TY - JOUR
T1 - Spontaneous conversion to quinolone and fluoroquinolone resistance among wild-type Escherichia coli isolates in relation to phylogenetic background and virulence genotype
AU - Johnson, James R.
AU - Johnston, Brian
AU - Kuskowski, Michael A.
AU - Colodner, Raul
AU - Raz, Raul
N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2005/11
Y1 - 2005/11
N2 - Human clinical isolates of Escherichia coli that are resistant to quinolone or fluoroquinolone agents typically exhibit fewer extraintestinal virulence factors (VFs) than susceptible isolates, along with a different phylogenetic background. To experimentally assess the basis for this as-yet-unexplained phenomenon, 40 E. coli strains (20 E. coli Reference collection members and 20 Israeli cystitis isolates) were subjected to serial selective passaging to obtain derivatives resistant to nalidixic acid (NA) and ciprofloxacin (C). PCR-based VF profiling and phylotyping were performed on the parents and their respective resistant derivatives. All 40 susceptible parent strains yielded NA- and C-resistant derivatives after a median of 6 (range, 4 to 12) serial selective passages on agar plates containing increasing concentrations of NA and C. The numbers of passages required for resistance did not differ by collection origin, phylogenetic group, basal VF profile, source (urine versus fecal), or host group (human versus animal). With the development of C resistance, only one VF was lost in a single strain. Resistant derivatives exhibited the same phylotype as their susceptible parents. These findings suggest that the sparse VF profiles and the low-virulence phylogenetic background of NA- and C-resistant E. coli clinical isolates probably are not attributable to the loss of VFs from intrinsically high-virulence strains during conversion to resistance or to enhanced emergence of drug resistance among intrinsically low-virulence strains. A more likely explanation is the importation of resistant strains from an as-yet-undeflned low-virulence external selection reservoir.
AB - Human clinical isolates of Escherichia coli that are resistant to quinolone or fluoroquinolone agents typically exhibit fewer extraintestinal virulence factors (VFs) than susceptible isolates, along with a different phylogenetic background. To experimentally assess the basis for this as-yet-unexplained phenomenon, 40 E. coli strains (20 E. coli Reference collection members and 20 Israeli cystitis isolates) were subjected to serial selective passaging to obtain derivatives resistant to nalidixic acid (NA) and ciprofloxacin (C). PCR-based VF profiling and phylotyping were performed on the parents and their respective resistant derivatives. All 40 susceptible parent strains yielded NA- and C-resistant derivatives after a median of 6 (range, 4 to 12) serial selective passages on agar plates containing increasing concentrations of NA and C. The numbers of passages required for resistance did not differ by collection origin, phylogenetic group, basal VF profile, source (urine versus fecal), or host group (human versus animal). With the development of C resistance, only one VF was lost in a single strain. Resistant derivatives exhibited the same phylotype as their susceptible parents. These findings suggest that the sparse VF profiles and the low-virulence phylogenetic background of NA- and C-resistant E. coli clinical isolates probably are not attributable to the loss of VFs from intrinsically high-virulence strains during conversion to resistance or to enhanced emergence of drug resistance among intrinsically low-virulence strains. A more likely explanation is the importation of resistant strains from an as-yet-undeflned low-virulence external selection reservoir.
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U2 - 10.1128/AAC.49.11.4739-4744.2005
DO - 10.1128/AAC.49.11.4739-4744.2005
M3 - Article
C2 - 16251319
AN - SCOPUS:27644582364
VL - 49
SP - 4739
EP - 4744
JO - Antimicrobial Agents and Chemotherapy
JF - Antimicrobial Agents and Chemotherapy
SN - 0066-4804
IS - 11
ER -