Amino-Acid-Conjugated Polymer-Rifampicin Combination: Effective at Tackling Drug-Resistant Gram-Negative Clinical Isolates

Abstract

Rapid emergence of multidrug-resistant Gram-negative pathogens coupled with their biofilm-forming capability have set a clinical ultimatum to global public health with an increasing rate of mortality. Recently, the World Health Organization (WHO) identified <i>Acinetobacter baumannii</i>, <i>Pseudomonas aeruginosa</i>, and enterobacteriaceae (<i>Klebsiella pneumoniae</i>, <i>E. coli</i>, etc.) as the pathogens of top priority because of their ability to cause difficult-to-treat life-threatening infections insusceptible to conventional antibiotic therapy. Hence, the severity of the current scenario necessitates the development of a potent therapeutic agent with a smart strategy. Toward this goal herein, we have explored the potency of membrane-active, amino-acid-conjugated polymers (ACPs) to combat notorious Gram-negative pathogens in combination with intrinsically resistant antibiotic rifampicin. The polymers were able to enhance the antibacterial potency of rifampicin against different drug-resistant Gram-negative bacteria by 4-66 fold. The combination, which consisted of glycine-conjugated polymer, ACP-<b>1</b> (Gly), and rifampicin was rapidly bactericidal in nature. This combination also exhibited significant potency to disrupt the preformed biofilms of drug-resistant strains of <i>P. aeruginosa</i> and <i>E. coli</i>. More importantly, a negligible propensity of resistance development was observed against this combination, whereas a high level of resistance development was observed against the last-resort antibiotic, colistin. Furthermore, ACP-<b>1</b> (Gly) displayed noticeably good 50% lethal dosage in different administration routes (LD₅₀ (subcutaneous) > 179 mg/kg and LD₅₀ (intraperitoneal) = 100 mg/kg) in a mouse model. Additionally, ACP-<b>1</b> (Gly) did not show any adverse effect on mouse skin even at 200 mg/kg. Therefore, the results ensured that the ACP-<b>1</b> (Gly) is suitable for both topical as well as systemic application. Altogether, the results indicated significant promises of the combination for further development as a therapeutic regimen to tackle the outbreak of critical Gram-negative bacteria.