{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,5]],"date-time":"2026-08-05T09:43:03Z","timestamp":1785922983376,"version":"3.56.0"},"reference-count":0,"publisher":"American Society for Microbiology","issue":"5","license":[{"start":{"date-parts":[[1989,5,1]],"date-time":"1989-05-01T00:00:00Z","timestamp":609984000000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["Antimicrob Agents Chemother"],"published-print":{"date-parts":[[1989,5]]},"abstract":"<jats:p>Quinolone antimicrobial agents rapidly kill bacteria by largely unknown mechanisms. To study this phenomenon, a strain of Escherichia coli inhibited but inefficiently killed by (i.e., partially tolerant to) norfloxacin was isolated and characterized. E. coli KL16 (norfloxacin MIC, 0.10 microgram\/ml; MBC, 0.20 microgram\/ml) was mutagenized with nitrosoguanidine and cyclically exposed to 3 micrograms of norfloxacin per ml. After five cycles, a bacterial strain (DS1) which was killed 1,000-fold less than KL16 during 3 h of drug exposure was isolated. The MIC and MBC of norfloxacin for DS1 were 0.20 and 1.5 micrograms\/ml, respectively. Over a range of norfloxacin concentrations, DS1 was killed 2 to 4 orders of magnitude less than KL16. DS1 grew more slowly than KL16 but after normalization for growth rate was killed four times less rapidly than KL16 at drug concentrations 10-fold higher than respective MICs. DS1 and KL16 cells filamented similarly upon exposure to norfloxacin. DS1 exhibited tolerance to other DNA gyrase A subunit antagonists (ofloxacin and ciprofloxacin) and DNA gyrase B subunit antagonists (novobiocin and coumermycin) but not to the aminoglycoside gentamicin, suggesting involvement of DNA gyrase. DS1 also appeared to be minimally tolerant to the beta-lactam cefoxitin. DS1 exhibited increased susceptibility to the mutagen methyl methanesulfonate, implying a defect in DNA repair. This report describes the first use of quinolone enrichment for isolation of a bacterial strain partially tolerant to quinolones. The study of defects in such tolerant strains offers an approach to an increased understanding of the mechanisms of bacterial killing by quinolones.<\/jats:p>","DOI":"10.1128\/aac.33.5.705","type":"journal-article","created":{"date-parts":[[2012,6,28]],"date-time":"2012-06-28T00:04:52Z","timestamp":1340841892000},"page":"705-709","update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":27,"title":["Isolation and characterization of an Escherichia coli strain exhibiting partial tolerance to quinolones"],"prefix":"10.1128","volume":"33","author":[{"given":"J S","family":"Wolfson","sequence":"first","affiliation":[{"name":"Infectious Disease Unit, Medical Services, Massachusetts General Hospital, Boston 02114."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"D C","family":"Hooper","sequence":"additional","affiliation":[{"name":"Infectious Disease Unit, Medical Services, Massachusetts General Hospital, Boston 02114."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"D J","family":"Shih","sequence":"additional","affiliation":[{"name":"Infectious Disease Unit, Medical Services, Massachusetts General Hospital, Boston 02114."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"G L","family":"McHugh","sequence":"additional","affiliation":[{"name":"Infectious Disease Unit, Medical Services, Massachusetts General Hospital, Boston 02114."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"M N","family":"Swartz","sequence":"additional","affiliation":[{"name":"Infectious Disease Unit, Medical Services, Massachusetts General Hospital, Boston 02114."}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"235","container-title":["Antimicrobial Agents and Chemotherapy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/journals.asm.org\/doi\/pdf\/10.1128\/AAC.33.5.705","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/journals.asm.org\/doi\/pdf\/10.1128\/AAC.33.5.705","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2022,2,21]],"date-time":"2022-02-21T15:06:14Z","timestamp":1645455974000},"score":1,"resource":{"primary":{"URL":"https:\/\/journals.asm.org\/doi\/10.1128\/AAC.33.5.705"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1989,5]]},"references-count":0,"journal-issue":{"issue":"5","published-print":{"date-parts":[[1989,5]]}},"alternative-id":["10.1128\/AAC.33.5.705"],"URL":"https:\/\/doi.org\/10.1128\/aac.33.5.705","relation":{},"ISSN":["0066-4804","1098-6596"],"issn-type":[{"value":"0066-4804","type":"print"},{"value":"1098-6596","type":"electronic"}],"subject":[],"published":{"date-parts":[[1989,5]]},"assertion":[{"value":"1989-05-01","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}]}}