{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,4]],"date-time":"2026-08-04T13:46:14Z","timestamp":1785851174962,"version":"3.56.0"},"reference-count":28,"publisher":"American Society for Microbiology","issue":"8","license":[{"start":{"date-parts":[[2026,8,5]],"date-time":"2026-08-05T00:00:00Z","timestamp":1785888000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,8,5]],"date-time":"2026-08-05T00:00:00Z","timestamp":1785888000000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"funder":[{"DOI":"10.13039\/501100001665","name":"Agence Nationale de la Recherche","doi-asserted-by":"publisher","award":["ANR-20-PAMR-0010"],"award-info":[{"award-number":["ANR-20-PAMR-0010"]}],"id":[{"id":"10.13039\/501100001665","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001677","name":"Institut National de la Sant\u00e9 et de la Recherche M\u00e9dicale","doi-asserted-by":"publisher","award":["UMR1184"],"award-info":[{"award-number":["UMR1184"]}],"id":[{"id":"10.13039\/501100001677","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Assistance Publique-H\u00f4pitaux de Paris","award":["Resist"],"award-info":[{"award-number":["Resist"]}]},{"DOI":"10.13039\/501100007241","name":"Universit\u00e9 Paris-Saclay","doi-asserted-by":"publisher","award":["Healthi"],"award-info":[{"award-number":["Healthi"]}],"id":[{"id":"10.13039\/501100007241","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Tunisian Ministry of Higher Education","award":["JPI-AMR- PAIRWISE"],"award-info":[{"award-number":["JPI-AMR- PAIRWISE"]}]}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["Antimicrob Agents Chemother"],"published-print":{"date-parts":[[2026,8,5]]},"abstract":"ABSTRACT<\/jats:title>\n \n \n \n Putative novel \u03b2-lactamase-encoding genes are increasingly identified in whole-genome sequencing (WGS) data, often without phenotypic or biochemical characterization. Here, we characterized the chromosome-encoded GUA-1 Ambler class A \u03b2-lactamase from the clinical isolate\n Pseudomonas guariconensis-like<\/jats:italic>\n 65411. Among the 40\n P. guariconensis<\/jats:italic>\n genomes available in the GenBank database, only 8 carried a\n bla<\/jats:italic>\n GUA-like<\/jats:sub>\n gene, whereas the others encoded an AmpC \u03b2-lactamase, suggesting the existence of two distinct subspecies. Notably, these eight isolates, despite originating from diverse geographical regions, all harbored the\n bla<\/jats:italic>\n GUA-like<\/jats:sub>\n gene inserted at the same chromosomal locus. Heterologous expression in\n Pseudomonas aeruginosa<\/jats:italic>\n and\n Escherichia coli<\/jats:italic>\n revealed a clavulanic-acid-inhibited cefotaximase-type ESBL. GUA-1 shared 72% amino acid sequence identity with putative Ambler class A \u03b2-lactamases from\n Pseudomonas fulva<\/jats:italic>\n ,\n Pseudomonas mosselii<\/jats:italic>\n , and\n Pseudomonas soli<\/jats:italic>\n , and 57% with LUT-1, a class A cephalosporinase from\n Pseudomonas luteola<\/jats:italic>\n . Kinetic analyses showed that GUA-1 hydrolyzed cefotaxime but not ceftazidime, similarly to LUT-1 and CTX-M-1-type ESBLs. IC\n 50<\/jats:sub>\n measurements indicated strong inhibition by clavulanic acid, tazobactam, and avibactam, but not by vaborbactam. Molecular modeling supported these findings, showing favorable binding of cefotaxime in the active site, whereas steric hindrance from Trp274 and electrostatic repulsion from Asp240 likely prevent ceftazidime binding. The\n bla<\/jats:italic>\n GUA-1<\/jats:sub>\n gene was chromosomally located, with no obvious promoter identified in the immediate upstream region. RT-PCR experiments revealed expression levels comparable to other \u03b2-lactamase genes present (\n bla<\/jats:italic>\n DHA<\/jats:sub>\n ,\n bla<\/jats:italic>\n CMY<\/jats:sub>\n ,\n bla<\/jats:italic>\n OXA-1<\/jats:sub>\n , and\n bla<\/jats:italic>\n OXA-204<\/jats:sub>\n ) and to the upstream-located\n Na+\/H<\/jats:italic>\n antiporter gene. 5\u2032 RACE experiments suggested that the\n bla<\/jats:italic>\n GUA-1<\/jats:sub>\n gene is co-transcribed along with the\n Na+\/H<\/jats:italic>\n gene. Overall, this study highlights the diversity of \u03b2-lactamases within\n Pseudomonas<\/jats:italic>\n species.\n <\/jats:p>\n <\/jats:sec>","DOI":"10.1128\/aac.00126-26","type":"journal-article","created":{"date-parts":[[2026,6,30]],"date-time":"2026-06-30T13:59:05Z","timestamp":1782827945000},"update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Characterization of GUA-1, a chromosomally encoded ESBL from\n Pseudomonas guariconensis-like<\/i>"],"prefix":"10.1128","volume":"70","author":[{"given":"Saoussen","family":"Oueslati","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/03xjwb503","id-type":"ROR","asserted-by":"publisher"}],"name":"Team 'Resist', UMR1184 IDMIT (INSERM, Universit\u00e9 Paris-Saclay, CEA), Faculty of Medicine","place":["Le Kremlin-Bic\u00eatre, France"]},{"id":[{"id":"https:\/\/ror.org\/05c9p1x46","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of 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