Varied Contribution of Phospholipid Shedding From Membrane to Daptomycin Tolerance in Staphylococcus aureus

Abstract

It has been suggested that daptomycin can be inactivated by lipids released by Staphylococcus aureus and that this effect is antagonized by phenol soluble modulins (PSMs), which bind to the shed lipids. PSM production is regulated by the Agr system, and others have shown that loss of the Agr function enhances S. aureus survival in the presence of daptomycin. Here we assessed the impact of Agr function on daptomycin activity and lipid metabolism under various conditions. Daptomycin activity was evaluated against three sets of isogenic strain series with wild-type or dysfunctional Agr using static daptomycin time-kills over 24 h and against one strain pair using in vitro pharmacokinetic/pharmacodynamic (PK/PD) models simulating clinical daptomycin exposure for 48 h. We performed comprehensive lipidomics on bacterial membranes and the spent media to correlate lipid shedding with survival. In static time-kill experiments, two agr-deficient strains (SH1000- and USA300 LAC ΔagrA) showed improved survival for 8 h compared with their corresponding wild-type strains as seen in previous studies, but this difference did not persist for 24 h. However, four other agr-deficient strains (SH1001 and JE2 agr KOs) did not demonstrate improved survival compared to isogenic wild-type strains at any time in the time-kills. Lipidomics analysis of SH1000, SH1001, and SH1000- strains showed daptomycin exposure increased lipid shedding compared to growth controls in all strains with phosphatidylglycerols (PGs), lysylPGs and cardiolipins predominating. In the cell pellets, PGs and lysylPGs decreased but cardiolipins were unchanged with daptomycin exposure. The shed lipid profiles in SH1001 and SH1000- were similar, suggesting that the inability to resist daptomycin by SH1001 was not because of differences in lipid shedding. In the PK/PD model, the agr mutant SH1000- strain did not show improved survival relative to SH1000 either. In conclusion, inactivation of daptomycin by shed lipids may be dependent on genetic background, the specific agr mutations, or the techniques used to generate these KOs rather than the overall function of the Agr system, and its contribution to daptomycin tolerance seems to be varied, transient, and growth-condition dependent.

Proteome profiling of evolved methicillin-resistant Staphylococcus aureus strains with distinct daptomycin tolerance and resistance phenotypes

“…For instance, S. aureus inactivates daptomycin by releasing membrane phospholipids into the extracellular space, thereby sequestering daptomycin and preventing it from inserting into the bacterial membrane ( Pader et al, 2016 ). Strains with different genetic backgrounds may exhibit different contributions of phospholipid shedding and hence have different tolerance levels to daptomycin ( Shen et al, 2021 ). Indeed, in our previous study, we found that reduced daptomycin tolerance in MRSA was associated with a reduced lipid metabolic process ( Sulaiman et al, 2021 ).…”

Polymyxin and lipopeptide antibiotics: membrane-targeting drugs of last resort

“…Furthermore, daptomycin-induced phospholipid release does not occur in all strains of S. aureus , which may provide a route to a greater mechanistic understanding of this phenomenon [205, 206].…”

“…This process appears require phospholipid biosynthesis, since the presence the fatty acid synthesis (FASII) inhibitor AFN-1252 blocks daptomycin-induced phospholipid release, suggesting it is not simply a consequence of daptomycin-mediated membrane damage [205]. Furthermore, daptomycin-induced phospholipid release does not occur in all strains of S. aureus, which may provide a route to a greater mechanistic understanding of this phenomenon [205,206].…”

Molecular phenotyping approaches for the detection and monitoring of carbapenem-resistant Enterobacteriaceae by mass spectrometry

“…Nonetheless, studies such as these lay the foundation for future work, with biomarker discovery not feasible without the availability of comprehensive profiles and initial exploratory analysis. Studies by Hines et al, however, circumvented these issues by employing a hydrophilic interaction LC-ion mobility-MS (HILIC-IM-MS) method to separate lipids based on both head group polarity and gas phase structure, facilitating more powerful discrimination [93] , [94] , [95] . Results validated those of Rashid et al, and revealed alterations in the lipid profiles of daptomycin-resistant MRSA and Corynebacterium striatum [92] , [93] .…”