Amphiphilic Cationic Macromolecules Highly Effective Against Multi-Drug Resistant Gram-Positive Bacteria and Fungi With No Detectable Resistance

Abstract

The ever increasing threats of Gram-positive superbugs such as methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Staphylococcus aureus (VRSA), and vancomycin-resistant Enterococccus faecium (VRE) are serious matter of concern worldwide toward public health. Such pathogens cause repeated recurrence of infections through the formation of biofilms which consist of metabolically inactive or slow growing dormant bacterial population in vast majority. Concurrently, dispersal of biofilms originates even more virulent dispersed cells responsible for pathogenesis. Along with this, fungal infections most commonly associated with Candida albicans also created a major complicacy in human healthcare. Moreover, concomitant survival of C. albicans and MRSA in a multispecies biofilms created extremely complicated polymicrobial infections. Surprisingly, infections associated with single species biofilm as well as multiple species biofilm (co-existence of MRSA and C. albicans) are almost untreatable with conventional antibiotics. Therefore, the situation demands an urgent development of antimicrobial agent which would tackle persistent infections associated with bacteria, fungi and their biofilms. Toward this goal, herein we developed a new class of branched polyethyleneimine based amphiphilic cationic macromolecules (ACMs) bearing normal alkyl, alkyl ester and alkyl amide moieties. An optimized compound with dual activity against drug-resistant bacteria (MIC = 2-4 µg/mL) and fungi (MIC = 4-8 µg/mL) was identified with minimal toxicity toward human erythrocytes (HC 50 = 270 µg/mL). The lead compound, ACM-A Hex (12) displayed rapid bactericidal and fungicidal kinetics (>5 log CFU/mL reduction within 1-4 h). It also killed metabolically dormant stationary (MRSA and VRE) and persister (S. aureus) cells. Moreover, this compound was able to disrupt the preformed biofilm of MRSA and reduced the bacterial burden related to the dispersed cells. It showed significant proficiencies to eliminate polymicrobial biofilms of MRSA and C. albicans. Bacteria also could not develop any resistant against this class of membrane active molecules even after 15 days of successive passages. Taken together this class of macromolecule can be developed further as a dual therapeutic agent to combat infections associated with bacterial and fungal coexistence .

Bactericidal Activity of a Self-Biodegradable Lysine-Containing Dendrimer against Clinical Isolates of Acinetobacter Genus

“…It should be noted that cases are rarely reported in the literature in which bactericidal behaviors of cationic materials towards various bacterial species lasted up to 24 h. Indeed, for cationic polymers, dendrimers and peptides, time-kill experiments up to 6 or 8 h of exposure have often been reported [ 58 , 59 , 60 ]. Furthermore, when for cationic bactericidal peptides, such as colistin [ 61 ] and dendrimers [ 28 ], the data are reported at 24 h; it can be observed that, while a rapid killing occurred even after only 5 min [ 61 ], and 1 h [ 28 ] from the contact with the cationic antibacterial device, on the contrary, after 24 h of action, an abundant bacterial regrowth happened.…”

Broad-Spectrum Bactericidal Activity of a Synthetic Random Copolymer Based on 2-Methoxy-6-(4-Vinylbenzyloxy)-Benzylammonium Hydrochloride

“…To the best of our knowledge, cases in which the bactericidal behaviors of cationic materials last up to 24 h are rarely reported in the literature. Commonly, for cationic antibacterial molecules, time-kill experiments are often not reported for more than 2, 4, 6, or 8 h [43][44][45]. In fact, for cationic bactericidal peptides, such as colistin [46] and dendrimers [24], for which data have been reported at 24 h, although rapid killing occurred even after just 5 min [46] and 1 h [24] after contact with the antibacterial device, an abundant bacterial regrowth arose after 24 h of action.…”

Macromolecular Nanotherapeutics and Antibiotic Adjuvants to Tackle Bacterial and Fungal Infections

“…In this context, our group introduced a series of amphiphilic cationic macromolecules (ACMs) by functionalizing 600 Da BPEI. [ 265 ] ACMs were synthesized via three simple synthetic steps involving Eschweiler–Clarke methylation followed by quaternization with activated long alkyl group or alkyl ester and amide. Based on structure activity relationship, ACM‐A Hex ( MA‐3 ) (consisting hexyl amide) was identified as the optimum macromolecule which displayed an appreciable antibacterial activity against a panel of MDR Gram‐positive bacteria and fungi including their clinical isolates.…”

“…[ 276 ] Also, the antifungal activity of the cationic polymers are less documented in literature. [ 94,123,265,277,278 ] Typically, developing an antifungal agents is a tough challenge as fungal cells are eukaryotic in nature. [ 279 ] Therefore, in cellular level they closely resemble to other eukaryotic species such as mammalian and plant cells, resulting in the poor selectivity of the conventional drugs.…”