Characterisation of a Staphylococcus aureus Isolate Carrying Phage-Borne Enterotoxin E from a European Badger (Meles meles)

Abstract

Staphylococcus (S.) aureus colonizes up to 30% of all humans and can occasionally cause serious infections. It is not restricted to humans as it can also often be found in livestock and wildlife. Recent studies have shown that wildlife strains of S. aureus usually belong to other clonal complexes than human strains and that they might differ significantly with regard to the prevalence of genes encoding antimicrobial resistance properties and virulence factors. Here, we describe a strain of S. aureus isolated from a European badger (Meles meles). For molecular characterisation, DNA microarray-based technology was combined with various next-generation sequencing (NGS) methods. Bacteriophages from this isolate were induced with Mitomycin C and characterized in detail by transmission electron microscopy (TEM) and NGS. The S. aureus isolate belonged to ST425 and had a novel spa repeat sequence (t20845). It did not carry any resistance genes. The uncommon enterotoxin gene see was detected in one of its three temperate bacteriophages. It was possible to demonstrate the induction of all three prophages, although only one of them was expected to be capable of excision based on its carriage of the excisionase gene xis. All three bacteriophages belonged to the family Siphoviridae. Minor differences in size and shape of their heads were noted in TEM images. The results highlight the ability of S. aureus to colonize or infect different host species successfully, which can be attributed to a variety of virulence factors on mobile genetic elements, such as bacteriophages. As shown in the strain described herein, temperate bacteriophages not only contribute to the fitness of their staphylococcal host by transferring virulence factors, but also increase mobility among themselves by sharing genes for excision and mobilization with other prophages.