{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T18:58:40Z","timestamp":1785437920138,"version":"3.56.0"},"reference-count":17,"publisher":"American Society for Microbiology","issue":"4","license":[{"start":{"date-parts":[[2026,4,8]],"date-time":"2026-04-08T00:00:00Z","timestamp":1775606400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,4,8]],"date-time":"2026-04-08T00:00:00Z","timestamp":1775606400000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"funder":[{"DOI":"10.13039\/100015257","name":"Northeastern University","doi-asserted-by":"publisher","award":["Carole Shapazian Research Co-op Fellowship"],"award-info":[{"award-number":["Carole Shapazian Research Co-op Fellowship"]}],"id":[{"id":"10.13039\/100015257","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100011495","name":"Massachusetts Life Science Center","doi-asserted-by":"crossref","award":["Novel Therapeutics Delivery Grant"],"award-info":[{"award-number":["Novel Therapeutics Delivery Grant"]}],"id":[{"id":"10.13039\/100011495","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["J Clin Microbiol"],"published-print":{"date-parts":[[2026,4,8]]},"abstract":"ABSTRACT<\/jats:title>\n \n \n \n Agar dilution is a reference susceptibility testing method uniquely or preferentially recommended for certain antimicrobials. However, the effort required to pour individual agar plates spanning a doubling dilution range precludes its practical implementation in hospital clinical laboratories. Here, we describe an on-demand replacement for agar dilution, specifically substituting Poloxamer 407 (also known as Pluronic F-127) for Bacto agar as the solidifying agent. Notably, 20% Poloxamer 407 solutions (e.g., with Mueller\u2013Hinton broth) remain liquid at refrigerated temperatures but solidify upon warming, enabling facile setup of poloxamer dilution testing in Petri dish or microwell format. For fosfomycin susceptibility testing, poloxamer dilution and reference agar dilution showed excellent categorical agreement (CA) and essential agreement (EA) for\n Escherichia coli<\/jats:italic>\n (100% and 87%, respectively,\n n<\/jats:italic>\n = 31). For other\n Enterobacterales<\/jats:italic>\n , excluding\n Klebsiella<\/jats:italic>\n spp., CA and EA were both 82% (\n n<\/jats:italic>\n = 17, respectively). For\n Pseudomonas aeruginosa<\/jats:italic>\n , CA and EA were 60% and 100% (\n n<\/jats:italic>\n = 10), respectively, with the lower CA reflecting the large number of strains tested with minimal inhibitory concentrations near categorical breakpoints. There were no very major errors, while major errors were only observed for\n Klebsiella<\/jats:italic>\n spp. Additionally, poloxamer dilution substantially reduced the number of skipped dilutions sixfold for\n E. coli<\/jats:italic>\n (\n P<\/jats:italic>\n < 0.0001) and inhibited swarming of\n Proteus<\/jats:italic>\n spp. We conclude that poloxamer dilution and agar dilution, an imperfect gold standard, have essentially equivalent practical performance and that poloxamer dilution can therefore serve as an on-demand alternative testing methodology in clinical laboratories for fosfomycin testing of gram-negative pathogens. A broader exploration of poloxamer dilution\u2019s utility is thus warranted.\n <\/jats:p>\n <\/jats:sec>\n \n IMPORTANCE<\/jats:title>\n \n Accurate antibiotic susceptibility testing is essential for guiding treatment of bacterial infections. For the antibiotic fosfomycin, used to treat\n Escherichia coli<\/jats:italic>\n urinary tract infections, the most reliable testing method requires solid media prepared by hand for each antibiotic concentration, which is too time-consuming for most clinical laboratories to perform. Our study shows that replacing agar with an alternative temperature-sensitive gelling agent called poloxamer enables laboratories to prepare solid test plates rapidly without special equipment. This approach, which is essentially identical to traditional agar dilution, provides a practical means for performing reference-quality minimal inhibitory concentration (MIC) testing near the point of patient care, as demonstrated for fosfomycin, for which current FDA-cleared methods do not provide MIC data. This strategy may also be applicable to other drugs for which agar dilution is the preferred testing method, supporting expedited testing to inform treatment decisions for bacterial infections.\n <\/jats:p>\n <\/jats:sec>","DOI":"10.1128\/jcm.01822-25","type":"journal-article","created":{"date-parts":[[2026,3,5]],"date-time":"2026-03-05T14:00:12Z","timestamp":1772719212000},"update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":1,"title":["Poloxamer dilution as an on-demand alternative to agar dilution-based antimicrobial susceptibility testing"],"prefix":"10.1128","volume":"64","author":[{"given":"Matthew T. J.","family":"Uy","sequence":"first","affiliation":[{"name":"Beth Israel Deaconess Medical Center","place":["Boston, USA"]},{"id":[{"id":"https:\/\/ror.org\/02ahky613","id-type":"ROR","asserted-by":"publisher"}],"name":"Northeastern University","place":["Boston, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andrea","family":"Kirmaier","sequence":"additional","affiliation":[{"name":"Beth Israel