{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,4]],"date-time":"2025-10-04T01:34:25Z","timestamp":1759541665535},"reference-count":0,"publisher":"American Society for Microbiology","issue":"6","license":[{"start":{"date-parts":[[1974,12,1]],"date-time":"1974-12-01T00:00:00Z","timestamp":155088000000},"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":[[1974,12]]},"abstract":"<jats:p>\n            A survey of clinical isolates from a hospital laboratory showed that\n            <jats:italic>Escherichia coli<\/jats:italic>\n            could be grouped into three classes of beta-lactam-antibiotic resistance by results of routine susceptibility testing to ampicillin, cephalothin, and carbenicillin.\n            <jats:italic>E. coli<\/jats:italic>\n            highly resistant to ampicillin and carbenicillin but not to cephalothin (class I) were found to have one of two levels of R factor-mediated, periplasmic-\u03b2-lactamase which resembled R\n            <jats:sub>TEM<\/jats:sub>\n            and was located behind a permeability barrier to penicillins but not to cephalosporins. This permeability barrier appeared to act synergistically with the \u03b2-lactamase in producing high levels of resistance to penicillins.\n            <jats:italic>E. coli<\/jats:italic>\n            highly resistant to ampicillin and cephalothin but not carbenicillin (class II) were found to have a \u03b2-lactamase with predominantly cephalosporinase activity which was neither transferable nor releasable by osmotic shock.\n            <jats:italic>E. coli<\/jats:italic>\n            moderately resistant to one or to all three of these antibiotics (class III) were found to have low levels of different \u03b2-lactamases including a transferable \u03b2-lactamase which resembled R\n            <jats:sub>1818<\/jats:sub>\n            . Thus, different mechanisms producing resistance to \u03b2-lactam antibiotics could be deduced from the patterns of resistance to ampicillin, cephalothin, and carbenicillin found on routine susceptibility testing.\n            <jats:italic>E. coli<\/jats:italic>\n            of class I were much more prevalent than the other classes and the proportion of\n            <jats:italic>E. coli<\/jats:italic>\n            that were class I increased with duration of patient hospitalization. The incidence of class I\n            <jats:italic>E. coli<\/jats:italic>\n            rose only slightly over the past 7 years and that of class II\n            <jats:italic>E. coli<\/jats:italic>\n            remained constant despite increased usage of both cephalothin and ampicillin. These observations emphasize that the properties of the apparently limited number of individual resistance mechanisms that exist in a bacterial flora, such as their genetic mobility and linkages and the spectrum of their antibiotic inactivating enzymes and permeability barriers, may govern the effect that usage of an antibiotic has upon the prevalence of resistance to it and to other antibiotics.\n          <\/jats:p>","DOI":"10.1128\/aac.6.6.791","type":"journal-article","created":{"date-parts":[[2012,6,27]],"date-time":"2012-06-27T23:57:02Z","timestamp":1340841422000},"page":"791-801","update-policy":"http:\/\/dx.doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":20,"title":["Characterization and Prevalence of the Different Mechanisms of Resistance to Beta-Lactam Antibiotics in Clinical Isolates of\n            <i>Escherichia coli<\/i>"],"prefix":"10.1128","volume":"6","author":[{"given":"Antone A.","family":"Medeiros","sequence":"first","affiliation":[{"name":"Department of Medicine, Peter Bent Brigham Hospital, and Harvard Medical School, Boston, Massachusetts 02115"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ralph L.","family":"Kent","sequence":"additional","affiliation":[{"name":"Department of Medicine, Peter Bent Brigham Hospital, and Harvard Medical School, Boston, Massachusetts 02115"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Thomas F.","family":"O'Brien","sequence":"additional","affiliation":[{"name":"Department of Medicine, Peter Bent Brigham Hospital, and Harvard Medical School, Boston, Massachusetts 02115"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"235","container-title":["Antimicrobial Agents and Chemotherapy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/journals.asm.org\/doi\/pdf\/10.1128\/AAC.6.6.791","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/journals.asm.org\/doi\/pdf\/10.1128\/AAC.6.6.791","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2022,2,21]],"date-time":"2022-02-21T23:12:15Z","timestamp":1645485135000},"score":1,"resource":{"primary":{"URL":"https:\/\/journals.asm.org\/doi\/10.1128\/AAC.6.6.791"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1974,12]]},"references-count":0,"journal-issue":{"issue":"6","published-print":{"date-parts":[[1974,12]]}},"alternative-id":["10.1128\/AAC.6.6.791"],"URL":"https:\/\/doi.org\/10.1128\/aac.6.6.791","relation":{},"ISSN":["0066-4804","1098-6596"],"issn-type":[{"value":"0066-4804","type":"print"},{"value":"1098-6596","type":"electronic"}],"subject":[],"published":{"date-parts":[[1974,12]]},"assertion":[{"value":"1974-12-01","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}]}}