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Antimicrobial Agents and Chemotherapy, January 2007, p. 198-207, Vol. 51, No. 1
0066-4804/07/$08.00+0     doi:10.1128/AAC.00609-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Molecular Characterization of Increasing Fluoroquinolone Resistance in Streptococcus pneumoniae Isolates in Canada, 1997 to 2005{triangledown},{dagger}

Heather J. Adam,1* Kristen N. Schurek,1 Kimberly A. Nichol,2 Chris J. Hoban,1 Trish J. Baudry,1 Nancy M. Laing,1 Daryl J. Hoban,1,2 and George G. Zhanel1,2,3

Department of Medical Microbiology, Faculty of Medicine, University of Manitoba,1 Departments of Medicine,3 Clinical Microbiology, Health Sciences Centre, Winnipeg, Manitoba, Canada2

Received 18 May 2006/ Returned for modification 20 August 2006/ Accepted 29 October 2006

Molecular characterization of fluoroquinolone-resistant Streptococcus pneumoniae in Canada was conducted from 1997 to 2005. Over the course of the study, 205 ciprofloxacin-resistant isolates were evaluated for ParC and GyrA quinolone resistance-determining region (QRDR) substitutions, substitutions in the full genes of ParC, ParE, and GyrA, reserpine sensitivity, and serotype and by pulsed-field gel electrophoresis. Rates of ciprofloxacin resistance of S. pneumoniae increased significantly, from less than 1% in 1997 to 4.2% in 2005. Ciprofloxacin resistance was greatest in people >64 years of age and least in those <16 years of age. Significant increases were also noted in rates of resistance to gatifloxacin, gemifloxacin, levofloxacin, and moxifloxacin, to the current rates of 1.6%, 1.0%, 1.1%, and 1.0%, respectively. The most common genotype observed consisted of QRDR substitutions in GyrA (Ser81Phe) and ParC (Ser79Phe). Substitutions outside the QRDR of GyrA, ParC, and ParE were not associated with fluoroquinolone resistance in this study. Overall, 21% of isolates were reserpine-sensitive and were thus assumed to be efflux positive. The ciprofloxacin-resistant isolates belonged to 35 different serotypes, but 10 (19F, 11A, 23F, 6B, 22F, 12F, 6A, 14, 9V, and 19A) accounted for 72% of all isolates. The majority of the isolates were found to be genetically unrelated by pulsed-field gel electrophoresis. Within the observed clusters, there was considerable genetic heterogeneity with regard to fluoroquinolone resistance mechanisms and serotypes. Continued surveillance and molecular analysis of fluoroquinolone-resistant S. pneumoniae in Canada are essential for appropriate empirical treatment of infections and early detection of novel resistance mechanisms.

* Corresponding author. Mailing address: Clinical Microbiology, Health Sciences Centre, MS673-820 Sherbrook St., Winnipeg, Manitoba R3A 1R9, Canada. Phone: (204) 787-4684. Fax: (204) 787-4699. E-mail: hjadam{at}gmail.com.

{triangledown} Published ahead of print on 6 November 2006.

{dagger} Supplemental material for this article may be found at http://aac.asm.org/.

Antimicrobial Agents and Chemotherapy, January 2007, p. 198-207, Vol. 51, No. 1
0066-4804/07/$08.00+0     doi:10.1128/AAC.00609-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.



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