Abstract
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.
Highlights
Amino acids (AA) are versatile molecules which have a multitude of functions and can be used as anti-biofilm agents, drug excipients, drug solubility enhancers, and drug adjuvants [1]
The current study investigates whether these counterions, L-aspartic acid (L-Asp) and L-glutamic acid (L-Glu), possess intrinsic anti-microbial activity on planktonic bacterial cells and if cotreatment with ciprofloxacin leads to further inhibition of planktonic growth
Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of the amino acids and Cip were conducted on the S. aureus strain NCTC 8325 and P. aeruginosa strain PAO1
Summary
Amino acids (AA) are versatile molecules which have a multitude of functions and can be used as anti-biofilm agents, drug excipients, drug solubility enhancers, and drug adjuvants [1]. It has been shown that both D- and L-isoforms of acidic amino acids are able to exhibit anti-biofilm activity on their own and act synergistically with Ciprofloxacin (Cip) [2]. The current study investigates whether these counterions, L-aspartic acid (L-Asp) and L-glutamic acid (L-Glu), possess intrinsic anti-microbial activity on planktonic bacterial cells and if cotreatment with ciprofloxacin leads to further inhibition of planktonic growth. Acidic amino acids as counterions of ciprofloxacin project. He was involved in project development and supervision. There are no declarations to be made relating to employment, consultancy, patents, products in development, or marketed products, etc
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