Key to Preventing Listeriosis Found in Gut Microbiome

BACTERIA discovered in the gut could prove invaluable for preventing Listeria infection, according to a new study from researchers at the Memorial Sloan Kettering Cancer Center, Rockville Centre, New York, USA. Caused by the bacterium Listeria monocytogenes, listeriosis is a potentially fatal disease that affects ~1,600 patients in the USA every year and is particularly dangerous to those with a hampered immune system, such as pregnant women and cancer patients undergoing chemotherapy.

The study began by comparing the gut microbiomes of mice treated with antibiotics and mice treated with chemotherapy drugs to a control group, after the introduction of L. monocytogenes. The results were illuminating: mice treated with antibiotics proved notably more vulnerable to the infection than those left untreated. In those animals, the infection quickly colonised the gastrointestinal tract, before moving into the circulatory system. The mice treated with chemotherapy showed an increased vulnerability, which was further exacerbated when they were also treated with antibiotics.

This discovery lead researchers to identify four species of gut bacteria from the Clostridiales family which appeared to protect against the Listeria infection. After promising laboratory results showed that the probiotic bacteria reduced the pathogens growth, researchers began animal trials by introducing the Clostridiales bacteria to germ-free mice before exposing them to L. monocytogenes. As hoped, the probiotic bacteria were shown to protect the mice from infection by reducing the ability of the infecting pathogens to colonise the gastrointestinal tract. “Augmenting colonisation resistance functions in immunocompromised patients by introducing these protective bacterial species might represent a novel clinical approach to prevent L. monocytogenes infection,” explained Dr Simone Becattini, Memorial Sloan Kettering Cancer Center.

Whilst further studies need to be performed on human subjects to validate these findings, the scope of these results has broad implications for the prevention of L. monocytogenes infection. “Our results also raise the possibility that in other at-risk categories for listeriosis, such as infants or pregnant women, disruptions in the gut microbiome could be a contributing factor to susceptibility,” noted Dr Becattini.

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