Type II Topoisomerase Quinolone Resistance-Determining Regions of Aeromonas caviae , A. hydrophila, and A. sobria Complexes and Mutations Associated with Quinolone Resistance

Abstract

Most Aeromonas strains isolated from two European rivers were previously found to be resistant to nalidixic acid. In order to elucidate the mechanism of this resistance, 20 strains of Aeromonas caviae (n ‫؍‬ 10), A. hydrophila (n ‫؍‬ 5), and A. sobria (n ‫؍‬ 5) complexes, including 3 reference strains and 17 environmental isolates, were investigated. Fragments of the gyrA, gyrB, parC, and parE genes encompassing the quinolone resistance-determining regions (QRDRs) were amplified by PCR and sequenced. Results obtained for the six sensitive strains showed that the GyrA, GyrB, ParC, and ParE QRDR fragments of Aeromonas spp. were highly conserved (>96.1% identity), despite some genetic polymorphism; they were most closely related to those of Vibrio spp., Pseudomonas spp., and members of the family Enterobacteriaceae (72.4 to 97.1% homology). All 14 environmental resistant strains carried a point mutation in the GyrA QRDR at codon 83, leading to the substitution Ser-833Ile (10 strains) or Ser-833Arg. In addition, seven strains harbored a mutation in the ParC QRDR either at position 80 (five strains), generating a Ser-803Ile (three strains) or Ser-803Arg change, or at position 84, yielding a Glu-843Lys modification. No amino acid alterations were discovered in the GyrB and ParE QRDRs. Double gyrA-parC missense mutations were associated with higher levels of quinolone resistance compared with the levels associated with single gyrA mutations. The most resistant strains probably had an additional mechanism(s) of resistance, such as decreased accumulation of the drugs. Our data suggest that, in mesophilic Aeromonas spp., as in other gram-negative bacteria, gyrase and topoisomerase IV are the primary and secondary targets for quinolones, respectively.

Unexpected Occurrence of Plasmid-Mediated Quinolone Resistance Determinants in EnvironmentalAeromonasspp.

“…punctata have already been associated with resistance in Aeromonas spp (18). QnrS2 may confer low-level resistance to quinolones, as known in E. coli.…”

“…PCR amplicons were sequenced on both strands (see below). The chromosome-encoded quinolone-resistance determining regions (QRDRs) of gyrA and parC genes were sequenced after PCR amplifi cation by using whole-cell DNA of qnr-positive isolates, as previously described (18).…”

Detection and Identification of Ciprofloxacin-Resistant Yersinia pestis by Denaturing High-Performance Liquid Chromatography

“…This enzyme has DNA decantation activity and is encoded by the parC and parE genes (11). Double gyrA-parC mutations have been associated with increased levels of quinolone resistance compared to single gyrA mutations (10). Several primer sets could be used to analyze the QRDRs of all genes involved in quinolone resistance.…”

Detection of the First QnrS Gene Positivity in Aquatic Aeromonas spp. Isolates in Turkey

“…Geniş antibakteriyel spektruma sahip olan kinolonlar, birçok enfeksiyonun tedavisinde kullanımlarının yanı sıra veterinerlikte de yaygın olarak kullanılmaktadır. Kinolonların dış çevrede değişmeden kalabilme özelliği, dirençli mutantların seçiminde etkili olabilir 7,8 . Kinolonların bakterisidal etkisi, DNA giraz ve topoizomeraz IV enzimlerini etkileyerek DNA sentezinin inhibisyonu ile olmaktadır.…”