Biofilm formation of Salmonella enterica serovar Enteritidis and its relation with virulence.

AYA CASTAñEDA MDR; NOTO LLANA M; SARNACKI S; GIACOMODONATO M; CERQUETTI M

Saint malo

Simposio; International Symposium Salmonella and Salmonellosis (I3S); 2016

I3S

Salmonella Enteritidis is currently the most common serovar involved in human salmonellosis. It has been demonstrated that several serovars of S. enterica are able to attach to and form biofilms on a variety of surfaces. This ability has been implicated in the persistence of non-typhoidal Salmonella in the environment, and in industrial, veterinary and medical settings, but the real connection to virulence is unknown yet. In this study, we analyzed the host response induced by S. Enteritidis biofilm and planktonic lifestyles in a murine model of infection. BALB/c mice were infected intragastrically with 2x103 CFU of S. Enteritidis 5694 prepared under two conditions. For biofilm, bacteria were grown in LB broth without salt at 28°C for 48 hours without agitation; for planktonic condition bacteria were grown to an optical density of 0.6 at 600 nm in LB broth at 37°C with agitation. Studies were performed 5 days after inoculation. Interestingly, we found that Salmonella biofilm is less aggressive and less invasive than planktonic bacteria. In this regard, all animals inoculated with Salmonella biofilm survived the infection whereas 25% of mice inoculated with bacteria grown under planktonic conditions died at day 5 post infection. Biofilm S. Enteritidis spleen burden was lower than the planktonic organ load; concomitantly, the intestinal structure was less affected during biofilm infection. In line with these results, biofilm-forming S. Enteritidis induced a lower expression of tumor necrosis factor, interleukins 6, 17, 1â and COX-2 than planktonic bacteria, in infected spleens. These differences could be attributed to changes in virulence factors that occur during planktonic to biofilm transition. Our results indicate that Salmonella-host interaction varies depending on the bacterial lifestyle, where biofilm Salmonella is less invasive, less virulent and generates lower inflammatory responses than the planktonic counterpart.