{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,18]],"date-time":"2026-06-18T07:02:56Z","timestamp":1781766176462,"version":"3.54.5"},"reference-count":58,"publisher":"Public Library of Science (PLoS)","issue":"6","license":[{"start":{"date-parts":[[2021,6,17]],"date-time":"2021-06-17T00:00:00Z","timestamp":1623888000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100000002","name":"National Institutes of Health","doi-asserted-by":"publisher","award":["1R01EB021331"],"award-info":[{"award-number":["1R01EB021331"]}],"id":[{"id":"10.13039\/100000002","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100008982","name":"National Science Foundation","doi-asserted-by":"publisher","award":["NNCI-1542081"],"award-info":[{"award-number":["NNCI-1542081"]}],"id":[{"id":"10.13039\/501100008982","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS ONE"],"abstract":"<jats:p><jats:italic>N<\/jats:italic>. <jats:italic>gonorrhoeae<\/jats:italic> is one of the most pressing antibiotic resistant threats of our time and low-cost diagnostics that can easily identify antibiotic resistance are desperately needed. However, <jats:italic>N<\/jats:italic>. <jats:italic>gonorrhoeae<\/jats:italic> responds so uniquely to growth conditions that it cannot be assumed gonorrhea will respond to common microbiological methods used for other pathogenic organisms. In this paper, we explore visual colorimetric indicators of <jats:italic>N<\/jats:italic>. <jats:italic>gonorrhoeae<\/jats:italic> growth that can be seen without a microscope or spectrophotometer. We evaluate growth media, pH indicators, resazurin-based dyes, and tetrazolium-based dyes for their use in simple colorimetric system. Overall, we identified Graver Wade media as the best at supporting robust gonococcal growth while also providing the least background when analyzing results of colorimetric tests. XTT, a tetrazolium-based dye, proved to show to brightest color change over time and not negatively impact the natural growth of <jats:italic>N<\/jats:italic>. <jats:italic>gonorrhoeae<\/jats:italic>. However, other dyes including PrestoBlue, MTT, and NBT are less expensive than XTT and work well when added after bacterial growth has already occurred. By identifying the specific use cases of these dyes, this research lays the groundwork for future development of a color-based antibiotic susceptibility low-cost test for <jats:italic>N<\/jats:italic>. <jats:italic>gonorrhoeae<\/jats:italic>.<\/jats:p>","DOI":"10.1371\/journal.pone.0252961","type":"journal-article","created":{"date-parts":[[2021,6,17]],"date-time":"2021-06-17T17:31:22Z","timestamp":1623951082000},"page":"e0252961","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":7,"title":["Visible colorimetric growth indicators of Neisseria gonorrhoeae for low-cost diagnostic applications"],"prefix":"10.1371","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8544-9656","authenticated-orcid":true,"given":"Taylor Mae","family":"Oeschger","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1624-9711","authenticated-orcid":true,"given":"David Carl","family":"Erickson","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"340","published-online":{"date-parts":[[2021,6,17]]},"reference":[{"key":"pone.0252961.ref001","author":"WHO","year":"2009","journal-title":"Global Health Risks"},{"key":"pone.0252961.ref002","article-title":"New Study Supports Expanded Testing for Gonorrhea and Chlamydia","author":"NIAID","year":"2019","journal-title":"NIAID NOW"},{"key":"pone.0252961.ref003","volume":"114","author":"United States Centers for Disease Control","year":"2013","journal-title":"Antibiotic resistance threats in the United States, 2013"},{"key":"pone.0252961.ref004","doi-asserted-by":"crossref","first-page":"1791","DOI":"10.1056\/NEJMp1812269","article-title":"Neisseria gonorrhoeae\u2014Rising Infection Rates, Dwindling Treatment Options","volume":"379","author":"S Blank","year":"2018","journal-title":"N Engl J Med"},{"key":"pone.0252961.ref005","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pone.0237424","article-title":"Developing target product profiles for Neisseria gonorrhoeae