An in vitro study on Staphylococcus schweitzeri virulence

Grossmann A, Froböse NJ, Mellmann A, Alabi AS, Schaumburg F, Niemann S

Abstract

Abstract Staphylococcus schweitzeribelongs to theStaphylococcus aureus-related complex and is mainly found in African wildlife; no infections in humans are reported yet. Hence, its medical importance is controversial. The aim of this work was to assess the virulence ofS. schweitzeriin vitro. The capacity of AfricanS. schweitzeri(n = 58) for invasion, intra- and extracellular cytotoxicity, phagolysosomal escape, coagulase activity, biofilm formation and host cell activation was compared withS. aureusrepresenting the most common clonal complexes in Africa (CC15, CC121, CC152). Whole genome sequencing revealed that theS. schweitzeriisolates belonged to five geographical clusters. Isolates from humans were found in two different clades.S. schweitzeriandS. aureusshowed a similar host cell invasion (0.9 vs. 1.2CFU/Vero cell), host cell activation (i.e. expression of pro-inflammatory cytokines, 4.1 vs. 1.7 normalized fold change in gene expression ofCCL5; 7.3 vs. 9.9 normalized fold change in gene expression ofIL8, A549 cells) and intracellular cytotoxicity (31.5% vs. 25% cell death, A549 cells). The extracellular cytotoxicity (52.9% vs. 28.8% cell death, A549 cells) was higher forS. schweitzerithan forS. aureus. Nearly all testedS. schweitzeri(n = 18/20) were able to escape from phagolysosomes. In conclusion, someS. schweitzeriisolates display virulence phenotypes comparable to AfricanS. aureus. S. schweitzerimight become an emerging zoonotic pathogen within the genusStaphylococcus.