T-2 toxin alters host-pathogen interactions of Salmonella Typhimurium in pigs

T-2 toxin is a very stable mycotoxin produced by Fusarium spp. which often ends up in the food and feed chain. It poses a threat to human and animal health, especially to pigs which appear to be one of the most sensitive species (Hussein and Brasel, 2001). Besides mycotoxins, Salmonella Typhimurium infections are a major issue in swine production. Therefore, the aim of the presented study was to investigate the effects of T-2 toxin on the course of a Salmonella Typhimurium infection in pigs. We conducted an animal trial in which 3-week-old Salmonella-free piglets were randomized into three groups of 5 piglets. During 23 days, they received ad libitum blank feed (control group), feed contaminated with 10 µg/kg T-2 toxin (10 ppb group) or feed contaminated with 100 µg/kg T-2 toxin (100 ppb group). The pigs were orally inoculated with 2 x 107 colony forming units (CFU) of Salmonella Typhimurium. Five days after inoculation, the pigs were humanely euthanized and samples of intestinal contents and tissues were taken for bacteriological analysis. Compared to the control group, the 10 ppb and 100 ppb group showed lower numbers of Salmonella Typhimurium in jejunum, cecum (p < 0.05) and colon tissue, and cecum (p < 0.05) and colon contents. These results show that the presence of low and in practice relevant concentrations of T-2 toxin in the feed reduces the colonization of Salmonella Typhimurium in the intestine. To elucidate the cause of this reduced colonization, we investigated the effects of T-2 toxin on the host-pathogen interactions of Salmonella Typhimurium and on the gene expression of the bacterium, in vitro. We showed that very low concentrations of T-2 toxin (1-10 ng/ml) promote the susceptibility of porcine alveolar macrophages (PAM) and intestinal porcine epithelial cells (IPEC-J2) to Salmonella Typhimurium invasion, but not to intracellular proliferation of the bacterium. Furthermore we demonstrated that T-2 toxin promotes the translocation of Salmonella Typhimurium over an IPEC-J2 monolayer, at concentrations (1-5 ng/ml) that did not exert a notable effect on porcine cell viability and transepithelial electrical resistance (TEER). These in vitro findings show that T-2 toxin might result in enhanced colonization of Salmonella Typhimurium in pigs. However, microarray analysis showed that T-2 toxin, at a concentration as low as 5 ng/ml, reduces expression of Salmonella Typhimurium motility genes flgL, flgM and flgK. It also causes a general downregulation of the metabolism of Salmonella Typhimurium, which could lead to a decreased colonization of the bacterium. Probably, in vivo, T-2 toxin influences the gene expression of the bacterium before the cell-mediated effect takes place. In conclusion, T-2 toxin significantly affects the gene expression and host-pathogen interactions of Salmonella Typhimurium resulting in a reduced colonization of the bacteria in pigs. References Hussein, H.S. and Brasel, J.M., 2001. Toxicity, metabolism, and impact of mycotoxins on humans and animals. Toxicology, 167, 101-134