Targeting Resistance Vulnerabilities of Clinical ESKAPE Isolates Using Lactoferrin and Its Functional Fragments

Antimicrobial resistance (AMR) poses a significant global health threat; a major group of AMR organisms are the ESKAPE pathogens. Among these, Gram-negative ESKAPE organisms are particularly concerning due to their extensive contribution to morbidity and mortality. These bacteria are highly adaptable to stressful environments and rapidly develop resistance to antibiotics, often within a few years. Consequently, there is an imperative need to identify novel pathways and molecules for their inhibition. Lactoferrin (LF) is a key innate immune protein recognized for its antimicrobial, immunomodulatory, iron-sequestering, and bacterial membrane-disrupting activities. This study explores the potential of LF and its functional fragments to combat multidrug-resistant (MDR) Gram-negative bacteria. We have evaluated the minimum inhibitory concentrations (MICs) of these molecules against both susceptible control strains and clinical isolates of Gram-negative ESKAPE pathogens. Using checkerboard assays, we assessed the synergy between LF and conventional antimicrobial agent, colistin against clinical isolates. The results demonstrate that Lactoferricin (LFcin) is the most potent biomolecule against ESKAPE pathogens, with an MIC of 125 µg/ml. Importantly, LF showed enhanced antibacterial activity specifically against MDR clinical isolates. Moreover, synergy testing revealed that LF significantly boosts the effectiveness of the antibiotic colistin against these clinical strains, resulting in a 2- to 83-fold improvement in activity depending on the strain.