Non-replicating Microorganisms
Non-replicating microorganisms (NRMs) are heat-treated probiotics, together with their culture medium, that are known to positively influence health even after they have been inactivated (rendered incapable of replicating).

NRMs have been shown to promote digestive health, improve fecal quality and stimulate natural defenses. Not all probiotics are good candidates for inactivation, and not all methods of inactivation will allow the bacteria to retain their health- promoting activity. Purina has found that a heat-treated lactobacillus blend (Lactobacillus fermentum and Lactobacillus delbrueckii) has proven health-promoting activity.

The science behind NRMs

NRMs retain their beneficial properties even after inactivation, as the bacterial cell walls themselves are able to trigger an immune response and contribute to the priming process.

Specifically, by acting as Toll-like receptor agonists – which are proteins that can activate parts of the immune system –  NRMs can affect pathways and mechanisms involved in inflammatory signaling that are activated by probiotic bacteria.

This mechanism could provide immune cells with increased tolerance and result in a decreased inflammatory response to mild stresses.

Additionally, metabolites released by the bacteria during the inactivation process would also be able to trigger an immune response and provide some protection against pathogens.

Finally, NRMs could be nutrients for other desirable microflora, supporting their replication and thereby improving gut health.1


Purina research showed that cats supplemented with NRMs experienced a significant beneficial effect on the gut immune system, as seen by higher levels of fecal IgA antibodies.2

Key things to remember
  • NRMs are inactivated, heat-treated probiotics known to positively influence health.
  • Not all probiotics are effective as NRMs, and must be selected carefully.
  • Even though the bacteria are rendered incapable of replicating, the cell walls of NRMs can positively affect the immune response.
  • NRM supplementation may provide the bridge between weaning and the development of a fully functioning immune system.
Find out more

1. Kataria, J., Li, N., Wynn, J. L., & Neu, J. (2009). Probiotic microbes: do they need to be alive to be beneficial? Nutrition Reviews, 67(9), 546–550. doi:10.1111/j.1753-4887.2009.00226.x 

2. Purina unpublished data, 2015.