Molecular Microbiology Research 2024, Vol.14, No.1, 1-9 http://microbescipublisher.com/index.php/mmr 3 Figure 1Salmonellaelectron microscopic image (SalmonellaTesting Technique, 2021) The growth characteristics and metabolic pathways of Salmonella have strong adaptability and diversity. It can utilize various organic and inorganic substances for metabolism, adapting to different environmental conditions and nutritional sources. This also provides a certain basis for Salmonella to survive and spread in the intestines or environment. 1.3 The virulence factors of Salmonella and their mechanism of action As a Gram-negative bacterium, Salmonella is one of the commensal bacteria in the intestines of humans and animals. Although Salmonella is not harmful to the human body under normal conditions, when they enter and multiply in the human body, they can cause various problems, including food poisoning and intestinal infections. The pathogenicity of Salmonella is mainly caused by various virulence factors. These virulence factors can help Salmonella invade host cells, disrupt the host immune system, and cause intestinal inflammation, etc. Among them, the surface antigens of Salmonella can help it adhere to the intestines, invade host cells, and evade attacks from the host immune system. The surface antigens of Salmonella include capsules, flagella, O antigens, H antigens, etc. Different combinations of these surface antigens form different strains and serotypes. For example, certain strains of Salmonella can evade attacks from the host immune system by changing the combination of capsules. It can also secrete various toxins, including endotoxins, cytotoxins, and exotoxins. These toxins can destroy the structure and function of host cells, causing cell death and tissue damage. The endotoxin of Salmonella is a lipopolysaccharide that can cause an inflammatory response in the host immune system, leading to symptoms such as vasodilation and hypotension. Its cytotoxin can destroy the membrane structure of host cells, leading to cell death. For example, Salmonella cytolysin is a cytotoxin that can destroy the membrane of host cells. The exotoxin of Salmonella can inhibit the signal transduction pathway of the host immune system and disrupt the immune response of host cells (Behnsen et al., 2015). Salmonella also has various transport proteins, including Salmonella pathogenicity island (SPI) 1, SPI-2, etc. These transport proteins can help Salmonella enter host cells and evade attacks from the host immune system, thereby causing infections. SPI-1 and SPI-2 are two different transport proteins that play roles in different stages of infection. SPI-1 can help Salmonella enter host intestinal epithelial cells, while SPI-2 can help Salmonella survive and multiply inside host cells.
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