Natural Predator Used as Live Antibiotic to Catch ’Prey’ Shigella

Highlights

• Scientists have now identified that superbug numbers in an infection can be lowered by using predatory bacterium.
• These predatory bacteria do not cause any harm to the host but attack the infectious agent.
• Bdellovibrio bacteriovorus works with the host immune system to kill Shigella

Superbugs or bugs that are resistant to antibiotic therapy have raised international concern as it is difficult to treat patients infected with these superbugs. A new study published in the journal Current Biology uses normally pathogenic bacteria that work with the immune system of zebrafish to fight against multi-drug resistant Shigella. Bdellovibrio bacteriovorus is a pathogenic bacterium that was used for the first time in the treatment of an infection. Multi-Drug Resistant Shigella
Shigellosis is an infection that is caused by Shigella. The symptoms associated with shigellosis include fever, vomiting, diarrhea and abdominal cramps. It is usually spread via food and is common among people who travel.

The rampant use of antibiotics in the treatment of various infections has resulted in a multi-drug resistant species of bacterium that do not respond to treatment with antibiotics. This makes treating these infections very difficult.

The multidrug-resistant Shigella infections are a cause of worry and according to the CDC Director Tom Frieden “Drug-resistant infections are harder to treat and because Shigella spreads so easily between people, the potential for more – and larger – outbreaks is a real concern. We’re moving quickly to implement a national strategy to curb antibiotic resistance because we can’t take for granted that we’ll always have the drugs we need to fight common infections.”

Shigellosis affects 160 million across the world with 1 million deaths each year. Researchers are trying to develop a different method of treatment for drug resistant Shigella.

Researchers from Imperial College London and Nottingham University have identified the use of Bdellovibrio bacteriovorus in the treatment of Shigella.

Effect of Bdellovibrio bacteriovorus on Shigella

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To study the effect of Bdellovibrio bacteriovorus on Shigella, the researchers initially injected zebra fish larvae with Shigella flexneri strain M90T. Then they injected the larval sites with Bdellovibrio bacteriovorus. The researchers found that

• There was a reduction in Shigella when Bdellovibrio bacteriovorus were injected
• The number of Shigella continued to rise when Bdellovibrio bacteriovorus was not injected.

Dr Serge Mostowy who is a Wellcome Research Career Development Fellow and lead author of the study said: "This study really shows what a unique and interesting bacterium Bdellovibrio is as it presents this amazing natural synergy with the immune system and persists just long enough to kill prey bacteria before being naturally cleared. It's an important milestone in research into the use of a living antibiotic that could be used in animals and humans."

Bdellovibrio Bacteriovorus

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Bdellovibrio bacteriovorus is a gram negative bacterium that is well known for its ability to prey on other gram negative bacterial like E. coli and Salmonella species. This bacterium is naturally pathogenic and its use in the treatment of infections was first determined when it was used to treat stomach infection in hens.

Bdellovibrio bacteriovorus was administered orally using antacids on hens that had normal gut microflora and on hens that were injected with Salmonella sp. It was found that these predatory bacteria lowered the numbers of Salmonella species based on bird gut cecal contents.

Immunocompromised Zebrafish

When zebra fish were depleted off white blood cells Bdellovibrio bacteriovorus were still found to lower Shigella load. However, there was maximum benefit and reduction when the immune system of the zebra fish was fully functional.

Co-lead author, Professor Liz Sockett said: "This has been a truly ground-breaking collaboration that shows therapeutic Bdellovibrio in action inside the translucent living zebrafish. The predatory action of the Bdellovibrio breaks the Shigella-pathogen cells and this stimulates the white blood cells; redoubling their 'efforts' against the pathogen and leading to increased survival of the zebrafish 'patients'."

This study could pave the way for better treatment strategies and enable provide a method to circumvent multi-drug resistance.

The Science portfolio advisor, Dr. Michael Chew said: "It may be unusual to use a bacterium to get rid of another, but in the light of the looming threat from drug-resistant infections the potential of beneficial bacteria-animal interactions should not be overlooked. We are increasingly relying on last line antibiotics, and this innovative study demonstrates how predatory bacteria could be an important additional tool to drugs in the fight against resistance."

There are further studies that are required to understand the spread of Bdellovibrio bacteriovorus and to understand its efficacy in its treatment. The success of this study would mean that patients who fall prey to hospital-borne infections can now be treated with an effective method, allaying fears about widespread epidemics caused due to multi-drug resistance infectious agents.

References:

1. Shigella – Shigellosis - (https://www.cdc.gov/shigella/)
2. Multidrug-resistant Shigellosis Spreading in the United States - (http://www.cdc.gov/media/releases/2015/p0402-multidrug-resistant-shigellosis.html)
3. Effects of Orally Administered Bdellovibrio bacteriovorus on the Well-Being and Salmonella Colonization of Young Chicks - (http://aem.asm.org/content/77/16/5794.full)

Source-Medindia