Acidic amino acids as counterions of ciprofloxacin:Effect on growth and pigment production in Staphylococcus aureus NCTC 8325 and Pseudomonas aeruginosa PAO1


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 P. aeruginosa was also observed. As evident from similar findings with tetracycline, these adjuvants, may be a way forward towards tackling antimicrobial resistance.

Publication DOI:
Divisions: College of Health & Life Sciences > Aston Pharmacy School
College of Health & Life Sciences
College of Health & Life Sciences > Chronic and Communicable Conditions
Additional Information: © 2021 Warraich et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The authors acknowledge BBSRC UKRI (BB/M017044/1) which funded AW.
Uncontrolled Keywords: Amino Acids, Acidic/pharmacology,Ciprofloxacin/pharmacology,Pigments, Biological/biosynthesis,Pseudomonas aeruginosa/drug effects,Staphylococcus aureus/drug effects,General
Publication ISSN: 1932-6203
Last Modified: 30 Apr 2024 07:26
Date Deposited: 30 Apr 2021 10:36
Full Text Link:
Related URLs: https://journal ... al.pone.0250705 (Publisher URL)
http://www.scop ... tnerID=8YFLogxK (Scopus URL)
PURE Output Type: Article
Published Date: 2021-04-29
Accepted Date: 2021-04-13
Submitted Date: 2020-09-27
Authors: Warraich, Annsar Ahmad
Mohammed, Afzal Ur Rahman (ORCID Profile 0000-0002-5212-3040)
Gibson, Hazel
Hussain, Majad
Rahman, Ayesha Sabah



Version: Published Version

License: Creative Commons Attribution

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