Reduction in fluoroquinolone use following introduction of ertapenem to hospital formulary associated with improvement in susceptibility of Pseudomonas aeruginosa to group 2 carbapenems: a 10-year study.
Department of Medicine, Division of Infectious Diseases, Brody School of Medicine at East Carolina University.
We examined the effect of the addition of ertapenem to our hospital formulary on the resistance of nosocomial Pseudomonas aeruginosa to group 2 carbapenems (imipenem, meropenem, and doripenem). This was a retrospective, observational study conducted between January 1, 2000 and January 31, 2009 at a large, tertiary-care hospital. ARIMA regression models were used to evaluate the effect of ertapenem use on the susceptibility of Pseudomonas aeruginosa to group 2 carbapenems as well as on the usage of the group 2 carbapenems, ciprofloxacin, and other anti-pseudonomal drugs (i.e., tobramycin, cefepime, and piperacillin-tazobactam). Resistance was expressed as a percentage of total isolates as well as the number of carbapenem-resistant bacterial isolates per 10,000 patient days. Pearson correlation was used to assess the relationship between antibiotic use and carbapenem resistance. Following the addition of ertapenem to the formulary, there was a statistically significant decrease in the percentage of Pseudomonas aeruginosa isolates resistant to the group 2 carbapenems (p=0.003). Group 2 carbapenem use and the number of carbapenem-resistant Pseudomonas aeruginosa isolates per 10,000 patient days did not change significantly over the time period. There was a large decrease in the use of ciprofloxacin (p=0.0033), and there was a correlation of ciprofloxacin use with the percentage of isolates resistant to the group 2 carbapenems (ρ=0.47, p=0.002). We suspect that the improvement in susceptibility of Pseudomonas aeruginosa to group 2 carbapenems was related to a decrease in ciprofloxacin use.
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