The Intra-Host Evolutionary Landscape And Pathoadaptation Of PersistentStaphylococcus aureusIn Chronic Rhinosinusitis

Chronic rhinosinusitis (CRS) is a common chronic sinonasal mucosal inflammation associated with Staphylococcus aureus biofilm and relapsing infections. This study aimed to determine rates of S. aureus persistence and pathoadaptation in CRS patients by investigating the genomic relatedness and antibiotic resistance/tolerance in longitudinally collected S. aureus clinical isolates. A total of 68 S. aureus isolates were sourced from 34 CRS patients at least six months apart. Isolates were grown into 48-hour biofilms and tested for tolerance to antibiotics. A hybrid sequencing strategy was used to obtain high-quality reference-grade assemblies of all isolates. Single nucleotide variants (SNV) divergence in the core genome and sequence type clustering were used to analyse the relatedness of the isolate pairs. Single nucleotide and structural genome variations, plasmid similarity, and plasmid copy numbers between pairs were examined. Our analysis revealed that 41% (14/34 pairs) of S. aureus isolates were persisters, while 59% (20/34 pairs) were non-persisters. Persister isolates showed episode-specific mutational changes over time with a bias towards events in genes involved in adhesion to the host and mobile genetic elements such as plasmids, prophages, and insertion sequences. A significant increase in the copy number of conserved plasmids of persister strains (p<0.05) was seen, indicating a role of the “mobilome” in promoting persistence. This was accompanied by a significant increase in biofilm tolerance against all tested antibiotics (p<0.001), which was linked to a significant increase in biofilm biomass (p<0.05) over time, indicating a biofilm central pathoadaptive process in persisters. In conclusion, our study provides important insights into the mutational changes underlying S. aureus persistence in CRS patients highlighting pathoadaptive mechanisms in S. aureus persisters culminating in increased biofilm biomass linked to an increase in plasmid copy number over time.