This study investigated the correlation between fluoroquinolone (ciprofloxacin or levofloxacin) use and rates of fluoroquinolone resistance in Pseudomonas aeruginosa isolates from patients with nosocomial infection at a medical centre in Taiwan. Antibiotic utilisation data were extracted on a monthly basis from the inpatient pharmacy computer system records from January 2003 to December 2008. Fluoroquinolone use was expressed as defined daily dose per 1000 patient-days and was correlated with rates of fluoroquinolone-resistant P. aeruginosa every 6 months. Regression analysis was performed to explore the relationship between ciprofloxacin and levofloxacin use (both parenteral and oral forms) and resistance of P. aeruginosa isolates. During the study period, the susceptibility of P. aeruginosa to fluoroquinolones decreased after increasing use of fluoroquinolones, and increased after decreasing use of levofloxacin. Parenteral levofloxacin use was significantly positively correlated with resistance of P. aeruginosa to ciprofloxacin (P = 0.015) and fluoroquinolones (either ciprofloxacin or levofloxacin, P = 0.014). Use of both parenteral and oral forms of levofloxacin was also significantly positively correlated with resistance of P. aeruginosa isolates to ciprofloxacin (P = 0.029), levofloxacin (P = 0.031) and fluoroquinolones (P = 0.010). The total amount of ciprofloxacin (oral and parenteral) and parenteral ciprofloxacin use were negatively correlated with resistance of P. aeruginosa isolates to fluoroquinolones. However, the amounts of oral ciprofloxacin, parenteral levofloxacin, oral levofloxacin and total levofloxacin use were each positively correlated with resistance of P. aeruginosa to fluoroquinolones. Levofloxacin use was associated with increased resistance of P. aeruginosa to fluoroquinolones, whereas ciprofloxacin use did not have a significant impact on fluoroquinolone resistance rates.
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