Phenotypic and genotypic characterization of clinical Staphylococcus lugdunensis isolates: a French retrospective cohort study

Despite its dominance as a commensal, Staphylococcus lugdunensis (SLU) is a particularly virulent coagulase-negative Staphylococcus that is predominantly associated with community-acquired soft-tissue and skin infections. The aim of our study was to identify genotypic and phenotypic traits associated with the clinical presentations of SLU-associated infections, such as prosthetic joint infections, infective endocarditis (IE), and skin and soft tissue infections. Between January 2001 and December 2016, 73 pathogenic (including 18 strains responsible for IE) and 3 nonpathogenic SLU strains were retrospectively collected from nine French hospitals. All the strains belonged to six clonal complexes (CC1 to CC6) and 12 sequence types (STs). Interestingly, the capacity of the IE-associated strains to bind the von Willebrand factor was greater than that of the other strains, regardless of the CC. Biofilm formation was significantly increased for the most common CCs involved in infections (CC1, CC2, and CC3) and for IE-associated strains. The ability of SLU to inhibit other pathogens varied depending on the CCs caused by specific mutations within the lug operon that resulted in truncated protein expression. Genetic variants from genome virulence genes such as agrC and atIL also vary according to STs. The Galleria mellonella infection model revealed that CC4 was more virulent than the other CCs. On the basis of a large sequenced collection of SLU strains, we found that important phenotypic variation occurred among clinical strains and seemed to be related to some type of infection.

IMPORTANCE

Staphylococcus lugdunensis is a coagulase-negative Staphylococcus recognized for its virulence in human clinical infections. However, few studies have focused on investigating the phenotypic and genotypic aspects, as well as the population characteristics, of clinical strains involved in severe invasive infections such as endocarditis or skin and soft tissue infections, or of strains associated with so-called cutaneous carriage. Here, we compared different virulence gene variants in terms of populational aspects and also highlighted important phenotypic trait changes according to the clinical presentation and site of isolation of the strains.