Salmonella’s ‘stealthy’ ways decoded

A new study has cracked the crafty modus operandi of the dreaded Salmonella bacteria, which infects millions with typhoid, gastroenteritis and reactive arthritis every year.

Salmonella uses a unique and ‘stealthy’ strategy to colonise its host’s cells to dodge and finally paralyse the immune system while also making its victim potentially susceptible to other diseases such as tuberculosis and E. coli, finds a research paper by scientists from the Indian Institute of Science (IISc.).

The paper on the “Novel strategy of Salmonella to avoid lysosomes” will be published in January 2010 by the American Society for Microbiology in Infection and Immunity, and has already been published online.

Salmonella, like many other bacteria, ensconces itself in the host cell’s nutrient-rich vesicles, but its novelty lies in the way it escapes the host cell’s enzyme-filled ‘lysosomes,’ which are integral parts of our defence mechanism, trapping and digestion pathogens.

Unlike any other pathogen, the ‘intelligent’ Salmonella changes the way the host cell behaves and gets the protective vesicle to divide with it, therefore encasing each bacterium in a protective bubble. This phenomenon also decreases the efficacy and growth of lysosomes, explains co-author Dipshikha Chakravortty of the Department of Microbiology and Cell Biology of the IISc.

“Most pathogenic bacteria multiply within a single vesicle making them easier targets for the body’s defences. Here, each bacterium gets a safe niche,” Dr. Chakravortty said. This finding also contradicts earlier theories about Salmonella’s strategies against lysosomes. Experiments on mice also showed that as the number of Salmonella vesicles grew, the number of lysosomes decreased.

“Because this peculiar behaviour of Salmonella reduces the microbicidal [elimination of pathogen] ability of the host cell, the host can potentially become susceptible to other intracellular… pathogens like E. coli, M. tuberculosis, etc.,” states the paper, co-authored by Sandeepa M. Eswarappa, also from the Department of Microbiology and Cell Biology, IISc.

It adds that the increase in number of vesicles “demands more investment from the host cell to counteract Salmonella… [which] potentially results in a condition where an infected cell is left with insufficient acidic lysosomes to target the increasing number of [vesicles].” The imbalance in the lysosome-vesicle ratio helps Salmonella to successfully increase its life-span and its boosts its ability to proliferate.

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Printable version | Jun 12, 2021 4:07:46 PM |

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