Genomic and Phenotypic Analysis Reveal the Emergence of an Atypical Salmonella Senftenberg Variant in China.

Abd El Ghany M1, Shi X2, Li Y2, Ansari HR3, Hill-Cawthorne GA4, Ho YS3, Naeem R3, Pickard D5, Klena JD6, Xu X7, Pain A1, Hu Q8.

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Abstract

Human infections with Salmonella enterica subspecies enterica serovar Senftenberg are often associated with exposure to poultry flocks, farm environments or contaminated food. The recent emergence of multidrug-resistant isolates has raised public health concerns. In this study comparative genomics and phenotypic analysis were used to characterize 14 clinical Salmonella Senftenberg isolates recovered from multiple outbreaks in Shenzhen and Shanghai, China between 2002 and 2011. Single nucleotide polymorphism analyses identified two phylogenetically distinct clades of S. Senftenberg, designated SC1 and SC2, harboring variations in Salmonella Pathogenicity Island-1 and 2 and exhibiting distinct biochemical and phenotypic signatures. Although both variants shared an identical serotype, the SC2 isolates of sequence type-14 (ST14) harbored intact SPI-1 and 2 and hence were characterized by possessing efficient invasion capabilities. In contrast, the SC1 isolates had structural deletion patterns in both SPI-1 and 2 that correlated with an impaired capacity to invade human cultured cells and also the year of their isolation. These atypical SC1 isolates also lacked the capacity to produce hydrogen sulfide. These findings highlight the emergence of atypical Salmonella Senftenberg variants in China and provide genetic validation that variants lacking SPI-1and regions of SPI-2, leading to impaired invasion capacity, can still cause clinical disease. These data have identified an emerging public health concern and highlight the need to strengthen surveillance to detect the prevalence and transmission of non-Typhoidal Salmonella species.