diagnostics in the context of antimicrobial resistance: An expert consensus","volume":"15","author":"C Ferreyra","year":"2020","journal-title":"PLoS One"},{"key":"pone.0252961.ref006","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1371\/journal.pone.0196209","article-title":"Beyond syndromic management: Opportunities for diagnosis-based treatment of sexually transmitted infections in low- and middle-income countries","volume":"13","author":"NJ Garrett","year":"2018","journal-title":"PLoS One"},{"key":"pone.0252961.ref007","doi-asserted-by":"crossref","first-page":"359","DOI":"10.1071\/SH19233","article-title":"Peer-delivered point-of-care testing for Chlamydia trachomatis and Neisseria gonorrhoeae within an urban community setting: A cross-sectional analysis","volume":"17","author":"SFE Bell","year":"2020","journal-title":"Sex Health"},{"key":"pone.0252961.ref008","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1371\/journal.ppat.1005611","article-title":"Antibiotic-Resistant Neisseria gonorrhoeae Spread Faster with More Treatment, Not More Sexual Partners","volume":"12","author":"SM Fingerhuth","year":"2016","journal-title":"PLoS Pathog"},{"key":"pone.0252961.ref009","doi-asserted-by":"crossref","first-page":"803","DOI":"10.1080\/14737159.2020.1778467","article-title":"Point-by-Point Progress: Gonorrhea Point of Care Tests","volume":"20","author":"CA Gaydos","year":"2020","journal-title":"Expert Rev Mol Diagn"},{"key":"pone.0252961.ref010","doi-asserted-by":"crossref","first-page":"118","DOI":"10.1093\/jac\/dkx333","article-title":"High levels of susceptibility to new and older antibiotics in Neisseria gonorrhoeae isolates from Saskatchewan (2003\u201315): Time to consider point-of-care or molecular testing for precision treatment?","volume":"73","author":"SD Thakur","year":"2018","journal-title":"J Antimicrob Chemother"},{"key":"pone.0252961.ref011","doi-asserted-by":"crossref","first-page":"514","DOI":"10.1071\/SH18235","article-title":"Agent-based modelling study of antimicrobial-resistant Neisseria gonorrhoeae transmission in men who have sex with men: Towards individualised diagnosis and treatment","volume":"16","author":"AK Zienkiewicz","year":"2019","journal-title":"Sex Health"},{"key":"pone.0252961.ref012","volume-title":"Gonococcal antimicrobial susceptibility","author":"World Health Organization","year":"2017"},{"key":"pone.0252961.ref013","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1136\/bmjopen-2016-015447","article-title":"Analysis of the potential for point-of-care test to enable individualised treatment of infections caused by antimicrobial-resistant and susceptible strains of Neisseria gonorrhoeae: A modelling study","volume":"7","author":"KM Turner","year":"2017","journal-title":"BMJ Open"},{"key":"pone.0252961.ref014","doi-asserted-by":"crossref","first-page":"1141","DOI":"10.1093\/infdis\/jix450","article-title":"Impact of rapid susceptibility testing and antibiotic selection strategy on the emergence and spread of antibiotic resistance in Gonorrhea","volume":"216","author":"AR Tuite","year":"2017","journal-title":"J Infect Dis"},{"key":"pone.0252961.ref015","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1186\/s12916-017-0881-x","article-title":"Detection of antibiotic resistance is essential for gonorrhoea point-of-care testing: A mathematical modelling study","volume":"15","author":"SM Fingerhuth","year":"2017","journal-title":"BMC Med"},{"key":"pone.0252961.ref016","doi-asserted-by":"crossref","first-page":"445","DOI":"10.1136\/sti.2010.044230","article-title":"Point-of-care antibiotic susceptibility testing for gonorrhoea: Improving therapeutic options and sparing the use of cephalosporins","volume":"86","author":"ST Sadiq","year":"2010","journal-title":"Sex Transm Infect"},{"key":"pone.0252961.ref017","doi-asserted-by":"crossref","first-page":"S65","DOI":"10.1136\/sextrans-2016-053072","article-title":"Rapid accurate point-of-care tests combining diagnostics and antimicrobial resistance prediction for Neisseria gonorrhoeae and Mycoplasma genitalium","volume":"93","author":"ST Sadiq","year":"2017","journal-title":"Sex Transm