Salmonella how does it attack

Most salmonella species infect the small intestines upon ingestion. Illness can be caused by as few as cells. The bacteria pass through the interior lining of the small intestines and into its middle layer, causing inflammation. Prolonged infection of salmonella can spread to the blood-stream and other organs, increasing disease length and severity.

The Typhi serotype spreads from the small intestines to the bloodstream and infects the lymph nodes, liver, and spleen. There are no vaccines for salmonellosis, but vaccines for typhoid fever are given to travelers going to countries where outbreaks are frequent. These vaccines, however, are not perfect and are more effective when questionable foods and drinks are avoided.

Antibiotics, specifically ampicillin, gentamicin, ciprofloxacin, and a combination of trimethoprim and sulfamethoxazole, are given to patients with typhoid fever or severe salmonellosis. Some serotypes have developed some antibiotics resistance due to its use in feed animals. Administering intravenous fluids and electrolytes can remedy severe dehydration due to diarrhea. Symptoms of salmonellosis begin 12 to 72 hours after infection and include nausea, diarrhea, fever, headaches, abdominal cramps, and vomiting.

Sun and her team figured out how salmonella is able to get your immune system to ignore it while it grows. The culprit is a protein called AvrA. Here is how it works: Usually, when your body is invaded by a bacteria , the bug causes tissue damage, releasing chemicals that lead to swelling and inflammation.

Physically, inflammation can isolate the invaders, making it difficult for them to travel to other parts of the body. Chemically, it attracts phagocytes, white blood cells that kill bad bacteria.

Salmonella has the ability to punch through the tight links of cells that make up the intestinal wall, using an arsenal of proteins and toxins it can inject into cells. Sun said scientists always thought AvrA was one of these, but, as her team reported June 4 in the online journal PloS One , AvrA actually has an opposite function. The study found that AvrA can maintain the tight structure of cell junctions in the intestinal cells, she said. Research from the Imperial team, published in the journal Cell Host and Microbe , shows that Salmonella prevents the immune cells from displaying digested bacterial fragments on their surface.

The bacterial cell is 'eaten' as normal, but the Imperial team found that once inside the cell, the bacteria release a specific protein that disrupts the transport of bacterial fragments to the cell surface.

This prevents the immune system's second wave of defence — the SAS cells - being activated. The scientists also found that the Salmonella protein works ingeniously - by hijacking machinery inside the immune cell and forcing it to destroy the fragments of bacteria, rather than taking them to the cell surface.

Professor David Holden , senior author of the study and Director of the MRC Centre for Molecular Bacteriology and Infection at Imperial said: "This is a very small protein but it packs a big punch — accounting in part for the ability of Salmonella to cause infections. Now we have this knowledge, we might be able to use it to enhance the effectiveness of vaccines against Salmonella and possibly other harmful bacteria and viruses.