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Topoisomerase alterations and ciprofloxacin resistance in clinical isolates of Klebsiella pneumoniae

Abstract number: P1228

Aathithan S., French G.

Objectives: To determine the frequency and distribution of amino acid alterations in the quinolone binding region (QBR) of GyrA and ParC and the effect of these changes in ciprofloxacin susceptibility amongst 78 clinical isolates of Klebsiella pneumoniae showing ciprofloxacin reduced susceptibility or resistance.

Methods: Sequencing of PCR derived amplicons from a 626bp region of gyrA, and a 388bp region of parC covering the extended quinolone resistance-determining regions (QRDR).

Results: There were 19 different combinations of topoisomerase variants amongst the 78 isolates. The most common mutation, in 97% of mutants, occurred at codon 83 in gyrA, mostly resulting in either S83Y or S83F substitutions in GyrA. There was a strong correlation (r=0.90, 95% CI 0.84–0.93) between the number of target alterations (particularly in GyrA) and ciprofloxacin MICs. No target alteration was found in the 6 isolates with only small reductions in susceptibility. 70/78 isolates with greater reduced susceptibility had target alterations: 29 had alterations in S83, and 1 in D87, of GyrA; 39 of the other 40 had different combinations of double or triple alterations in GyrA and ParC; one had S83Y and F147Y alterations in GyrA and ParC, respectively. The figure shows the association between topoisomerase gene mutations and ciprofloxacin MICs. In this figure a circle=isolates with wild-type sequence in QRDR of both gyrA and parC; triangle=single gyrA mutation; open square=single gyrA mutation at codon D87; inverted triangle=gyrA double mutations at S83 and D87; solid square=gyrA double mutations at S83 and D87 and parC single mutation at S80; solid circle=S83F and D87N in GyrA and E84K in ParC; solid triangle=one mutation in each of gyrA and parC. 00:00=wild type for S83 and D87 in GyrA and S80 and E84 in ParC in the QBR; X0:00=change at S83 in GyrA but not in ParC; 0X:00= change at D87 in GyrA but not in ParC; XX:00=changes at S83 and D87 in GyrA and not in ParC; XX:X0=changes at S83 and D87 in GyrA and at S80 in ParC; XX:0X= changes at S83 and D87 in GyrA and at E84 in ParC; X0:X0=changes at S83 in GyrA and at S80 in ParC.

Conclusion: Mutations in the QRDR of gyrA play a major role in ciprofloxacin resistance in these isolates and the degree of resistance is related to the number of mutations. Double GyrA alterations alone can produce highly resistant ciprofloxacin phenotypes.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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