Molecular Microbiology Research 2024, Vol.14, No.1, 1-9 http://microbescipublisher.com/index.php/mmr 4 2 The Process of SalmonellaInfection 2.1 The routes and processes of Salmonella infection Salmonella typically survives and reproduces in the intestines of humans and animals. People can contract Salmonella by consuming contaminated food or drinking contaminated water. In addition, they can also become infected with this bacterium through contact with animals infected with Salmonella, or by directly touching objects contaminated with Salmonella (Figure 2). The process of Salmonella infection can be divided into invasion, survival, and reproduction stages. In the invasion stage, Salmonella adheres to and invades host cells through intestinal epithelial cells. Salmonella utilizes structures such as flagella and capsules on its surface to adhere to and invade host cells. Additionally, Salmonella can secrete various toxins, such as Salmonella cytolysin, to disrupt the membrane structure of host cells, promoting cell adhesion and invasion (Sahler et al., 2018) (Figure 2). In the survival stage, Salmonella needs to evade attacks from the host immune system to survive in the host body. To achieve this, Salmonella can utilize its transport proteins, such as SPI-1, to enter the interior of cells, thereby avoiding attacks from the host immune system. Salmonella also secretes various toxins such as endotoxins and cytotoxins to suppress the immune response of the host immune system and reduce inflammation. In the reproduction stage, Salmonella utilizes its transport proteins, such as SPI-2, to acquire nutrients from within host cells, allowing it to reproduce and survive. Additionally, Salmonella secretes various enzymes and proteases to disrupt the structure and function of host cells, promoting its growth and reproduction (Hornef et al., 2002). After reproducing inside the cell for a period of time, Salmonella leaves the host cell and further spreads to other host cells or tissues. They escape by disrupting the host cell membrane or are directly phagocytosed by host cells and survive within them. Figure 2 Land Bridge ESMSalmonellachromogenic agar (GB 4789.4-2010 Food Microbiology Examination - SalmonellaTesting) Note: Salmonella: Purple-red colonies; Non-Salmonella: Blue-green, colorless, or inhibited 2.2 The life cycle of Salmonella within the host body The process of Salmonella within the host body is quite complex. After infecting the host, Salmonella needs to evade the attack of the host immune system to survive within the host. Salmonella adheres to the host cell surface using specific structures such as flagella and pili, and further invades the host cell by releasing virulence factors and secreting systems. Once successfully invading the host cell, Salmonella begins intracellular replication. It utilizes the nutrients and metabolic mechanisms provided by the host cell to synthesize DNA, RNA, and proteins, and continuously replicates itself through the process of division. In this way, Salmonella is able to multiply in large numbers and continue to infect the host.
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