Eliciting improved antibacterial efficacy of host proteins in the presence of antibiotics

Abstract

We recently reported the aptitude of a membrane-active lipopeptide (COOcO) to sensitize gram-negative bacilli (GNB) to host antibacterial proteins. Here we explored the potential of harnessing such capacity in the presence of antibiotics. For this purpose, we compared sensitization to antibiotics in broth and plasma; assessed inner and outer membrane damages using scanning electron microscopy, dyes, and mutant strains; and assessed the ability to affect disease course using the mouse peritonitis-sepsis model for mono- and combination therapies. We found that by altering permeability of both outer and inner membranes, subinhibitory concentrations of COOcO can transiently sensitize GNB to diverse cytoplasm-targeting antibiotics in simple media. Sensitization was maintained in plasma, where COOcO instigated greater bactericidal activities, including in the presence of a bacteriostatic antibiotic (erythromycin). Single-dose administrations of rifampin and COOcO to -infected mice resulted in 55% 0, and 36% viability, respectively, for combined and individual treatments. Combining COOcO and erythromycin has similarly improved mice protection from developing fatal sepsis. Consequently, the data confirmed that COOcO renders GNB sensitive to both endogenous and exogenous antibacterials, and suggested that the tripartite concomitant presence increases therapeutic efficacy synergistically. This approach might expand the available treatment options to comprise antimicrobials with low permeability and/or efflux issues.-Jammal, J., Zaknoon, F., Mor, A. Eliciting improved antibacterial efficacy of host proteins in the presence of antibiotics.

An efflux-susceptible antibiotic-adjuvant with systemic efficacy against mouse infections

“…Similar relationships were recorded with another isogenic pair of Salmonella enterica serovar Typhimurium. These outcomes would sit well with the notion that C 10 BBc 12 B is an efflux substrate, very much as previously proposed for its analogs C 10 KKc 12 K 26 and C 10 OOc 12 O 29 , unlike C 14 OOc 12 O 23 or C 14 KKc 12 K 24 . Accordingly, the polymyxins (e.g., PMB or colistin), often described as unlikely efflux-substrates 43 – 45 are in fact efficient CM-destabilizers that swiftly dissipate the TMP, thereby obstructing the proper proton-dependent function of resistance-nodulation-division (RND) efflux pumps, including the AcrAB-TolC system commonly expressed in Enterobacteriaceae.…”

“…, 80% mortality in control mice was reached at two–three days post-infection, using similar inoculum size) mice treated with C 10 BBc 12 B or rifampin displayed roughly comparable (40 and 50%, respectively) improved survival rates, as compared to the vehicle control, whereas the combination treatment reached 90% survival. The fact that C 10 BBc 12 B showed some efficacy even in absence of rifampin evokes our previous findings 22 , 29 where using a similar infection model and treatment, C 10 OOc 12 O has also exhibited significant monotherapy efficacy. While the molecular basis for the pentamers’ abilities to prevent mice death in absence of an exogenous antibiotic is yet to be elucidated, we provided various lines of evidence arguing for the possible role played by one or more endogenous antimicrobials that may have substituted for rifampin’s role.…”

“… Compound MIC a (µM) in LB References E. coli S . Typhimurium Wild-Type Mutant Wild-Type Mutant Erythromycin > 50 10.9 > 50 6.8 46 Rifampin 19.4 19.4 19.4 19.4 46 Polymyxin B 0.7 0.7 0.7 0.7 Current study C 14 KKc 12 K 6.2 6.2 3.1 3.1 24 C 10 KKc 12 K > 50 6.2 > 50 25 26 C 10 OOc 12 O > 50 6.2 > 50 6.2 29 C 10 BBc 12 B 50 6.2 > 50 12.5 Current study a Minimal inhibitory concentrations determined using the broth microdilution method, as respectively assessed against wild-type (Ag100 and 14028) and efflux deficient (Ag100a and 1...…”

Mechanistic Studies of Antibiotic Adjuvants Reducing Kidney’s Bacterial Loads upon Systemic Monotherapy

“…Yet, it is reminiscent of reports concerning PMB [47] and related cyclic lipopeptides whose direct antibacterial potency was de-facto substituted for potentiation activity [48] merely by reducing molecular hydrophobicity (e.g., by deleting the fatty acid tail). Furthermore, the overall properties itemized in Table 1 were also reminiscent of previous findings using an OAC analog C 10 OOc 12 O [29,30] proposed to elicit improved activity of innate antibacterial proteins, allegedly through increasing OM permeability. Thus, to corroborate the possibility that similar principles might prevail for C 14(ω5) OOc 10 O, this analog was similarly tested.…”

“…From this perspective, the AMP mimetic approach based on oligomeric acylated cations (OAC) [26] appears particularly suitable for engineering membrane active selective compounds [10,27,28], as it provides a simple, sensitive, and systematic tool for dissecting the relative importance of two most critical AMP attributes, charge and hydrophobicity, as will be illustrated herein. Recent OAC designs [29][30][31][32][33] have concentrated on the pentameric formula A 1 C 1 C 2 A 2 C 3 , where As and Cs represent acyl derivatives and cationic amino acids, respectively. Among the sequences investigated so far, C 14 KKc 12 K (Figure 1a) revealed broad-spectrum bactericidal properties [32].…”