Helicobacter pylori biofilms are disrupted by nanostructured lipid carriers: A path to eradication?

Abstract

Bacterial biofilms account for 80% of all chronic infections, with cells being up to 1000 times more resistant to antibiotics than their planktonic counterparts. The recently discovered ability of Helicobacter pylori to form biofilms once again highlights why this bacterium is one of the most successful human pathogens. The current treatments failure rate reaches 40% of cases, emphasizing that new therapeutic options are a pressing need. Nanostructured lipid carriers (NLC), with and without docosahexaenoic acid (DHA), were very effective against H. pylori planktonic cells but their effect on H. pylori biofilms was unknown. Here, DHA-loaded NLC (DHA-NLC) and NLC without any drug (blank NLC) were tested on an optimized H. pylori in vitro floating mature biofilm model. DHA-NLC and blank NLC reduced the total biofilm biomass and had a bactericidal effect against both biofilm and planktonic bacteria in all the concentrations tested (0.125-2 mg/mL). DHA-NLC achieved biofilm biomass reduction in a concentration ~ 8 times lower than blank NLC (0.125 vs 1 mg/mL, respectively). Both NLC were bactericidal at the lowest concentration tested (0.125 mg/mL) although with different efficiency, i.e. a decrease of ∼6 log₁₀ for DHA-NLC and ∼5 log₁₀ for blank NLC. In addition, the equivalent amount of free DHA (3.1 μM) only reduced bacterial viability in ∼2 log₁₀, demonstrating the synergistic effect of DHA and NLC in the treatment of H. pylori biofilms. Nevertheless, although viable bacteria were not detected by colony forming unit (CFU) counting after treatment with both NLC, confocal microscopy imaging highlighted that some H. pylori cells remained alive. In addition, scanning electron microscopy (SEM) analysis confirmed an increase in bacteria with a coccoid morphology after treatment, suggesting a transition to a viable but non-culturable (VBNC) state. Altogether, it is herein established that NLC, even without any drug, are promising for the management of H. pylori bacteria organized in biofilms, opening new perspectives for the eradication of this gastric pathogen.

Keywords: Antibiotic-free therapies; Bioengineered therapies; Helicobacter pylori biofilm; Nanostructured lipid carriers (NLC).