{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T13:59:18Z","timestamp":1790171958499,"version":"4.1.0"},"reference-count":18,"publisher":"American Society for Microbiology","license":[{"start":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T00:00:00Z","timestamp":1790121600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T00:00:00Z","timestamp":1790121600000},"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":["Microbiol Spectr"],"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title\/>\n                    <jats:p>\n                      <jats:italic toggle=\"yes\">Pseudomonas aeruginosa<\/jats:italic>\n                      can develop carbapenem resistance through chromosomal mechanisms and\/or by acquiring plasmid-mediated carbapenemases, including the most prevalent metallo-\u03b2-lactamases (MBLs) and\/or extended-spectrum \u03b2-lactamases (ESBLs). Conventional \u03b2-lactam susceptibility testing does not reliably discriminate MBL\/ESBL-producing carbapenem-resistant\n                      <jats:italic toggle=\"yes\">P. aeruginosa<\/jats:italic>\n                      (MBL\/ESBL-CRPA) from non-carbapenemase-producing isolates, here referred to as AmpC-hyperproducers. However, these groups exhibit distinct susceptibility patterns to novel \u03b2-lactam\/\u03b2-lactamase inhibitor (BL\/BLI) combinations, including ceftolozane\/tazobactam (C\/T), ceftazidime\/avibactam (C\/A), imipenem\/relebactam (I\/R), and meropenem\/vaborbactam (M\/V). We investigated potential screening cut-offs for detecting MBL\/ESBL production in CRPA using the VITEK-2 AST-N443 and Phoenix NMIC-486 cards. Antimicrobial susceptibility testing was performed using the VITEK-2 AST-N443 and Phoenix NMIC-486 cards on 135 whole-genome-sequenced international CRPA isolates resistant by disc diffusion to ceftazidime, cefepime, imipenem, and\/or meropenem. The collection included 71 MBL-producing isolates, of which nine co-produced ESBLs, as well as one KPC-2-, one GES-5-, and twelve ESBL-only producers. The remaining 50 represented AmpC-hyperproducers. MIC distributions were analyzed to identify discriminatory screening cut-offs. C\/T was the most discriminatory BL\/BLI combination for differentiating MBL\/ESBL-CRPA from AmpC-hyperproducers. For the VITEK-2 AST-N443, a C\/T MIC \u226532 mg\/L achieved 100% sensitivity for MBL\u00b1ESBL detection (71\/71) and 91.7% sensitivity for ESBL-only producers (11\/12), with 82% specificity (41\/50). For the Phoenix NMIC-486, a C\/T MIC &gt;8 mg\/L achieved 100% sensitivity for both MBL and ESBL detection, with 80% specificity (40\/50). Combining additional BL\/BLI agents did not further improve specificity. Elevated C\/T MICs represent reliable phenotypic screening markers for MBL and ESBL production in CRPA using both the VITEK-2 AST-N443 and Phoenix NMIC-486 systems.\n                    <\/jats:p>\n                    <jats:sec>\n                      <jats:title>IMPORTANCE<\/jats:title>\n                      <jats:p>\n                        Rapid identification of the underlying resistance mechanism in carbapenem-resistant\n                        <jats:italic toggle=\"yes\">Pseudomonas aeruginosa<\/jats:italic>\n                        (CRPA) is essential for effective treatment and infection control. Differentiating high-level resistance acquired via plasmid-borne carbapenemases and\/or extended-spectrum \u03b2-lactamases (ESBLs) from resistance driven by intrinsic mechanisms, including AmpC-type \u03b2-lactamase hyperproduction, remains challenging because conventional antimicrobial susceptibility testing (AST) using classic \u03b2-lactams cannot reliably separate these phenotypes. This distinction is relevant because many recently introduced \u03b2-lactam\/\u03b2-lactamase inhibitor combinations are inactive against metallo-\u03b2-lactamase (MBL) carbapenemase-producing isolates but may remain active against strains in which resistance is driven by intrinsic mechanisms. Detection of acquired carbapenemases may also trigger enhanced infection-control measures and epidemiological investigations. Our study identifies reliable screening cut-offs for MBL- and ESBL-production in CRPA using standard VITEK 2 and Phoenix automated AST panels. This readily available approach may accelerate detection, support routine laboratory workflows, reduce unnecessary confirmatory testing, and facilitate earlier targeted therapy and infection-control interventions in laboratories using these systems worldwide without requiring additional specialized testing or infrastructure.\n                      <\/jats:p>\n                    <\/jats:sec>\n                  <\/jats:sec>","DOI":"10.1128\/spectrum.02235-26","type":"journal-article","created":{"date-parts":[[2026,9,23]],"date-time":"2026-09-23T13:00:17Z","timestamp":1790168417000},"update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Phenotypic screening for metallo-\u03b2-lactamases and extended-spectrum \u03b2-lactamases in\n                    <i>Pseudomonas aeruginosa<\/i>\n                    using the VITEK-2 AST-N443 and Phoenix NMIC-486 cards"],"prefix":"10.1128","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4516-5952","authenticated-orcid":true,"given":"Stefano","family":"Mancini","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/02crff812","id-type":"ROR","asserted-by":"publisher"}],"name":"Institute of Medical Microbiology, University of Zurich","place":["Z\u00fcrich, Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Linda","family":"Mueller","sequence":"additional","affiliation":[{"name":"Istituto di Medicina di Laboratorio EOC","place":["Bellinzona, Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9492-9088","authenticated-orcid":true,"given":"Silvio D.","family":"Brugger","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/02crff812","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Infectious Diseases and Hospital Epidemiology, University of Zurich, University Hospital Zurich","place":["Z\u00fcrich, Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6082-5114","authenticated-orcid":true,"given":"Helena M. B.","family":"Seth-Smith","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/02crff812","id-type":"ROR","asserted-by":"publisher"}],"name":"Institute of Medical Microbiology, University of Zurich","place":["Z\u00fcrich, Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2890-5384","authenticated-orcid":true,"given":"Peter M.","family":"Keller","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/02s6k3f65","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Laboratory Medicine, Clinical Bacteriology\/Mycology, University of Basel","place":["Basel, Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Natalia","family":"Kolesnik-Goldmann","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/02crff812","id-type":"ROR","asserted-by":"publisher"}],"name":"Institute of Medical Microbiology, University of Zurich","place":["Z\u00fcrich, Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Muhammad Ali","family":"Syed","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/05vtb1235","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Microbiology, The University of Haripur","place":["Haripur, Pakistan"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3435-4723","authenticated-orcid":true,"given":"Tim","family":"Roloff","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/02crff812","id-type":"ROR","asserted-by":"publisher"}],"name":"Institute of Medical Microbiology, University of Zurich","place":["Z\u00fcrich, Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1761-0812","authenticated-orcid":true,"given":"Oliver","family":"Nolte","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/02crff812","id-type":"ROR","asserted-by":"publisher"}],"name":"Institute of Medical Microbiology, University of Zurich","place":["Z\u00fcrich, Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"235","published-online":{"date-parts":[[2026,9,23]]},"reference":[{"key":"e_1_3_2_2_2","unstructured":"WHO. 2024. 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