Biology subjects

Davies, J. C.

Publications and source records attributed to Davies, J. C..

3 recordsLinked to original sources

bioRxiv2023

Antimicrobial peptide glatiramer acetate targets Pseudomonas aeruginosa lipopolysaccharides to breach membranes without altering lipopolysaccharide modification

Antimicrobial peptides (AMPs) are key components of innate immunity across all kingdoms of life. Both natural and synthetic AMPs are receiving renewed attention in the efforts to combat the antimicrobial resistance (AMR) crisis and the loss of antibiotic efficacy. The gram-negative pathogen Pseudomonas aeruginosa is one of the most concerning infectious bacteria in AMR, particularly in people with cystic fibrosis (CF) where respiratory infections are difficult to eradicate and are associated with increased morbidity and mortality. Cationic AMPs exploit the negative charge of lipopolysaccharides (LPS) on P. aeruginosa to bind to and disrupt the bacterial membrane(s) and cause lethal damage. P. aeruginosa modifies its LPS, via environmental or genetic factors, to neutralise the charge of the cell and evade AMP killing. Free-LPS is also a component of CF sputum, as is anionic extracellular DNA (eDNA), each of which can bind AMPs by electrostatic interaction. Both free LPS and eDNA also feed into pro-inflammatory cycles. Glatiramer acetate (GA) is a random peptide co-polymer of glycine, lysine, alanine, and tyrosine and used as drug in the treatment of multiple sclerosis (MS); we have previously shown GA to be an AMP which synergises with tobramycin against P. aeruginosa from CF, functioning via bacterial membrane disruption. Here, we demonstrate direct binding and sequestration/neutralisation of P. aeruginosa LPS in keeping with GAs ability to disrupt the outer membrane. Binding and neutralisation of eDNA was also seen. At CF-relevant concentrations, however, neither strongly inhibited membrane disruption by GA. Furthermore, in both type strains and clinical CF isolates of P. aeruginosa, exposure to GA did not result in increased modification of the Lipid A portion of LPS or in increased expression of genetically encoded systems involved in AMP sensing and LPS modification. With this low selective pressure on P. aeruginosa for known AMP resistance mechanisms, the potential to neutralise pro-inflammatory CF sputum components, as well as the previously described enhancement of antibiotic function, GA is a promising candidate for drug repurposing.

microbiology↗

bioRxiv2022

Synergistic Activity of Repurposed Peptide Drug Glatiramer Acetate with Tobramycin Against Cystic Fibrosis Pseudomonas aeruginosa

Pseudomonas aeruginosa is the most common pathogen infecting the lungs of people with cystic fibrosis (CF), causing both acute and chronic infections. Intrinsic and acquired antibiotic resistance, coupled with the physical barriers resulting from desiccated CF sputum, allow P. aeruginosa to colonise and persist in spite of antibiotic treatment. As well as the specific difficulties in eradicating P. aeruginosa from CF lungs, P. aeruginosa is also subject to the wider, global issue of antimicrobial resistance. Glatiramer acetate (GA) is a peptide drug, used in the treatment of multiple sclerosis (MS), which has been shown to have moderate anti-pseudomonal activity. Other antimicrobial peptides (AMPs) have been shown to be antibiotic resistance breakers; potentiating the activities of antibiotics when given in combination restoring and/or enhancing antibiotic efficacy. Growth, viability, minimum inhibitory concentration (MIC)-determination and synergy analysis showed that GA improved the efficacy of TOB against reference strains of P. aeruginosa, reducing TOB MICs and synergising with the aminoglycoside. This was also the case for clinical strains from people with CF. GA significantly reduced the concentration of TOB required to inhibit 50% (MIC50) of viable cells (from 1.69 [95%CI 0.26-8.97] to 0.62 [95%CI 0.15-3.94] mg/L, p=0.002) and inhibit 90% (MIC90) (from 7.00 [95%CI 1.18-26.50] to 2.20 [95%CI 0.99-15.03] mg/L, p=0.001) compared with TOB-only. Investigating mechanisms of GA activity showed that GA resulted in significant disruption of outer membranes, depolarisation of cytoplasmic membranes and permeabilisation of P. aeruginosa and was the only agent tested (including cationic AMPs) to significantly affect all three.

microbiology↗

bioRxiv2020

Response of Pseudomonas aeruginosa to the innate immune system-derived oxidants hypochlorous acid and hypothiocyanous acid

Pseudomonas aeruginosa is a significant nosocomial pathogen and associated with lung infections in cystic fibrosis (CF). Once established, P. aeruginosa infections persist and are rarely eradicated despite the host immune cells producing antimicrobial oxidants, including hypochlorous acid (HOCl) and hypothiocyanous acid (HOSCN). There is limited knowledge as to how P. aeruginosa senses, responds to, and survives attack from HOCl and HOSCN, and the contribution of such responses to its success as a CF pathogen. We investigated the P. aeruginosa response to these oxidants by screening 707 transposon mutants, with mutations in regulatory genes, for altered growth following HOCl exposure. We identified regulators involved in antibiotic resistance, methionine biosynthesis and catabolite repression, and PA14_07340, the homologue of the Escherichia coli HOCl-sensor RclR (30% identical), that were required for HOCl survival. We have shown that RclR (PA14_07340) protects specifically against HOCl and HOSCN stress, and responds to both oxidants by upregulating expression of a putative peroxiredoxin, rclX (PA14_07355). While there was specificity in the transcriptional response to HOCl (231 genes upregulated) and HOSCN (105 genes upregulated) there was considerable overlap, with 74 genes upregulated by both oxidants. These included genes encoding the type III secretion system (T3SS), sulphur and taurine transport, and the MexEF-OprN efflux pump. RclR coordinated the transcriptional response to HOCl and HOSCN, including upregulation of pyocyanin biosynthesis genes, and in response to HOSCN alone RclR downregulated chaperone genes. These data indicate that the P. aeruginosa response to HOCl and HOSCN is multifaceted, with RclR playing an essential role.

microbiology↗