Infect"},{"key":"pone.0252961.ref018","doi-asserted-by":"crossref","first-page":"197","DOI":"10.1136\/sextrans-2012-050829","article-title":"Evolution of Neisseria gonorrhoeae is a continuing challenge for molecular detection of gonorrhoea: False negative gonococcal porA mutants are spreading internationally","volume":"89","author":"CA Ison","year":"2013","journal-title":"Sex Transm Infect"},{"key":"pone.0252961.ref019","doi-asserted-by":"crossref","first-page":"367","DOI":"10.1016\/j.ijantimicag.2016.06.009","article-title":"Antibacterial activity of resazurin-based compounds against Neisseria gonorrhoeae in vitro and in vivo","volume":"48","author":"DM Schmitt","year":"2016","journal-title":"Int J Antimicrob Agents"},{"key":"pone.0252961.ref020","doi-asserted-by":"crossref","DOI":"10.1007\/978-1-4939-6960-9","author":"D Gilbert","year":"2017","journal-title":"Cell Viability Assays, Methods and Protocols"},{"key":"pone.0252961.ref021","article-title":"M100 Performance Standards for Antimicrobial Susceptibility Testing","volume":"27","author":"Clinical and Laboratory Standards Institution","year":"2017","journal-title":"J Serv Mark"},{"key":"pone.0252961.ref022","author":"American Type Culture Collection","year":"2006","journal-title":"Neisseria gonorrhoeae (ATCC 49226)"},{"key":"pone.0252961.ref023","volume-title":"United States Centers for Disease Control","year":"2020"},{"key":"pone.0252961.ref024","doi-asserted-by":"crossref","first-page":"3096","DOI":"10.1093\/jac\/dkw288","article-title":"The novel 2016 WHO Neisseria gonorrhoeae reference strains for global quality assurance of laboratory investigations: Phenotypic, genetic and reference genome characterization","volume":"71","author":"M Unemo","year":"2016","journal-title":"J Antimicrob Chemother"},{"key":"pone.0252961.ref025","first-page":"1","article-title":"Laboratory maintenance of Neisseria gonorrhoeae","author":"JM Spence","year":"2008","journal-title":"Curr Protoc Microbiol."},{"key":"pone.0252961.ref026","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1111\/j.1574-6968.2007.00776.x","article-title":"A fully defined, clear and protein-free liquid medium permitting dense growth of Neisseria gonorrhoeae from very low inocula","volume":"273","author":"JJ Wade","year":"2007","journal-title":"FEMS Microbiol Lett"},{"key":"pone.0252961.ref027","first-page":"150","article-title":"Phenotypic MicroArray Screening of Neisseria gonorrhoeae in Chemically Defined Liquid Medium.","author":"BI Baarda","year":"2019","journal-title":"Neisseria gonorrhoeae"},{"key":"pone.0252961.ref028","doi-asserted-by":"crossref","first-page":"4321","DOI":"10.1128\/JCM.43.9.4321-4327.2005","article-title":"Cultivation of Neisseria gonorrhoeae in liquid media and determination of its in vitro susceptibilities to quinolones","volume":"43","author":"M Takei","year":"2005","journal-title":"J Clin Microbiol"},{"key":"pone.0252961.ref029","doi-asserted-by":"crossref","first-page":"49","DOI":"10.17221\/412\/2011-PSE","article-title":"A new simple method for the enumeration of nitrifying bacteria in different environments","volume":"58","author":"KH Elbanna","year":"2012","journal-title":"Plant, Soil Environ."},{"key":"pone.0252961.ref030","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1016\/j.foodcont.2017.06.028","article-title":"On-package dual sensors label based on pH indicators for real-time monitoring of beef freshness","volume":"82","author":"B Kuswandi","year":"2017","journal-title":"Food Control"},{"key":"pone.0252961.ref031","doi-asserted-by":"crossref","first-page":"517","DOI":"10.1097\/00003226-200007000-00023","article-title":"Colorimetric indicators of microbial contamination in corneal preservation medium","volume":"19","author":"YI Chu","year":"2000","journal-title":"Cornea"},{"key":"pone.0252961.ref032","first-page":"141","article-title":"Simple method for detecting penicillinase-producing Neisseria gonorrhoeae and Staphylococcus aureus","volume":"57","author":"EH Sng","year":"1981","journal-title":"Br J Vener Dis"},{"key":"pone.0252961.ref033","doi-asserted-by":"crossref","first-page":"340","DOI":"10.1046\/j.1472-765X.2001.00916.x","article-title":"Application of resazurin for estimating abundance of contaminant-degrading micro-organisms","volume":"32","author":"TF Guerin","year":"2001","journal-title":"Lett Appl Microbiol"},{"key":"pone.0252961.ref034","first-page":"2","author":"PromoKine","year":"2015","journal-title":"Fluorometric Cell Viability Kit I (Resazurin)."