{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,7]],"date-time":"2026-10-07T16:24:40Z","timestamp":1791390280974,"version":"4.3.3"},"reference-count":24,"publisher":"American Society for Microbiology","issue":"7","license":[{"start":{"date-parts":[[2025,7,1]],"date-time":"2025-07-01T00:00:00Z","timestamp":1751328000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2025,7,1]],"date-time":"2025-07-01T00:00:00Z","timestamp":1751328000000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"funder":[{"DOI":"10.13039\/501100006306","name":"Sigrid Jus\u00e9liuksen S\u00e4\u00e4ti\u00f6","doi-asserted-by":"crossref","id":[{"id":"10.13039\/501100006306","id-type":"DOI","asserted-by":"crossref"}]},{"DOI":"10.13039\/501100010711","name":"Cancer foundation Finland","doi-asserted-by":"crossref","id":[{"id":"10.13039\/501100010711","id-type":"DOI","asserted-by":"crossref"}]},{"name":"Turku University hospital foundation"},{"name":"Finnish Governmental Special Funding"},{"name":"Turku Combined Research Funding"}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["Microbiol Spectr"],"published-print":{"date-parts":[[2025,7]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title\/>\n                    <jats:p>\n                      The purpose of this study was to evaluate how ciprofloxacin, pefloxacin, and nalidixic acid disks perform in screening fluoroquinolone resistance mechanisms in 278\n                      <jats:italic toggle=\"yes\">Escherichia coli<\/jats:italic>\n                      isolates collected from a prospective clinical material. Antimicrobial susceptibility testing of ciprofloxacin, pefloxacin, and nalidixic acid was performed with the disk diffusion method. PCR-based and sequencing methods were used to detect chromosomal mutations in the\n                      <jats:italic toggle=\"yes\">gyrA<\/jats:italic>\n                      and\n                      <jats:italic toggle=\"yes\">parC<\/jats:italic>\n                      genes and the presence of plasmid-mediated\n                      <jats:italic toggle=\"yes\">qnr<\/jats:italic>\n                      and\n                      <jats:italic toggle=\"yes\">aac(6\u2032)-1b-cr<\/jats:italic>\n                      genes. In addition, whole-genome sequencing was used to confirm these results. Our results show that fluoroquinolone resistance mechanisms were discovered, even in ciprofloxacin-susceptible isolates, and plasmid-mediated low-level fluoroquinolone resistance is easily missed if only ciprofloxacin disk is used.\n                      <jats:italic toggle=\"yes\">E. coli<\/jats:italic>\n                      strains with chromosomal\n                      <jats:italic toggle=\"yes\">gyrA<\/jats:italic>\n                      and\/or\n                      <jats:italic toggle=\"yes\">parC<\/jats:italic>\n                      mutations were well detected with pefloxacin disk. However, nalidixic acid was a superior tool to detect and differentiate between low- (plasmid-mediated) and high-level (chromosomal mutations) fluoroquinolone resistance in\n                      <jats:italic toggle=\"yes\">E. coli<\/jats:italic>\n                      . Thus, more clinical studies are needed to evaluate the clinical relevance of fluoroquinolone resistance mechanisms in enteric bacteria and pathogens that show potential but are not yet phenotypically fluoroquinolone-resistant.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>IMPORTANCE<\/jats:title>\n                    <jats:p>\n                      We show in our clinical setting that fluoroquinolone resistance mechanisms are discovered, even among phenotypically fluoroquinolone-susceptible\n                      <jats:italic toggle=\"yes\">Escherichia coli<\/jats:italic>\n                      isolates. When plasmid-mediated quinolone-resistance determinants are present, they are a potential risk for treatment failures due to accumulation of resistance mechanisms during the antimicrobial treatment. Therefore, when it is clinically relevant, fluoroquinolone resistance mechanisms in\n                      <jats:italic toggle=\"yes\">E. coli<\/jats:italic>\n                      should be monitored more closely, and we also recommend testing nalidixic acid susceptibility.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.1128\/spectrum.01974-24","type":"journal-article","created":{"date-parts":[[2025,5,22]],"date-time":"2025-05-22T09:00:43Z","timestamp":1747904443000},"update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":6,"title":["Nalidixic acid\u2014a good marker of fluoroquinolone resistance mechanisms in\n                    <i>Escherichia coli<\/i>"],"prefix":"10.1128","volume":"13","author":[{"given":"Sofia","family":"Kalinen","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05vghhr25","id-type":"ROR","asserted-by":"publisher"}],"name":"Institute of Biomedicine, 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