Molecular mechanisms of quinolone resistance in clinical isolates of Aeromonas caviae and Aeromonas veronii bv. sobria Authors Antonina Arias Microbiology Department, “Lozano Blesa” University Clinical Hospital, Zaragoza, Spain Cristina Seral Microbiology Department, “Lozano Blesa” University Clinical Hospital, Zaragoza, Spain. Department of Microbiology, Faculty of Medicine, University of Zaragoza, Spain M. José Gude Microbiology Department, “Lozano Blesa” University Clinical Hospital, Zaragoza, Spain F. Javier Castillo Microbiology Department, “Lozano Blesa” University Clinical Hospital, Zaragoza, Spain. Department of Microbiology, Faculty of Medicine, University of Zaragoza, Spain Keywords: Aeromonas spp., quinolone resistance, nalidixic acid resistance, ciprofloxacin Abstract Mutations in quinolone targets were studied together with quinolone efflux pump activation and plasmid-mediated quinolone resistance determinants in nalidixic-acid-resistant isolates of Aeromonas caviae and Aeromonas veronii. Among 135 clinical Aeromonas spp. isolated from stools of patients with gastrointestinal symptoms, 40 nalidixic acid-resistant strains belonging to A. caviae and A. veronii were selected and their susceptibility to different quinolones (ciprofloxacin, norfloxacin, ofloxacin) further evaluated. Susceptibility to nalidixic acid and ciprofloxacin in the presence/absence of Phe- Arg-β-naphthylamide was also determined. The 16 nalidixic-acid-resistant strains identified as A. caviae were more resistant than the 24 A. veronii bv. sobria strains to ciprofloxacin, norfloxacin, and ofloxacin. All strains showed a mutation (single or double) at position 83 of the QRDR sequence of gyrA, with Ser-83 → Ile as the most frequent substitution. By contrast, no mutations were found at position 87 of gyrA. Double substitutions (GyrA-ParC) were detected in 50% of A. veronii bv. sobria isolates and in 43.75% of A. caviae strains. Both species showed decreases in the MICs of ciprofloxacin. A qnrS gene was found in an A. caviae strain. Thus, in the two species of nalidixic-acid-resistant Aeromonas isolates examined, resistance mediated by efflux pumps contributed only slightly to ciprofloxacin resistance. While two isolates were positive for the aac(6′)-Ib gene, no -cr variants were detected. [Int Microbiol 2010; 13(3):135-141] Author Biographies Antonina Arias, Microbiology Department, “Lozano Blesa” University Clinical Hospital, Zaragoza, Spain Microbiology Department, “Lozano Blesa” University Clinical Hospital, Zaragoza, Spain. Cristina Seral, Microbiology Department, “Lozano Blesa” University Clinical Hospital, Zaragoza, Spain. Department of Microbiology, Faculty of Medicine, University of Zaragoza, Spain Microbiology Department, “Lozano Blesa” University Clinical Hospital, Zaragoza, Spain. Department of Microbiology, Faculty of Medicine, University of Zaragoza, Spain M. José Gude, Microbiology Department, “Lozano Blesa” University Clinical Hospital, Zaragoza, Spain Microbiology Department, “Lozano Blesa” University Clinical Hospital, Zaragoza, Spain. F. Javier Castillo, Microbiology Department, “Lozano Blesa” University Clinical Hospital, Zaragoza, Spain. Department of Microbiology, Faculty of Medicine, University of Zaragoza, Spain Microbiology Department, “Lozano Blesa” University Clinical Hospital, Zaragoza, Spain.Department of Microbiology, Faculty of Medicine, University of Zaragoza, Spain Downloads PDF Published 2010-09-28 Issue Vol. 13 No. 3 (2010) Section Research Articles License Submission of a manuscript to International Microbiology implies: that the work described has not been published before, including publication in the World Wide Web (except in the form of an Abstract or as part of a published lecture, review, or thesis); that it is not under consideration for publication elsewhere; that all the coauthors have agreed to its publication. 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