Changes in fluoroquinolone resistance over 5 years (CANWARD 2007-11) in bacterial pathogens isolated in Canadian hospitals.

OBJECTIVES

The purpose of this study was to analyse Canadian national surveillance data, specifically fluoroquinolone resistance, from 2007 to 2011 inclusive, to determine trends in resistance over time and to assess correlations with patient demographic factors.

METHODS

All isolates of Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus pneumoniae collected by the 10 sites that participated in the annual CANWARD surveillance studies in each of the 5 years were included in this analysis. A multifactorial logistic regression model was used to determine the variables with significant impact on fluoroquinolone resistance.

RESULTS

The proportion of E. coli isolates resistant to ciprofloxacin increased significantly (P = 0.0005) between 2007 (20.0%) and 2011 (29.2%), although similar increases were not seen in K. pneumoniae, E. cloacae, P. aeruginosa and S. pneumoniae (tested against levofloxacin) (P > 0.05). Among isolates of S. aureus, there was a significant decrease in ciprofloxacin resistance from 34.4% in 2007 to 24.6% in 2011 (P < 0.0001). Resistance to ciprofloxacin was a component of most multidrug-resistant (MDR) phenotypes for E. coli, K. pneumoniae, E. cloacae, P. aeruginosa and S. aureus.

CONCLUSIONS

A significant increase in the percentage of ciprofloxacin-resistant E. coli, primarily among urine isolates, and a significant decrease in the percentage of ciprofloxacin-resistant S. aureus occurred between 2007 and 2011. Notably, MDR isolates were frequently fluoroquinolone resistant for all organisms studied, except S. pneumoniae.