Multi-strain Tn-Seq reveals common daptomycin resistance determinants in Staphylococcus aureus.

Area of Science:

• Microbiology
• Genetics
• Drug Discovery

Background:

• Antibiotic-resistant Staphylococcus aureus is a major cause of mortality.
• A continuous pipeline of new antibiotics is essential to combat multi-drug resistant infections.
• Identifying essential genes is a key step in prioritizing targets for new drug development.

Purpose of the Study:

• To directly compare multiple strains of S. aureus using transposon sequencing.
• To identify genes consistently required for survival across different S. aureus strains.
• To assess the impact of strain-dependent differences on essential genes under daptomycin exposure.

Main Methods:

• Transposon sequencing (Tn-Seq) was performed on multiple S. aureus strains.
• Mutant fitness was analyzed to identify essential genes.
• Libraries were treated with daptomycin to evaluate survival pathways.
• Transposons with outward-facing promoters were used to identify resistance mechanisms.

Main Results:

• Mutant fitness varied significantly across different S. aureus strains.
• The lipoteichoic acid pathway consistently promoted survival under daptomycin exposure.
• Strain-dependent differences in gene importance were observed.
• Clinically relevant gain-of-function resistance mechanisms were identified.

Conclusions:

• Comparing Tn-Seq results across multiple strains provides nuanced insights into bacterial essentiality.
• Conserved vulnerabilities, such as in the lipoteichoic acid pathway, can be exploited to resensitize daptomycin-nonsusceptible isolates.
• Daptomycin's mode of action affects the cell envelope and cell division, with identified resistance mechanisms offering therapeutic targets.