Journal Article

The Molecular Epidemiology of <i>Streptococcus pneumoniae</i> with Quinolone Resistance Mutations

S. S. Richter, K. P. Heilmann, S. E. Beekmann, N. J. Miller, C. L. Rice and G. V. Doern

in Clinical Infectious Diseases

Published on behalf of Infectious Diseases Society of America

Volume 40, issue 2, pages 225-235
Published in print January 2005 | ISSN: 1058-4838
Published online January 2005 | e-ISSN: 1537-6591 | DOI: http://dx.doi.org/10.1086/426817
The Molecular Epidemiology of Streptococcus pneumoniae with Quinolone Resistance Mutations

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Background. The purpose of this study was to determine the prevalence of fluoroquinolone resistance and quinolone resistance—determining region (QRDR) mutations among Streptococcus pneumoniae isolates in the United States during the period of 2001–2002. A second objective was to examine the genetic relatedness of pneumococcal isolates with parC and/or gyrA mutations during the period of 1994–2002.

Methods. Susceptibility testing was performed for 1902 S. pneumoniae isolates collected in the United States during the period of 2001–2002. On the basis of the minimum inhibitory concentration (MIC) of ciprofloxacin, 146 isolates were selected from the 2001–2002 study for QRDR analysis of parC, parE, gyrA, and gyrB genes. The genetic relatedness of isolates with parC and/or gyrA mutations from 2001–2002 (n = 55) and from 3 US surveillance studies conducted during 1994–2000 (n = 56) was determined by pulsed-field gel electrophoresis (PFGE).

Results. Between 1999–2000 and 2001–2002, there was a 2-fold increase in the rate of ciprofloxacin resistance (MIC, ⩾4 µg/mL), from 1.2% to 2.7%, and in the rate of levofloxacin nonsusceptibility (MIC, ⩾4 µg/mL), from 0.6% to 1.3%. The 111 isolates with parC and/or gyrA mutations were assigned to 48 different PFGE types. Forty-four isolates (40%) belonged to 8 PFGE types that were closely related to widespread clones. Fifteen of the 43 levofloxacin-nonsusceptible pneumococci (LNSP) belonged to 4 PFGE types that were closely related to major clones (Spain23F-1 [n = 6]; Spain6B-2 [n = 5], Taiwan19F-14 [n = 2], and Tennessee23F-4 [n = 2]).

Conclusion. The population of fluoroquinolone-resistant S. pneumoniae in the United States has increased but remains genetically diverse. However, 35% of LNSP were related to widespread pneumococcal clones, increasing the potential for the rapid spread of quinolone resistance in this species.

Journal Article.  4068 words.  Illustrated.

Subjects: Infectious Diseases ; Immunology ; Public Health and Epidemiology ; Microbiology

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