{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,3]],"date-time":"2026-05-03T00:21:48Z","timestamp":1777767708479,"version":"3.51.4"},"reference-count":0,"publisher":"S. Karger AG","license":[{"start":{"date-parts":[[2009,9,10]],"date-time":"2009-09-10T00:00:00Z","timestamp":1252540800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/karger.com\/pages\/terms-and-conditions"},{"start":{"date-parts":[[2009,9,10]],"date-time":"2009-09-10T00:00:00Z","timestamp":1252540800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/karger.com\/pages\/terms-and-conditions"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Chemotherapy"],"abstract":"<jats:p>Phenotypic resistance to \u03b2-lactam antibiotics is mainly due to the prevalence of \u03b2-lactamases. The most common enzymes responsible for resistance to aminopenicillins and older (1st generation) cephalosporins are the TEM-1, TEM-2, OXA-1 and SHV-1 enzymes, all of which are plasmid-mediated. The recent development of oral cephalosporins sharing structural features and an antimicrobial spectrum comparable to that of 3rd-generation cephalosporins has provided highly active compounds for the management of outpatient infections. Two principal mechanisms, however, may cause resistance to these new compounds: the overproduction of chromosomally encoded \u03b2-lactamases with predominating cephalosporinase activity, and the recently observed extended-spectrum \u03b2-lactamases. The overproduction of chromosomally mediated \u03b2-lactamases has been observed only in some species (Enterobacter cloacae, Citrobacter freundii, Serratia spp.) which cause mainly nosocomial infections and are therefore of minor importance in outpatients. The extended-spectrum \u03b2-lactamases TEM-3 to TEM-12 and SHV-2 to SHV-7 have been observed in various countries, they derived from the original enzymes by point mutations and occurred in intensive-care units. These enzymes may cause resistance to 3rd-generation cephalosporins including the recently developed orally active compounds. Moderate resistance to cefetamet is observed only in strains producing either the TEM-3 or the TEM-4 enzyme, whereas the prevalence of the other enzymes is of no consequence for the activity of cefetamet. Consequently, cefetamet will not exhibit a marked selection pressure favoring the spread of extended-spectrum \u03b2-lactamase-producing strains.<\/jats:p>","DOI":"10.1159\/000239092","type":"journal-article","created":{"date-parts":[[2009,9,11]],"date-time":"2009-09-11T09:12:33Z","timestamp":1252660353000},"page":"10-17","source":"Crossref","is-referenced-by-count":5,"title":["The Threat of Resistance to the New Oral Cephalosporins"],"prefix":"10.1159","author":[{"given":"W.","family":"Cullmann","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"127","published-online":{"date-parts":[[2009,9,10]]},"container-title":["Chemotherapy"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.karger.com\/Article\/Pdf\/239092","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/karger.com\/article-pdf\/doi\/10.1159\/000239092","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,29]],"date-time":"2026-04-29T15:43:40Z","timestamp":1777477420000},"score":1,"resource":{"primary":{"URL":"https:\/\/karger.com\/article\/doi\/10.1159\/000239092"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2009,9,10]]},"references-count":0,"URL":"https:\/\/doi.org\/10.1159\/000239092","archive":["Portico"],"relation":{},"ISSN":["0009-3157","1421-9794"],"issn-type":[{"value":"0009-3157","type":"print"},{"value":"1421-9794","type":"electronic"}],"subject":[],"published":{"date-parts":[[2009,9,10]]}}}