Impact of Bacterial Membrane Fatty Acid Composition on the Failure of Daptomycin To Kill Staphylococcus aureus

Abstract

Daptomycin is a last-resort membrane-targeting lipopeptide approved for the treatment of drug-resistant staphylococcal infections, such as bacteremia and implant-related infections. Although cases of resistance to this antibiotic are rare, increasing numbers of clinical,in vitro, and animal studies report treatment failure, notably againstStaphylococcus aureus. The aim of this study was to identify the features of daptomycin and its target bacteria that lead to daptomycin treatment failure. We show that daptomycin bactericidal activity againstS. aureusvaries significantly with the growth state and strain, according to the membrane fatty acid composition. Daptomycin efficacy as an antibiotic relies on its ability to oligomerize within membranes and form pores that subsequently lead to cell death. Our findings ascertain that daptomycin interacts with tolerant bacteria and reaches its membrane target, regardless of its bactericidal activity. However, the final step of pore formation does not occur in cells that are daptomycin tolerant, strongly suggesting that it is incapable of oligomerization. Importantly, membrane fatty acid contents correlated with poor daptomycin bactericidal activity, which could be manipulated by fatty acid addition. In conclusion, daptomycin failure to treatS. aureusis not due to a lack of antibiotic-target interaction, but is driven by its capacity to form pores, which depends on membrane composition. Manipulation of membrane fluidity to restoreS. aureusdaptomycin bactericidal activityin vivocould open the way to novel antibiotic treatment strategies.

More Than a Pore: A Current Perspective on the In Vivo Mode of Action of the Lipopeptide Antibiotic Daptomycin

“…Even when cultures were treated with an overkill of 25-100× MIC, it still took about 5 min to achieve maximum membrane depolarization and influx of the membrane-impermeable DNA-binding fluorescence dye Sytox green [74]. Similar results were found at 80× MIC using BacLight as a reporter [57]. In line with these findings on S. aureus, depolarization in Staphylococcus epidermidis occurred at 2-4× MIC after 60 min of treatment and it took 16× MIC to observe depolarization at only 15 min.…”

“…A later study used different lipid mixtures, including 3:1 DMPC/DMPG and 1:1 POPC/POPG (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol), and found that daptomycin pores are likely selective for potassium ions [55]. In fact, some studies have observed potassium leakage from bacterial cells [56][57][58]. Several studies supported the model of a more or less organized daptomycin pore.…”

“…These vastly conflicting observations are most likely due to differences in model membrane composition and peptide concentration [49,[60][61][62]. Thus, studies have found that the ability of daptomycin to permeabilize model membranes does not only depend on the presence of PG, but also on fatty acid chain length and membrane fluidity [49,57,62].…”

Increased resistance of a methicillin-resistant Staphylococcus aureus Δagr mutant with modified control in fatty acid metabolism

“…MRSA strains have acquired several Song et al AMB Expr (2020) 10:64 mechanisms to inactivate or block the effects of antibiotics. For example, formation of a thick biofilm can act as a physical barrier to antibiotics, and structural differences have also evolved, including variations in membrane composition and modifications of the target of antibiotics (Boudjemaa et al 2018;Craft et al 2019;Fishovitz et al 2014). Therefore, the antibiotic resistance of MRSA poses a significant treatment challenge and gaining greater insight into the mechanisms contributing to this resistance can help to guide treatment and control strategies.…”

Bacteriophages Promote Metabolic Changes in Bacteria Biofilm

“…Biofilm production is the response of bacteria to adverse environmental conditions [2], such as the presence of antibiotics, or the need to establish a chronic colonization [3][4][5]. The creation of a (thick) biofilm represents a physical barrier to antibiotics, and structural modifications can also develop in membrane composition and in the antibiotics' targets [6,7]. At present, microbial biofilm production represents a major economic and clinical problem, and its prevention and treatment are therefore a major concern.…”