Chronic lung infection by Pseudomonas aeruginosa biofilm is cured by L-Methionine in combination with antibiotic therapy

Abstract

Bacterial biofilms are associated with 80–90% of infections. Within the biofilm, bacteria are refractile to antibiotics, requiring concentrations >1,000 times the minimum inhibitory concentration. Proteins, carbohydrates and DNA are the major components of biofilm matrix. Pseudomonas aeruginosa (PA) biofilms, which are majorly associated with chronic lung infection, contain extracellular DNA (eDNA) as a major component. Herein, we report for the first time that L-Methionine (L-Met) at 0.5 μM inhibits Pseudomonas aeruginosa (PA) biofilm formation and disassembles established PA biofilm by inducing DNase expression. Four DNase genes (sbcB, endA, eddB and recJ) were highly up-regulated upon L-Met treatment along with increased DNase activity in the culture supernatant. Since eDNA plays a major role in establishing and maintaining the PA biofilm, DNase activity is effective in disrupting the biofilm. Upon treatment with L-Met, the otherwise recalcitrant PA biofilm now shows susceptibility to ciprofloxacin. This was reflected in vivo, in the murine chronic PA lung infection model. Mice treated with L-Met responded better to antibiotic treatment, leading to enhanced survival as compared to mice treated with ciprofloxacin alone. These results clearly demonstrate that L-Met can be used along with antibiotic as an effective therapeutic against chronic PA biofilm infection.

Targeting microbial biofilms: current and prospective therapeutic strategies

“…In addition to pH modulatory effects 83 , L-Arg also repressed genes involved in the production of insoluble EPS and bacteriocin in S. mutans , while increasing hydrogen peroxide (used against S. mutans ) production by S. gordonii 84 L-Arg reduced biomass and altered EPS architecture in S. gordonii biofilms 85 , and also destabilized multispecies oral biofilms, thus reducing viability and increasing susceptibility to cetylpyridinium chloride 86 . An alternative amino acid, L-methionine, was also identified as a promising adjuvant for treating P. aeruginosa biofilms, triggering disassembly and increasing sensitivity towards ciprofloxacin in a mouse model of chronic pneumonia, and enhancing survival of infected mice 87 . This activity was attributed to up-regulation of four different DNase genes and the subsequent degradation of eDNA in the EPS matrix, although the exact pathways that regulate this response were not determined.…”

Synergistic Activity of Berberine with Azithromycin against Pseudomonas Aeruginosa Isolated from Patients with Cystic Fibrosis of Lung In Vitro and In Vivo

“…Several reports displayed that both AZM and BER could target efflux pumps (MexXY) [40, 45] and eDNA [26, 30] in PA. However, macrolides were supposed to be difficult of diffusion across the outer membrane of most gram-negative bacteria [46].…”

“…The medium free of agent was set as control. The biofilm formation (%) were measured by crystal violet (CV) staining, which was equal to OD 545 of sample treated/OD 545 of control [30]. …”

l‐Methionine anti‐biofilm activity against Pseudomonas aeruginosa is enhanced by the cystic fibrosis transmembrane conductance regulator potentiator, ivacaftor

“…The highest dose‐specific inhibition of biofilm growth was observed with 0.5 μM l ‐methionine (OD 590 : 0.29 ± 0.03), significantly lower than controls (OD 590 : 0.41 ± 0.06; p = 0.003; Fig. ), consistent with previous studies . Anti‐biofilm activity diminished as the concentration of l ‐methionine increased from 2.5 μM (OD 590 : 0.307 ± 0.023; p = 0.009) to 5 μM (OD 590 : 0.39 ± 0.033; p = 0.9).…”

“…To treat bacterial biofilms without using such intense drug therapies, alternative approaches with unconventional agents that disrupt or inhibit biofilms have garnered significant attention . Amino acids, such as d ‐amino acids and l ‐tryptophan, are commonly secreted by biofilms during later stages of development and have been among several agents recently studied for their potential anti‐biofilm activity . d ‐Amino acids are effective at disassembling existing biofilms, whereas l ‐ tryptophan inhibits the formation of biofilms.…”