{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,19]],"date-time":"2026-06-19T17:41:35Z","timestamp":1781890895776,"version":"3.54.5"},"reference-count":47,"publisher":"Public Library of Science (PLoS)","issue":"4","license":[{"start":{"date-parts":[[2021,4,29]],"date-time":"2021-04-29T00:00:00Z","timestamp":1619654400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000268","name":"Biotechnology and Biological Sciences Research Council","doi-asserted-by":"publisher","award":["BB\/M017044\/1"],"award-info":[{"award-number":["BB\/M017044\/1"]}],"id":[{"id":"10.13039\/501100000268","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS ONE"],"abstract":"<jats:p>Antimicrobial resistance (AMR) is emerging as a global threat to public health. One of the strategies employed to combat AMR is the use of adjuvants which act to enhance or reinstate antimicrobial activity by inhibiting resistance mechanisms. However, these adjuvants are themselves not immune to selecting resistant phenotypes. Thus, there is a need to utilise mechanisms which are either less likely to or unable to trigger resistance. One commonly employed mechanism of resistance by microorganisms is to prevent antimicrobial uptake or efflux the antibiotic which manages to permeate its membrane. Here we propose amino acids as antimicrobial adjuvants that may be utilizing alternate mechanisms to fight AMR. We used a modified ethidium bromide (EtBr) efflux assay to determine its efflux in the presence of ciprofloxacin within Staphylococcus aureus (NCTC 8325) and Pseudomonas aeruginosa (PAO1). In this study, aspartic acid and glutamic acid were found to inhibit growth of both bacterial species. Moreover, a reduced production of toxic pigments, pyocyanin and pyoverdine by <jats:italic>P<\/jats:italic>. <jats:italic>aeruginosa<\/jats:italic> was also observed. As evident from similar findings with tetracycline, these adjuvants, may be a way forward towards tackling antimicrobial resistance.<\/jats:p>","DOI":"10.1371\/journal.pone.0250705","type":"journal-article","created":{"date-parts":[[2021,4,29]],"date-time":"2021-04-29T17:54:53Z","timestamp":1619718893000},"page":"e0250705","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":5,"title":["Acidic amino acids as counterions of ciprofloxacin: Effect on growth and pigment production in Staphylococcus aureus NCTC 8325 and Pseudomonas aeruginosa PAO1"],"prefix":"10.1371","volume":"16","author":[{"given":"Annsar Ahmad","family":"Warraich","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Afzal Ur Rahman","family":"Mohammed","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hazel","family":"Gibson","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Majad","family":"Hussain","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6971-8825","authenticated-orcid":true,"given":"Ayesha Sabah","family":"Rahman","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"340","published-online":{"date-parts":[[2021,4,29]]},"reference":[{"issue":"6","key":"pone.0250705.ref001","article-title":"Multimodal Role of Amino Acids in Microbial Control and Drug Development","volume":"9","author":"M Idrees","year":"2020","journal-title":"Antibiotics (Basel)"},{"issue":"1","key":"pone.0250705.ref002","doi-asserted-by":"crossref","first-page":"9021","DOI":"10.1038\/s41598-020-66082-x","article-title":"Evaluation of anti-biofilm activity of acidic amino acids and synergy with ciprofloxacin on Staphylococcus aureus biofilms","volume":"10","author":"AA Warraich","year":"2020","journal-title":"Sci Rep"},{"key":"pone.0250705.ref003","article-title":"Preparation and Evaluation of Amino Acid Based Salt Forms of Model Zwitterionic Drug Ciprofloxacin","author":"AOD ElShaer","year":"2013","journal-title":"Journal of Pharmaceutics and Drug Delivery Research"},{"key":"pone.0250705.ref004","volume-title":"Amino acids in oral drug delivery: salts, ion-pairs and transcriptomics","author":"A ElShaer","year":"2013"},{"issue":"4","key":"pone.0250705.ref005","doi-asserted-by":"crossref","first-page":"173","DOI":"10.7257\/1053-816X.2016.36.4.173","article-title":"Ciprofloxacin Resistance: A Review of Patients in East London Undergoing Prostate Biopsy","volume":"36","author":"B Turner","year":"2016","journal-title":"Urologic nursing"},{"key":"pone.0250705.ref006","unstructured":"Committee JF. 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