Abstract
Streptococcus (S.) suis is a globally important swine pathogen, which comprises certain zoonotic serotypes. In this study, a detailed characterization of 88 porcine S. suis isolates was performed by analyzing capsular (cps) types, multilocus sequence typing (MLST) and investigation of the minimum core genome (MCG). In order to focus on the virulence potential of presumable invasive disease-associated S. suis isolates, virulence-associated gene profiles were assessed followed by screening a chosen subset of S. suis strains with a molecular pathotyping tool. Results showed a high genetic variability within this strain collection. In total, seventeen cps types were identified with a predominance of cps type 9 (15.9%) and 6 (14.8%). MLST revealed 48 sequence types (STs) including 41 novel ones. The population structure of S. suis was heterogenous and isolates belonged to eight different clonal complexes (CCs) including CC28 (9.1%), CC1109 (8%), CC13/149 (6.8%), CC1237 (5.7%), CC1 (3.4%), CC17 (3.4%), CC87 (2.3%), and CC1112 (1.1%), whereas a significant portion of isolates (60.2%) could not be assigned to any described CCs. Virulence-associated markers, namely extracellular protein factor (epf), muramidase-released protein (mrp), and suilysin (sly), showed a link with STs rather than with cps types. With this study an expanded knowledge about the population structure and the genetic diversity of S. suis could be achieved, which helps to contribute to an optimal public health surveillance system by promoting a focus on strains with an increased virulence and zoonotic potential.
Highlights
Streptococcus suis (S. suis) is a Gram-positive bacterium recognized to be an important swine pathogen responsible for various diseases including septicemia with sudden death, meningitis, endocarditits, polyserositis, and arthritis [1]
Characterization of S. suis isolates by cps typing and multilocus sequence typing (MLST) Cps typing of the isolates identified a distribution of seventeen different cps types comprising 89.8% of isolates, whereas in 10.2% of cases no cps type could be assigned and were classified as nontypeable (NT) (Additional file 1)
All 13 isolates identified as cps6 comprised a single clone of ST1104, which was not associated to any Clonal complex (CC)
Summary
Streptococcus suis (S. suis) is a Gram-positive bacterium recognized to be an important swine pathogen responsible for various diseases including septicemia with sudden death, meningitis, endocarditits, polyserositis, and arthritis [1]. S. suis colonizes the upper respiratory tract with commensal strains giving rise to carrier pigs [2]. Infection with S. suis leads to major economic problems due to important losses in pig production worldwide, but the bacterium is capable of infecting humans. In Western countries, infection of humans usually involves a single person such as pig farmers, veterinarians, people who work at abattoir, or butchers. Infection mainly takes place through direct contact of skin wounds with contaminated pork even in cases where no obvious wound is present [4]. In Scherrer et al Vet Res (2020) 51:85
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