Initiating and monitoring natural infection of mice by bioluminescent Citrobacter rodentium v1

Citrobacter rodentium is a Gram-negative bacterium that infects laboratory mice in a similar way to how enteropathogenic Escherichia coli (EPEC) and enterohaemorrhagic E. coli (EHEC) infect humans. We routinely use a bioluminescent derivative of C. rodentium called ICC180 so that we can monitor infection dynamics non-invasively using biophotonic imaging. Experimental infection is typically initiated via oral gavage but we have previously shown that C. rodentium rapidly spreads between infected and uninfected animals and that bacteria shed from infected mice are 1000 times more infectious than laboratory-grown bacteria with a different tissue tropism.1,2 In this collection of protocols, we describe the different methods for establishing infection by natural transmission and how to monitor infection dynamics using biophotonic imaging, viable counts, and luminometry.3 1. Wiles, S., Dougan, G., & Frankel, G. (2005). Emergence of a 'hyperinfectious' bacterial state after passage of Citrobacter rodentium through the host gastrointestinal tract. Cellular microbiology, 7(8), 1163–1172. https://doi.org/10.1111/j.1462-5822.2005.00544.x 2. Bishop, A. L., Wiles, S., Dougan, G., & Frankel, G. (2007). Cell attachment properties and infectivity of host-adapted and environmentally adapted Citrobacter rodentium.Microbes and infection,9(11), 1316–1324. https://doi.org/10.1016/j.micinf.2007.06.006 3. Read, H. M., Mills, G., Johnson, S., Tsai, P., Dalton, J., Barquist, L., Print, C. G., Patrick, W. M., & Wiles, S. (2016). The in vitro and in vivo effects of constitutive light expression on a bioluminescent strain of the mouse enteropathogen Citrobacter rodentium. PeerJ, 4, e2130. https://doi.org/10.7717/peerj.2130