 95% CI, 0.975–0.987).
Discussion
Our study demonstrates either cessation in (K. pneumoniae)or reversal of (Acinetobacter spp, E. cloacae, and P. aeruginosa)FQ resistance for hospital isolates which correlates with the imple- mentation of an FQ restriction policy within the hospital that has been sustained for more than a decade. Interestingly, the FQ resistance rates not only stabilized, we also observed a reemer- gence of overall population susceptibility for certain species. The timing of these improvements varied, but we observed a 10% improvement in FQ susceptibilities within the first 2 years of implementing the restriction program for these 4 classically healthcare-associated pathogens. In contrast, E. coli isolates continued to demonstrate
Fig. 2. Linear annual trends in fluoroquinolone-susceptibility rates before and after implementation of a policy requiring prior authorization for fluoroquinolone prescription.
Fluoroquinolone susceptibility
The FQ susceptibilities were assessed for 5 common gram- negative organisms: Acinetobacter spp, E. cloacae, E. coli, K. pneumoniae, and P. aeruginosa (Table 1, Figure 2). In the pre- intervention period (1998–2005), all 5 isolates had decreasing rates of susceptibility to FQs. Acinetobacter spp susceptibility declined from 76% to 35% (annual trend RR, 0.871; 95% CI, 0.833–0.912); E. cloacae susceptibility declined from 99% to 55% (annual trend RR, 0.898; 95% CI, 0.870–0.926); E. coli suscept- ibility declined from 99% to 71% (annual trend RR, 0.952; 95% CI, 0.941–0.964); K. pneumoniae susceptibility declined from 94% to 80% (annual trend RR, 0.976; 95% CI, 0.964–0.989); and P.
decreasing FQ susceptibility despite declining FQ use, although at a notably slower rate compared to the preimplementation period. Although some stewardship programs have shown more success in improving hospital E. coli resistance rates, these studies were followed for shorter periods, focused on only 1 type of isolate, excluded isolates from primary care, or focused on nosocomial infections alone.22–24 Langford et al25 found that selectively withholding FQ susceptibility results on cultures involving E. coli significantly halted the increase in the resistance rate. Interest- ingly, these researchers did not observe a significant change in P. aeruginosa susceptibility rates despite a decrease in FQ use.24,25 These mixed observations demonstrate that reversing the resis- tance trends in gram-negative bacteria is a very complex process, especially with respect to enteric bacteria such as E. coli, and that antimicrobial restriction programs are likely be more effective if both inpatient and outpatient settings are targeted. However, these restriction programs were only followed for 2–3 years, while our ongoing FQ restriction program has been sustained for more than a decade. Although our FQ restriction program did not result in an improvement of susceptibility to E. coli, we were able to demonstrate an improvement in the rate of the decline in sus- ceptibility. We hypothesize that the continued decline in FQ
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