# Anti-Biofilm Agents to Overcome _Pseudomonas aeruginosa Antibiotic Resistance_
## 3 Anti-Biofilm Agents to Tackle _P. aeruginosa_
### Eradication of Biofilm-Associated Infections: Combinatorial Approach AVA/ATB  
The use of anti-biofilm agents could prevent biofilm formation and/or help dispersing existing biofilms. Combining an anti-biofilm agent with a conventional antibiotic could thus restore or even potentiate its efficacy against chronic and hard-to-treat infections. **ABA-4**, developed by [PERSON] et al. as a c-di-GMP pathway inhibitor, shows very interesting efficacy in synergy with ciprofloxacin or botramycin by promoting biofilm disruption, thus enabling the killing of dispersed cells by both ATBs in vitro [46]. While ciprofloxacin and botramycin only eradicated 33 and 8% of bacteria, respectively, the pre-treatment with 100 \(\upmu\)M of **ABA-4** led to the elimination of 84 and 57% of bacteria, respectively (Table 1). This antimicrobial activity enhancement is also observed in vivo on a murine model of PAO1 biofilm infection for which the administration of **ABA-4** prior to the ATB treatment improved bacterial clearance. This molecule could be a lead for the development of drugs to be used in combination with ATBs for the treatment of cystic fibrosis lung, wound or urinary tract infections as well as VAP. Another compound, **ABA-58**, described by [PERSON] et al. also restored ciprofloxacin's efficacy against  
Figure 16: Targeted transport of ATB/ABA with cationic pegylated liposomes. _P. aeruginosa_ biofilms [106]. This molecule is not a very potent ABA but diminishes the levels of eDNA, polysaccharides and proteins which constitute the biofilm matrix. Therefore, while the single use of ciprofloxacin eradicated 28% of PA14 bacterial cells in an in vitro biofilm assay, its combination with 50 \(\upmu\)M of **ABA-58** significantly increased its efficacy, up to 62%. In the same way, the benzamide-benzimidazole hybrid **M64 (ABA-36)** has an in vitro synergistic activity from 10 \(\upmu\)M with meropenem or tobramycin against _P. aeruginosa_ PA14 biofilms. Together, they decrease cell viability by 34% and 66%, respectively, vs. 3 and 24%, respectively, in ATB monotherapy [79; 80]. The authors demonstrated that **M64** potentiates the ability of both ATBs to disrupt biofilms in pre-treatment or concomitant treatment. Then, the quinazolinione **ABA-59** developed by [PERSON] et al. revealed an original dual-efficacy with tobramycin against mixed-species biofilms of _P. aeruginosa_ and _S. aureus_[107]. Indeed, the single use of **ABA-59** thus unusually eradicated _S. aureus_ but not _P. aeruginosa_, whereas a monotherapy with tobramycin only killed the pseudomol species (60% eradication at 214 \(\upmu\)M). However, the combination of both **ABA-59** and tobramycin resulted in 95% eradication of both species in the biofilm. In fact, the ABA notably inactivates the production by _P. aeruginosa_ of the QS secondary metabolite HQNO, which is able to decrease the sensitivity of _S. aureus_ to tetracyclines. The ability of **ABA-59** to potentialize the efficacy of tobramycin against these mixed-species biofilms could be of great use for the treatment of cystic fibrosis infections in which both bacteria often co-exist. [PERSON] et al. [62] also evaluated the synergistic anti-biofilm potential of **ABA-18** with tobramycin. When cultured in the presence of **ABA-18**, the biomass was diminished without any effect on cell viability and a subsequent treatment with tobramycin improved biofilm eradication compared to a tobramycin monotherapy (95% inhibition of cell viability in dual therapy vs. 75% in ATB monotherapy). Finally, the compound **GM-50 (ABA-60)** described by [PERSON] et al. potentiated in combination the capacity of aztreonam to disrupt biofilms (60% biofilm dispersal vs. 40% in monotherapy) [108]. Interestingly, the molecular docking study indicated an affinity of **GM-50** towards RhIR. Some AMPs with interesting anti-biofilm activities have also been studied for their ability to potentiate ATBs' efficacy against biofilm-related infections (Table 2).