},{"key":"pone.0252961.ref035","doi-asserted-by":"crossref","first-page":"2731","DOI":"10.1021\/acs.analchem.9b04991","article-title":"CAST: Capillary-Based Platform for Real-Time Phenotypic Antimicrobial Susceptibility Testing","volume":"92","author":"R Wang","year":"2020","journal-title":"Anal Chem"},{"key":"pone.0252961.ref036","first-page":"1","article-title":"Point-of-care semen analysis of patients with infertility via smartphone and colorimetric paper-based diagnostic device","author":"YT Tsao","year":"2020","journal-title":"Bioeng Transl Med"},{"key":"pone.0252961.ref037","doi-asserted-by":"crossref","first-page":"1","DOI":"10.3390\/mi10080495","article-title":"Paper-based resazurin assay of inhibitor-treated porcine sperm","volume":"10","author":"K Matsuura","year":"2019","journal-title":"Micromachines"},{"key":"pone.0252961.ref038","doi-asserted-by":"crossref","first-page":"174","DOI":"10.1016\/j.snb.2012.10.011","article-title":"Resazurin reduction based colorimetric antibiogram in microfluidic plastic chip","volume":"176","author":"T Elavarasan","year":"2013","journal-title":"Sensors Actuators, B Chem"},{"key":"pone.0252961.ref039","doi-asserted-by":"crossref","first-page":"1961","DOI":"10.1093\/jac\/dkx113","article-title":"A new rapid resazurin-based microdilution assay for antimicrobial susceptibility testing of Neisseria gonorrhoeae","volume":"72","author":"S Foerster","year":"2017","journal-title":"J Antimicrob Chemother"},{"key":"pone.0252961.ref040","unstructured":"Invitrogen. PrestoBlue \u00ae Cell Viability Reagent Product Information Sheet. 2019; 0\u20131. Available: https:\/\/assets.thermofisher.com\/TFS-Assets\/LSG\/manuals\/MAN0018370-PrestoBlueCellViabilityReagent-PI.pdf."},{"key":"pone.0252961.ref041","doi-asserted-by":"crossref","first-page":"1","DOI":"10.3389\/fcimb.2013.00093","article-title":"The use of resazurin as a novel antimicrobial agent against Francisella tularensis","volume":"3","author":"DM Schmitt","year":"2013","journal-title":"Front Cell Infect Microbiol"},{"key":"pone.0252961.ref042","doi-asserted-by":"crossref","first-page":"127","DOI":"10.1016\/S1387-2656(05)11004-7","article-title":"Herst PM, Tan AS. Tetrazolium dyes as tools in cell biology: New insights into their cellular reduction","volume":"11","author":"M-V. Berridge","year":"2005","journal-title":"Biotechnol Annu Rev"},{"key":"pone.0252961.ref043","doi-asserted-by":"crossref","first-page":"911","DOI":"10.1002\/jhet.5570250340","article-title":"The synthesis of XTT: A new tetrazolium reagent that is bioreducible to a water\u2010soluble formazan","volume":"25","author":"KD Paull","year":"1988","journal-title":"J Heterocycl Chem"},{"key":"pone.0252961.ref044","doi-asserted-by":"crossref","first-page":"431","DOI":"10.1530\/REP-20-0205","article-title":"Patterns of MTT reduction in mammalian spermatozoa","volume":"160","author":"RJ Aitken","year":"2020","journal-title":"Reproduction"},{"key":"pone.0252961.ref045","first-page":"4827","article-title":"Evaluation of a Soluble Tetrazolium\/Formazan Assay for Cell Growth and Drug Sensitivity in Culture Using Human and Other Tumor Cell Lines","volume":"48","author":"DA Scudiero","year":"1988","journal-title":"Cancer Res"},{"key":"pone.0252961.ref046","first-page":"584","article-title":"Feasibility of Drug Screening with Panels of Human Tumor Cell Lines Using a Microculture Tetrazolium Assay","volume":"48","author":"MC Alley","year":"1988","journal-title":"Cancer Res"},{"key":"pone.0252961.ref047","doi-asserted-by":"crossref","first-page":"303","DOI":"10.1016\/j.acthis.2018.03.007","article-title":"Current methodology of MTT assay in bacteria\u2013A review","volume":"120","author":"E Grela","year":"2018","journal-title":"Acta