Metrics details. It has been suggested that prophages in the ST S. We carried out the first characterization of the various prophages carried by 76 ST bloodstream infection BSI isolates obtained over 9 years of observation. The analysis of prophage content in all 76 BSI isolates showed an increasing prevalence of polylysogeny over time.
Overall, over the course of the last 10 years, the BSI isolates appear to have acquired increasing numbers of genetic features previously shown to contribute to bacterial adaptation and virulence in animal models of staphylococcal infections. We hypothesize that lysogeny has played a significant role in increasing the ability of the ST clone to cause infections in humans. Staphylococcus aureus sequence type ST is a lineage initially described in the early s in colonized livestock pigs and in humans living in close contact with these animals [ 1 , 2 ].
Evidence for two major evolutionary changes in the ST lineage was recently provided by studies conducted worldwide [ 3 — 9 ]. First, there has been a widening of the infection spectrum of these bacteria to include humans living in animal-free environments and companion and livestock animals other than pigs.
Through an active BSI surveillance program conducted since in a cohort of hospitals [ 10 ], we identified, in , the first cases of STBSIs in French patients living in animal-free environments [ 7 ]. ST has since become established as a major S. The molecular mechanisms driving the adaptation of the ST lineage in humans remain unclear.
Some studies have suggested a key role for prophages in the epidemiological changes currently taking place in this lineage [ 8 , 11 , 12 ]. However, the prophages carried by the human-adapted isolates remain poorly characterized. Here, we analyzed the prophage content of a complete cohort of STBSI isolates recovered during a continuous study carried out over a period of 15 years in the same health centers [ 10 ].
