Quinolone-resistant Escherichia coli

Abstract

Quinolones (nalidixic acid--NAL, norfloxacin--NOR, ciprofloxacin--CIP and gatifloxacin--GAT) were tested against Escherichia coli isolated from urine (385 patient samples) by disk diffusion (DD) and agar dilution (AD) methods. Fifty-three samples (13.8%) were classified as resistant to at least one of the quinolones tested. CIP and NOR susceptibilities were the same (91.4%) and they were similar to GAT (92.7%). Susceptibility to NAL, detected by the disk diffusion method, was used to predict susceptibility to NOR, CIP and GAT by the agar dilution method. The sensitivity and specificity of NAL were 100% and 95%, respectively. Twelve samples were analyzed for mutations in the quinolone resistance-determining region (QRDR) of the gyrA and parC genes. Sequencing of these genes failed to find any mutations in the quinolone-sensitive isolates. However, three mutations were observed in the isolates resistant to all the quinolones tested--two in gyrA and one in parC. A single mutation in gyrA was found in the strains that were resistant to nalidixic acid but fluoroquinolone-sensitive. These findings support the suggestion that NAL could be used as a marker for susceptibility to fluoroquinolones in routine microbiology laboratories. The overall resistance rate to quinolones in the present study was 13.8%, which is higher than that observed in other studies carried out in developed countries. Our findings serve as a warning that resistance to this group of antimicrobial agents is increasing.

Antimicrobial Resistance of Uropathogenic Escherichia coli from Elderly Patients at a General Hospital, Argentina

“…In Italy and Romania, ciprofloxacin resistance presented a similar prevalence than the one in this study, 41.4% and over 50%, respectively. In Brazil, 33/49 nalidixic-resistant E.coli isolates also expressed resistance to ciprofloxacin, showing that nalidic acid is still a marker for quinolones susceptibility [19,25,27] Resistance to TMS was osberved by E.coli isolates in this investigation (37.6%). In Argentina, on recent years, resistance to this antimicrobial showed a preavalence range between 28.1% and 45.7% in eldery patients with UTI.…”

Chicken as Reservoir for Extraintestinal PathogenicEscherichia coliin Humans, Canada

“…Sampling was conducted in proportion to the susceptibility levels for each animal species within the whole CIPARS collection. However, we included all 5 nalidixic acid–resistant isolates because this agent can be used as an indicator of resistance to fluoroquinolones ( 24 ). …”

The Impact of Mutations in Topoisomerase Genes and the Plasmid-Mediated Quinolone Resistance (PMQR) Determinants on the Resistance to Fluoroquinolones in Klebsiella pneumoniae

“…Mutations at codon 426 and 447 of gyrB usually make a low-level of resistance to fluoroquinolones (11,12). Mutations in the amino acid 78, 80 and 84 positions of parC in K. pneumoniae resistant to fluoroquinolones have also been reported worldwide although with different rates (10,13).…”

“…Mutations in gyrA are more common than gyrB gene (9). In gyrA, mutations usually occur at nucleotide 201 to 320 encoded amino acids 67 to 106, in particular at serine 83 and aspartate 87 (10). Mutations at codon 426 and 447 of gyrB usually make a low-level of resistance to fluoroquinolones (11,12).…”