Histochem"},{"key":"pone.0252961.ref048","doi-asserted-by":"crossref","first-page":"109","DOI":"10.1016\/j.mimet.2008.05.016","article-title":"Colorimetric cell proliferation assay for microorganisms in microtiter plate using water-soluble tetrazolium salts","volume":"75","author":"T Tsukatani","year":"2008","journal-title":"J Microbiol Methods"},{"key":"pone.0252961.ref049","doi-asserted-by":"crossref","first-page":"156","DOI":"10.1016\/j.mimet.2008.05.010","article-title":"Tetrazolium salts for MIC determination in microplates: Why? Which salt to select? How?","volume":"75","author":"M Grare","year":"2008","journal-title":"J Microbiol Methods"},{"key":"pone.0252961.ref050","doi-asserted-by":"crossref","first-page":"4587","DOI":"10.1128\/aem.62.12.4587-4593.1996","article-title":"Toxic effects on bacterial metabolism of the redox dye 5-cyano-2,3- ditolyl tetrazolium chloride","volume":"62","author":"S Ullrich","year":"1996","journal-title":"Appl Environ Microbiol"},{"key":"pone.0252961.ref051","doi-asserted-by":"crossref","first-page":"2941","DOI":"10.1099\/mic.0.029678-0","article-title":"Experimental conditions affect the site of tetrazolium violet reduction in the electron transport chain of Lactococcus lactis","volume":"155","author":"S Tachon","year":"2009","journal-title":"Microbiology"},{"key":"pone.0252961.ref052","doi-asserted-by":"crossref","first-page":"279","DOI":"10.1038\/bjc.1987.190","article-title":"A study of some variables in a tetrazolium dye (MTT) based assay for cell growth and chemosensitivity","volume":"56","author":"PR Twentyman","year":"1987","journal-title":"Br J Cancer"},{"key":"pone.0252961.ref053","doi-asserted-by":"crossref","first-page":"1048","DOI":"10.1002\/jps.2600650723","article-title":"Biehl ER, Kenner CT. Effect of Solvent on Tetrazolium Reaction","volume":"65","author":"R. Graham","year":"1976","journal-title":"J Pharm Sci"},{"key":"pone.0252961.ref054","doi-asserted-by":"crossref","first-page":"15","DOI":"10.1155\/2005\/323082","article-title":"The laboratory diagnosis of Neisseria gonorrhoeae","volume":"16","author":"LK Ng","year":"2005","journal-title":"Can J Infect Dis Med Microbiol"},{"key":"pone.0252961.ref055","doi-asserted-by":"crossref","first-page":"1879","DOI":"10.1128\/AAC.48.5.1879-1881.2004","article-title":"Rapid Colorimetric Assay for Antimicrobial Susceptibility Testing of Pseudomonas aeruginosa","volume":"48","author":"MM Tunney","year":"2004","journal-title":"Antimicrob Agents Chemother"},{"key":"pone.0252961.ref056","doi-asserted-by":"crossref","first-page":"244","DOI":"10.1016\/S0924-8579(02)00350-3","article-title":"Comparison of the susceptibility testing of clinical isolates of Mycobacterium tuberculosis by the XTT colorimetric method and the NCCLS standards method","volume":"21","author":"A De Logu","year":"2003","journal-title":"Int J Antimicrob Agents"},{"key":"pone.0252961.ref057","first-page":"498","article-title":"A novel colorimetric broth microdilution method to determine the minimum inhibitory concentration (MIC) of antibiotics and essential oils against Helicobacter pylori","volume":"60","author":"A Weseler","year":"2005","journal-title":"Pharmazie"},{"key":"pone.0252961.ref058","doi-asserted-by":"crossref","first-page":"1410","DOI":"10.1021\/acsomega.0c05060","article-title":"Paper-Based Semi-quantitative Antimicrobial Susceptibility Testing","volume":"6","author":"R Wang","year":"2021","journal-title":"ACS Omega"}],"container-title":["PLOS ONE"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0252961","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2021,6,17]],"date-time":"2021-06-17T17:32:15Z","timestamp":1623951135000},"score":1,"resource":{"primary":{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0252961"}},"subtitle":[],"editor":[{"given":"Paulo Lee","family":"Ho","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"editor"}]}],"short-title":[],"issued":{"date-parts":[[2021,6,17]]},"references-count":58,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2021,6,17]]}},"URL":"https:\/\/doi.org\/10.1371\/journal.pone.0252961","relation":{},"ISSN":["1932-6203"],"issn-type":[{"value":"1932-6203","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,6,17]]}}}