{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,5,14]],"date-time":"2025-05-14T04:17:53Z","timestamp":1747196273019,"version":"3.40.5"},"reference-count":30,"publisher":"Public Library of Science (PLoS)","issue":"7","license":[{"start":{"date-parts":[[2022,7,8]],"date-time":"2022-07-08T00:00:00Z","timestamp":1657238400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS ONE"],"abstract":"<jats:sec id=\"sec001\">\n<jats:title>Introduction<\/jats:title>\n<jats:p>Thymine auxotrophic in vitro mutants of <jats:italic>Escherichia coli<\/jats:italic> were first reported in the mid-20th century. Later, thymine-dependent clinical strains of <jats:italic>E<\/jats:italic>. <jats:italic>coli<\/jats:italic> as well as other Enterobacterales, <jats:italic>Enterococcus faecalis<\/jats:italic> and <jats:italic>Staphylococcus aureus<\/jats:italic> have been recognized as the cause of persistent and recurrent infections.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec002\">\n<jats:title>Objectives<\/jats:title>\n<jats:p>The aim of this study was to characterize the phenotype and investigate the molecular basis of thymine auxotrophy in ten <jats:italic>E<\/jats:italic>. <jats:italic>coli<\/jats:italic> isolates obtained at different time points from a patient with recurrent bloodstream infection (BSI) due to a chronic aortic graft infection treated with Trimethoprim\/sulfamethoxazole (TMP-SMX).<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec003\">\n<jats:title>Methods<\/jats:title>\n<jats:p>Clinical data was obtained from hospital records. Growth characterization and antimicrobial susceptibility testing to TMP-SMX was performed on M9 agar and in MH broth with different thymine concentrations (0.5, 2, 5, 10 and 20 \u03bcg\/mL), on Mueller-Hinton (MH) and blood agar. Whole genome sequencing (WGS) was performed on all <jats:italic>E<\/jats:italic>. <jats:italic>coli<\/jats:italic> isolates.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec004\">\n<jats:title>Results<\/jats:title>\n<jats:p><jats:italic>E<\/jats:italic>. <jats:italic>coli<\/jats:italic> were isolated from ten consecutive BSI episodes from a patient with chronic aortic graft infection. Six of these isolates were resistant to TMP-SMX when assayed on blood agar. Growth experiments with added thymine confirmed that these isolates were thymine-dependent (<jats:italic>thy-<\/jats:italic>), and revealed growth defects (slower growth rate and smaller colony size) in these isolates relative to <jats:italic>thy+<\/jats:italic> isolates (n = 4). WGS indicated that all isolates were of the same clonal lineage of sequence type 7358. Genomic analysis revealed a G172C substitution in <jats:italic>thyA<\/jats:italic> in all TMP-SMX resistant isolates, while mutations affecting genes involved in the deoxyribose salvage pathway (<jats:italic>deoB<\/jats:italic> and <jats:italic>deoC<\/jats:italic>) were identified in eight isolates.<\/jats:p>\n<\/jats:sec>\n<jats:sec id=\"sec005\">\n<jats:title>Conclusion<\/jats:title>\n<jats:p>This case highlights the risk of resistance development to TMP-SMX, especially for long-term treatment, and the possible pitfalls in detection of growth-deficient subpopulations from chronic infections, which could lead to treatment failure.<\/jats:p>\n<\/jats:sec>","DOI":"10.1371\/journal.pone.0270256","type":"journal-article","created":{"date-parts":[[2022,7,8]],"date-time":"2022-07-08T18:01:46Z","timestamp":1657303306000},"page":"e0270256","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":4,"title":["Phenotypic and genotypic characterisation of thymine auxotrophy in Escherichia coli isolated from a patient with recurrent bloodstream infection"],"prefix":"10.1371","volume":"17","author":[{"given":"Aleksandra","family":"Jakovljev","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2489-4179","authenticated-orcid":true,"given":"Jan Egil","family":"Afset","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kjersti","family":"Haugum","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Harald Otto","family":"Steinum","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Torunn","family":"Gresdal R\u00f8nning","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5525-2614","authenticated-orcid":true,"given":"\u00d8rjan","family":"Samuelsen","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9605-3283","authenticated-orcid":true,"given":"Christina Gabrielsen","family":"\u00c5s","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"340","published-online":{"date-parts":[[2022,7,8]]},"reference":[{"key":"pone.0270256.ref001","first-page":"1201","volume-title":"Manual of Clinical Microbiology","author":"James S. 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