Epsilon-poly-l-lysine inhibits biofilm formation and aids dispersion in Acinetobacter baumannii

Abstract

Acinetobacter baumannii is a prominent hospital-associated bacterium whose eradication is increasingly challenging due to its remarkable ability to resist antibiotics. The most common illnesses caused by antibiotic-resistant A. baumannii are biofilm-associated. Therefore, novel methods to combat A. baumannii are urgently needed. Application of antimicrobial peptides (AMPs) is one of the avenues to be explored. Epsilon poly-l-lysine (ε-PL) is an antimicrobial peptide with low mammalian toxicity. It is commonly used as a food preservative and has advantages such as biodegradability, good water solubility, and thermal stability.

Therefore, the antimicrobial activity of ε-PL against clinical isolates of A. baumannii was investigated. The effect of ε-PL on antimicrobial sensitivity was determined by broth dilution assay. The effect of ε-PL on biofilm formation and dispersion was studied using a crystal violet assay. The changes in the expression of quorum sensing related and virulence genes (abaI, csuE, pilT, bap, and luxI) were analyzed using qPCR by the Δ Δ CT method.

All the A. baumannii clinical isolates (n = 28) tested, were resistant to multiple drugs. The treatment with ε-PL resulted in a significant (p < 0.05) reduction in the biofilm formation abilities of all the clinical isolates of A. baumannii. Also, ε-PL caused a significant (p < 0.05) decrease in the dispersion of preformed biofilms. The reduction in the biofilm formation could be attributed to the inhibition of autoinducer synthase (abaI) which is required for biofilm development in A. baumannii. Also, it could be due to altering of expression of biofilm-related genes like csuE, pilT, bap, and luxI. These results suggest that ε-PL could be effective in the elimination of A. baumannii biofilms and decreasing its virulence.