News feature: Next-generation antibiotics

Tailored liposomal nanotraps for the treatment of Streptococcal infections

BACKGROUND

Streptococcal infections are associated with life-threatening pneumonia and sepsis. The rise in antibiotic resistance calls for novel approaches to treat bacterial diseases. Anti-virulence strategies promote a natural way of pathogen clearance by eliminating the advantage provided to bacteria by their virulence factors. In contrast to antibiotics, anti-virulence agents are less likely to exert selective evolutionary pressure, which is a prerequisite for the development of drug resistance. As part of their virulence mechanism, many bacterial pathogens secrete cytolytic exotoxins (hemolysins) that destroy the host cell by destabilizing their plasma membrane. Liposomal nanotraps, mimicking plasmalemmal structures of host cells that are specifically targeted by bacterial toxins are being developed in order to neutralize-by competitive sequestration-numerous exotoxins.

RESULTS

In this study, the liposomal nanotrap technology is further developed to simultaneously neutralize the whole palette of cytolysins produced by Streptococcus pneumoniae, Streptococcus pyogenes and Streptococcus dysgalactiae subspecies equisimilis-pathogens that can cause life-threatening streptococcal toxic shock syndrome. We show that the mixture of liposomes containing high amounts of cholesterol and liposomes composed exclusively of choline-containing phospholipids is fully protective against the combined action of exotoxins secreted by these pathogens.

CONCLUSIONS

Unravelling the universal mechanisms that define targeting of host cells by streptococcal cytolysins paves the way for a broad-spectrum anti-toxin therapy that can be applied without a diagnostic delay for the treatment of bacterial infections including those caused by antibiotic-resistant pathogens.

Antibiotic Hybrids: the Next Generation of Agents and Adjuvants against Gram-Negative Pathogens?

The global incidence of drug-resistant Gram-negative bacillary infections has been increasing, and there is a dire need to develop novel strategies to overcome this problem. Intrinsic resistance in Gram-negative bacteria, such as their protective outer membrane and constitutively overexpressed efflux pumps, is a major survival weapon that renders them refractory to current antibiotics. Several potential avenues to overcome this problem have been at the heart of antibiotic drug discovery in the past few decades. We review some of these strategies, with emphasis on antibiotic hybrids either as stand-alone antibacterial agents or as adjuvants that potentiate a primary antibiotic in Gram-negative bacteria. Antibiotic hybrid is defined in this review as a synthetic construct of two or more pharmacophores belonging to an established agent known to elicit a desired antimicrobial effect. The concepts, advances, and challenges of antibiotic hybrids are elaborated in this article. Moreover, we discuss several antibiotic hybrids that were or are in clinical evaluation. Mechanistic insights into how tobramycin-based antibiotic hybrids are able to potentiate legacy antibiotics in multidrug-resistant Gram-negative bacilli are also highlighted. Antibiotic hybrids indeed have a promising future as a therapeutic strategy to overcome drug resistance in Gram-negative pathogens and/or expand the usefulness of our current antibiotic arsenal.