Presence of Salmonella pathogenicity island 2 genes in seafood-associated Salmonella serovars and the role of the sseC gene in survival of Salmonella enterica serovar Weltevreden in epithelial cells

Abstract

The type III secretion system encoded by theSalmonellapathogenicity island 2 (SPI-2) has a central role in the pathogenesis of systemic infections bySalmonella. Sixteen genes (ssaU,ssaB,ssaR,ssaQ,ssaO,ssaS,ssaP,ssaT,sscB,sseF,sseG,sseE,sseD,sseC,ssaDandsscA) of SPI-2 were targeted for PCR amplification in 57 seafood-associated serovars ofSalmonella. ThesseCgene of SPI-2 was found to be absent in two isolates ofSalmonella entericaserovar Weltevreden, SW13 and SW39. Absence ofsseCwas confirmed by sequencing using flanking primers. SW13 had only 66 bp sequence of thesseCgene and SW39 had 58 bp sequence of this gene. A clinical isolate,S. Weltevreden – SW3, 10 : r : z6 – was used to construct a deletion mutant for thesseCgene. Significant reduction in the survival of SW3, 10 : r : z6 ΔsseCand natural mutants SW13 and SW39 in HeLa cells suggests thatsseChas a crucial role in the intracellular survival ofS. Weltevreden. Expression ofsseCwas upregulated during the intracellular phase of bothS. entericaserovar Typhimurium and clinical isolateS. Weltevreden SW3, 10 : r : z6, suggesting a crucial role for this gene in the survival ofS. Weltevreden inside host cells.