A highly pathogenic strain of Salmonella, and one resistant to several antimicrobials, has been studied in order to find out how the organism survives and with the aim of pinpointing vulnerability.

Salmonella is an infectious agent with many faces, appearing in a multitude of strains affecting animals and humans. The particular strain is a variant of the bacterium Salmonella enterica serovar Typhimurium. Isolates are more often recovered from blood rather than from the gastrointestinal tract, which makes the organism particularly dangerous. In the affected parts of Africa, the organism has been causing several illnesses in children including many aged under five years.

To explore this organism further, researchers are looking a shear forces and how these affect the progression of the organism. Shearing forces are unaligned forces pushing one part of an organism in one direction, and another part of the organism in the opposite direction. Under high shear forces, the infectious bacteria progresses faster.

Here strain ST313 behaves differently to other types of Salmonella. This suggests the shear forces within the human gut, where most Salmonella infections occur, differ to those in blood. This suggests differences in evolutionary adaption by different strains of the organism.

The studying of bacteria and how they progress, in relation to shear forces, is an emerging sub-field in microbiology. The term “mechanotransduction” (the ability of bacterial cells to sense and respond to physical forces) has been coined for the study area.

To study the ST313 strain, a research group put together a special device called a rotating wall vessel bioreactor. The reactor is designed to culture cells under different fluid shear levels. Through this the ability of ST313 to infect a person, colonize tissue, and cause illness can be studied.

The results to date suggest new strategies should be possible to slowdown progression of the disease in the human body. These could center on altering the resistance of the organism to pH, bile salts and various fluid-derived stress conditions.

The findings are published in the journal npj Microgravity, within a paper titled “Physiological fluid shear alters the virulence potential of invasive multidrug-resistant non-typhoidal Salmonella Typhimurium D23580.”