{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,14]],"date-time":"2026-07-14T13:47:02Z","timestamp":1784036822952,"version":"3.55.0"},"reference-count":48,"publisher":"American Society for Microbiology","issue":"1","license":[{"start":{"date-parts":[[2012,1,1]],"date-time":"2012-01-01T00:00:00Z","timestamp":1325376000000},"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":[[2012,1]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n          <jats:p>\n            A clonal strain of\n            <jats:named-content xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" content-type=\"genus-species\" xlink:type=\"simple\">Klebsiella pneumoniae<\/jats:named-content>\n            producing the plasmid-encoded cephalosporinase DHA-1 was isolated from four patients admitted to the teaching hospital of Clermont-Ferrand, France, in 2006. It was responsible for severe infections in three of the patients; the fourth was colonized only in the gastrointestinal tract. The strain had at least two plasmids encoding resistance to antibiotics (quinolones, aminoglycosides, chloramphenicol, sulfonamides, and trimethoprim), as shown by disk diffusion assay, and harbored only a few genes for virulence factors (\n            <jats:italic>wabG<\/jats:italic>\n            and\n            <jats:italic>mrkD<\/jats:italic>\n            ), as shown by PCRs. DHA-1 synthesis is regulated by an upstream, divergently transcribed gene,\n            <jats:italic>ampR<\/jats:italic>\n            , which is also involved in the expression of virulence factors in\n            <jats:named-content xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" content-type=\"genus-species\" xlink:type=\"simple\">Pseudomonas aeruginosa<\/jats:named-content>\n            . To investigate the role of AmpR in\n            <jats:named-content xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" content-type=\"genus-species\" xlink:type=\"simple\">K. pneumoniae<\/jats:named-content>\n            , we cloned the wild-type\n            <jats:italic>ampR<\/jats:italic>\n            gene from the DHA-1 clonal isolate into a previously characterized\n            <jats:named-content xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" content-type=\"genus-species\" xlink:type=\"simple\">K. pneumoniae<\/jats:named-content>\n            background plasmid-cured strain, CH608.\n            <jats:italic>ampR<\/jats:italic>\n            was also introduced into a CH608 isogenic mutant deleted of\n            <jats:italic>ampD<\/jats:italic>\n            , in which AmpR is present only in its activator form, resulting in constitutive hyperproduction of the \u03b2-lactamase. We showed that\n            <jats:italic>ampR<\/jats:italic>\n            was involved in the upregulation of capsule synthesis and therefore in resistance to killing by serum. AmpR also modulated biofilm formation and type 3 fimbrial gene expression, as well as colonization of the murine gastrointestinal tract and adhesion to HT-29 intestinal epithelial cells. These results show the pleiotropic role of\n            <jats:italic>ampR<\/jats:italic>\n            in the pathogenesis process of\n            <jats:named-content xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" content-type=\"genus-species\" xlink:type=\"simple\">K. pneumoniae<\/jats:named-content>\n            .\n          <\/jats:p>","DOI":"10.1128\/aac.00164-11","type":"journal-article","created":{"date-parts":[[2011,10,11]],"date-time":"2011-10-11T05:29:43Z","timestamp":1318310983000},"page":"288-294","update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":37,"title":["Characterization of a DHA-1-Producing Klebsiella pneumoniae Strain Involved in an Outbreak and Role of the AmpR Regulator in Virulence"],"prefix":"10.1128","volume":"56","author":[{"given":"Claire","family":"Hennequin","sequence":"first","affiliation":[{"name":"Clermont Universit\u00e9, Universit\u00e9 d'Auvergne, UFR Pharmacie, Laboratoire de Bact\u00e9riologie, Clermont-Ferrand, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fr\u00e9d\u00e9ric","family":"Robin","sequence":"additional","affiliation":[{"name":"CHU de Clermont-Ferrand, Laboratoire de Bact\u00e9riologie Clinique, Clermont-Ferrand, France"},{"name":"Clermont Universit\u00e9, Universit\u00e9 d'Auvergne, JE2526 (Evolution des Bact\u00e9ries Pathog\u00e8nes et Susceptibilit\u00e9 G\u00e9n\u00e9tique de l'H\u00f4te), Clermont-Ferrand, France"},{"name":"INRA, USC2018, Clermont-Ferrand, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nad\u00e8ge","family":"Cabrolier","sequence":"additional","affiliation":[{"name":"Clermont Universit\u00e9, Universit\u00e9 d'Auvergne, UFR Pharmacie, Laboratoire de Bact\u00e9riologie, Clermont-Ferrand, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Richard","family":"Bonnet","sequence":"additional","affiliation":[{"name":"CHU de Clermont-Ferrand, Laboratoire de Bact\u00e9riologie Clinique, Clermont-Ferrand, France"},{"name":"Clermont Universit\u00e9, Universit\u00e9 d'Auvergne, JE2526 (Evolution des Bact\u00e9ries Pathog\u00e8nes et Susceptibilit\u00e9 G\u00e9n\u00e9tique de l'H\u00f4te), Clermont-Ferrand, France"},{"name":"INRA, USC2018, Clermont-Ferrand, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Christiane","family":"Forestier","sequence":"additional","affiliation":[{"name":"Clermont Universit\u00e9, Universit\u00e9 d'Auvergne, UFR Pharmacie, Laboratoire de Bact\u00e9riologie, Clermont-Ferrand, France"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"235","reference":[{"key":"e_1_3_1_2_2","doi-asserted-by":"publisher","DOI":"10.1016\/S1369-5274(99)00005-3"},{"key":"e_1_3_1_3_2","doi-asserted-by":"crossref","first-page":"685","DOI":"10.1111\/j.1462-2920.2007.01491.x","article-title":"The characterization of functions involved in the establishment and maturation of Klebsiella pneumoniae in vitro biofilm reveals dual roles for surface exopolysaccharides","volume":"10","author":"Balestrino D","year":"2008","unstructured":"BalestrinoD GhigoJM CharbonnelN HaagensenJA ForestierC. 2008. 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