Searching for new strategies against biofilm infections: Colistin-AMP combinations against <i>Pseudomonas aeruginosa</i> and <i>Staphylococcus aureus</i> single- and double-species biofilms

Antimicrobial research is being pressured to look for more effective therapeutics for the ever-growing antibiotic-resistant infections, and antimicrobial peptides (AMP) and antimicrobial combinations are promising solutions. This work evaluates colistin-AMP combinations against two major pathogens, Pseudomonas aeruginosa and Staphylococcus aureus, encompassing non- and resistant strains. Colistin (CST) combined with the AMP temporin A (TEMP-A), citropin 1.1 (CIT-1.1) and tachyplesin I linear analogue (TP-I-L) was tested against planktonic, single- and double-species biofilm cultures. Overall synergy for planktonic P. aeruginosa and synergy/additiveness for planktonic S. aureus were observed. Biofilm growth prevention was achieved with synergy and additiveness. Pre-established 24 h-old biofilms were harder to eradicate, especially for S. aureus and double-species biofilms; still, some synergy and addictiveness was observed for higher concentrations, including for the biofilms of resistant strains. Different treatment times and growth media did not greatly influence AMP activity. CST revealed low toxicity compared with the other AMP but its combinations were toxic for high concentrations. Overall, combinations reduced effective AMP concentrations, mainly in prevention scenarios. Improvement of effectiveness and toxicity of therapeutic strategies will be further investigated.抗菌研究正面临迫切需求，需为持续增多的抗生素耐药感染开发更高效的治疗手段，而抗菌肽（Antimicrobial Peptides, AMP）与抗菌联合疗法均为极具前景的解决方案。本研究针对两种主要病原菌——铜绿假单胞菌（Pseudomonas aeruginosa）与金黄色葡萄球菌（Staphylococcus aureus，包含非耐药及耐药菌株），评估了粘菌素（Colistin, CST）与AMP的联合抗菌效果。实验将粘菌素（CST）分别与temporin A（TEMP-A）、citropin 1.1（CIT-1.1）以及tachyplesin I线性类似物（TP-I-L）联合，对浮游态、单物种及双物种生物膜培养物开展测试。结果显示，浮游态铜绿假单胞菌呈现整体协同效应，浮游态金黄色葡萄球菌则呈现协同/相加效应。联合疗法可通过协同与相加作用实现生物膜生长抑制。预先形成的24小时龄生物膜更难被清除，尤其是金黄色葡萄球菌及双物种生物膜；但在高浓度条件下，仍可观察到部分协同与相加效应，包括耐药菌株的生物膜。不同处理时长与培养基对AMP的抗菌活性无显著影响。与其他AMP相比，粘菌素毒性较低，但其联合疗法在高浓度下会产生毒性。总体而言，联合疗法可降低AMP的有效使用浓度，在生物膜生长预防场景中效果尤为显著。本研究将进一步探索优化治疗策略的抗菌效果与毒性表现的方法。