Deaconess Medical Center","place":["Boston, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lindsey M.","family":"Rudtner","sequence":"additional","affiliation":[{"name":"Beth Israel Deaconess Medical Center","place":["Boston, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Aidan","family":"Pine","sequence":"additional","affiliation":[{"name":"Beth Israel Deaconess Medical Center","place":["Boston, USA"]},{"id":[{"id":"https:\/\/ror.org\/02ahky613","id-type":"ROR","asserted-by":"publisher"}],"name":"Northeastern University","place":["Boston, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0392-4500","authenticated-orcid":true,"given":"James E.","family":"Kirby","sequence":"additional","affiliation":[{"name":"Beth Israel Deaconess Medical Center","place":["Boston, USA"]},{"name":"Harvard Medical School","place":["Boston, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"235","reference":[{"key":"e_1_3_3_2_2","volume-title":"Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically; approved standard - tenth edition","author":"CLSI","year":"2015","unstructured":"CLSI. 2015. CLSI document M07-A10. In Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically; approved standard - tenth edition. Clinical and Laboratory Standards Institute, Wayne, PA."},{"key":"e_1_3_3_3_2","volume-title":"Methods for antimicrobial dilution and disk susceptibility testing of infrequently isolated or fastidious bacteria","author":"CLSI","year":"2016","unstructured":"CLSI. 2016. CLSI guideline M45. In Methods for antimicrobial dilution and disk susceptibility testing of infrequently isolated or fastidious bacteria, 3rd ed. Clinical and Laboratory Standards Institute, Wayne, PA.","edition":"3"},{"key":"e_1_3_3_4_2","volume-title":"Performance standards for antimicrobial susceptibility testing; twenty-seventh informational supplement","author":"Clinical and Laboratory Standards Institute (CLSI)","year":"2017","unstructured":"Clinical and Laboratory Standards Institute (CLSI). 2017. CLSI document M100\u2013S27. In Performance standards for antimicrobial susceptibility testing; twenty-seventh informational supplement. Clinical and Laboratory Standards Institute, Wayne, PA."},{"key":"e_1_3_3_5_2","doi-asserted-by":"publisher","DOI":"10.1086\/647952"},{"key":"e_1_3_3_6_2","doi-asserted-by":"publisher","DOI":"10.1128\/spectrum.04205-23"},{"key":"e_1_3_3_7_2","doi-asserted-by":"publisher","DOI":"10.1093\/jac\/dkx241"},{"key":"e_1_3_3_8_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.jgar.2020.01.003"},{"key":"e_1_3_3_9_2","unstructured":"European Committee on Antimicrobial Susceptibility Testing (EUCAST). 2026. Breakpoint tables for interpretation of MICs and zone diameters. Version 16.0. V\u00e4xj\u00f6 Sweden"},{"key":"e_1_3_3_10_2","doi-asserted-by":"publisher","DOI":"10.1016\/S1473-3099(09)70325-1"},{"key":"e_1_3_3_11_2","doi-asserted-by":"publisher","DOI":"10.1177\/2472630317727721"},{"key":"e_1_3_3_12_2","doi-asserted-by":"publisher","DOI":"10.3390\/molecules27103063"},{"key":"e_1_3_3_13_2","doi-asserted-by":"publisher","DOI":"10.3390\/polym13193376"},{"key":"e_1_3_3_14_2","doi-asserted-by":"publisher","DOI":"10.3390\/polym14245353"},{"key":"e_1_3_3_15_2","doi-asserted-by":"publisher","DOI":"10.1128\/JCM.01415-17"},{"key":"e_1_3_3_16_2","doi-asserted-by":"publisher","DOI":"10.1128\/AAC.01374-19"},{"key":"e_1_3_3_17_2","doi-asserted-by":"publisher","unstructured":"Brennan-Krohn T Kirby JE. 2019. Antimicrobial synergy testing by the inkjet printer-assisted automated checkerboard array and the manual time-kill method. J Vis Exp. doi:10.3791\/58636","DOI":"10.3791\/58636"},{"key":"e_1_3_3_18_2","doi-asserted-by":"publisher","DOI":"10.1128\/JCM.00932-16"}],"container-title":["Journal of Clinical Microbiology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/journals.asm.org\/doi\/pdf\/10.1128\/jcm.01822-25","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/journals.asm.org\/doi\/pdf\/10.1128\/jcm.01822-25","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,8]],"date-time":"2026-04-08T13:00:45Z","timestamp":1775653245000},"score":1,"resource":{"primary":{"URL":"https:\/\/journals.asm.org\/doi\/10.1128\/jcm.01822-25"}},"subtitle":[],"editor":[{"given":"Jennifer","family":"Dien Bard","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"editor"}]}],"short-title":[],"issued":{"date-parts":[[2026,4,8]]},"references-count":17,"journal-issue":{"issue":"4","published-print":{"date-parts":[[2026,4,8]]}},"alternative-id":["10.1128\/jcm.01822-25"],"URL":"https:\/\/doi.org\/10.1128\/jcm.01822-25","relation":{"has-preprint":[{"id-type":"doi","id":"10.64898\/2025.12.09.693179","asserted-by":"object"}]},"ISSN":["0095-1137","1098-660X"],"issn-type":[{"value":"0095-1137","type":"print"},{"value":"1098-660X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,4,8]]},"assertion":[{"value":"2025-12-08","order":0,"name":"received","label":"Received","group":{"name":"publication_history","label":"Publication History"}},{"value":"2026-01-25","order":2,"name":"accepted","label":"Accepted","group":{"name":"publication_history","label":"Publication History"}},{"value":"2026-03-05","order":3,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}],"article-number":"e01822-25"}}