Recent advances in therapeutic targets identification and development of treatment strategies towards Pseudomonas aeruginosa infections

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TL;DR

This review summarizes recent advances in understanding Pseudomonas aeruginosa pathogenesis, including biofilm formation, quorum sensing, and immune evasion, and highlights novel therapeutic strategies such as anti-virulence agents, bacteriophages, and vaccines. Key findings include the identification of new drug targets like the LecB lectin and the AlpA antiterminator, as well as promising antimicrobials like the synthetic lipopeptide F365 and the combination of colistin with alginate oligosaccharide. The clinical significance lies in addressing the urgent need for effective treatments against multidrug-resistant P. aeruginosa, a critical priority pathogen.

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**Background:** Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen causing severe nosocomial infections, particularly in immunocompromised and cystic fibrosis (CF) patients. It exhibits intrinsic and acquired resistance to many antibiotics, including carbapenems, and forms biofilms that can be up to 1000-fold more tolerant to antibiotics. The World Health Organization lists P. aeruginosa as a critical priority pathogen requiring novel treatments. This review discusses recent discoveries in pathogenesis, identification of new therapeutic targets, and development of antimicrobial strategies, including vaccines and monoclonal antibodies.

**Methods:** This is a narrative review summarizing recent literature (primarily from 2020-2022) on P. aeruginosa pathogenesis, drug targets, diagnostics, antimicrobial agents, and vaccines. The authors synthesized findings from multiple studies, including those on quorum sensing (QS), biofilm formation, secretion systems, and host-pathogen interactions. They also reviewed in vitro and in vivo studies of novel antimicrobial compounds, combination therapies, and vaccine candidates.

**Key Results:** The review highlights several key findings: - **Pathogenesis:** The fucose-binding lectin LecB mediates high-affinity host-cell binding via a unique calcium-dependent mechanism. Defective lasR mutants constitutively express a biofilm-adapted profile. The small protein PA2146 regulates biofilm architecture and antimicrobial tolerance. P. aeruginosa escapes immune clearance by redirecting metabolism to produce exopolysaccharides (EPS) in response to host itaconate. - **New therapeutic targets:** The denitrification pathway, the AlpA antiterminator (which controls programmed cell death and survival genes), and the rhamnolipid-mediated transport of toxic compounds are potential targets. Targeting mechanisms specific to P. aeruginosa could yield narrow-spectrum antimicrobials. - **Diagnostics:** Rapid detection methods include PCR/qPCR targeting novel genes (Wang et al.), a 4-hour antimicrobial susceptibility test using tail fiber protein-functionalized magnetic particles, and a portable RT-LAMP assay detecting P. aeruginosa in <2 hours. Xanthine is identified as a potential biomarker. - **Antimicrobial strategies:** - **Biofilm inhibition:** Octenidine with rotating magnetic field, graphene oxide-lignin/silk fibroin/ZnO nanobiocomposite, and N-(2-hydroxyphenyl)-2-phenazinamine show antibiofilm activity. Dextran-based nanoparticles with DNase I enhance tobramycin activity. - **Quorum sensing inhibition:** Plant extracts (e.g., Dioon spinulosum, Andrographis paniculata) and compounds like cinnamaldehyde, 6-gingerol, and curcumin downregulate QS genes and reduce virulence factors. - **Novel antimicrobials:** The synthetic lipopeptide F365 (QPX9003) shows a wider therapeutic window and reduced nephrotoxicity compared to polymyxins. The de novo-engineered peptide E35 kills extensively-resistant isolate PA239. Otilonium bromide restores colistin efficacy. Vitamin C and epsilon-poly-L-lysine show antibiofilm activity without cytotoxicity. - **Bacteriophages:** Phage LUZ19 targets QS via the Qst protein, and phage LUZ24 produces a peptide Igy that inhibits gyrase even in fluoroquinolone-resistant isolates. - **Vaccines:** Trivalent vaccines (OprF, OprI, PopB) with GM-CSF adjuvant stimulate Th1/Th2 responses in burned rat models. LPS-PLGA and OPS-PLGA nano-vaccines induce IgM, IgA, IgG antibodies in mice. A whole-cell X-ray-inactivated vaccine triggers cGAS-STING pathway and protects against MDR isolates. A glycoconjugate vaccine with core LPS tetrasaccharide linked to diphtheria toxin mutant shows promise. - **Monoclonal antibodies:** Anti-PcrV IgY antibodies enhance opsonophagocytic killing and reduce bacterial invasion in murine pneumonia and burn models. DNA-delivered monoclonal antibodies (DMAbs) targeting P. aeruginosa strain 6077 protect mice against lethal pneumonia and act synergistically with meropenem. However, MEDI3902 (gremubamab) failed to reduce nosocomial pneumonia incidence in ventilated patients.

**Clinical Implications:** The review underscores the urgent need for novel strategies against MDR P. aeruginosa. Anti-virulence approaches (e.g., QS inhibitors) may reduce resistance selection. Combination therapies (e.g., colistin with alginate oligosaccharide) can enhance antibiotic efficacy. Vaccines and monoclonal antibodies offer preventive and therapeutic options, though some candidates (e.g., MEDI3902) have failed in clinical trials. Natural compounds and bacteriophages represent promising alternatives. Future efforts should focus on translating these strategies into clinical applications to combat infections in high-risk populations.