Characterization of the outer membrane subproteome of the virulent strain Salmonella Typhimurium SL1344

Outer membrane proteins (OMPs) play an important role in the interaction of bacterial pathogens with host cells. Indeed, some OMPs from different Gram-negative bacteria have been recognized as important virulence factors for host immune recognition. This scenario has led to the study of the outer membrane (OM) subproteome of pathogenic bacteria as an essential step for gaining insight into the mechanisms of pathogenesis and for the identification of virulence factors. Although progress in the characterization of the OM has recently been reported, detailed protein composition of this subcellular localization has not been clearly defined for most pathogens. Salmonella enterica serovar Typhimurium is not only a leading cause of human gastroenteritis in high-income countries but is also one of the main causes of invasive non-typhoidal salmonellosis (iNTS) in middle- and low-income countries. The incidence of non-typhoidal salmonellosis is increasing worldwide, causing millions of infections and deaths among humans each year. Regrettably, antimicrobial resistance to a broad spectrum of antibiotics is common among non-Typhi Salmonella strains. Therefore, the development of vaccines targeting this leading invasive pathogen is warranted. In the present study we have identified the OM protein profile of the virulent S. Typhimurium strain SL1344 by means of sarkosyl extraction.

Salmonella enterica serovar Typhimurium causes food-borne gastroenteritis around the world, but is also responsible for a more serious manifestation of the disease through a form of invasive illness, invasive non-typhoidal Salmonella (iNTS) disease, which is considered a major public health problem in low- and middle-income countries. Even though some studies have been carried out in order to characterize the outer membrane subproteome of this human pathogen, as far as we know, this is the first report in which the most indicated methodology has been used in order to extract the outer membrane proteins and to check the presence of the proteins in the SL1344 genome; indeed all the previous studies were carried out before the genome sequence was available in 2012. Outer membrane proteins are key elements for the interaction of Gram-negative bacteria with their environment – including the host – and have fundamental roles in both infection and resistance processes. Therefore, a detailed knowledge of the outer membrane composition will certainly play a key role in providing new targets to fight this pathogen in further studies.