Presence and genetic variability of Staphylococcus aureus subsp. anaerobius isolated from small ruminants in Central Europe

Staphylococcus aureus subsp. anaerobius (SAAN) causes abscesses in small ruminants, known as Morel's Disease. This study describes the presence of SAAN for the first time in Germany and Austria and examines the phylogenetic relationship among these isolates and previously described European and Sudanese ones. A total of 35 sheep and 10 goat isolates from 12 herds in Germany were available for analysis. SAAN isolates from four Polish goats and three Austrian sheep from different herds were included. Genome comparisons and phylogenetic analyses were conducted using core genome multilocus sequence typing. The comparison of the 52 SAAN core genomes revealed a close phylogenetic relationship among most German isolates (n = 38), with allelic differences ≤ 6 in two clusters associated with ST4581. In contrast, distinct clusters of the same ST included the four Polish goat isolates and two ovine isolates from Austria, respectively. A fifth cluster of ST3756 strains was identified on three German farms (six sheep, one goat) and an Austrian sheep. Tight phylogenetic relationships were observed irrespective of the host species. All isolates shared a common set of virulence genes and few known antimicrobial resistance determinants. The introduction of SAAN into herds is mostly unknown, but purchases appear to play a critical role.