Listeria grow better when oxygen is restricted

In this study, published in BMC Microbiology journal, scientists Bjarke Christensen and Tine Licht, together with colleagues from Denmark’s National Food Institute, investigated whether the growth conditions of Listeria had an effect on its virulence in the gut.

Guinea pigs were fed food infected by Listeria monocytogenes, grown either in an oxygen-rich or oxygen free environment. Christenses and Licht measured the presence of the bacteria in the intestine, liver and spleen after periods of four and seven days.

The scientists discovered that although oxygen-restriction does not help the bacteria to multiply in the gut, it speeds up its path into organs such as the liver and spleen.

Listeria grown under normal conditions was detected in the livers and intestines of two animals, and in the spleens of four animals, while Listeria grown under oxygen-restricted conditions prior to dosage was recovered from livers, spleens and intestines of 18, 12, and 14 animals respectively.

It was concluded that cultures of L. monocytogenes under oxygen-restricted conditions were approximately 100 fold more invasive, and so more likely to cause infection.