{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,24]],"date-time":"2026-03-24T03:01:47Z","timestamp":1774321307057,"version":"3.50.1"},"reference-count":20,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2025,1,21]],"date-time":"2025-01-21T00:00:00Z","timestamp":1737417600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"CINTESIS","award":["UIDP\/4255\/2020"],"award-info":[{"award-number":["UIDP\/4255\/2020"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJMS"],"abstract":"<jats:p>Urinary tract infections caused by Gram-negative bacteria (GNB) are among the most common infections and a significant cause of sepsis. The increasing prevalence of multidrug-resistant (MDR) bacteria poses challenges to empirical treatment. Colistin may be used a last-resort antibiotic for treating MDR infections, but this requires the rapid determination of susceptibility to colistin. Traditional susceptibility testing methods can take up to 48 h, and there are specific challenges in determining colistin susceptibility. This study evaluates a novel, rapid method for determining colistin susceptibility directly from positive urine samples using the FASTcolistin MIC kit from FASTinov\u00ae. A total of 100 urine samples positive for Gram-negative bacilli when screened by the UF-1000i system were included in this study. After a simple sample prep, the same bacterial suspension was used for identification on MALDI-TOF and inoculated in the FASTcolistin MIC panel for our AST; after incubation at 37 \u00b0C for 1 h, it was analyzed via flow cytometry using a CytoFLEX cytometer (Beckman Coulter, Brea, CA, USA). The categorical susceptibility to colistin according to EUCAST or CLSI standards as well as the MIC values were given by bioFAST software (bioFAST 2.0). The essential agreement (EA) and bias were calculated. Different species of Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter spp. were correctly identified by MALDI-TOF directly from the FASTcolistin MIC sample prep. The essential agreement between the two methods was 99%, with a bias of \u221217%. Both identification and susceptibility were obtained in less than 2 h. This study presents a rapid and accurate method for determining colistin MIC directly from urine samples. The shortness of time required to produce a result, 2 h versus 48 h with the conventional methods, will significantly impact treatment decisions, especially in urinary tract infections difficult to treat.<\/jats:p>","DOI":"10.3390\/ijms26030883","type":"journal-article","created":{"date-parts":[[2025,1,21]],"date-time":"2025-01-21T08:46:26Z","timestamp":1737449186000},"page":"883","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Rapid Determination of Colistin Susceptibility by Flow Cytometry Directly from Positive Urine Samples\u2014Preliminary Results"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-6244-9987","authenticated-orcid":false,"given":"Daniela","family":"Fonseca-Silva","sequence":"first","affiliation":[{"name":"Department of Clinical Pathology, Instituto Portugu\u00eas de Oncologia, 4200-072 Porto, Portugal"}]},{"given":"Ros\u00e1rio","family":"Gomes","sequence":"additional","affiliation":[{"name":"FASTinov SA, 4200-135 Porto, Portugal"}]},{"given":"In\u00eas","family":"Martins-Oliveira","sequence":"additional","affiliation":[{"name":"FASTinov SA, 4200-135 Porto, Portugal"}]},{"given":"Ana","family":"Silva-Dias","sequence":"additional","affiliation":[{"name":"FASTinov SA, 4200-135 Porto, Portugal"},{"name":"RISE\u2014Health Department of Pathology, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal"}]},{"given":"Maria Helena","family":"Ramos","sequence":"additional","affiliation":[{"name":"Department of Microbiology, Centro Hospitalar e Universit\u00e1rio do Porto, 4099-001 Porto, Portugal"}]},{"given":"Cid\u00e1lia","family":"Pina-Vaz","sequence":"additional","affiliation":[{"name":"FASTinov SA, 4200-135 Porto, Portugal"},{"name":"RISE\u2014Health Department of Pathology, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal"},{"name":"Department of Microbiology, Faculty of Medicine, University of Porto, 4200-319 Porto, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2025,1,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"191","DOI":"10.2147\/CEOR.S234840","article-title":"Contributing Factors to the Clinical and Economic Burden of Patients with Laboratory-Confirmed Carbapenem-Nonsusceptible Gram-Negative Urinary Tract Infections","volume":"12","author":"McCann","year":"2020","journal-title":"Clin. 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