Antibacterial activity of polyunsaturated fatty acids related to chronic wound infections

Wound infections present major health problems worldwide. It has been revealed thatbacterial biofilm communities frequently colonise chronic wounds.Biofilms with Multidrugresistant organisms (MDRO) such as Methicillin Resistant Staphylococcus aureus (MRSA)and Pseudomonas aeruginosa are increasingly implicated in chronic wound infections. Thelimited therapeutic options are further compromised by the fact that wound-infecting bacteriaoften co-exist within a polymicrobial biofilm community, which enhances bacterial toleranceor resistance to antimicrobials. The polyunsaturated fatty acid (PUFA) compounds includingDocosahexaenoic acid (DHA) and Eicosapentaenoic acid (EPA) offer bothimmunomodulatory and antimicrobial properties that could enhance wound healing. This study evaluated the activity and efficiency of these compounds against woundpathogens and compared them to common antibiotics Linezolid (LZD) and vancomycin(VAN). Standard antibiotic sensitivity assays were used to determine the ability of PUFAs toinhibit growth and biofilm formation. Most activity was observed against S. aureus strains.The bacteriostatic activity (minimum inhibitory concentration - MIC) of DHA and EPA for S.Aureus SA3 and P. aeruginosa PA01 was 65 and 117 μgml-1respectively. Meanwhile, the bacteriocidal activity required higher concentrations (MBC) of 260 and 468 μgml-1respectively. The antibiotic LZD was most active against Gram positive bacteria (MIC rangefrom 1.9 µg ml-1 to 3.9 µg ml-1). However, vancomycin was the most potent biofilm disrupter, with MBECs ranging from 5-12.5 µg ml-1. These concentrations were 35-fold lower than the MBECs recorded for linezolid (125 -500 µg ml-1). Considerably higher concentrations ofPUFA compounds were required to disrupt biofilms. The MBECs of DHA ranged between750 and 3125 µg ml-1. EPA was found to be more disruptive than DHA (MBECs ranging between 500 and 2250 µg ml-1), while the MBECs of combination treatment with bothPUFAs (DHA+EPA) ranged from 750 - 1500 µg ml-1. The antimicrobial activity of different concentrations of PUFAs was furtherAssessed by monitoring inhibition of growth of a clinical wound isolate of S. aureus (SA3)for24 h. PUFAs were shown to differentially affect expression of global gene regulators usingRT-qPCR. DHA and EPA were found to upregulate agrA and icaA but downregulate sarA atthe same concentrations and exposure times. Two different infection models were used to assess the activity of PUFAs in vivo (Galleria mellonella) and on ex-vivo skin compared to common antibiotics (LZD andVAN). PUFAs reduced virulence of SA3 in G.mellonella, protecting the larvae from death.Furthermore, prolonged exposure to sub-inhibitory concentrations affected growthEfficiency of SA3 in vivo. Whole genome sequencing of parent vs PUFA and antibiotics adapted strains of S. aureus SA3 revealed some common mutations in sarA and clfB genes, thatmay contribute to altered virulence and susceptibility to treatment. Preliminary studies withthe ex-vivo skin model suggested that this may be a useful system for testing the efficacy ofantimicrobial compounds for wound-treatment. Differences in SA3 survival and growth weremeasurable in the presence of PUFAs or absence of PUFAs. In conclusion, PUFAs (DHA and EPA) showed weak antimicrobial activitycompared to common antibiotics against common wound-associated bacteria. However, thisstudy shows evidence that PUFAs have additional desirable properties, including disruptionof global gene regulation, reduction of virulence and low potential to promote developmentof resistance.

Level dc:type.qualificationlevel

Doctoral (Level 8)

Year dc:date.issued

2026

Author dc:creator

• Eshlak, MS

Language dc:language

en

Identifier

oai:salford-repository.worktribe.com:1370213

OAI identifier oai:identifier

oai:salford-repository.worktribe.com:1370213