Selective labelling and eradication of antibiotic-tolerant bacterial populations in Pseudomonas aeruginosa biofilms

Abstract

Drug resistance and tolerance greatly diminish the therapeutic potential of antibiotics against pathogens. Antibiotic tolerance by bacterial biofilms often leads to persistent infections, but its mechanisms are unclear. Here we use a proteomics approach, pulsed stable isotope labelling with amino acids (pulsed-SILAC), to quantify newly expressed proteins in colistin-tolerant subpopulations of Pseudomonas aeruginosa biofilms (colistin is a ‘last-resort' antibiotic against multidrug-resistant Gram-negative pathogens). Migration is essential for the formation of colistin-tolerant biofilm subpopulations, with colistin-tolerant cells using type IV pili to migrate onto the top of the colistin-killed biofilm. The colistin-tolerant cells employ quorum sensing (QS) to initiate the formation of new colistin-tolerant subpopulations, highlighting multicellular behaviour in antibiotic tolerance development. The macrolide erythromycin, which has been previously shown to inhibit the motility and QS of P. aeruginosa, boosts biofilm eradication by colistin. Our work provides insights on the mechanisms underlying the formation of antibiotic-tolerant populations in bacterial biofilms and indicates research avenues for designing more efficient treatments against biofilm-associated infections.

Reactive oxygen species drive evolution of pro-biofilm variants in pathogens by modulating cyclic-di-GMP levels

“…We also found that the mutations were not attributed to highly mutagenic growth conditions, as there was no significant increase in mutation rates with ROS treatment (electronic supplementary material, figure S2) compared with control medium, with the mutation rates similar to previous reports [38]. Moreover, the cell populations did not develop mutations in the mutS gene, which is important in mismatch repair and its mutation can lead to the emergence of multiple phenotypic variants [53].…”

Pseudomonas aeruginosa Psl Exopolysaccharide Interacts with the Antimicrobial Peptide LG21

“…Figure S4 shows the structural evolution of the LG21 peptide when it interacts with the Psl. It is observed that the middle residues (6)(7)(8)(9)(10)(11)(12)(13)(14) are the main contributors to the helical conformation. The reason could be that the presence of carbohydrate chain (Psl) in the solution decreases the polar nature of water to form hydrogen bonds with the middle residues and the increasing hydrophobic interactions within the peptide induces the helical structure, whereas the terminal residues still have a random-coil structure by being exposed to the aqueous solution.…”

Biofilm formation – what we can learn from recent developments

“…On the other hand, when revisited, widely used natural antimicrobial compounds demonstrated a broad efficacy against biofilm-forming microorganisms ([14–17]; Table 1). For example, the established antimicrobial preservative acetic acid is highly effective in the treatment of chronic wounds infected with biofilm-forming P. aeruginosa [18].…”

“…Thereby, treatment with the last resort polymyxin antibiotic colistin is more effective compared to many other antibiotics under anaerobic conditions [11]. In vitro treatment of biofilms, though, induces the formation of a subpopulation of colistin-tolerant cells that can subsequently be killed combining colistin with erythromycin, ciprofloxacin or tetracycline [12][13][14]. established antimicrobial preservative acetic acid is highly effective in the treatment of chronic wounds infected with biofilm-forming P. aeruginosa [18].…”