An in vitro study on Staphylococcus schweitzeri virulence

Abstract

Staphylococcus schweitzeri belongs to the Staphylococcus 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 of S. schweitzeri in vitro. The capacity of African S. schweitzeri (n = 58) for invasion, intra- and extracellular cytotoxicity, phagolysosomal escape, coagulase activity, biofilm formation and host cell activation was compared with S. aureus representing the most common clonal complexes in Africa (CC15, CC121, CC152). Whole genome sequencing revealed that the S. schweitzeri isolates belonged to five geographical clusters. Isolates from humans were found in two different clades. S. schweitzeri and S. aureus showed a similar host cell invasion (0.9 vs. 1.2 CFU/Vero cell), host cell activation (i.e. expression of pro-inflammatory cytokines, 4.1 vs. 1.7 normalized fold change in gene expression of CCL5; 7.3 vs. 9.9 normalized fold change in gene expression of IL8, 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 for S. schweitzeri than for S. aureus. Nearly all tested S. schweitzeri (n = 18/20) were able to escape from phagolysosomes. In conclusion, some S. schweitzeri isolates display virulence phenotypes comparable to African S. aureus. S. schweitzeri might become an emerging zoonotic pathogen within the genus Staphylococcus.

Pseudomonas aeruginosa and Staphylococcus aureus virulence factors as biomarkers of infection

“…Although the previous studies showed that the cultureindependent assays based on detection of MNase activity could provide needed specificity for the detection of S. aureus, homologs of the nuc gene were also found in other species of the S. aureus complex (Grossmann et al 2021). Therefore, we cannot exclude a possibility that infections caused by Staphylococcus schweitzeri (possessing nuc M ) or uncommon coagulase-negative staphylococci may yield false-positive identifications since they were not examined previously (Burghardt et al 2016;López-Álvarez et al 2020).…”

Staphylococcus schweitzeri—An Emerging One Health Pathogen?

“…The isolates were obtained almost exclusively from animals, fruit bats, non-human primates and a gorilla. In three cases, colonization in humans was detected, but these were probably spillover events from handling animals that carried S. schweitzeri [3,10,30]. This low rate was actually surprising, because S. schweitzeri has been found in animals that serve as bushmeat [9].…”

“…Recent studies applied multilocus sequence typing (MLST) or whole genome sequencing to distinguish the members of the S. aureus-related complex [5,6,10,31]. Phylogenetic trees are constructed to identify the closest related species within the S. aureus complex.…”

“…Such a delineation in different species-related clades holds true for other phylogenetic methods (e.g., maximum likelihood method, Supplementary Figure S2). Similarly, the core genome MLST (cgMLST) for S. aureus including 1861 targets can be used to construct phylogenetic trees with a higher resolution [10].…”

Canine Staphylococcus argenteus: Case Report from The Netherlands

“…Several more clonal complexes have been described to belong to S. argenteus since and multiple studies have elaborated on its worldwide spread, including Australia, Africa, Asia, America and Europe [2]. S. aureus and S. argenteus have been implicated in disease in humans and non-humans [2,3], whereas the closely related S. schweitzeri has been found primarily in bats and non-human primates and no human infections have been described to date [4,5]. Human S. argenteus infections are associated with serious morbidity, mortality and nosocomial infection in humans [3,6], and isolates have been shown to harbor most of the virulence genes of S. aureus [5].…”