Salmonella pathogenicity island 1 (SPI-1) (SPI-1)

Salmonella pathogenicity island 1 (SPI-1) is a 40-kb chromosomal region in Salmonella enterica that encodes a Type III Secretion System (T3SS), a complex needle-like apparatus used to inject bacterial effector proteins into the cytoplasm of host cells [1][3]. This system is fundamentally required for the invasion of non-phagocytic intestinal epithelial cells, making it a critical determinant of Salmonella-induced gastroenteritis [2][4]. The activity of SPI-1 is primarily controlled by the master transcriptional regulator HilA, which coordinates the expression of structural components and effectors like SipA, SipB, and SptP [5]. Because SPI-1 is essential for pathogenesis but not for bacterial viability under standard growth conditions, it is an attractive target for anti-virulence drugs that aim to reduce pathogenicity without exerting the high selective pressure typical of traditional antibiotics [6][7]. Experimental small molecules, such as salicylidene acylhydrazides and various natural flavonoids, have been shown to inhibit SPI-1 mediated invasion by disrupting either the transcriptional regulation or the secretory function of the T3SS [8][9]. Targeted inhibition of this island represents a promising strategy for managing antibiotic-resistant Salmonella infections by neutralizing the pathogen's ability to colonize and invade host tissues [10]. Sources: [1] Galán, J. E. (2001). Salmonella interactions with host cells: Type III secretion at work. Annual Review of Cell and Developmental Biology. [2] Mills, D. M., et al. (1995). Salmonella typhimurium invasion genes at the centisome 63 pathogenicity island. Molecular Microbiology. [3] Lostroh, C. P., & Lee, C. A. (2001). The Salmonella pathogenicity island-1 type III secretion system. Microbes and Infection. [4] Ellermeier, C. D., & Slauch, J. M. (2007). Adaptation to the host environment: regulation of Salmonella virulence genes. Current Opinion in Microbiology. [5] Bajaj, V., et al. (1995). HilA is a novel ompR/toxR family member that activates expression of Salmonella typhimurium invasion genes. Molecular Microbiology. [6] Keyser, P., et al. (2008). Virulence blockers as alternatives to antibiotics: type III secretion inhibitors against Gram-negative bacteria. Journal of Internal Medicine. [7] Felise, H. B., et al. (2008). An inhibitor of gram-negative bacterial virulence protein secretion. Cell Host & Microbe. [8] Gantois, I., et al. (2006). Quercetin inhibits Salmonella enterica serovar Typhimurium invasion of epithelial cells by reducing the expression of the SPI-1 genes. Applied and Environmental Microbiology. [9] Tsou, L. K., et al. (2016). Antibacterial antivirulence agents—surmounting the challenges. Chemical Biology & Drug Design. [10] Kouretas, D., et al. (2022). Flavonoids as potential anti-virulence agents against Salmonella. Frontiers in Microbiology.

Other names

SPI1Salmonella type III secretion system 1SptP-dependent invasion systemCentisome 63 pathogenicity island

Inhibition of the type III secretion system (T3SS) needle assembly, suppression of transcriptional regulators such as HilA, and blockage of effector protein translocation into host cells [1][2][6].