{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,10]],"date-time":"2026-11-10T01:47:08Z","timestamp":1794275228359,"version":"4.9.0"},"reference-count":38,"publisher":"American Society for Microbiology","issue":"12","license":[{"start":{"date-parts":[[2000,12,1]],"date-time":"2000-12-01T00:00:00Z","timestamp":975628800000},"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":[[2000,12]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n          <jats:p>\n            An amoxicillin-resistant (Amox\n            <jats:sup>r<\/jats:sup>\n            ) strain of\n            <jats:italic>Helicobacter pylori<\/jats:italic>\n            was selected for by culturing an amoxicillin-sensitive (Amox\n            <jats:sup>s<\/jats:sup>\n            ) strain in increasingly higher concentrations of amoxicillin, resulting in a 133-fold increase in MIC, from 0.03 to 0.06 \u03bcg\/ml to 4 to 8 \u03bcg\/ml. This resistance was stable upon freezing for at least 6 months and conferred cross-resistance to seven other \u03b2-lactam antibiotics. \u03b2-Lactamase activity was not detected in this Amox\n            <jats:sup>r<\/jats:sup>\n            strain; however, analysis of the penicillin-binding protein (PBP) profiles generated from isolated bacterial membranes of the Amox\n            <jats:sup>s<\/jats:sup>\n            parental strain and the Amox\n            <jats:sup>r<\/jats:sup>\n            strain revealed a significant decrease in labeling of PBP 1 by biotinylated amoxicillin (bio-Amox) in the Amox\n            <jats:sup>r<\/jats:sup>\n            strain. Comparative binding studies of PBP 1 for several \u03b2-lactams demonstrated that PBP 1 in the Amox\n            <jats:sup>r<\/jats:sup>\n            strain had decreased affinity for mezlocillin but not significantly decreased affinity for penicillin G. In addition, PBP profiles prepared from whole bacterial cells showed decreased labeling of PBP 1 and PBP 2 in the Amox\n            <jats:sup>r<\/jats:sup>\n            strain at all bio-Amox concentrations tested, suggesting a diffusional barrier to bio-Amox or a possible antibiotic efflux mechanism. Uptake analysis of\n            <jats:sup>14<\/jats:sup>\n            C-labeled penicillin G showed a significant decrease in uptake of the labeled antibiotic by the Amox\n            <jats:sup>r<\/jats:sup>\n            strain compared to the Amox\n            <jats:sup>s<\/jats:sup>\n            strain, which was not affected by pretreatment with carbonyl cyanide\n            <jats:italic>m<\/jats:italic>\n            -chlorophenylhydrazone, eliminating the possibility of an efflux mechanism in the resistant strain. These results demonstrate that alterations in PBP 1 and in the uptake of \u03b2-lactam antibiotics in\n            <jats:italic>H. pylori<\/jats:italic>\n            can be selected for by prolonged exposure to amoxicillin, resulting in increased resistance to this antibiotic.\n          <\/jats:p>","DOI":"10.1128\/aac.44.12.3368-3373.2000","type":"journal-article","created":{"date-parts":[[2002,7,27]],"date-time":"2002-07-27T10:06:42Z","timestamp":1027764402000},"page":"3368-3373","update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":60,"title":["Characterization of an In Vitro-Selected Amoxicillin-Resistant Strain of\n            <i>Helicobacter pylori<\/i>"],"prefix":"10.1128","volume":"44","author":[{"given":"Cindy R.","family":"DeLoney","sequence":"first","affiliation":[{"name":"<!--label omitted: 1-->Division of Biomedical Sciences, University of California, Riverside, Riverside, California 92521"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Neal L.","family":"Schiller","sequence":"additional","affiliation":[{"name":"<!--label omitted: 1-->Division of Biomedical Sciences, University of California, Riverside, Riverside, California 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