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.
This rapid high resolution melting (HRM) assay allows distinguishing between Streptococcus suis serotype pairs 2 and 1/2 as well as 1 and 14, respectively, based on a single‐nucleotide polymorphism within capsular polysaccharide synthesis gene cluster K. This assay is easy to implement and identifies potential zoonotic serotypes.
Here we report the whole-genome sequences of 15 clinical Streptococcus suis strains isolated from pigs in Switzerland. Although they originated from the same host and geographic origin, the strains showed a large amount of diversity.
This study investigated the microbiological quality and presence of bacterial foodborne pathogens in 51 raw milk cheeses (mainly semihard and hard cheese) and 53 raw meat products (cured meat products and sausages) marketed at farm level. With regard to Enterobacteriaceae, Escherichia (E.) coli, and coagulase-positive staphylococci (CPS), the examined products were generally of a good microbiological quality. Enterobacteriaceae were found in seven cheeses (1.0×102 – 8.8×104 CFU/g) and one sausage (2.0×102 CFU/g). Three of these cheeses were also positive for E. coli. CPS results were comparable for cheeses (5.9%; 1.0-6.0×102 CFU/g) and meat products (3.8%; 1.0-2.0×102 CFU/g). On the other hand, such raw products may harbor potential health hazards as Listeria (L.) monocytogenes, Shiga toxin-producing E. coli (STEC), and staphylococcal enterotoxin (SE)-producing Staphylococcus (S.) aureus. L. monocytogenes were found in one sausage and the isolate belonged to the serotype 1/2c. The two STEC isolates harbored stx1a (cheese) or stx2e (sausage), but both lacked eae and did not belong to the top five-serogroups. Of the five S. aureus isolates, the three cheese isolates belonged to the clonal complex (CC) 8, CC22, and CC705, the two sausage isolates belonged to CC7, and all isolates harbored genes for SEs. Thus, to avoid contaminations and to prevent foodborne pathogens from entering the food chain, strict compliance with good hygiene practices during milk and cheese production or meat production is of central importance.
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